- Email: [email protected]
Are cases of Methicillin-resistant Staphylococcus aureus clonal complex (CC) 398 among humans still livestock-associated?
International Journal of Medical Microbiology 305 (2015) 110–113
Contents lists available at ScienceDirect
International Journal of Medical Microbiology journal homepage: www.elsevier.com/locate/ijmm
Are cases of Methicillin-resistant Staphylococcus aureus clonal complex (CC) 398 among humans still livestock-associated? Christian Deiters a,b , Volker Günnewig b , Alexander W. Friedrich c , Alexander Mellmann a , Robin Köck a,∗ a
Institute of Hygiene, University Hospital Münster, Robert-Koch-Str. 41, 48149 Münster, Germany Christophorus-Kliniken GmbH, Hagenstraße 35, 48301 Nottuln, Germany c Department of Medical Microbiology, University Medical Centre Groningen, University of Groningen, Hanzeplain 1, 9700 RB Groningen, The Netherlands b
a r t i c l e
i n f o
Article history: Received 19 September 2014 Received in revised form 6 November 2014 Accepted 9 November 2014 Keywords: MRSA Livestock Germany spa CC398 Risk
a b s t r a c t Methicillin-resistant Staphylococcus aureus (MRSA) of clonal complex (CC) 398 are widespread among pigs, cattle and poultry as well as among humans who have contact to these livestock animals. However, there is limited data on livestock-independent dissemination of MRSA CC398 in the general population. Methods: In this case–control study MRSA isolates derived (between July 2013 and June 2014) from patients of four hospitals located in a livestock-dense region were S. aureus protein A (spa) typed and risk factors for MRSA acquisition were assessed from patients colonized or infected with MRSA CC398 vs. other MRSA molecular types (MRSA non-CC398). Results: Of 384 patients, 21% were colonized with MRSA CC398. Contact with livestock (Odds Ratio (OR) 46.03) and residence directly on a pig farm (OR 12.82) were associated with MRSA CC398. Of 55 patients with MRSA CC398, 21 (38%) did not report direct livestock contact. Among the latter we identified several risk factors that could have facilitated indirect transmission, such as living on farms (without being farmer), private contact with known MRSA carriers or previous hospitalization. Discussion: This study suggests that MRSA CC398 is still mostly disseminated via direct contact to livestock. However, a substantial proportion of patients seem to acquire MRSA CC398 via other pathways. © 2014 Elsevier GmbH. All rights reserved.
Introduction Since more than ten years, it is known that Methicillin-resistant Staphylococcus aureus has emerged in pigs, cattle and poultry across Europe (Köck et al., 2014). The isolates detected in livestock animals are mostly non-typeable (NT) using pulsed-field gel electrophoresis following conventional SmaI-based digestion and are associated with clonal complex (CC) 398 when applying multilocus sequence typing (MLST) (van Loo et al., 2007). Multiple studies have shown that MRSA CC398 is very effectively transmitted to humans with direct occupational contact to livestock and have described that 24–100% of pig farmers, 37% of poultry farmers, 30–38% of cattle farmers and up to 45% of veterinarians are colonized with MRSA CC398 in the nares (reviewed in Köck et al., 2014). In addition, early studies demonstrated that nasal colonization with MRSA CC398 among hospital inpatients was significantly associated with direct livestock contact leading to the
∗ Corresponding author. Tel.: +49 251 83 55348; fax: +49 251 83 55688. E-mail address: [email protected] (R. Köck). http://dx.doi.org/10.1016/j.ijmm.2014.11.007 1438-4221/© 2014 Elsevier GmbH. All rights reserved.
introduction of the term “livestock-associated” (LA) MRSA (Köck et al., 2009b; van Loo et al., 2007). However, in the past five years, surveillance data suggested that not all cases of MRSA CC398 occurring among humans are related to animals. In a case–control study in Germany, it was found that 38/100 patients colonized with MRSA CC398 reported no direct contact with pigs and 75/100 had no contact with cattle, respectively (Köck et al., 2009b). The same was found for 19/30 (63%) patients with MRSA CC398 in a Dutch hospital (Wulf et al., 2012). MRSA surveillance in Northern Denmark found no occupational livestock contact for ten of 26 (38%) cases of MRSA CC398 (Omland and Hoffmann, 2012) and data from a national surveillance system in the Netherlands demonstrated that for 20% of MRSA CC398 colonized or infected persons (n = 1738), contact with livestock was not documented (Lekkerkerk et al., 2012). Potential alternative pathways for the transmission of MRSA CC398 from livestock to people in the general population include the dissemination in healthcare facilities, the emission of dust or manure from farms, contact with contaminated food items and personal or indirect (i.e. via objects and surfaces) contact with farmers.
C. Deiters et al. / International Journal of Medical Microbiology 305 (2015) 110–113
In Germany, where no mandatory notification system for MRSA cases (except cases of bacteraemia) is implemented and no casetracing is done routinely by public health authorities, current data on the association of MRSA CC398 and livestock is lacking. Therefore, we performed this case–control study in which MRSA isolates from patients admitted to four hospitals located in a rural area characterized by a high density of livestock production were typed and information on animal-contact was assessed from the patients. In addition, this study was planned to indicate potential alternative, non-occupation-related pathways for the acquisition of MRSA CC398. Methods This study was performed in four hospitals located in Northwestern Germany (district DEA35 according to the European Nomenclature for Territorial Units (NUTS); pig density 781 pigs/km2 ). During a one-year period (July 2013–June 2014) every first MRSA isolate of each patient detected in clinical or admission screening specimens was subjected to S. aureus protein A (spa) sequence-typing (Mellmann et al., 2006). Culture-based nasopharyngeal MRSA admission screening was routinely done, if a patient had at least one of the risk factors history of MRSA colonization or infection, contact to an MRSA carrier, hospitalization (>3 days) within 12 months prior to admission, direct transfer from another healthcare institution, direct contact with livestock, or, if a patient had at least two of the risk factors chronic need for nursing care, antibiotic treatment within six months prior to admission, the presence of indwelling devices, chronic need for dialysis and chronic diseases of the skin.spa types were considered to belong to MRSA CC398, if this was demonstrated in a previous study (i.e. for t011, t034, t108, t571, t899, t1250, t1451, t1456, t1255, t1344, t1580, t2011, t2330 t2346, t2510, t2576 and t2970) (Köck et al., 2013), or if the spa repeat pattern indicated very close relatedness (additionally t1793) according to the Based Upon Repeat Pattern (BURP) algorithm of the Ridom StaphTypeTM software (Ridom GmbH, Münster, Germany) (Mellmann et al., 2008). All patients colonized or infected with MRSA CC398 were asked to participate in a personal interview and to answer a standardized questionnaire assessing potential risk factors for MRSA carriage. In addition, for every MRSA CC398 patient asked for participation, one patient colonized or infected with MRSA other than CC398 (MRSA non-CC398) was asked to answer the questionnaire as well. These patients were chosen randomly. Ethical agreement to perform this study was obtained by the Ethical committee of the University of Münster (2006-268-f-S). Univariate statistical analysis was done using Chi-Square or Fisher’s Exact tests and t-test to compare categorical and continuous variables, respectively (SPSS, version 22); (two-tailed) p-values < 0.05 were considered significant. All variables with p-values < 0.2 in univariate analysis were entered in a multivariate stepwise backward model in which “MRSA CC398” was the dependent variable (SPSS, version 22). Results Overall, a total of 384 different MRSA patients were identified during the one-year period. Of these n = 81 (21%) were colonized or infected with spa types indicative for MRSA CC398 (t011 (n = 35), t034 (n = 31), t108 (n = 4), t2011 (n = 3), t1451, t1793 and t2970 (each n = 2), t899 and t2510 (each n = 1)). Of all patients in whom MRSA CC398 was found, 55 (68%) were available for interviews regarding risk factors. The interview participation rate was similar (p = 0.16) among patients with MRSA non-CC398 (64 of 81 asked for participation). Age was significantly (p < 0.001) lower in the group of patients colonized or infected with MRSA CC398 (median 66
111
years, mean 60 years, range: 2–92 years) compared with patients associated with MRSA non-CC398 (median 81 years, mean 76 years, range: 0–94 years). In a univariate analysis (Table 1), direct (occupational) contact with livestock (p < 0.001) and residence directly on pig and cattle farms (p < 0.001) were significantly associated with patients colonized or infected by MRSA CC398, while hospitalization within the previous six months was associated with patients carrying other MRSA molecular types than MRSA CC398 (p = 0.01). After including the variables residence directly on a pig farm, directly on a cattle farm and in the neighbourhood of a poultry farm, as well as direct livestock contact and hospitalization within the past six months (all associated with p < 0.2 in univariate testing) in logistic regression modelling, the final regression model indicated that only the variables contact with livestock (Odds Ratio (OR) 46.03; 95% confidence interval (CI) 5.65–374.96; p < 0.001) and residence directly on a pig farm (OR 12.82; 95% CI 2.45–67.07; p = 0.003) were independently associated with MRSA CC398. Of all 55 patients colonized or infected with MRSA CC398, 34 (62%) reported any type of contact with livestock (27/34 with pigs, 13/34 with cattle and 6/34 with poultry). The majority (n = 29) of these 34 patients were livestock farmers; the other five patients had occupational contact in other employments (e.g. veterinarians, butcher, slaughterhouse employees). The risk factors for the remaining 21 (38% of all patients with MRSA CC398) patients with MRSA CC398, but without livestock contact are shown in Table 2 for each individual patient. Of these, six patients (29%) lived directly on a pig (n = 5) or poultry (n = 1) farm. Five patients (29%) reported to live in the direct neighbourhood of pig or cattle farms. One patient had contact with farms as he used direct marketing (of food items) and three reported that they had contact with a known MRSA carrier (private contact outside healthcare facilities). Ten of the 21 patients (48%) reported previous hospital stays within one year prior to the interview and for 7/10 patients this was the only positive risk factor. Two of the 21 patients (10%) were not associated with any of the non-occupation related risk factors assessed.
Discussion MRSA CC398 is a pathogen that colonizes global livestock populations. Usually this is not associated with infections among the animals. However, MRSA CC398 effectively causes severe (or fatal) diseases among humans including pneumonia, endocarditis, skin and soft tissue infections or cases of bacteraemia. The occupationrelated acquisition of MRSA CC398 has been analyzed in many investigations and there is no doubt that humans exposed to livestock have a high risk of getting colonized (Köck et al., 2014). This is supported by our finding that direct livestock contact was very significantly associated with MRSA CC398. On the other hand, two studies from the Netherlands recently suggested spread of MRSA CC398 independently from livestock contact in areas characterized by high densities of pig production (Feingold et al., 2012; van Rijen et al., 2014). Another study from the United States suggested that proximity to crop-field application of manure and livestock operations might be a risk for MRSA infections in the general population (Casey et al., 2013) and one investigation indicated association of MRSA carriage with consumption of poultry meat (van Rijen et al., 2013). Constraints of these studies are that they either have not proven that livestock and people in rural areas are indeed infected with the identical MRSA genotypes (Casey et al., 2013), or that they did not assess details on potential indirect contact with livestock (such as residence on or close to farms, private visits on farms etc.) (Feingold et al., 2012; van Rijen et al., 2013, 2014).
112
C. Deiters et al. / International Journal of Medical Microbiology 305 (2015) 110–113
Table 1 Risk factors for MRSA carriage among patients colonized with MRSA CC398 vs patients with other MRSA clonal lineages (MRSA non-CC398). Risk factor
Category
Patients with MRSA CC398 (n = 55)
Patients with MRSA non-CC398 (n = 64)
Univariate p 0.734
Gender
Male
31
33
Distance of residence to a pig farm
Directly on farm Direct neighbourhood (excl. directly on pig farm) >1 km, but <5 km
29 10 8
2 6 9
<0.001 0.257 1.0
Distance of residence to a cattle farm
Directly on farm Direct neighbourhood (excl. directly on pig farm) >1 km, but <5 km
13 6 7
1 4 6
<0.001 0.510 0.772
Distance of residence to a poultry farm
Directly on farm Direct neighbourhood (excl. directly on pig farm) >1 km, but <5 km
4 8 3
2 3 3
0.413 0.110 1.0
33
1
<0.001
Work in healthcare facilities
1
2
1.0
Use of direct marketing at farms
5
6
1.0
Direct contact with livestock animalsc
Contact with MRSA carrier
a
Yes No Unknown
Hospital stay within past 6 months
b
11 13 31
7 19 38
0.358
28
48
0.011
Numbers indicate the number of patients associated with the respective risk factors. a n = 11 private contact, n = 0 contact in healthcare facilities. b n = 5 private contact, n = 2 contact in healthcare facilities. c Pigs (n = 27 of patients with MRSA CC398 vs. n = 1 of patients with MRSA non-CC398), cattle (n = 13 of patients with MRSA CC398 vs. n = 0 of patients with MRSA non-CC398), poultry (n = 6 of patients with MRSA CC398 vs. n = 0 of patients with MRSA non-CC398).
In this study, we found that 62% of persons colonized with MRSA CC398 reported direct (occupational) contact with livestock animals and that 38% did not. This finding is in agreement with previous reports (Köck et al., 2009b; Lekkerkerk et al., 2012; Omland and Hoffmann, 2012; Wulf et al., 2012). In contrast to these reports, this study was planned to assess several other risk factors, which could explain transmission of MRSA CC398 to these persons. We found that a substantial proportion (29%) of persons lived directly (e.g. in historical farm houses, retired farmers) on pig, cattle or poultry farms, which were still in operation; further 29% lived in the direct neighbourhood of such farms. Hence, acquisition could have occurred via transmission from the environment or via contact with
the farmers who operate the livestock holdings. In this context, it should be noted that three patients (Table 2) reported that they had private contact with known MRSA carriers outside healthcare settings (i.e. probably farmers). Another 48% of the patients without livestock contact had been hospitalized within six months prior to MRSA detection. As MRSA CC398 represents a substantial proportion of all MRSA prevalent in regional hospitals (21% in this study; 23–31% in previous studies) (Köck et al., 2013; Schaumburg et al., 2012), nosocomial transmission could also be the origin of MRSA CC398 in these patients. Although it is known that meat at retail is contaminated in high frequencies (Köck et al., 2014), food is mostly not considered as
Table 2 Risk factors for MRSA carriage among patients colonized with MRSA CC398 without any occupational livestock contact. Patient
Distance of residence to pig holding
Distance of residence to cattle holding
Distance of residence to poultry holding
Market
Contact with MRSA carrier
Hospital staya
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
>1 km, <5 km >1 km, <5 km >1 km, <5 km >1 km, <5 km Direct neighbourhood (< 1 km) Directly on the farm Directly on the farm Directly on the farm Directly on the farm >5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km Direct neighbourhood (<1 km) Direct neighbourhood (<1 km) Directly on the farm direct neighbourhood (<1 km)
Direct neighbourhood (<1 km) >5 km >1 km, <5 km >1 km, <5 km >1 km, <5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km Direct neighbourhood (<1 km) Direct neighbourhood (<1 km)
>1 km, <5 km Directly on the farm >5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km Direct neighbourhood (<1 km) Direct neighbourhood (<1 km) Direct neighbourhood (<1 km)
No No No No No No No No No No No No No No Yes No No No No No No
Unknown No No Unknown Unknown No Unknown Yesb No No No No Unknown Unknown Unknown Unknown Unknown Yesb Unknown Yesb Unknown
Yes Yes Yes Yes No No No No No Yes Yes Yes Yes No Yes No Yes No No No Yes
a b
Within the past six months. Reported to known MRSA carrier contact outside healthcare facilities.
C. Deiters et al. / International Journal of Medical Microbiology 305 (2015) 110–113
an important route of transmission (Wendlandt et al., 2013). We identified one patient colonized with MRSA CC398, who reported buying at a farm shop as a potential risk factor for indirect acquisition. In this study, we did not assess the impact of potential foodborne transmission of MRSA CC398 via ingestion or handling of raw meat in the private kitchen, as we believe that this risk factor is difficult to evaluate retrospectively and the associated risk is also dependent on other aspects such as frequency of consumption or compliance with kitchen hygiene. Hence, we cannot exclude that for a minority of MRSA CC398 patients, especially those two of 21 patients who lacked any of the non-occupation related risk factors, food items could be a transmission route. As the admission prevalence of MRSA among patients in the study region (including the hospitals involved in this study) was demonstrated to be 1.6% (Köck et al., 2009a) and as 21% of patients were colonized with MRSA CC398, one can estimate from our data that about 3.4 of 1000 patients admitted are colonized with MRSA CC398. Of these, 62% have acquired MRSA CC398 via direct livestock contact resulting in 1.3/1000 patients with MRSA CC398 for whom acquisition cannot be explained by this transmission pathway. However, the data of this study provide an estimate for other potential indirect ways of MRSA CC398 acquisition and indicate that for the majority of patients with MRSA CC398 but lacking direct livestock contact, living directly on farms causing contact to the environment of livestock animals or contact to the farmers, are the most likely transmission routes. The risk factors foodborne acquisition or acquisition via airborne emissions cannot be ruled out completely, but our data support the findings of other studies that these transmission routes seem to be of minor importance for MRSA CC398 dissemination (Bisdorff et al., 2012; Wendlandt et al., 2013). Conflict of interest All authors report no conflicts of interest relevant to this article. Acknowledgements This work was supported by the German Ministry for Education and Research (BMBF) within the framework of the MedVetStaph research consortium (no. 01KI1301A) and the European Commission (“EurSafety Health-net”, INTERREG IV A no. III-102=073). We thank the infection control staff at the four hospitals for performing interviews and Helga Gräf for expert microbiological assistance. References Bisdorff, B., Scholholter, J.L., Claussen, K., Pulz, M., Nowak, D., Radon, K., 2012. MRSA-ST398 in livestock farmers and neighbouring residents in a rural area in Germany. Epidemiol. Infect. 140, 1800–1808.
113
Casey, J.A., Curriero, F.C., Cosgrove, S.E., Nachman, K.E., Schwartz, B.S., 2013. Highdensity livestock operations, crop field application of manure, and risk of community-associated methicillin-resistant Staphylococcus aureus infection in Pennsylvania. JAMA Intern. Med. 173, 1980–1990. Feingold, B.J., Silbergeld, E.K., Curriero, F.C., van Cleef, B.A., Heck, M.E., Kluytmans, J.A., 2012. Livestock density as risk factor for livestock-associated methicillin-resistant Staphylococcus aureus, the Netherlands. Emerg. Infect. Dis. 18, 1841–1849. Köck, R., Brakensiek, L., Mellmann, A., Kipp, F., Henderikx, M., Harmsen, D., Daniels-Haardt, I., von Eiff, C., Becker, K., Hendrix, M.G., Friedrich, A.W., 2009a. Cross-border comparison of the admission prevalence and clonal structure of meticillin-resistant Staphylococcus aureus. J. Hosp. Infect. 71, 320–326. Köck, R., Harlizius, J., Bressan, N., Laerberg, R., Wieler, L.H., Witte, W., Deurenberg, R.H., Voss, A., Becker, K., Friedrich, A.W., 2009b. Prevalence and molecular characteristics of methicillin-resistant Staphylococcus aureus (MRSA) among pigs on German farms and import of livestock-related MRSA into hospitals. Eur. J. Clin. Microbiol. Infect. Dis. 28, 1375–1382. Köck, R., Schaumburg, F., Mellmann, A., Koksal, M., Jurke, A., Becker, K., Friedrich, A.W., 2013. Livestock-associated methicillin-resistant Staphylococcus aureus (MRSA) as causes of human infection and colonization in Germany. PLOS ONE 8, e55040. Köck, R., Ballhausen, B., Bischoff, M., Cuny, C., Eckmanns, T., Fetsch, A., Harmsen, D., Goerge, T., Oberheitmann, B., Schwarz, S., Selhorst, T., Tenhagen, B.A., Walther, B., Witte, W., Ziebuhr, W., Becker, K., 2014. The burden of zoonotic MRSA colonization and infection in Germany. Berl. Munch. Tierarztl. Wochenschr. 127, 384–398. Lekkerkerk, W.S., van de Sande-Bruinsma, N., van der Sande, M.A., Tjon, A.T.A., Groenheide, A., Haenen, A., Timen, A., van den Broek, P.J., van Wamel, W.J., de Neeling, A.J., Richardus, J.H., Verbrugh, H.A., Vos, M.C., 2012. Emergence of MRSA of unknown origin in the Netherlands. Clin. Microbiol. Infect. 18, 656–661. Mellmann, A., Friedrich, A.W., Rosenkötter, N., Rothgänger, J., Karch, H., Reintjes, R., Harmsen, D., 2006. Automated DNA sequence-based early warning system for the detection of methicillin-resistant Staphylococcus aureus outbreaks. PLoS Med. 3, e33. Mellmann, A., Weniger, T., Berssenbrügge, C., Keckevoet, U., Friedrich, A.W., Harmsen, D., Grundmann, H., 2008. Characterization of clonal relatedness among the natural population of Staphylococcus aureus strains by using spa sequence typing and the BURP (based upon repeat patterns) algorithm. J. Clin. Microbiol. 46, 2805–2808. Omland, O., Hoffmann, L., 2012. Occupational acquisition of methicillin-resistant Staphylococcus aureus in humans—a description of MRSA carrier and infected cases from the region of North Jutland in Denmark. Ann. Agric. Environ. Med. 19, 637–640. Schaumburg, F., Köck, R., Mellmann, A., Richter, L., Hasenberg, F., Kriegeskorte, A., Friedrich, A.W., Gatermann, S., Peters, G., von Eiff, C., Becker, K., 2012. Population dynamics among methicillin resistant Staphylococcus aureus in Germany during a 6-year period. J. Clin. Microbiol. 50, 3186–3192. van Loo, I., Huijsdens, X., Tiemersma, E., de Neeling, A., van de Sande-Bruinsma, N., Beaujean, D., Voss, A., Kluytmans, J., 2007. Emergence of methicillin-resistant Staphylococcus aureus of animal origin in humans. Emerg. Infect. Dis. 13, 1834–1839. van Rijen, M.M., Kluytmans-van den Bergh, M.F., Verkade, E.J., Ten Ham, P.B., Feingold, B.J., Kluytmans, J.A., on behalf of the C.A.M.S.G., 2013. Lifestyle-associated risk factors for community-acquired methicillin-resistant Staphylococcus aureus carriage in the Netherlands: an exploratory hospital-based case–control study. PLOS ONE 8, e65594. van Rijen, M.M., Bosch, T., Verkade, E.J., Schouls, L., Kluytmans, J.A., Group, C.A.M.S., 2014. Livestock-associated MRSA carriage in patients without direct contact with livestock. PLOS ONE 9, e100294. Wendlandt, S., Schwarz, S., Silley, P., 2013. Methicillin-resistant Staphylococcus aureus: a food-borne pathogen? Annu. Rev. Food Sci. Technol. 4, 117–139. Wulf, M.W., Verduin, C.M., van Nes, A., Huijsdens, X., Voss, A., 2012. Infection and colonization with methicillin resistant Staphylococcus aureus ST398 versus other MRSA in an area with a high density of pig farms. Eur. J. Clin. Microbiol. Infect. Dis. 31, 61–65.
Contents lists available at ScienceDirect
International Journal of Medical Microbiology journal homepage: www.elsevier.com/locate/ijmm
Are cases of Methicillin-resistant Staphylococcus aureus clonal complex (CC) 398 among humans still livestock-associated? Christian Deiters a,b , Volker Günnewig b , Alexander W. Friedrich c , Alexander Mellmann a , Robin Köck a,∗ a
Institute of Hygiene, University Hospital Münster, Robert-Koch-Str. 41, 48149 Münster, Germany Christophorus-Kliniken GmbH, Hagenstraße 35, 48301 Nottuln, Germany c Department of Medical Microbiology, University Medical Centre Groningen, University of Groningen, Hanzeplain 1, 9700 RB Groningen, The Netherlands b
a r t i c l e
i n f o
Article history: Received 19 September 2014 Received in revised form 6 November 2014 Accepted 9 November 2014 Keywords: MRSA Livestock Germany spa CC398 Risk
a b s t r a c t Methicillin-resistant Staphylococcus aureus (MRSA) of clonal complex (CC) 398 are widespread among pigs, cattle and poultry as well as among humans who have contact to these livestock animals. However, there is limited data on livestock-independent dissemination of MRSA CC398 in the general population. Methods: In this case–control study MRSA isolates derived (between July 2013 and June 2014) from patients of four hospitals located in a livestock-dense region were S. aureus protein A (spa) typed and risk factors for MRSA acquisition were assessed from patients colonized or infected with MRSA CC398 vs. other MRSA molecular types (MRSA non-CC398). Results: Of 384 patients, 21% were colonized with MRSA CC398. Contact with livestock (Odds Ratio (OR) 46.03) and residence directly on a pig farm (OR 12.82) were associated with MRSA CC398. Of 55 patients with MRSA CC398, 21 (38%) did not report direct livestock contact. Among the latter we identified several risk factors that could have facilitated indirect transmission, such as living on farms (without being farmer), private contact with known MRSA carriers or previous hospitalization. Discussion: This study suggests that MRSA CC398 is still mostly disseminated via direct contact to livestock. However, a substantial proportion of patients seem to acquire MRSA CC398 via other pathways. © 2014 Elsevier GmbH. All rights reserved.
Introduction Since more than ten years, it is known that Methicillin-resistant Staphylococcus aureus has emerged in pigs, cattle and poultry across Europe (Köck et al., 2014). The isolates detected in livestock animals are mostly non-typeable (NT) using pulsed-field gel electrophoresis following conventional SmaI-based digestion and are associated with clonal complex (CC) 398 when applying multilocus sequence typing (MLST) (van Loo et al., 2007). Multiple studies have shown that MRSA CC398 is very effectively transmitted to humans with direct occupational contact to livestock and have described that 24–100% of pig farmers, 37% of poultry farmers, 30–38% of cattle farmers and up to 45% of veterinarians are colonized with MRSA CC398 in the nares (reviewed in Köck et al., 2014). In addition, early studies demonstrated that nasal colonization with MRSA CC398 among hospital inpatients was significantly associated with direct livestock contact leading to the
∗ Corresponding author. Tel.: +49 251 83 55348; fax: +49 251 83 55688. E-mail address: [email protected] (R. Köck). http://dx.doi.org/10.1016/j.ijmm.2014.11.007 1438-4221/© 2014 Elsevier GmbH. All rights reserved.
introduction of the term “livestock-associated” (LA) MRSA (Köck et al., 2009b; van Loo et al., 2007). However, in the past five years, surveillance data suggested that not all cases of MRSA CC398 occurring among humans are related to animals. In a case–control study in Germany, it was found that 38/100 patients colonized with MRSA CC398 reported no direct contact with pigs and 75/100 had no contact with cattle, respectively (Köck et al., 2009b). The same was found for 19/30 (63%) patients with MRSA CC398 in a Dutch hospital (Wulf et al., 2012). MRSA surveillance in Northern Denmark found no occupational livestock contact for ten of 26 (38%) cases of MRSA CC398 (Omland and Hoffmann, 2012) and data from a national surveillance system in the Netherlands demonstrated that for 20% of MRSA CC398 colonized or infected persons (n = 1738), contact with livestock was not documented (Lekkerkerk et al., 2012). Potential alternative pathways for the transmission of MRSA CC398 from livestock to people in the general population include the dissemination in healthcare facilities, the emission of dust or manure from farms, contact with contaminated food items and personal or indirect (i.e. via objects and surfaces) contact with farmers.
C. Deiters et al. / International Journal of Medical Microbiology 305 (2015) 110–113
In Germany, where no mandatory notification system for MRSA cases (except cases of bacteraemia) is implemented and no casetracing is done routinely by public health authorities, current data on the association of MRSA CC398 and livestock is lacking. Therefore, we performed this case–control study in which MRSA isolates from patients admitted to four hospitals located in a rural area characterized by a high density of livestock production were typed and information on animal-contact was assessed from the patients. In addition, this study was planned to indicate potential alternative, non-occupation-related pathways for the acquisition of MRSA CC398. Methods This study was performed in four hospitals located in Northwestern Germany (district DEA35 according to the European Nomenclature for Territorial Units (NUTS); pig density 781 pigs/km2 ). During a one-year period (July 2013–June 2014) every first MRSA isolate of each patient detected in clinical or admission screening specimens was subjected to S. aureus protein A (spa) sequence-typing (Mellmann et al., 2006). Culture-based nasopharyngeal MRSA admission screening was routinely done, if a patient had at least one of the risk factors history of MRSA colonization or infection, contact to an MRSA carrier, hospitalization (>3 days) within 12 months prior to admission, direct transfer from another healthcare institution, direct contact with livestock, or, if a patient had at least two of the risk factors chronic need for nursing care, antibiotic treatment within six months prior to admission, the presence of indwelling devices, chronic need for dialysis and chronic diseases of the skin.spa types were considered to belong to MRSA CC398, if this was demonstrated in a previous study (i.e. for t011, t034, t108, t571, t899, t1250, t1451, t1456, t1255, t1344, t1580, t2011, t2330 t2346, t2510, t2576 and t2970) (Köck et al., 2013), or if the spa repeat pattern indicated very close relatedness (additionally t1793) according to the Based Upon Repeat Pattern (BURP) algorithm of the Ridom StaphTypeTM software (Ridom GmbH, Münster, Germany) (Mellmann et al., 2008). All patients colonized or infected with MRSA CC398 were asked to participate in a personal interview and to answer a standardized questionnaire assessing potential risk factors for MRSA carriage. In addition, for every MRSA CC398 patient asked for participation, one patient colonized or infected with MRSA other than CC398 (MRSA non-CC398) was asked to answer the questionnaire as well. These patients were chosen randomly. Ethical agreement to perform this study was obtained by the Ethical committee of the University of Münster (2006-268-f-S). Univariate statistical analysis was done using Chi-Square or Fisher’s Exact tests and t-test to compare categorical and continuous variables, respectively (SPSS, version 22); (two-tailed) p-values < 0.05 were considered significant. All variables with p-values < 0.2 in univariate analysis were entered in a multivariate stepwise backward model in which “MRSA CC398” was the dependent variable (SPSS, version 22). Results Overall, a total of 384 different MRSA patients were identified during the one-year period. Of these n = 81 (21%) were colonized or infected with spa types indicative for MRSA CC398 (t011 (n = 35), t034 (n = 31), t108 (n = 4), t2011 (n = 3), t1451, t1793 and t2970 (each n = 2), t899 and t2510 (each n = 1)). Of all patients in whom MRSA CC398 was found, 55 (68%) were available for interviews regarding risk factors. The interview participation rate was similar (p = 0.16) among patients with MRSA non-CC398 (64 of 81 asked for participation). Age was significantly (p < 0.001) lower in the group of patients colonized or infected with MRSA CC398 (median 66
111
years, mean 60 years, range: 2–92 years) compared with patients associated with MRSA non-CC398 (median 81 years, mean 76 years, range: 0–94 years). In a univariate analysis (Table 1), direct (occupational) contact with livestock (p < 0.001) and residence directly on pig and cattle farms (p < 0.001) were significantly associated with patients colonized or infected by MRSA CC398, while hospitalization within the previous six months was associated with patients carrying other MRSA molecular types than MRSA CC398 (p = 0.01). After including the variables residence directly on a pig farm, directly on a cattle farm and in the neighbourhood of a poultry farm, as well as direct livestock contact and hospitalization within the past six months (all associated with p < 0.2 in univariate testing) in logistic regression modelling, the final regression model indicated that only the variables contact with livestock (Odds Ratio (OR) 46.03; 95% confidence interval (CI) 5.65–374.96; p < 0.001) and residence directly on a pig farm (OR 12.82; 95% CI 2.45–67.07; p = 0.003) were independently associated with MRSA CC398. Of all 55 patients colonized or infected with MRSA CC398, 34 (62%) reported any type of contact with livestock (27/34 with pigs, 13/34 with cattle and 6/34 with poultry). The majority (n = 29) of these 34 patients were livestock farmers; the other five patients had occupational contact in other employments (e.g. veterinarians, butcher, slaughterhouse employees). The risk factors for the remaining 21 (38% of all patients with MRSA CC398) patients with MRSA CC398, but without livestock contact are shown in Table 2 for each individual patient. Of these, six patients (29%) lived directly on a pig (n = 5) or poultry (n = 1) farm. Five patients (29%) reported to live in the direct neighbourhood of pig or cattle farms. One patient had contact with farms as he used direct marketing (of food items) and three reported that they had contact with a known MRSA carrier (private contact outside healthcare facilities). Ten of the 21 patients (48%) reported previous hospital stays within one year prior to the interview and for 7/10 patients this was the only positive risk factor. Two of the 21 patients (10%) were not associated with any of the non-occupation related risk factors assessed.
Discussion MRSA CC398 is a pathogen that colonizes global livestock populations. Usually this is not associated with infections among the animals. However, MRSA CC398 effectively causes severe (or fatal) diseases among humans including pneumonia, endocarditis, skin and soft tissue infections or cases of bacteraemia. The occupationrelated acquisition of MRSA CC398 has been analyzed in many investigations and there is no doubt that humans exposed to livestock have a high risk of getting colonized (Köck et al., 2014). This is supported by our finding that direct livestock contact was very significantly associated with MRSA CC398. On the other hand, two studies from the Netherlands recently suggested spread of MRSA CC398 independently from livestock contact in areas characterized by high densities of pig production (Feingold et al., 2012; van Rijen et al., 2014). Another study from the United States suggested that proximity to crop-field application of manure and livestock operations might be a risk for MRSA infections in the general population (Casey et al., 2013) and one investigation indicated association of MRSA carriage with consumption of poultry meat (van Rijen et al., 2013). Constraints of these studies are that they either have not proven that livestock and people in rural areas are indeed infected with the identical MRSA genotypes (Casey et al., 2013), or that they did not assess details on potential indirect contact with livestock (such as residence on or close to farms, private visits on farms etc.) (Feingold et al., 2012; van Rijen et al., 2013, 2014).
112
C. Deiters et al. / International Journal of Medical Microbiology 305 (2015) 110–113
Table 1 Risk factors for MRSA carriage among patients colonized with MRSA CC398 vs patients with other MRSA clonal lineages (MRSA non-CC398). Risk factor
Category
Patients with MRSA CC398 (n = 55)
Patients with MRSA non-CC398 (n = 64)
Univariate p 0.734
Gender
Male
31
33
Distance of residence to a pig farm
Directly on farm Direct neighbourhood (excl. directly on pig farm) >1 km, but <5 km
29 10 8
2 6 9
<0.001 0.257 1.0
Distance of residence to a cattle farm
Directly on farm Direct neighbourhood (excl. directly on pig farm) >1 km, but <5 km
13 6 7
1 4 6
<0.001 0.510 0.772
Distance of residence to a poultry farm
Directly on farm Direct neighbourhood (excl. directly on pig farm) >1 km, but <5 km
4 8 3
2 3 3
0.413 0.110 1.0
33
1
<0.001
Work in healthcare facilities
1
2
1.0
Use of direct marketing at farms
5
6
1.0
Direct contact with livestock animalsc
Contact with MRSA carrier
a
Yes No Unknown
Hospital stay within past 6 months
b
11 13 31
7 19 38
0.358
28
48
0.011
Numbers indicate the number of patients associated with the respective risk factors. a n = 11 private contact, n = 0 contact in healthcare facilities. b n = 5 private contact, n = 2 contact in healthcare facilities. c Pigs (n = 27 of patients with MRSA CC398 vs. n = 1 of patients with MRSA non-CC398), cattle (n = 13 of patients with MRSA CC398 vs. n = 0 of patients with MRSA non-CC398), poultry (n = 6 of patients with MRSA CC398 vs. n = 0 of patients with MRSA non-CC398).
In this study, we found that 62% of persons colonized with MRSA CC398 reported direct (occupational) contact with livestock animals and that 38% did not. This finding is in agreement with previous reports (Köck et al., 2009b; Lekkerkerk et al., 2012; Omland and Hoffmann, 2012; Wulf et al., 2012). In contrast to these reports, this study was planned to assess several other risk factors, which could explain transmission of MRSA CC398 to these persons. We found that a substantial proportion (29%) of persons lived directly (e.g. in historical farm houses, retired farmers) on pig, cattle or poultry farms, which were still in operation; further 29% lived in the direct neighbourhood of such farms. Hence, acquisition could have occurred via transmission from the environment or via contact with
the farmers who operate the livestock holdings. In this context, it should be noted that three patients (Table 2) reported that they had private contact with known MRSA carriers outside healthcare settings (i.e. probably farmers). Another 48% of the patients without livestock contact had been hospitalized within six months prior to MRSA detection. As MRSA CC398 represents a substantial proportion of all MRSA prevalent in regional hospitals (21% in this study; 23–31% in previous studies) (Köck et al., 2013; Schaumburg et al., 2012), nosocomial transmission could also be the origin of MRSA CC398 in these patients. Although it is known that meat at retail is contaminated in high frequencies (Köck et al., 2014), food is mostly not considered as
Table 2 Risk factors for MRSA carriage among patients colonized with MRSA CC398 without any occupational livestock contact. Patient
Distance of residence to pig holding
Distance of residence to cattle holding
Distance of residence to poultry holding
Market
Contact with MRSA carrier
Hospital staya
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
>1 km, <5 km >1 km, <5 km >1 km, <5 km >1 km, <5 km Direct neighbourhood (< 1 km) Directly on the farm Directly on the farm Directly on the farm Directly on the farm >5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km Direct neighbourhood (<1 km) Direct neighbourhood (<1 km) Directly on the farm direct neighbourhood (<1 km)
Direct neighbourhood (<1 km) >5 km >1 km, <5 km >1 km, <5 km >1 km, <5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km Direct neighbourhood (<1 km) Direct neighbourhood (<1 km)
>1 km, <5 km Directly on the farm >5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km >5 km Direct neighbourhood (<1 km) Direct neighbourhood (<1 km) Direct neighbourhood (<1 km)
No No No No No No No No No No No No No No Yes No No No No No No
Unknown No No Unknown Unknown No Unknown Yesb No No No No Unknown Unknown Unknown Unknown Unknown Yesb Unknown Yesb Unknown
Yes Yes Yes Yes No No No No No Yes Yes Yes Yes No Yes No Yes No No No Yes
a b
Within the past six months. Reported to known MRSA carrier contact outside healthcare facilities.
C. Deiters et al. / International Journal of Medical Microbiology 305 (2015) 110–113
an important route of transmission (Wendlandt et al., 2013). We identified one patient colonized with MRSA CC398, who reported buying at a farm shop as a potential risk factor for indirect acquisition. In this study, we did not assess the impact of potential foodborne transmission of MRSA CC398 via ingestion or handling of raw meat in the private kitchen, as we believe that this risk factor is difficult to evaluate retrospectively and the associated risk is also dependent on other aspects such as frequency of consumption or compliance with kitchen hygiene. Hence, we cannot exclude that for a minority of MRSA CC398 patients, especially those two of 21 patients who lacked any of the non-occupation related risk factors, food items could be a transmission route. As the admission prevalence of MRSA among patients in the study region (including the hospitals involved in this study) was demonstrated to be 1.6% (Köck et al., 2009a) and as 21% of patients were colonized with MRSA CC398, one can estimate from our data that about 3.4 of 1000 patients admitted are colonized with MRSA CC398. Of these, 62% have acquired MRSA CC398 via direct livestock contact resulting in 1.3/1000 patients with MRSA CC398 for whom acquisition cannot be explained by this transmission pathway. However, the data of this study provide an estimate for other potential indirect ways of MRSA CC398 acquisition and indicate that for the majority of patients with MRSA CC398 but lacking direct livestock contact, living directly on farms causing contact to the environment of livestock animals or contact to the farmers, are the most likely transmission routes. The risk factors foodborne acquisition or acquisition via airborne emissions cannot be ruled out completely, but our data support the findings of other studies that these transmission routes seem to be of minor importance for MRSA CC398 dissemination (Bisdorff et al., 2012; Wendlandt et al., 2013). Conflict of interest All authors report no conflicts of interest relevant to this article. Acknowledgements This work was supported by the German Ministry for Education and Research (BMBF) within the framework of the MedVetStaph research consortium (no. 01KI1301A) and the European Commission (“EurSafety Health-net”, INTERREG IV A no. III-102=073). We thank the infection control staff at the four hospitals for performing interviews and Helga Gräf for expert microbiological assistance. References Bisdorff, B., Scholholter, J.L., Claussen, K., Pulz, M., Nowak, D., Radon, K., 2012. MRSA-ST398 in livestock farmers and neighbouring residents in a rural area in Germany. Epidemiol. Infect. 140, 1800–1808.
113
Casey, J.A., Curriero, F.C., Cosgrove, S.E., Nachman, K.E., Schwartz, B.S., 2013. Highdensity livestock operations, crop field application of manure, and risk of community-associated methicillin-resistant Staphylococcus aureus infection in Pennsylvania. JAMA Intern. Med. 173, 1980–1990. Feingold, B.J., Silbergeld, E.K., Curriero, F.C., van Cleef, B.A., Heck, M.E., Kluytmans, J.A., 2012. Livestock density as risk factor for livestock-associated methicillin-resistant Staphylococcus aureus, the Netherlands. Emerg. Infect. Dis. 18, 1841–1849. Köck, R., Brakensiek, L., Mellmann, A., Kipp, F., Henderikx, M., Harmsen, D., Daniels-Haardt, I., von Eiff, C., Becker, K., Hendrix, M.G., Friedrich, A.W., 2009a. Cross-border comparison of the admission prevalence and clonal structure of meticillin-resistant Staphylococcus aureus. J. Hosp. Infect. 71, 320–326. Köck, R., Harlizius, J., Bressan, N., Laerberg, R., Wieler, L.H., Witte, W., Deurenberg, R.H., Voss, A., Becker, K., Friedrich, A.W., 2009b. Prevalence and molecular characteristics of methicillin-resistant Staphylococcus aureus (MRSA) among pigs on German farms and import of livestock-related MRSA into hospitals. Eur. J. Clin. Microbiol. Infect. Dis. 28, 1375–1382. Köck, R., Schaumburg, F., Mellmann, A., Koksal, M., Jurke, A., Becker, K., Friedrich, A.W., 2013. Livestock-associated methicillin-resistant Staphylococcus aureus (MRSA) as causes of human infection and colonization in Germany. PLOS ONE 8, e55040. Köck, R., Ballhausen, B., Bischoff, M., Cuny, C., Eckmanns, T., Fetsch, A., Harmsen, D., Goerge, T., Oberheitmann, B., Schwarz, S., Selhorst, T., Tenhagen, B.A., Walther, B., Witte, W., Ziebuhr, W., Becker, K., 2014. The burden of zoonotic MRSA colonization and infection in Germany. Berl. Munch. Tierarztl. Wochenschr. 127, 384–398. Lekkerkerk, W.S., van de Sande-Bruinsma, N., van der Sande, M.A., Tjon, A.T.A., Groenheide, A., Haenen, A., Timen, A., van den Broek, P.J., van Wamel, W.J., de Neeling, A.J., Richardus, J.H., Verbrugh, H.A., Vos, M.C., 2012. Emergence of MRSA of unknown origin in the Netherlands. Clin. Microbiol. Infect. 18, 656–661. Mellmann, A., Friedrich, A.W., Rosenkötter, N., Rothgänger, J., Karch, H., Reintjes, R., Harmsen, D., 2006. Automated DNA sequence-based early warning system for the detection of methicillin-resistant Staphylococcus aureus outbreaks. PLoS Med. 3, e33. Mellmann, A., Weniger, T., Berssenbrügge, C., Keckevoet, U., Friedrich, A.W., Harmsen, D., Grundmann, H., 2008. Characterization of clonal relatedness among the natural population of Staphylococcus aureus strains by using spa sequence typing and the BURP (based upon repeat patterns) algorithm. J. Clin. Microbiol. 46, 2805–2808. Omland, O., Hoffmann, L., 2012. Occupational acquisition of methicillin-resistant Staphylococcus aureus in humans—a description of MRSA carrier and infected cases from the region of North Jutland in Denmark. Ann. Agric. Environ. Med. 19, 637–640. Schaumburg, F., Köck, R., Mellmann, A., Richter, L., Hasenberg, F., Kriegeskorte, A., Friedrich, A.W., Gatermann, S., Peters, G., von Eiff, C., Becker, K., 2012. Population dynamics among methicillin resistant Staphylococcus aureus in Germany during a 6-year period. J. Clin. Microbiol. 50, 3186–3192. van Loo, I., Huijsdens, X., Tiemersma, E., de Neeling, A., van de Sande-Bruinsma, N., Beaujean, D., Voss, A., Kluytmans, J., 2007. Emergence of methicillin-resistant Staphylococcus aureus of animal origin in humans. Emerg. Infect. Dis. 13, 1834–1839. van Rijen, M.M., Kluytmans-van den Bergh, M.F., Verkade, E.J., Ten Ham, P.B., Feingold, B.J., Kluytmans, J.A., on behalf of the C.A.M.S.G., 2013. Lifestyle-associated risk factors for community-acquired methicillin-resistant Staphylococcus aureus carriage in the Netherlands: an exploratory hospital-based case–control study. PLOS ONE 8, e65594. van Rijen, M.M., Bosch, T., Verkade, E.J., Schouls, L., Kluytmans, J.A., Group, C.A.M.S., 2014. Livestock-associated MRSA carriage in patients without direct contact with livestock. PLOS ONE 9, e100294. Wendlandt, S., Schwarz, S., Silley, P., 2013. Methicillin-resistant Staphylococcus aureus: a food-borne pathogen? Annu. Rev. Food Sci. Technol. 4, 117–139. Wulf, M.W., Verduin, C.M., van Nes, A., Huijsdens, X., Voss, A., 2012. Infection and colonization with methicillin resistant Staphylococcus aureus ST398 versus other MRSA in an area with a high density of pig farms. Eur. J. Clin. Microbiol. Infect. Dis. 31, 61–65.