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OL-048 Antimicrobial resistance of the bacterial isolates from skin infections
Free Paper Presentation 10: Antibiotics including MRSA OL-046 Comparative mutant prevention concentrations of linezolid and vancomycin against methicillin-resistant Staphylococcus aureus J.-H. Zhao1,2 , J. Li1 *, S.-J. Sun3 , H.B. Zhao1 , D.-Y. Shi1 , J.-H. Li1 , X. Wang1 , X. Lu4 , X.-L. Liu5 , W.-J. Song1 , Q. Ye6 , S.-M. Zhang6 , L. Shi4 . 1 Department of Clinical Microbiology, Second Hospital, Hebei Medical University, Shijiazhuang, Hebei Province, China, 2 Hebei Provincial Centre for Clinical Laboratories, 3 College of Public Health, Hebei Medical University, Shijiazhuang, Hebei Province, China, 4 College of Light Industry and Food Sciences, South China University of Technology, Guangzhou, China, 5 Second Hospital, Hebei Medical University, Shijiazhuang, Hebei Province, China, 6 Chinese National Institute for the Control of Pharmaceutical and Biological Products (NICPBP), Beijing, China Objectives: This study aimed to compare the ability of linezolid and vancomycin to prevent the clinical methicillinresistant Staphylococcus aureus (MRSA) resistant mutant by determining mutant prevention concentration (MPC). Methods: Fifty-six clinical MRSA isolates were enriched in broth, and the bacterial concentration was adjusted to 1010 CFU/mL for MPC determination. Wild-type strains and mutant strains selected by vancomycin during MPC determination were characterized by pulsed-field gel electrophoresis (PFGE), Sau-PCR assay, denaturing gradient gel electrophoresis (DGGE), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Results: Our results showed that both linezolid and vancomycin might have great ability to restrict the selection of resistant mutants of MRSA. Linezolid had a narrower mutant selection window against the MRSA isolates than vancomycin. Sau-PCR assay and PFGE revealed that prescanning and post-scanning strains selected by vancomycin during the experimental process of MPC had different DNA profiles. TEM and SEM showed that the mutant strains had slightly thicker cell walls than the wild-type strains. DDGE was used to probe for mutations in the graS gene, but no different banding patterns were observed on the electrophoretogram spectrum. Conclusion: Linezolid showed greater ability to restrict the selection of resistant mutants of MRSA than vancomycin. In wild-type strains and mutant strains selected by vancomycin during the experimental process of MPC, there may be mutations in genes other than the graS gene or existence of other resistant mechanisms. Acknowledgments: This study was supported by the Chinese National Science and Technology Infrastructure Program (2005DKA21202 6), Ministry of Science and Technology of the People’s Republic of China. We also thank the support from Health Bureau of Hebei Province (08075) and the Second Hospital of Hebei Medical University (2h0200805). OL-047 Risk factors associated with methicillin-resistant Staphylococcus aureus in a tertiary-care hospital W.M. Kyaw1,2 *, A. Chow1,2 , D. Lye1,2 , K.K. Thinn1,2 , V. Lee1,2 , B. Ang1,2 . 1 Communicable Disease Centre, 2 Tan Tock Seng Hospital, Singapore Objectives: Methicillin-resistant Staphylococcus aureus (MRSA) prolongs hospitalisation and leads to poorer clinical outcomes. We aim to evaluate risk factors for MRSA incidence among inpatients at Tan Tock Seng Hospital (TTSH), Singapore. Methods: We conducted a retrospective case control study of 1200 inpatients from January to December 2006 with a S. aureus clinical culture. 600 cases were randomly selected from patients with a positive MRSA clinical culture for the
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first time, and 600 controls with a positive methicillinsensitive S. aureus (MSSA) clinical culture without a positive MRSA in the last 5 years. Results: MRSA patients were older (median age 69 vs. 55 years, p = 0.000), and more likely to be Chinese than MSSA patients (OR 2.0, 95%CI 1.6 2.7, p = 0.000). On univariate analysis, hospitalisation in the preceding year (OR 4.5, 95%CI 3.5 5.8, p = 0.000), presence of a percutaneous device (OR 2.9, 95%CI 2.3 3.8; p = 0.000), use of a cephalosporin (OR 6.4, 95%CI 4.8 8.6, p = 0.000) and use of a fluoroquinolone (OR 11.8, 95%CI 6.9 21.5, p = 0.000), use of a carbapenam (OR 20.5, 95%CI 8.3 64.9, p = 0.000) and hospital stay 5 days prior to positive culture (OR 11.8, 95%CI 8.3 17.0, p= 0.000) were found to be significantly associated with MRSA positivity. On multivariate analysis, history of cardiac disease (adjusted OR 2.5, 95% CI 1.1 5.7, p = 0.033), alcohol abuse (adjusted OR 6.1, 95%CI 1.2 31.1, p = 0.03), fluoroquinolone use (adjusted OR 29.7, 95%CI 3.0 291.5, p = 0.004), and hospital stay 5 days (adjusted OR 6.7, 95%CI 2.1 21.5, p = 0.001) were independent predictors of MRSA. Conclusion: A history of cardiac disease, alcohol abuse, prior flouroquinolone use, and hospital stay 5 days prior to positive culture were independent risk factors of MRSA incidence among inpatients at TTSH. Infection control measures such as early screening and contact precautions for high-risk patients should be considered. OL-048 Antimicrobial resistance of the bacterial isolates from skin infections C. Popescu1,2 , L.C. Gavriliu1,2 *, G.A. Popescu1,2 , V. Arama1,2 , S. Gliga1 , C. Gubavu1 , M. Ion1 . 1 “Prof Dr. Matei Bals” National Institute of Infectious Diseases, Bucharest, Romania, 2 “Carol Davila” University of Medicine, Bucharest, Romania Background: Most skin infections are attributed to Gram positive cocci like Staphylococcus aureus. Nowadays the increasing involvement of other bacteria is noticed, particularly Gram-negative bacteria. Objective: To establish bacterial species involved in skin infections and their resistance to antibiotics. Methods: We analysed the susceptibility tests for the bacterial strains isolated from skin and soft tissue infections from patients hospitalized in the Matei Bals National Institute over a twelve-month period (July 2008 to June 2009). The susceptibility tests were carried out using semiautomatic methods (Microscan, Vitek, API, disk diffusion). Results: We analysed 252 bacterial isolates: 134 strains of Staphylococcus aureus (53.17%), 41 strains of Pseudomonas aeruginosa (16.26%), 47 strains of Enterobacteriaceae (18.65%), 10 strains of Acinetobacter baumannii (3.96%), 8 strains of Enterococcus spp. (3.17%), 11 strains of other GNB (4.36%). 35% of Staphylococcus aureus isolates were MRSA. Staphylococcus aureus showed high levels of resistance to: macrolides 44% and tetracycline 48.5%. Staphylococcus susceptibility remains good for fluorquinolones 94.77%; rifampicin 92.53%; cotrimoxazole 97.7%; chloramphenicol 91.8%. There were no strains resistant to vancomycin and linezolid. The level of antibiotic resistance of Pseudomonas aeruginosa strains is high: fluoroquinolones 60.9%; cefepime 57.5%; ceftazidim 48.78%; imipenem 42.5%; piperacillin/tazobactam 42.5%. In addition, we noticed an important number of Klebsiella spp. and E. coli strains resistant to cephalosporins, including cefepime (8/11 strains and 7/20 strains respectively), 2 strains of Klebsiella spp. resistant
S22 or intermediate to ertapenem and the emergence of P. mirabilis isolates resistant to imipenem. Acinetobacter baumannii showed a worryingly high level of resistance: 9/10 strains resistant to cefepime, 8/10 to carbapenems. Conclusions: Over 40% of skin and soft tissue infections are produced by Gram-negative bacteria with increased antibiotic resistance. The level of MRSA was over 30%, higher that what we found in former studies performed in this clinic. OL-049 Epidemiology and molecular characteristics of community-associated methicillin-resistant and methicillin-susceptible Staphylococcus aureus from skin/soft tissue infections in Beijing Children’s Hospital, China D.J. Wu1 *, W.J. Geng1 , Y.H. Yang1 , X.Z. Shen1 . 1 Beijing Children’s Hospital affiliated to Capital Medical University, China Background: Recently, community-associated methicillinresistant Staphylococcus aureus (CA-MRSA) have rapidly emerged worldwide. And majority of CA-MRSA infections are skin and soft tissue infections (SSTIs) involving children without health care-associated risk factors. Methods: Prospective community-acquired S. aureus SSTIs surveillance was conducted at the Beijing Children’s Hospital, Beijing, China, for a 12-month period from August 1, 2008, to July 30, 2009. Susceptibility to 12 antimicrobials was determined by the agar dilution method. Genotypic characteristics of CA-MRSA isolates were tested by SCCmec typing, spa typing, and multilocus sequence typing (MLST). Panton-Valentine leukocidin gene was detected. spa typing analysis of 120 MSSA isolates was performed, followed by pulsed-field gel electrophoresis and MLST of a selected number of isolates. Result: Of 1104 cases, 31.8% (351) were communityacquired S. aureus. The most common lesions caused by community-acquired S. aureus strains were abscess (33.9%), paronychia (26.5%), and omphalitis (17.4%), followed by wound infection (14%), impetigo (4%), furuncles (2%), congenital deformity infection (1.4%), and carbuncle (0.9%). CA-MRSA accounted for 4% (14) of S. aureus. Among 14 CA-MRSA and 120 MSSA isolates tested, 100% and 91.7% were multidrug resistant, respectively. ST59-MRSA-IVa-t437 (42.9%) was the most common form of CA-MRSA. The most common spa types among MSSA were t084 (8.3%), t091 (5.8%), t034 (5%), t127 (4.2%), t002 (4.2%), and t796 (4.2%). No predominant spa type was seen. Of the MSSA isolates that could be classified into spa-CCs, 15.0% had a genetic background observed in CA-MRSA clones (spa-CC437, spaCC342, and spa-CC377). 71.4% of CA-MRSA and 4.17% of MSSA isolates harbored pvl. Conclusion: CA-MRSA infections are not common among Chinese children with SSTIs. ST59-MRSA-IVa-t437 is circulating in this community. And MSSA strains have diverse genetic backgrounds. OL-050 Clinical and economic impact of imipenem-resistant Acinetobacter baumannii in a teaching hospital in China N. Cui1 *, B. Cao1 , Y.-M. Liu1 , L.-R. Liang1 , L. Gu1 , S.-F. Song1 , P. Guo1 , Y.-D. Yin1 , F. Li1 , B.-B. Li1 , L.-L. Su1 , C.-X. Yang1 , C.-L. Wang1 . 1 Department of Infectious Diseases and Clinical Microbiology, Beijing Chao-Yang Hospital, Capital Medical University. Background: The description of imipenem-resistant Acinetobacter baumannii (IRAB) strains is increasingly more common, but the impact of this antimicrobial resistance on
Abstracts, 4th DICID clinical and economic outcomes among hospitalized patients is not very clearly now. Objective: To investigate the impact of antimicrobial resistance on clinical and economic outcomes among hospitalized patients with IRAB infection in a tertiary care university teaching hospital in China. Methods: A retrospective matched case control (1:1) study was performed to compare the differences in clinical and economic outcomes of patients with IRAB infection and patients with imipenem-susceptive A. baumannii (ISAB) infection at a tertiary care university teaching hospital in China from January 2007 to June 2009. Case patients were matched to control patients on the basis of sex, age, severity of underlying diseases, source of infection, duration of the same period (±3 months) and length of hospital stay before onset of infection. Results: One hundred and thirty eight (90.8%) of 152 cases with IRAB infection were eligible for the study and matched with appropriate controls. The crude mortality rate for IRAB infection patients was higher than that for ISAB infection patients significantly (39.1% vs 20.3%; P = 0.001). For the 72 matched case control pairs had concordant outcomes, cases and controls had a significantly difference in length of ICU stay (14.5 days vs 0 days; P = 0.05), total hospital stay (28.5 days vs 23.0 days; P = 0.014), total hospitalization cost (US$ 13487.2 vs US$ 6933.9; P = 0.001), and antibiotic therapy cost (US$ 2388.0 vs US$ 1260.6; P < 0.001) after the onset of infection. Conclusions: Patients with IRAB infection had a higher mortality rate and greater medical costs than patients with ISAB infection.
Free Paper Presentation 11: Tuberculosis Sunday, July 18, 2010, 07:30 08:30 Convention Hall 2C PL-011 Plasmid based DNA vaccines against tuberculosis M.I. Shahzad1,2 *, I. Khan2 , A. Khanum1 , P. Luciw2 . 1 PMAS Arid Agriculture University Rawalpindi, Pakistan, 2 Center for Comparative Medicine, UCDavis, California, USA TB is a pre-historic disease and it is a significant cause of morbidity and mortality in human and cattle, in many parts of world. The problem has further exacerbated due to emergence of increasingly more resistant strains of M. tb and failure of BCG vaccine. By keeping in view, DNA vaccination which is more efficacious and cost effective way to protect against TB, six M. tb genes (hspx, cfp10, ag85a, ag85b, ag85c and esat6) were selected and used in this study. The genes were cloned in pcDNA3.1 Topo (Invitrogen, USA) vector with Kozak sequences upstream the ATG and finally ligated in pND-a mammalian expression vector. The cell line expression of the conscructs were checked by Western blots analyses. All of the M. tb gene constructs in pND gave good expression under in vitro conditions except esat6 gene. The endotoxin free pND-M. tb gene constructs were subjected to eight weeks old female Balb/c mice @ of 50 mg DNA/leg intramuscularly and 25 mg interdermally. The animals were divided into six groups including positive and negative control groups. Eight animals were used for hspx-pND vaccine, eight for cfp10-pND vaccine, two for esat6-pND vaccine and two for equally mixed (ag85a, b and c)-pND vaccines. Blood collection was done by tail bleeding and
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first time, and 600 controls with a positive methicillinsensitive S. aureus (MSSA) clinical culture without a positive MRSA in the last 5 years. Results: MRSA patients were older (median age 69 vs. 55 years, p = 0.000), and more likely to be Chinese than MSSA patients (OR 2.0, 95%CI 1.6 2.7, p = 0.000). On univariate analysis, hospitalisation in the preceding year (OR 4.5, 95%CI 3.5 5.8, p = 0.000), presence of a percutaneous device (OR 2.9, 95%CI 2.3 3.8; p = 0.000), use of a cephalosporin (OR 6.4, 95%CI 4.8 8.6, p = 0.000) and use of a fluoroquinolone (OR 11.8, 95%CI 6.9 21.5, p = 0.000), use of a carbapenam (OR 20.5, 95%CI 8.3 64.9, p = 0.000) and hospital stay 5 days prior to positive culture (OR 11.8, 95%CI 8.3 17.0, p= 0.000) were found to be significantly associated with MRSA positivity. On multivariate analysis, history of cardiac disease (adjusted OR 2.5, 95% CI 1.1 5.7, p = 0.033), alcohol abuse (adjusted OR 6.1, 95%CI 1.2 31.1, p = 0.03), fluoroquinolone use (adjusted OR 29.7, 95%CI 3.0 291.5, p = 0.004), and hospital stay 5 days (adjusted OR 6.7, 95%CI 2.1 21.5, p = 0.001) were independent predictors of MRSA. Conclusion: A history of cardiac disease, alcohol abuse, prior flouroquinolone use, and hospital stay 5 days prior to positive culture were independent risk factors of MRSA incidence among inpatients at TTSH. Infection control measures such as early screening and contact precautions for high-risk patients should be considered. OL-048 Antimicrobial resistance of the bacterial isolates from skin infections C. Popescu1,2 , L.C. Gavriliu1,2 *, G.A. Popescu1,2 , V. Arama1,2 , S. Gliga1 , C. Gubavu1 , M. Ion1 . 1 “Prof Dr. Matei Bals” National Institute of Infectious Diseases, Bucharest, Romania, 2 “Carol Davila” University of Medicine, Bucharest, Romania Background: Most skin infections are attributed to Gram positive cocci like Staphylococcus aureus. Nowadays the increasing involvement of other bacteria is noticed, particularly Gram-negative bacteria. Objective: To establish bacterial species involved in skin infections and their resistance to antibiotics. Methods: We analysed the susceptibility tests for the bacterial strains isolated from skin and soft tissue infections from patients hospitalized in the Matei Bals National Institute over a twelve-month period (July 2008 to June 2009). The susceptibility tests were carried out using semiautomatic methods (Microscan, Vitek, API, disk diffusion). Results: We analysed 252 bacterial isolates: 134 strains of Staphylococcus aureus (53.17%), 41 strains of Pseudomonas aeruginosa (16.26%), 47 strains of Enterobacteriaceae (18.65%), 10 strains of Acinetobacter baumannii (3.96%), 8 strains of Enterococcus spp. (3.17%), 11 strains of other GNB (4.36%). 35% of Staphylococcus aureus isolates were MRSA. Staphylococcus aureus showed high levels of resistance to: macrolides 44% and tetracycline 48.5%. Staphylococcus susceptibility remains good for fluorquinolones 94.77%; rifampicin 92.53%; cotrimoxazole 97.7%; chloramphenicol 91.8%. There were no strains resistant to vancomycin and linezolid. The level of antibiotic resistance of Pseudomonas aeruginosa strains is high: fluoroquinolones 60.9%; cefepime 57.5%; ceftazidim 48.78%; imipenem 42.5%; piperacillin/tazobactam 42.5%. In addition, we noticed an important number of Klebsiella spp. and E. coli strains resistant to cephalosporins, including cefepime (8/11 strains and 7/20 strains respectively), 2 strains of Klebsiella spp. resistant
S22 or intermediate to ertapenem and the emergence of P. mirabilis isolates resistant to imipenem. Acinetobacter baumannii showed a worryingly high level of resistance: 9/10 strains resistant to cefepime, 8/10 to carbapenems. Conclusions: Over 40% of skin and soft tissue infections are produced by Gram-negative bacteria with increased antibiotic resistance. The level of MRSA was over 30%, higher that what we found in former studies performed in this clinic. OL-049 Epidemiology and molecular characteristics of community-associated methicillin-resistant and methicillin-susceptible Staphylococcus aureus from skin/soft tissue infections in Beijing Children’s Hospital, China D.J. Wu1 *, W.J. Geng1 , Y.H. Yang1 , X.Z. Shen1 . 1 Beijing Children’s Hospital affiliated to Capital Medical University, China Background: Recently, community-associated methicillinresistant Staphylococcus aureus (CA-MRSA) have rapidly emerged worldwide. And majority of CA-MRSA infections are skin and soft tissue infections (SSTIs) involving children without health care-associated risk factors. Methods: Prospective community-acquired S. aureus SSTIs surveillance was conducted at the Beijing Children’s Hospital, Beijing, China, for a 12-month period from August 1, 2008, to July 30, 2009. Susceptibility to 12 antimicrobials was determined by the agar dilution method. Genotypic characteristics of CA-MRSA isolates were tested by SCCmec typing, spa typing, and multilocus sequence typing (MLST). Panton-Valentine leukocidin gene was detected. spa typing analysis of 120 MSSA isolates was performed, followed by pulsed-field gel electrophoresis and MLST of a selected number of isolates. Result: Of 1104 cases, 31.8% (351) were communityacquired S. aureus. The most common lesions caused by community-acquired S. aureus strains were abscess (33.9%), paronychia (26.5%), and omphalitis (17.4%), followed by wound infection (14%), impetigo (4%), furuncles (2%), congenital deformity infection (1.4%), and carbuncle (0.9%). CA-MRSA accounted for 4% (14) of S. aureus. Among 14 CA-MRSA and 120 MSSA isolates tested, 100% and 91.7% were multidrug resistant, respectively. ST59-MRSA-IVa-t437 (42.9%) was the most common form of CA-MRSA. The most common spa types among MSSA were t084 (8.3%), t091 (5.8%), t034 (5%), t127 (4.2%), t002 (4.2%), and t796 (4.2%). No predominant spa type was seen. Of the MSSA isolates that could be classified into spa-CCs, 15.0% had a genetic background observed in CA-MRSA clones (spa-CC437, spaCC342, and spa-CC377). 71.4% of CA-MRSA and 4.17% of MSSA isolates harbored pvl. Conclusion: CA-MRSA infections are not common among Chinese children with SSTIs. ST59-MRSA-IVa-t437 is circulating in this community. And MSSA strains have diverse genetic backgrounds. OL-050 Clinical and economic impact of imipenem-resistant Acinetobacter baumannii in a teaching hospital in China N. Cui1 *, B. Cao1 , Y.-M. Liu1 , L.-R. Liang1 , L. Gu1 , S.-F. Song1 , P. Guo1 , Y.-D. Yin1 , F. Li1 , B.-B. Li1 , L.-L. Su1 , C.-X. Yang1 , C.-L. Wang1 . 1 Department of Infectious Diseases and Clinical Microbiology, Beijing Chao-Yang Hospital, Capital Medical University. Background: The description of imipenem-resistant Acinetobacter baumannii (IRAB) strains is increasingly more common, but the impact of this antimicrobial resistance on
Abstracts, 4th DICID clinical and economic outcomes among hospitalized patients is not very clearly now. Objective: To investigate the impact of antimicrobial resistance on clinical and economic outcomes among hospitalized patients with IRAB infection in a tertiary care university teaching hospital in China. Methods: A retrospective matched case control (1:1) study was performed to compare the differences in clinical and economic outcomes of patients with IRAB infection and patients with imipenem-susceptive A. baumannii (ISAB) infection at a tertiary care university teaching hospital in China from January 2007 to June 2009. Case patients were matched to control patients on the basis of sex, age, severity of underlying diseases, source of infection, duration of the same period (±3 months) and length of hospital stay before onset of infection. Results: One hundred and thirty eight (90.8%) of 152 cases with IRAB infection were eligible for the study and matched with appropriate controls. The crude mortality rate for IRAB infection patients was higher than that for ISAB infection patients significantly (39.1% vs 20.3%; P = 0.001). For the 72 matched case control pairs had concordant outcomes, cases and controls had a significantly difference in length of ICU stay (14.5 days vs 0 days; P = 0.05), total hospital stay (28.5 days vs 23.0 days; P = 0.014), total hospitalization cost (US$ 13487.2 vs US$ 6933.9; P = 0.001), and antibiotic therapy cost (US$ 2388.0 vs US$ 1260.6; P < 0.001) after the onset of infection. Conclusions: Patients with IRAB infection had a higher mortality rate and greater medical costs than patients with ISAB infection.
Free Paper Presentation 11: Tuberculosis Sunday, July 18, 2010, 07:30 08:30 Convention Hall 2C PL-011 Plasmid based DNA vaccines against tuberculosis M.I. Shahzad1,2 *, I. Khan2 , A. Khanum1 , P. Luciw2 . 1 PMAS Arid Agriculture University Rawalpindi, Pakistan, 2 Center for Comparative Medicine, UCDavis, California, USA TB is a pre-historic disease and it is a significant cause of morbidity and mortality in human and cattle, in many parts of world. The problem has further exacerbated due to emergence of increasingly more resistant strains of M. tb and failure of BCG vaccine. By keeping in view, DNA vaccination which is more efficacious and cost effective way to protect against TB, six M. tb genes (hspx, cfp10, ag85a, ag85b, ag85c and esat6) were selected and used in this study. The genes were cloned in pcDNA3.1 Topo (Invitrogen, USA) vector with Kozak sequences upstream the ATG and finally ligated in pND-a mammalian expression vector. The cell line expression of the conscructs were checked by Western blots analyses. All of the M. tb gene constructs in pND gave good expression under in vitro conditions except esat6 gene. The endotoxin free pND-M. tb gene constructs were subjected to eight weeks old female Balb/c mice @ of 50 mg DNA/leg intramuscularly and 25 mg interdermally. The animals were divided into six groups including positive and negative control groups. Eight animals were used for hspx-pND vaccine, eight for cfp10-pND vaccine, two for esat6-pND vaccine and two for equally mixed (ag85a, b and c)-pND vaccines. Blood collection was done by tail bleeding and