- Email: [email protected]
Climate and genotypes of Pneumocystis jirovecii
Research Notes 445
Lancefield collection emm53-ST11 isolate. The new subtypes and sequence types from this study have been submitted to the central worldwide database. ACKNOWLEDGEMENTS This study was supported, in part, by the 5th Framework European Commission DG RTD programme QLK2.CT.2002-. 01398 ‘Severe Streptococcus pyogenes disease in Europe’ and Czech Project IGA MH CR No.NI-7382-3. The data have been presented, in part, at the XVIth Lancefield International Symposium on Streptococci and Streptococcal Diseases, Cairns, Australia. We thank all clinicians of the Czech StrepEURO working group for the isolates supplied, and K. Jolley (University of Oxford, UK) for kindly editing the text.
13. Grivea IN, Al-Lahham A, Katopodis GD, Syrogiannopoulos GA, Reinert RR. Resistance to erythromycin and telithromycin in Streptococcus pyogenes isolates obtained between 1999 and 2002 from Greek children with tonsillopharyngitis: phenotypic and genotypic analysis. Antimicrob Agents Chemother 2006; 50: 256–261. 14. Silva-Costa C, Ramirez M, Melo-Cristino J, the Portuguese Surveillance Group for the Study of Respiratory Pathogens. Rapid inversion of the prevalences of macrolide resistance phenotypes paralleled by a diversification of T and emm types among Streptococcus pyogenes in Portugal. Antimicrob Agents Chemother.2005; 49: 2109–2111.
RESEARCH NOTE
REFERENCES 1. Jasir A, Schalen C, Strep-EURO Study Group. Strep-EURO: progress in analysis and research into severe streptococcal disease in Europe, 2003–2004. Euro Surveill 2005; 10: E0502033. 2. Strakova L, Motlova J, Urbaskova P, Krizova P. Pracovni skupina Strep-EURO. Surveillance of serious diseases caused by group A streptococci in the Czech Republic in 2003—the Strep-EURO project. Epidemiol Mikrobiol Imunol 2004; 53: 106–111. 3. Urbaskova P, Jakubu V. Pracovni skupina pro monitorovani antibioticke rezistence. Resistance to macrolides in the species Streptococcus pyogenes in the Czech Republic in 1996–2003. Epidemiol Mikrobiol Imunol 2004; 53: 196–202. 4. Johnson DR, Kaplan E, Sramek J et al. Laboratory diagnosis of group A streptococcal infections. Geneva: World Health Organization, 1996. 5. Whatmore AM, Kapur V, Sulliman DJ, Mussar JM, Kehoe MA. Non-congruent relationships between variation in emm gene sequences and the population genetic structure of group A streptococci. Mol Microbiol 1994; 14: 619–631. 6. Benson JA, Ferrieri P. Rapid pulsed-field gel electrophoresis method for group B streptococcus isolates. J Clin Microbiol 2001; 39: 3006–3008. 7. Tenover FC, Arbeit RD, Goering RV et al. Interpreting chromosomal DNA restriction patterns produced by pulsed-field gel electrophoresis: criteria for bacterial strain typing. J Clin Microbiol 1995; 33: 2233–2239. 8. Seppala H, Nissinen A, Yu Q, Huovinen P. Three different phenotypes of erythromycin-resistant Streptococcus pyogenes in Finland. J Antimicrob Chemother 1993; 32: 885–891. 9. Clinical Laboratory Standards Institute. Performance standards for antimicrobial susceptibility testing. Document M100-S15. Wayne, PA: CLSI, 2005. 10. Siljander T, Toropainen M, Muotiala A, Hoe NP, Musser JM, Vuopio-Varkila J. Emm-typing of invasive T28 group A streptococci 1995–2004, Finland. Clin Microbiol Infect 2005; 11 (suppl 2): 567. 11. Szczypa K, Sadowy E, Izdebski R, Hryniewicz W. A rapid increase in macrolide resistance in Streptococcus pyogenes isolated in Poland during 1996–2002. J Antimicrob Chemother 2004; 54: 828–831. 12. Bingen E, Bidet P, Mihaila-Amrouche L et al. Emergence of macrolide-resistant Streptococcus pyogenes strains in French children. Antimicrob Agents Chemother, 2004; 48: 3559–3562.
Climate and genotypes of Pneumocystis jirovecii R. F. Miller, H. E. R. Evans, A. J. Copas and J. A. Cassell Centre for Sexual Health and HIV Research, Department of Population Sciences and Primary Care, Royal Free and University College Medical School, University College London, London, UK
ABSTRACT This study explored whether seasonal and ⁄ or climatic factors influenced detection of specific genotypes of Pneumocystis jirovecii. Between 1989 and 2001, 155 isolates of P. jirovecii were obtained from patients undergoing bronchoscopic alveolar lavage. For each isolate, the month and climatic conditions were noted. Genotypes of P. jirovecii were distinguished by polymorphisms in the mitochondrial large-subunit rRNA gene. There were monthly and seasonal variations in the frequency of detection of mixed genotypes (p 0.018 and p 0.031, respectively) and genotype 2 (p 0.029 and p 0.086, respectively). There was no association between month ⁄ season and genotypes 1, 3 and 4, or between monthly temperature or rainfall and any genotype. Corresponding author and reprint requests: R. F. Miller, Centre for Sexual Health and HIV Research, Department of Population Sciences and Primary Care, Mortimer Market Centre, Royal Free and University College Medical School, University College London, off Capper Street, London WC1E 6JB, UK E-mail: [email protected]
2006 Copyright by the European Society of Clinical Microbiology and Infectious Diseases, CMI, 13, 430–456
446 Clinical Microbiology and Infection, Volume 13 Number 4, April 2007
Keywords Climatic factors, genotypes, Pneumocystis jirovecii, rainfall, seasons Original Submission: 5 July 2006; Revised Submission: 13 September 2006; Accepted: 17 September 2006
Clin Microbiol Infect 2007; 13: 445–448 10.1111/j.1469-0691.2006.01641.x Pneumocystis is a fungus of the phylum Ascomycota [1]. Clinical disease is thought to arise from de-novo infection, probably acquired via airborne exposure [2]. Climatic factors, including temperature and humidity, are associated with variations in concentrations of ascomycetous and other fungi in air [3,4]. Seasonal variations in the incidence of Pneumocystis pneumonia (PCP) occur in humans [5–9], and seasonal variations in the detection of Pneumocystis have been described in field voles, common shrews [10], Japanese field mice [11] and crab-eating macaques [12]. Genotypic variation has been described among isolates of Pneumocystis jirovecii in the UK [13], but it is not known whether specific genotypes of P. jirovecii predominate at different times of the year [6–8]. The present study examined whether the season of the year and ⁄ or climatic factors (temperature and rainfall) were associated with the identification of specific genotypes of P. jirovecii. Between January 1989 and November 2001, 155 isolates of P. jirovecii were obtained from 155 patients undergoing bronchoscopic alveolar lavage for investigation of respiratory symptoms; 120 patients, of whom 115 were infected with human immunodeficiency virus, had PCP, and 35 (18 infected with human immunodeficiency virus) were colonised with P. jirovecii (as defined previously) [13,14]. Genotyping of 152 of these isolates has been described previously [13]. Extraction of P. jirovecii DNA from bronchoalveolar lavage fluid samples and DNA amplification were performed as described previously [13] and the amplicons were sequenced [14]. Polymorphisms at positions 85 and 248 of the mitochondrial largesubunit rRNA gene were used to distinguish genotypes of P. jirovecii [15]. For each of the 167 months of the study, climatic data, comprising mean maximum and minimum temperatures, from which the average temperatures were calculated, and total rainfall (mm), were obtained for London from the Meteorological
Office (http://www.metoffice.gov.uk/climate/ uk/stationdata/greenwichdata.txt). A possible association between season and climatic factors and the identification of specific P. jirovecii genotypes was tested in three ways: (i) seasonal trends were assessed by calendar month and by season; (ii) associations with climatic factors were explored; and (iii) a periodic pattern of incidence over the year (a single peak and a single trough, 6 months apart) were tested by including sine and cosine terms in a regression model. These analyses were based on Poisson regression, adjusting for year and for the area of residence of patients, assuming independence of events, and were tested through the ‘goodness of fit’ of the model. Statistical analyses were performed using STATA v.9 (Stat Corp., College Station, TX, USA), with p <0.05 considered significant. Sixty-one isolates of P. jirovecii were genotype 1 (14 patients were colonised), 40 were genotype 2 (nine patients were colonised), 30 were genotype 3 (five patients were colonised), and eight were genotype 4 (six patients were colonised); 16 cases were ‘mixed’, yielding two genotypes (one patient was colonised). Mixed genotypes showed a significant association with calendar month and with season (p 0.0818 and p 0.031, respectively). There was a significant association between detection of genotype 2 and the calendar month of isolation (p 0.029), and some evidence of an association by season (p 0.086) (Table 1). No association was
Table 1. Association between calendar month, mean temperature and total rainfall and the detection of specific genotypes of Pneumocystis jiroveciia
Genotype of P. jirovecii
Relative risk (95% CI) and p value Calendar month Temperature Rainfall (January– (increase of 10 cm) December) Season (increase of 10C)
Genotype 1
p 0.204
Genotype 2
p 0.029
Genotype 3
p 0.178
Genotype 4
p 0.156
Mixed p 0.018 genotypes All genotypes p 0.999
p 0.317 0.350 (0.023, 5.323) p 0.449 p 0.086 21.618 (0.74, 625.303) p 0.073 p 0.295 0.192 (0.004, 9.739) p 0.410 p 0.295 19.155 (0.011, 32 500.84) p 0.436 p 0.030 8.897 (0.046, 1721.825) p 0.416 p 0.999 1.463 (0.270, 7.927) p 0.659
1.199 (0.518, p 0.672 0.496 (0.156, p 0.233 1.153 (0.339, p 0.820 0.064 (0.002, p 0.117 2.517 (0.513, p 0.255 0.947 (0.550, p 0.844
2776) 1.571) 3.916) 1.780) 12.338) 1.630)
a
Analysis was based on disaggregated climate and P. jirovecii detection data for the 167 months of the study, adjusted for year of detection and for area of residence (North, South, East or West London or ‘other’ (i.e., outside London).
2006 Copyright by the European Society of Clinical Microbiology and Infectious Diseases, CMI, 13, 430–456
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Research Notes 447
F M A M J J A S O N D Month
Fig. 1. Detection of specific genotypes of Pneumocystis jirovecii by calendar month and by monthly average temperature (broken line) and rainfall (solid line). Graphs are based on aggregated data in order to describe the frequency of detection by calendar month (January–December).
identified between frequencies and month of detection for genotypes 1, 3 and 4. There was some evidence of a positive association between the frequency of isolating genotype 2 and average temperature (p 0.073), but not with rainfall (p 0.233) (Fig. 1, Table 1). There was no association between average temperature or rainfall and frequency of detection of genotypes 1 and 3, or mixed genotypes. There were too few samples of genotype 4 to show an association. There was a periodic pattern in incidence for genotype 2. For each Poisson model, the ‘goodness of fit’ was found to be adequate overall and also for individual genotypes. There was evidence of an association between detection of mixed genotypes or genotype 2 and the month ⁄ season of the year, with some evidence of an association between detection of genotype 2 and the average monthly temperature. Genotype 1, the genotype identified most commonly, appeared to peak in May, and was least common
in January and August–September. While its frequency did not show a statistical association with the climatic factors considered, season, or a periodic pattern, its relationship to other climatic or seasonal phenomena requires further investigation. The observed seasonal variation in detection of mixed genotypes and genotype 2 suggests that different genotypes of P. jirovecii may have differing physical requirements for survival in the environment and ⁄ or for transmission of the organism. Previous studies have demonstrated seasonal variations in the incidence of PCP. The Multicentre AIDS Cohort Study (MACS), which investigated patients in four North American cities, revealed that PCP diagnosis peaked in May–June and was lowest in November–December [5]. In the MACS study, the overall incidence of PCP was greater in colder cities (Pittsburgh and Chicago) than in warmer cities (Los Angeles and Baltimore) [5]. A similar observation has been
2006 Copyright by the European Society of Clinical Microbiology and Infectious Diseases, CMI, 13, 430–456
448 Clinical Microbiology and Infection, Volume 13 Number 4, April 2007
reported for several European countries [16], and a previous study from London (1989–1991) showed similar seasonal peaks in June–July and September, following periods with low rainfall and temperatures of <13C [6]. A study from Geneva also showed peaks in incidence of PCP in June–September [7]. In contrast, no correlation with temperature, but a correlation with low rainfall, was identified elsewhere in London [8], and an inverse correlation between incidence of PCP and mean temperature, with a peak in the winter months when the mean minimum temperature was between 12C and 14C, was observed in southern Spain [9]. Evidence of the influence of climatic factors on the detection of specific types of Pneumocystis has recently been described [17]. Fluctuations in the prevalence of Pneumocystis carinii and Pneumocystis wakefieldiae within a laboratory rat colony were observed over a 6-year period. Higher relative humidity was associated with the isolation of P. carinii, and higher temperature with the isolation of P. wakefieldiae. The coexistence of high relative humidity and temperature (which occurred during the summer months at the study site) was associated with detection of both species [17]. In summary, these data suggest that season, and possibly climatic factors, may influence detection of specific genotypes of P. jirovecii. Further studies using multilocus genotyping [14] and larger numbers of samples are needed in order to explore the influence of season and climate on detection of particular ‘strains’ of P. jirovecii. REFERENCES 1. Redhead SA, Cushion MT, Frenkel JK, Stringer JR. Pneumocystis and Trypanosoma cruzi: nomenclature and typifications. J Eukaryot Microbiol 2006; 53: 2–11. 2. Miller RF, Ambrose HE, Novelli V, Wakefield AE. Probable mother-to-infant transmission of Pneumocystis carinii f. sp. hominis infection. J Clin Microbiol 2002; 40: 1555–1557.
3. Bush RK. Aerobiology of pollen and fungal allergens. J Allergy Clin Immunol 1989; 84: 1120–1124. 4. Mezzari A, Perin C, Santos SA, Bernd LA. Airborne fungi in the city of Porto Alegre, Rio Grande do Sul, Brazil. Rev Inst Med Trop Sao Paulo 2002; 44: 269–272. 5. Hoover DR, Graham NM, Bacellar H et al. Epidemiologic patterns of upper respiratory illness and Pneumocystis carinii pneumonia in homosexual men. Am Rev Respir Dis 1991; 144: 756–759. 6. Miller RF, Grant AD, Foley NM. Seasonal variation in presentation of Pneumocystis carinii pneumonia. Lancet 1992; 339: 747–748. 7. Vanhems P, Hirschel B, Morabia A. Seasonal incidence of Pneumocystis carinii pneumonia. Lancet 1992; 339: 1182. 8. Lubis N, Baylis D, Short A et al. Prospective cohort study showing changes in the monthly incidence of Pneumocystis carinii pneumonia. Postgrad Med J 2003; 79: 164–166. 9. Varela JM, Regorda´n C, Medrano FJ et al. Climatic factors and Pneumocystis jiroveci infection in southern Spain. Clin Microbiol Infect 2004; 10: 770–772. 10. Laakkonen J, Henttonen H, Niemimaa J, Soveri T. Seasonal dynamics of Pneumocystis carinii in the field vole, Microtus agrestis, and in the common shrew, Sorex araneus, in Finland. Parasitology 1999; 118: 1–5. 11. Shiota T, Kurimto H, Yoshida Y. Prevalence of Pneumocystis carinii in wild rodents in Japan. Zentralbl Bakteriol Mikrobiol Hyg [A] 1986; 261: 381–389. 12. Demanche C, Wanert F, Barthe´lemy M et al. Molecular and serological evidence of Pneumocystis circulation in a social organization of healthy macaques (Macaca fascicularis). Microbiology 2005; 151: 3117–3125. 13. Miller RF, Lindley AR, Copas A, Ambrose HE, Davies RJO, Wakefield AE. Genotypic variation in Pneumocystis jirovecii isolates in Britain. Thorax 2005; 60: 679–682. 14. Wakefield AE, Lindley AR, Ambrose HE, Denis C-M, Miller RF. Limited asymptomatic carriage of Pneumocystis jiroveci in human immunodeficiency virus-infected patients. J Infect Dis 2003; 187: 901–908. 15. Beard CB, Carter JL, Keely SP et al. Genetic variation in Pneumocystis carinii isolates from different geographic regions: implications for transmission. Emerg Infect Dis 2000; 6: 265–272. 16. Delmas MC, Schwoebel V, Heisterkamp SH, Downs AM, Ancelle-Park RA, Brunet JB. Recent trends in Pneumocystis carinii pneumonia as AIDS-defining disease in nine European countries. J AIDS 1995; 9: 74–80. 17. Icenhour CR, Arnold J, Medvedovic M, Cushion MT. Competitive coexistence of two Pneumocystis species. Infect Genet Evol 2006; 6: 177–186.
2006 Copyright by the European Society of Clinical Microbiology and Infectious Diseases, CMI, 13, 430–456
Lancefield collection emm53-ST11 isolate. The new subtypes and sequence types from this study have been submitted to the central worldwide database. ACKNOWLEDGEMENTS This study was supported, in part, by the 5th Framework European Commission DG RTD programme QLK2.CT.2002-. 01398 ‘Severe Streptococcus pyogenes disease in Europe’ and Czech Project IGA MH CR No.NI-7382-3. The data have been presented, in part, at the XVIth Lancefield International Symposium on Streptococci and Streptococcal Diseases, Cairns, Australia. We thank all clinicians of the Czech StrepEURO working group for the isolates supplied, and K. Jolley (University of Oxford, UK) for kindly editing the text.
13. Grivea IN, Al-Lahham A, Katopodis GD, Syrogiannopoulos GA, Reinert RR. Resistance to erythromycin and telithromycin in Streptococcus pyogenes isolates obtained between 1999 and 2002 from Greek children with tonsillopharyngitis: phenotypic and genotypic analysis. Antimicrob Agents Chemother 2006; 50: 256–261. 14. Silva-Costa C, Ramirez M, Melo-Cristino J, the Portuguese Surveillance Group for the Study of Respiratory Pathogens. Rapid inversion of the prevalences of macrolide resistance phenotypes paralleled by a diversification of T and emm types among Streptococcus pyogenes in Portugal. Antimicrob Agents Chemother.2005; 49: 2109–2111.
RESEARCH NOTE
REFERENCES 1. Jasir A, Schalen C, Strep-EURO Study Group. Strep-EURO: progress in analysis and research into severe streptococcal disease in Europe, 2003–2004. Euro Surveill 2005; 10: E0502033. 2. Strakova L, Motlova J, Urbaskova P, Krizova P. Pracovni skupina Strep-EURO. Surveillance of serious diseases caused by group A streptococci in the Czech Republic in 2003—the Strep-EURO project. Epidemiol Mikrobiol Imunol 2004; 53: 106–111. 3. Urbaskova P, Jakubu V. Pracovni skupina pro monitorovani antibioticke rezistence. Resistance to macrolides in the species Streptococcus pyogenes in the Czech Republic in 1996–2003. Epidemiol Mikrobiol Imunol 2004; 53: 196–202. 4. Johnson DR, Kaplan E, Sramek J et al. Laboratory diagnosis of group A streptococcal infections. Geneva: World Health Organization, 1996. 5. Whatmore AM, Kapur V, Sulliman DJ, Mussar JM, Kehoe MA. Non-congruent relationships between variation in emm gene sequences and the population genetic structure of group A streptococci. Mol Microbiol 1994; 14: 619–631. 6. Benson JA, Ferrieri P. Rapid pulsed-field gel electrophoresis method for group B streptococcus isolates. J Clin Microbiol 2001; 39: 3006–3008. 7. Tenover FC, Arbeit RD, Goering RV et al. Interpreting chromosomal DNA restriction patterns produced by pulsed-field gel electrophoresis: criteria for bacterial strain typing. J Clin Microbiol 1995; 33: 2233–2239. 8. Seppala H, Nissinen A, Yu Q, Huovinen P. Three different phenotypes of erythromycin-resistant Streptococcus pyogenes in Finland. J Antimicrob Chemother 1993; 32: 885–891. 9. Clinical Laboratory Standards Institute. Performance standards for antimicrobial susceptibility testing. Document M100-S15. Wayne, PA: CLSI, 2005. 10. Siljander T, Toropainen M, Muotiala A, Hoe NP, Musser JM, Vuopio-Varkila J. Emm-typing of invasive T28 group A streptococci 1995–2004, Finland. Clin Microbiol Infect 2005; 11 (suppl 2): 567. 11. Szczypa K, Sadowy E, Izdebski R, Hryniewicz W. A rapid increase in macrolide resistance in Streptococcus pyogenes isolated in Poland during 1996–2002. J Antimicrob Chemother 2004; 54: 828–831. 12. Bingen E, Bidet P, Mihaila-Amrouche L et al. Emergence of macrolide-resistant Streptococcus pyogenes strains in French children. Antimicrob Agents Chemother, 2004; 48: 3559–3562.
Climate and genotypes of Pneumocystis jirovecii R. F. Miller, H. E. R. Evans, A. J. Copas and J. A. Cassell Centre for Sexual Health and HIV Research, Department of Population Sciences and Primary Care, Royal Free and University College Medical School, University College London, London, UK
ABSTRACT This study explored whether seasonal and ⁄ or climatic factors influenced detection of specific genotypes of Pneumocystis jirovecii. Between 1989 and 2001, 155 isolates of P. jirovecii were obtained from patients undergoing bronchoscopic alveolar lavage. For each isolate, the month and climatic conditions were noted. Genotypes of P. jirovecii were distinguished by polymorphisms in the mitochondrial large-subunit rRNA gene. There were monthly and seasonal variations in the frequency of detection of mixed genotypes (p 0.018 and p 0.031, respectively) and genotype 2 (p 0.029 and p 0.086, respectively). There was no association between month ⁄ season and genotypes 1, 3 and 4, or between monthly temperature or rainfall and any genotype. Corresponding author and reprint requests: R. F. Miller, Centre for Sexual Health and HIV Research, Department of Population Sciences and Primary Care, Mortimer Market Centre, Royal Free and University College Medical School, University College London, off Capper Street, London WC1E 6JB, UK E-mail: [email protected]
2006 Copyright by the European Society of Clinical Microbiology and Infectious Diseases, CMI, 13, 430–456
446 Clinical Microbiology and Infection, Volume 13 Number 4, April 2007
Keywords Climatic factors, genotypes, Pneumocystis jirovecii, rainfall, seasons Original Submission: 5 July 2006; Revised Submission: 13 September 2006; Accepted: 17 September 2006
Clin Microbiol Infect 2007; 13: 445–448 10.1111/j.1469-0691.2006.01641.x Pneumocystis is a fungus of the phylum Ascomycota [1]. Clinical disease is thought to arise from de-novo infection, probably acquired via airborne exposure [2]. Climatic factors, including temperature and humidity, are associated with variations in concentrations of ascomycetous and other fungi in air [3,4]. Seasonal variations in the incidence of Pneumocystis pneumonia (PCP) occur in humans [5–9], and seasonal variations in the detection of Pneumocystis have been described in field voles, common shrews [10], Japanese field mice [11] and crab-eating macaques [12]. Genotypic variation has been described among isolates of Pneumocystis jirovecii in the UK [13], but it is not known whether specific genotypes of P. jirovecii predominate at different times of the year [6–8]. The present study examined whether the season of the year and ⁄ or climatic factors (temperature and rainfall) were associated with the identification of specific genotypes of P. jirovecii. Between January 1989 and November 2001, 155 isolates of P. jirovecii were obtained from 155 patients undergoing bronchoscopic alveolar lavage for investigation of respiratory symptoms; 120 patients, of whom 115 were infected with human immunodeficiency virus, had PCP, and 35 (18 infected with human immunodeficiency virus) were colonised with P. jirovecii (as defined previously) [13,14]. Genotyping of 152 of these isolates has been described previously [13]. Extraction of P. jirovecii DNA from bronchoalveolar lavage fluid samples and DNA amplification were performed as described previously [13] and the amplicons were sequenced [14]. Polymorphisms at positions 85 and 248 of the mitochondrial largesubunit rRNA gene were used to distinguish genotypes of P. jirovecii [15]. For each of the 167 months of the study, climatic data, comprising mean maximum and minimum temperatures, from which the average temperatures were calculated, and total rainfall (mm), were obtained for London from the Meteorological
Office (http://www.metoffice.gov.uk/climate/ uk/stationdata/greenwichdata.txt). A possible association between season and climatic factors and the identification of specific P. jirovecii genotypes was tested in three ways: (i) seasonal trends were assessed by calendar month and by season; (ii) associations with climatic factors were explored; and (iii) a periodic pattern of incidence over the year (a single peak and a single trough, 6 months apart) were tested by including sine and cosine terms in a regression model. These analyses were based on Poisson regression, adjusting for year and for the area of residence of patients, assuming independence of events, and were tested through the ‘goodness of fit’ of the model. Statistical analyses were performed using STATA v.9 (Stat Corp., College Station, TX, USA), with p <0.05 considered significant. Sixty-one isolates of P. jirovecii were genotype 1 (14 patients were colonised), 40 were genotype 2 (nine patients were colonised), 30 were genotype 3 (five patients were colonised), and eight were genotype 4 (six patients were colonised); 16 cases were ‘mixed’, yielding two genotypes (one patient was colonised). Mixed genotypes showed a significant association with calendar month and with season (p 0.0818 and p 0.031, respectively). There was a significant association between detection of genotype 2 and the calendar month of isolation (p 0.029), and some evidence of an association by season (p 0.086) (Table 1). No association was
Table 1. Association between calendar month, mean temperature and total rainfall and the detection of specific genotypes of Pneumocystis jiroveciia
Genotype of P. jirovecii
Relative risk (95% CI) and p value Calendar month Temperature Rainfall (January– (increase of 10 cm) December) Season (increase of 10C)
Genotype 1
p 0.204
Genotype 2
p 0.029
Genotype 3
p 0.178
Genotype 4
p 0.156
Mixed p 0.018 genotypes All genotypes p 0.999
p 0.317 0.350 (0.023, 5.323) p 0.449 p 0.086 21.618 (0.74, 625.303) p 0.073 p 0.295 0.192 (0.004, 9.739) p 0.410 p 0.295 19.155 (0.011, 32 500.84) p 0.436 p 0.030 8.897 (0.046, 1721.825) p 0.416 p 0.999 1.463 (0.270, 7.927) p 0.659
1.199 (0.518, p 0.672 0.496 (0.156, p 0.233 1.153 (0.339, p 0.820 0.064 (0.002, p 0.117 2.517 (0.513, p 0.255 0.947 (0.550, p 0.844
2776) 1.571) 3.916) 1.780) 12.338) 1.630)
a
Analysis was based on disaggregated climate and P. jirovecii detection data for the 167 months of the study, adjusted for year of detection and for area of residence (North, South, East or West London or ‘other’ (i.e., outside London).
2006 Copyright by the European Society of Clinical Microbiology and Infectious Diseases, CMI, 13, 430–456
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‘Mixed’ Genotypes
50 60 Mean rainfall (mm)
12 10 8 6
40
4 2
30
4
Isolates of Pneumocystis jirovecii
6
20 10 15 Mean temperature (°C)
70 40 50 60 Mean rainfall (mm)
8
30
Isolates of Pneumocystis jirovecii
10
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4
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10
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70
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12
10 15 Mean temperature (°C)
(b)
Genotype 1
30
Isolates of Pneumocystis jirovecii
(a)
20
Research Notes 447
F M A M J J A S O N D Month
Fig. 1. Detection of specific genotypes of Pneumocystis jirovecii by calendar month and by monthly average temperature (broken line) and rainfall (solid line). Graphs are based on aggregated data in order to describe the frequency of detection by calendar month (January–December).
identified between frequencies and month of detection for genotypes 1, 3 and 4. There was some evidence of a positive association between the frequency of isolating genotype 2 and average temperature (p 0.073), but not with rainfall (p 0.233) (Fig. 1, Table 1). There was no association between average temperature or rainfall and frequency of detection of genotypes 1 and 3, or mixed genotypes. There were too few samples of genotype 4 to show an association. There was a periodic pattern in incidence for genotype 2. For each Poisson model, the ‘goodness of fit’ was found to be adequate overall and also for individual genotypes. There was evidence of an association between detection of mixed genotypes or genotype 2 and the month ⁄ season of the year, with some evidence of an association between detection of genotype 2 and the average monthly temperature. Genotype 1, the genotype identified most commonly, appeared to peak in May, and was least common
in January and August–September. While its frequency did not show a statistical association with the climatic factors considered, season, or a periodic pattern, its relationship to other climatic or seasonal phenomena requires further investigation. The observed seasonal variation in detection of mixed genotypes and genotype 2 suggests that different genotypes of P. jirovecii may have differing physical requirements for survival in the environment and ⁄ or for transmission of the organism. Previous studies have demonstrated seasonal variations in the incidence of PCP. The Multicentre AIDS Cohort Study (MACS), which investigated patients in four North American cities, revealed that PCP diagnosis peaked in May–June and was lowest in November–December [5]. In the MACS study, the overall incidence of PCP was greater in colder cities (Pittsburgh and Chicago) than in warmer cities (Los Angeles and Baltimore) [5]. A similar observation has been
2006 Copyright by the European Society of Clinical Microbiology and Infectious Diseases, CMI, 13, 430–456
448 Clinical Microbiology and Infection, Volume 13 Number 4, April 2007
reported for several European countries [16], and a previous study from London (1989–1991) showed similar seasonal peaks in June–July and September, following periods with low rainfall and temperatures of <13C [6]. A study from Geneva also showed peaks in incidence of PCP in June–September [7]. In contrast, no correlation with temperature, but a correlation with low rainfall, was identified elsewhere in London [8], and an inverse correlation between incidence of PCP and mean temperature, with a peak in the winter months when the mean minimum temperature was between 12C and 14C, was observed in southern Spain [9]. Evidence of the influence of climatic factors on the detection of specific types of Pneumocystis has recently been described [17]. Fluctuations in the prevalence of Pneumocystis carinii and Pneumocystis wakefieldiae within a laboratory rat colony were observed over a 6-year period. Higher relative humidity was associated with the isolation of P. carinii, and higher temperature with the isolation of P. wakefieldiae. The coexistence of high relative humidity and temperature (which occurred during the summer months at the study site) was associated with detection of both species [17]. In summary, these data suggest that season, and possibly climatic factors, may influence detection of specific genotypes of P. jirovecii. Further studies using multilocus genotyping [14] and larger numbers of samples are needed in order to explore the influence of season and climate on detection of particular ‘strains’ of P. jirovecii. REFERENCES 1. Redhead SA, Cushion MT, Frenkel JK, Stringer JR. Pneumocystis and Trypanosoma cruzi: nomenclature and typifications. J Eukaryot Microbiol 2006; 53: 2–11. 2. Miller RF, Ambrose HE, Novelli V, Wakefield AE. Probable mother-to-infant transmission of Pneumocystis carinii f. sp. hominis infection. J Clin Microbiol 2002; 40: 1555–1557.
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2006 Copyright by the European Society of Clinical Microbiology and Infectious Diseases, CMI, 13, 430–456