International Journal of Infectious Diseases (2009) 13, e131—e132
http://intl.elsevierhealth.com/journals/ijid
LETTER TO THE EDITOR Prevalence of Panton—Valentine leukocidin genes among carriage and invasive Staphylococcus aureus isolates in Malaysia KEYWORDS PVL; Malaysia; MRSA; Nasal carriage
Staphylococcus aureus nasal colonization is common among humans, and causality between carriage and invasive diseases has been substantiated.1 The pathogenicity of S. aureus is determined by a variety of bacterial cell wall surface components and exoproteins. Panton—Valentine leukocidin (PVL), one of these pathogenic determinants, is a bicomponent cytotoxin encoded by the pvl genes luk-S-PV and luk-FPV. PVL destroys leukocytes by creating pores in the mitochondrial membrane.2 The PVL genes are predominantly associated with S. aureus strains that cause communityacquired infections, including skin and soft-tissue abscesses, necrotizing pneumonia and invasive osteomyelitis.3 Recent reports of increasing numbers of S. aureus infections caused by PVL-positive organisms worldwide prompted us to investigate the prevalence of such strains in Malaysia. The study was conducted on S. aureus strains collected from the anterior nares of two different populations (age 1— 80 years) after institutional ethical approval. Strains were derived from (i) an indigenous community known locally as ‘Orang asli’ (n = 47) and (ii) rural people (n = 41) living in a village that belongs to a federal land development authority (Felda). Strains derived from these people were compared with a set of invasive methicillin-resistant S. aureus (MRSA) (n = 40) strains (blood culture, skin and soft-tissue infections) collected in a public hospital. All strains (128) were subjected to PVL toxin gene PCR.4 PVL-positive strains were typed by multi locus sequence typing (MLST). MRSA strains with the PVL genes were further characterized by staphylococcal cassette chromosome mec (SCCmec) typing.5 Forty-seven (22.5%) of 208 indigenous, and 41 (19.24%) of 213 rural people appeared to be colonized with methicillinsusceptible S. aureus. One (2.1%) of 47 indigenous and three
(7.3%) of 41 rural population isolates were PVL PCR positive, which was confirmed by sequencing. Two clinical (5%) MRSA isolates (SCCmec type V) from breast and scrotum abscesses amplified the PVL genes. Overall, 4.5% of carriage and 5% of invasive isolates were PVL PCR positive. Allelic profiling of PVL-positive strains by MLST identified four known sequence types (STs) (Table 1). S. aureus carriage (20.9%) among healthy individuals in Malaysia is within the worldwide reported range. Also, lack of MRSA supports earlier investigations showing that MRSA carriage is very low outside the healthcare environment in Malaysia.6 PVL prevalence among carriage S. aureus (4.5%) isolates is slightly higher than many previous reports,2,7 whereas the 5% prevalence of invasive strains is within the reported range.4,8 We have to emphasize, however, that the number of strains studied here is relatively low. Isolation of PVL-positive strains from abscesses is in agreement with the proposed involvement of PVL in severe and invasive (softtissue) staphylococcal infections.7 The combination of PVL genes and SCCmec type V is different from the usual situation, in which the PVL locus has been found exclusively in SCCmec type IV positive MRSA strains, except for some isolates from Australia and Taiwan.9,10 The presence of the PVL gene in ST188 (a predominant clone in our country) is new, suggesting that the ST188 lineage easily accommodates phage insertion. The local ST772 clone, a variant of ST1 that differs in only two bases changes of the phosphate acetyltransferase gene, could have been imported from Bangladesh, where it was first reported, as many Bangladeshis are working in Malaysia. In conclusion, PVL-positive isolates from diverse genetic backgrounds, including the regionally predominant ST188 clone, have now been identified in Malaysia. Although the PVL prevalence in either carriage or invasive strains is still less than 5%, their potential in acquiring methicillin resistance is a possible source of concern. Continued surveillance of the molecular epidemiology of PVL-positive strains is essential to monitor their spread in the community and its association with infections.
Acknowledgements This work was supported by the Ministry of Science, Technology and Innovation (MOSTI) Malaysia. We thank Professor Keiichi Hiramatsu and Professor Teruyo Ito from Juntendo
1201-9712/$36.00 # 2008 International Society for Infectious Diseases. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.ijid.2008.07.009
e132 Table 1
Letter to the Editor Molecular pattern of PVL-positive isolates of S. aureus and MRSA.
Isolate number
mecA gene detection
PVL gene detection
Allelic profile by MLST
Sequence type
SCCmec type
R46 R47 R95 OA7 C34 C79
Negative Negative Negative Negative Positive Positive
Positive Positive Positive Positive Positive Positive
3-1-1-8-1-1-1 1-1-1-1-1-1-1 3-1-1-8-1-1-1 3-1-1-8-1-1-1 1-1-1-1-1-1-1 1-1-1-1-22-1-1
188 1 188 188 1 772
V V
University, Tokyo, Japan and Dr. Li Yang Hsu from the National University of Singapore for providing PVL and SCCmec positive control isolates. Conflict of interest: No conflict of interest to declare.
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8. McClure JA, Conly JM, Lau V, Elsayed S, Louie T, Hutchins W, et al. Novel multiplex PCR assay for detection of the staphylococcal virulence marker Panton—Valentine leukocidin genes and simultaneous discrimination of methicillin-susceptible from resistant staphylococci. J Clin Microbiol 2006;44:1141—4. 9. Coombs GW, Pearson JC, O’Brien FG, Murray RJ, Grubb WB, Christiansen KJ. Methicillin-resistant Staphylococcus aureus clones, Western Australia. Emerg Infect Dis 2006;12:241—7. 10. Boyle-Vavra S, Ereshefsky B, Wang C, Daum RS. Successful multiresistant community-associated methicillin-resistant Staphylococcus aureus lineage from Taipei, Taiwan, that carries either the novel Staphylococcal chromosome cassette mec (SCCmec) type VT or SCCmec type IV. J Clin Microbiol 2005;43:4719—30.
VasanthaKumari Neela* Ghaznavi Rad Ehsanollah Sekawi Zamberi Alex Van Belkum Nor S. Mariana Universiti Putra Malaysia Serdang, Selangor, Malaysia *Corresponding author. Tel.: +60 3 89472507; fax: +60 3 89413802 E-mail address:
[email protected] (V. Neela) Corresponding Editor: J. Peter Donnelly
26 February 2008
