High Prevalence of Exfoliative Toxins Among Carrier Isolates of Staphylococcus aureus from Healthy Individuals from Vari
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IGINAL ARTICLE
High Prevalence of Exfoliative Toxins Among Carrier Isolates of Staphylococcus aureus from Healthy Individuals from Various Communities in Chennai, South India Nagarajan Abimanyu • Saravanan Murugesan Padma Krishnan
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Received: 14 May 2012 / Accepted: 17 January 2013 / Published online: 3 February 2013 Ó Association of Microbiologists of India 2013
Abstract Staphylococcus aureus causes infections both in community and hospital settings, nasal carriage is the important source of these infections. A total of 103 carrier isolates of S. aureus from 352 asymptomatic individuals were screened for methicillin-resistant S. aureus (MRSA) and exfoliative toxins (A, B and D) by two sets of multiplex PCRs. The overall nasal carriage of MRSA was found to be 13/352 (3.7 %), of which 4 were found to be positive for Panton valentine leucocidin (PVL). Twelve (11.65 %) strains were found to carry exfoliative toxins and belonged to one of the following spa types t159, t209 and t1515. High prevalence of exfoliative toxins, pvl and MRSA pose a major threat to public health, since the isolates were from the healthy in various community settings. Keywords CA-MRSA pvl Exfoliative toxins t159 t209 SCCmec
Staphylococcus aureus is a ubiquitous pathogen which causes infections both in healthy individuals as well as in hospitalized patients, the clinical spectrum of which varies from mild skin infections to life threatening manifestations such as invasive pyogenic infections, pneumonia and septicemia. The type and severity of the infections by S. aureus depends on the presence or absence of virulence factors carried on the mobile genetic elements (MGEs). Exfoliative toxins (ETs) are exotoxins of S. aureus, associated with staphylococcal scalded skin syndrome (SSSS) or Ritter disease and bullous impetigo [1]. The mechanism N. Abimanyu S. Murugesan P. Krishnan (&) Department of Microbiology, University of Madras, Chennai 600113, India e-mail: [email protected]
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of action of ET is by intra-epidermal splitting by specific cleavage of desmoglein-1, a desmosomal cadherin protein that mediates cell–cell adhesion of keratinocytes [1]. There are four serotypes of ETs- A, B, C and D of which ETA and ETB were associated with human infections. These toxins are carried by about 1–2 % of S. aureus isolates causing human infections [1, 2]. ETD was also associated with human infections, but is less common than the above two. ETD producing isolates are mainly isolated from furuncles or cutaneous abscesses, and not from SSSS. ETC is associated with animal infections. ETs encoding genes eta, etb and etd are carried on MGEs (phage, plasmid and pathogenicity island, respectively) and thus can potentially be transmitted to other isolates. In this study, a high prevalence of ET producing S. aureus were detected among asymptomatic individuals from various closed communities (orphanages, old age homes and sports teams) while screening for an array of toxin genes by PCR assays. A total of 352 nasal swabs were collected from asym
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