High Prevalence of Exfoliative Toxins Among Carrier Isolates of Staphylococcus aureus from Healthy Individuals from Various Communities in Chennai, South India

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.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 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 asymptomatic individuals from old-age homes (n = 100), orphanages (n = 77) and sports teams (n = 175) in Chennai, South India between the period of March and May 2011. Demographic data including age, sex and history of hospitalization along with underlying disease were recorded. Individuals with hospital associations such as currently employed, previous hospitalization within a period of 1 year were not included to provide community background to the study. The study population included both male (n = 216) and female (n = 136) with the age ranging from 6 to 72 years. The study was approv...

Prevalence and Genetic Characteristics of Staphylococcus aureus and Staphylococcus argenteus Isolates Harboring Panton-Valentine Leukocidin, Enterotoxins, and TSST-1 Genes from Food Handlers in Myanmar

“…In contrast, from tropical countries in the African continent (Burkina Faso, Congo, Gabon, Mali, Nigeria, Senegal), high detection rates (24–53%) of pvl were evidenced for S. aureus from nasal carriage [ 17 , 19 , 35 , 36 , 37 , 38 ]. Similarly, high pvl -positive rates were observed in local communities in south India, Ukraine, and Iowa state in the US [ 39 , 40 , 41 ]. In the present study, the detection rate of pvl among healthy food handlers (13.6%, nasal cavity) was found to be relatively higher than those from other Asian countries, Europe, and America, except for some local communities, suggesting that Myanmar is a prevalent area of pvl -carrying S. aureus , which may be relevant to the finding of a high pvl -positive rate (40%) among clinical isolates of S. aureus in Myanmar [ 20 ].…”

Molecular Characteristics and Exotoxins of Methicillin-Resistant Staphylococcus aureus

“…ETs, also known as specific serine proteases, are secreted virulence factors produced by staphylococci (Shopsin et al, 2003;Abimanyu et al, 2013). These proteases have high has not yet been associated with human diseases.…”

Investigating prevalence of pathogenic genes (ETA and TSST-1) in Staphylococcus aureus isolated from different wards of the hospitals by PCR method

“…Three isoforms of exfoliative toxin have been isolated from human; the maximum frequency belongs to ETA and ETB, and the minimum frequency belongs to ETD. However, ETC has been isolated from animal infections and is not pathogenic to humans [8]. In this study, we are investigating prevalence of pathogenic genes tst and eta isolated from different wards of the hospital by PCR method.…”