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Subcutaneous Infection of Methicillin Resistant Staphylococcus Aureus (MRSA)
Published on: February 9, 2011
Emergence of methicillin-resistant, vancomycin-intermediate Staphylococcus aureus among patients associated with
Shanmugaraj Gowrishankar1, Ramalingam Thenmozhi, Kannan Balaji
1Department of Biotechnology, Alagappa University, Karaikudi 630 003, Tamil Nadu, India.
Abstract:
Beyond Staphylococcus aureus being an etiological agent for several serious clinical complications, the foot prints of S. aureus in pharyngitis infection has also been recently recognized. With due response to the fact, a prospective study was conducted between 2009 and 2010 to describe the molecular epidemiology of S. aureus in throat swabs of pharyngitis patients. A total of 63 methicillin-resistant S. aureus (MRSA) and 102 methicillin-susceptible S. aureus (MSSA) isolates were recovered from 265 throat swabs, representing a community-acquired outpatient population from Tamil Nadu, India. Molecular characterization of MRSA was done by two conventional multiplex PCR assays including Panton-Valentine leukocidin (PVL), mecA and nuc genes, and staphylococcal cassette chromosome mec (SCCmec) typing. Among 165 S. aureus isolates, methicillin resistance was observed in 38.2% (n=63), in which 69.8% (n=44/63) of the MRSA along with 55.9% (n=57/102) of MSSA harbored PVL toxin genes. SCCmec typing showed 50.8% of isolates as SCCmec V (n=32), 44.4% as SCCmec III (n=28), and 1.6% as SCCmec types I, II and IVa (n=1). Multilocus sequence typing performed for 26 selected MRSA isolates resulted in 12 different sequence types (ST), including a novel ST2129/SCCmec III, PVL-positive. Ten MRSA isolates were categorized as ST772 (38.5%)/SCCmec V, PVL-positive, and three isolates as ST368 (11.5%)/SCCmec III, PVL-negative. Though the prominent clones of ST772/SCCmec V were multidrug-susceptible worldwide, they were highly multidrug-resistant in the current study, including four clones intermediate to vancomycin. Totally, 10 (15.9%) out of 63 MRSA isolates were documented as vancomycin-intermediate S. aureus (VISA). Collectively, the present study for the first time portrayed the high prevalence of active MRSA pharyngitis infection and also emphasizes an alarming need for discrimination of pharyngeal-asymptomatic carriers of S. aureus from those with an active S. aureus pharyngitis infection.
Insights
This study found a high prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in pharyngitis infections in India. It highlights the need to distinguish active infections from asymptomatic carriage of S. aureus.
Area of Science:
- Microbiology
- Epidemiology
- Infectious Diseases
Background:
- Staphylococcus aureus is a known pathogen causing serious infections.
- Recent recognition of S. aureus's role in pharyngitis necessitates further investigation.
- Understanding the molecular epidemiology of S. aureus in throat infections is crucial.
Purpose of the Study:
- To describe the molecular epidemiology of S. aureus in throat swabs of pharyngitis patients.
- To characterize methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) isolates.
- To identify prevalent strains and resistance patterns.
Main Methods:
- Prospective study conducted from 2009-2010 in Tamil Nadu, India.
- Collected throat swabs from 265 pharyngitis patients.
- Molecular characterization using multiplex PCR for PVL, mecA, nuc genes, SCCmec typing, and multilocus sequence typing (MLST).
Main Results:
- Isolated 63 MRSA and 102 MSSA from 265 throat swabs.
- 38.2% of S. aureus isolates were MRSA.
- High prevalence of Panton-Valentine leukocidin (PVL) toxin genes in both MRSA (69.8%) and MSSA (55.9%).
- SCCmec V and SCCmec III were the predominant types.
- Identified a novel ST2129/SCCmec III, PVL-positive MRSA strain.
- ST772/SCCmec V MRSA isolates showed high multidrug resistance, with 15.9% being vancomycin-intermediate S. aureus (VISA).
Conclusions:
- The study demonstrates a high prevalence of active MRSA pharyngitis.
- Urgent need to differentiate pharyngeal S. aureus carriers from active infection cases.
- Identified concerning multidrug-resistant MRSA strains, including VISA, in the community setting.
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