Use of a Single-Nucleotide Polymorphism Genotyping System To Demonstrate the Unique Epidemiology of Methicillin-Resistant Staphylococcus aureus in Remote Aboriginal Communities

Abstract

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) has emerged as a major public health problem in Australia, as in many other parts of the world. High rates of CA-MRSA skin and soft tissue infection have been reported from Aboriginal communities. We used a single-nucleotide polymorphism (SNP) genotyping typing system based on the multilocus sequence type (MLST) database to investigate the epidemiology of CA-MRSA and methicillin-sensitive S. aureus (MSSA) over a 12-month period in three remote Aboriginal communities of Northern Australia. This was supplemented by real-time PCR for Panton-Valentine leukocidin (PVL) genes, staphylococcal cassette chromosome mec (SCCmec) typing, and antimicrobial susceptibility testing. S. aureus was recovered from pyoderma lesions on 221 occasions and throat swabs on 44 occasions. The median monthly recovery rate of S. aureus from skin sores was 58% (interquartile range, 62 to 78%), and there was no seasonal variation. Twenty-three percent of isolates were CA-MRSA; the proportion was similar across the communities and did not vary over the study period. Erythromycin resistance was found in 47% of CA-MRSA and 21% of MSSA. SNP-based typing identified 14 different clonal complexes (cc); however, cc75 was predominant, accounting for 71% of CA-MRSA isolates. These were confirmed as ST75-like by using an additional SNP and MLST of selected isolates. All but one of the cc75 isolates had SSCmec type IV (one had type V), and all were PVL negative. Monthly tracking of SNP-based cc types showed a highly dynamic process. ST75-MRSA-IV appears to be unique to the region and probably evolved de novo in remote Aboriginal communities.

Staphylococcus aureus Infections: Epidemiology, Pathophysiology, Clinical Manifestations, and Management

“…In general, impetigo presents as bullous or papular lesions that progress to crusted lesions, without accompanying systemic symptoms, on exposed areas of the body (usually the face or extremities). Recent studies of impetiginous lesions found recovery rates of 29 to 90% and 57 to 81% for Streptococcus pyogenes and S. aureus, respectively (313)(314)(315)(316).…”

Phylogenetically Distinct Staphylococcus aureus Lineage Prevalent among Indigenous Communities in Northern Australia

“…They accounted for 23% of all isolates and 70% of MRSA isolates recovered during a community study of impetigo (16), and clinical isolates were associated with a variety of disease states (22). Similar to other incidents of community-acquired MRSA, the majority of SCCmec cassettes found in CC75 were type IV (16).…”

“…Surveillance of staphylococcal carriage and disease in the tropical northern region of the Northern Territory of Australia yielded methicillin-susceptible and methicillin-resistant Staphylococcus isolates that are highly divergent from S. aureus at the MLST loci and are therefore difficult to classify. These isolates were shown to be closely related to each other and were designated clonal complex 75 (CC75) (16). They accounted for 23% of all isolates and 70% of MRSA isolates recovered during a community study of impetigo (16), and clinical isolates were associated with a variety of disease states (22).…”

The current role of pulsed-field gel electrophoresis in methicillin-resistantStaphylococcus aureus(MRSA) typing and the retrospective identification of outbreaks

“…The comparison of single-nucleotide polymorphisms (SNP) is also a sequence-based typing method [20] and provides the basis for real-time PCR or low-density arraybased methods [21]. SNP analysis of three Staphylococcus enterotoxin genes (set2, set5, and set7) was reported to have even higher discriminatory power than MLST [22].…”