ABSTRACT
A multidrug-resistant, methicillin-resistant Staphylococcus aureus (MRSA) clone, PVL-positive ST772-MRSA-V, named the Bengal Bay clone, is emerging worldwide. In Norway, where MRSA prevalence is low, a sudden increase in ST772-MRSA-V initiated a nationwide molecular epidemiological study. Clinical data were obtained from the Norwegian Surveillance System for Communicable Diseases (MSIS). S. aureus isolates were characterised by antibiotic susceptibility profiles and comprehensive genotyping (spa typing, MLVA, DNA microarray). ST772-MRSA was detected in 145 individuals during 2004-2014, with 60% of cases occurring in 2013-2014. Median age was 31 years and male/female ratio 1.16. The majority had a family background from the Indian subcontinent (70%). MRSA acquisition was mainly reported as unknown (39%) or abroad (42%), the latter associated with a home-country visit (59%), tourism (16%), and immigration (13%). Clinical infection was present in 75%, predominantly by SSTI (83%), 18% were admitted to hospital and 42% were linked to small-scale outbreaks (n = 25). All isolates were multidrug-resistant. Most isolates were resistant to erythromycin, gentamicin and norfloxacin. Genotyping revealed a conserved clone predominated by spa type t657 (83%), MLVA-type 432 (67%) and the genes lukF/S, sea, sec/sel, egc, scn, cna, ccrAA/ccrC, agrII and cap5. A few untypical ccr gene combinations were detected. Bengal Bay isolates have likely been imported on several occasions and revision of infection control guidelines may prevent further spread.
Subject(s)
Genotype , Methicillin-Resistant Staphylococcus aureus/classification , Methicillin-Resistant Staphylococcus aureus/isolation & purification , Staphylococcal Infections/epidemiology , Staphylococcal Infections/microbiology , Adolescent , Adult , Aged , Aged, 80 and over , Child , Child, Preschool , Female , Humans , Infant , Infant, Newborn , Male , Methicillin-Resistant Staphylococcus aureus/genetics , Microbial Sensitivity Tests , Middle Aged , Molecular Epidemiology , Molecular Typing , Norway/epidemiology , Young AdultABSTRACT
BACKGROUND: The Bengal Bay clone, ST772-MRSA-V, associated with multi-drug resistance, Panton-Valentine leukocidin (PVL) and skin and soft tissue infections, is emerging worldwide. In Norway, a country with low prevalence of meticillin-resistant Staphylococcus aureus (MRSA), increased occurrence of ST772-MRSA-V has also caused hospital outbreaks. The conserved nature of this clone challenged the outbreak investigations. AIM: To evaluate the usefulness of S. aureus protein A (spa) typing, multiple-locus variable number tandem repeat fingerprinting/analysis (MLVF/MLVA) and pulsed-field gel electrophoresis (PFGE) when investigating outbreaks with a conserved MRSA clone. METHODS: A panel of 25 MRSA isolates collected in 2004-2014, consisting of six hospital outbreak isolates and 19 sporadic isolates, were analysed using spa typing, polymerase chain reaction detection of genes encoding PVL, MLVF/MLVA and PFGE. FINDINGS: All isolates were ST772-MRSA-V-t657 and resistant to erythromycin, gentamicin and norfloxacin, and 88% were PVL positive. PFGE could not discriminate between the isolates (≥85% similarity). MLVF resolved five types [Simpson's index of diversity (SID)=0.56], MLVA resolved six types (SID=0.66), and both methods separated the hospital isolates into two defined outbreaks. CONCLUSION: MLVF/MLVA could not discriminate all epidemiologically unlinked cases and identical genotypes originated from a timespan of 10 years. MLVA was regarded as most suitable due to its higher discriminatory power and ability to provide unambiguous profiles. However, the Bengal Bay clone may require higher resolution methods for exact demarcation of outbreaks due to low diversity among isolates.
