Abstract
Staphylococcus aureus is a globally important human pathogen, especially among children and immunocompromised patients. The emergence and spread of community-associated methicillin-resistant S. aureus (CA-MRSA) has become a serious public health problem worldwide. The aim of this study was to investigate the prevalence, molecular characteristics and virulence profiles of CA-MRSA infections from pediatric patients in a university hospital in Shanghai, China. A total of 80 CA-MRSA isolates were collected from July 2012 to December 2013 in Shanghai Children's Medical Center and analyzed by multilocus sequence typing, staphylococcus chromosomal cassette mec (SCCmec) typing, and spa typing. The detection of Panton-Valentine Leukocidin (pvl), superantigenic and exfoliative toxins, and adhesin genes was also performed. Overall, 16 distinct sequence types (STs) were identified among the 80 isolates. Among them, ST59 was found to be the most prevalent, followed by ST398 (11.3%, 9/80) and ST88 (8.8%, 7/80). SCCmec types IV and V were observed, at 60 and 40%, respectively. Thirty spa types were identified, spa t437 (23.8%) was the most predominant type. All 80 isolates exhibited carriage of at least four virulence genes. Thirty-four (42.5%, 34/80) isolates harbored ≥10 tested virulence genes. Adhesion genes were present in most of the MRSA isolates, including the following: icaA (100%), clfA (100%), sdrC (95%), and sdrE (63.8%). The prevalence of pvl gene was 20%, and multidrug resistance was observed in 36% of all strains. In addition, ST59-MRSA-IV with t437 accounted for 21.3% of occurrences, making it the most prevalent clone. Isolates that were carriers of toxin genes, and hla (100%) and hlg (87.5%) were the most frequent. In conclusion, simultaneous carriage of multiple virulence genes and genetically considerable diversity were very common among CA-MRSA from pediatric patients in Shanghai. ST59-MRSA-IV with t437 was still the most predominant type. The combination of virulence gene profiles and antibiotic resistance may help ST59 to be successfully spread among children.
Highlights
Staphylococcus aureus is one of the most prevalent human pathogens, causing a broad variety of diseases ranging from mild skin and soft-tissue infections to severe systemic infections such as sepsis and necrotizing pneumonia (Lowy, 1998; Deresinski, 2005)
Eighty methicillin-resistant S. aureus (MRSA) isolates were obtained from patients 10 days to 11 years old with local or systemic infection and all the isolates were positive for the mecA genes
From the clinical medical records, respiratory infection was the most frequently determined infection type caused by community-associated methicillin-resistant S. aureus (CA-MRSA); 82.5% (66/80) of the isolates were from the respiratory tract, and 5% (4/80) of the isolates were associated with bloodstream infection (BSI)
Summary
Staphylococcus aureus is one of the most prevalent human pathogens, causing a broad variety of diseases ranging from mild skin and soft-tissue infections to severe systemic infections such as sepsis and necrotizing pneumonia (Lowy, 1998; Deresinski, 2005). During the last 55 years, various hospital-associated MRSA (HA-MRSA) clones have disseminated worldwide, including Europe, United States, North Africa, the Middle East, and East Asia. Compared to HA-MRSA strains, most CAMRSA isolates that harbor SCCmec types IV or V, do not have multi-antibiotic resistance (except to β lactams), and many possess different exotoxin gene profiles (e.g., PVL genes; Dinges et al, 2000). Another MRSA clone from animals (LAMRSA) has emerged in humans exposed to livestock since 2005. For LA-MRSA, ST398 is the overwhelmingly dominant lineage in Europe, whereas ST9 predominates in most Asian countries (Fluit, 2012; Chuang and Huang, 2015)
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