Abstract
Staphylococcus aureus colonization and infection occur more commonly among persons living or working in crowded conditions, but characterization of S. aureus colonization within medical communities in China is lacking. A total of 144 (15.4%, 144/935) S. aureus isolates, including 28 (3.0%, 28/935) MRSA isolates, were recovered from the nares of 935 healthy human volunteers residing on a Chinese medical college campus. All S. aureus isolates were susceptible to vancomycin, quinupristin/dalfopristin and linezolid but the majority were resistant to penicillin (96.5%), ampicillin/sulbactam (83.3%) and trimethoprim/sulfamethoxazole (93.1%). 82%, (23/28) of the MRSA isolates and 66% (77/116) of the MSSA isolates were resistant to multiple antibiotics, and 3 MRSA isolates were resistant to mupirocin—an agent commonly used for nasal decolonization. 16 different sequence types (STs), as well as SCCmec genes II, III, IVd, and V, were represented among MRSA isolates. We also identified, for the first time, two novel STs (ST1778 and ST1779) and 5 novel spa types for MRSA. MRSA isolates were distributed in different sporadic clones, and ST59-MRSA-VId- t437 was found within 3 MRSA isolates. Moreover, one isolate with multidrug resistance belonging to ST398-MRSA-V- t571 associated with animal infections was identified, and 3 isolates distributed in three different clones harbored PVL genes. Collectively, these data indicate a high prevalence of nasal MRSA carriage and molecular heterogeneity of S. aureus isolates among persons residing on a Chinese medical college campus. Identification of epidemic MRSA clones associated with community infection supports the need for more effective infection control measures to reduce nasal carriage and prevent dissemination of MRSA to hospitalized patients and health care workers in this community.
Highlights
Staphylococcus aureus is one of the most prevalent and clinically significant pathogens worldwide, causing a variety of illnesses ranging from benign, superficial skin eruptions to life-threatening infections with bacteraemia, endocarditis, pneumonia and toxic shock syndrome [1]
The nasal carriage rate of S. aureus was 15.4% (144/935). 19.4% (28/144) of S. aureus isolates were identified as methicillin-resistant S. aureus (MRSA)
Three MRSA isolates with no zone of inhibition to mupirocin (2.1%, 3/144) were resistant to mupirocin
Summary
Staphylococcus aureus is one of the most prevalent and clinically significant pathogens worldwide, causing a variety of illnesses ranging from benign, superficial skin eruptions to life-threatening infections with bacteraemia, endocarditis, pneumonia and toxic shock syndrome [1]. Determination of the prevalence of S. aureus nasal carriage, as well as antimicrobial resistance profiles and molecular typing for nasal S. aureus isolates, in healthy populations is beneficial for identifying risk factors associated with S. aureus infection [8,9,10]. Two major epidemic MRSA clones, ST239-MRSA-SCCmec type III and ST5-MRSA-SCCmec type II, are distributed across China in unique geographic patterns [14] These data suggest that dissemination of virulent MRSA clones among healthy persons in China may contribute to the presence of clinically significant MRSA infections in some locations. There are limited published studies characterizing MRSA isolates recovered from nares of healthy individuals in China who work and reside in the health care setting. We sought to determine the prevalence, antimicrobial resistance profiles, and molecular characteristics of nasal S. aureus isolates from students on a large medical college campus in China
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