Abstract
BackgroundStaphylococcus aureus (S. aureus) with accessory gene regulator (agr) dysfunction occurs in health care settings. This study evaluated the prevalence and the molecular and drug resistance characteristics of S. aureus with dysfunctional agr in a pediatric population in Beijing, China.ResultsA total of 269 nonduplicate S. aureus clinical isolates were isolated from Beijing Children’s Hospital, including 211 methicillin-resistant S. aureus (MRSA) from September 2010–2017 and 58 methicillin-sensitive S. aureus (MSSA) from February 2016–2017. Only 8 MRSA and 2 MSSA isolates were identified as agr dysfunction, and the overall prevalence rate was 3.7%. For MRSA isolates, ST59-SCCmec IV and ST239-SCCmec III were the most common clones, and the prevalence rate of agr dysfunction in ST239-SCCmec III isolates (17.39%) was significantly higher than in ST59-SCCmec IV (1.69%) and other genotype strains (P = 0.006). Among the agr dysfunctional isolates, only one MRSA ST59 isolate and one MSSA ST22 isolate harbored pvl. No significant difference was detected between agr dysfunction and agr functional isolates regarding the biofilm formation ability (P = 0.4972); however, 9/10 agr dysfunctional isolates could effectuate strong biofilm formation and multidrug resistance. Among MRSA, the non-susceptibility rates to ciprofloxacin, gentamicin, and trimethoprim-sulfamethoxazole were significantly higher in agr dysfunctional isolates than in isolates with functional agr (P < 0.05). Two isolates belonging to ST239 had no mutations in agr locus, but a synonymous mutation was found in agrA in another ST239 isolate. The inactivating mutations were detected in other seven agr dysfunctional isolates. The variants were characterized by non-synonymous changes (n = 5) and frameshift mutations (insertions, n = 2), which mainly occurred in agrC and agrA.ConclusionsThe results showed that agr dysfunctional S. aureus was not common in Chinese children, and ST59-SCCmec IV was associated with lower prevalence of agr dysfunction as compared to ST239-SCCmec III isolates. The agr dysfunctional isolates were healthcare-associated, multidrug resistant and form strong biofilm, which suggested that agr dysfunction might offer potential advantages for S. aureus to survive in a medical environment.
Highlights
Staphylococcus aureus (S. aureus) with accessory gene regulator dysfunction occurs in health care settings
In the case of strains isolated from the same patient, if the genotyping studies revealed identical genotype, only one of them was included in the study, which ensured that all strains involved in the current study were non-repetitive
The variants were characterized by nonsynonymous changes (n = 5) and frameshift mutations, which mainly occurred in agrC and agrA (Table 6)
Summary
Staphylococcus aureus (S. aureus) with accessory gene regulator (agr) dysfunction occurs in health care settings. Staphylococcus aureus (S. aureus) continues to be a leading cause of both community-and healthcare-associated infections, including skin and soft tissue infections, bacteremia, pneumonia, osteomyelitis, and endocarditis. Virulence factors play a major role in the pathogenesis of S. aureus, such as Panton-Valentine leukocidin (PVL). The PVL-producing strains have been associated with the onset of skin and soft tissue infections (SSTIs) and can cause severe invasive infections (necrotizing pneumonia, etc) [1]. S. aureus can form biofilms in biological samples and surfaces of medical devices and in tissues [2]. The successful eradication of S. aureus infections is difficult, rendering biofilm as a vital factor in chronic infections
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