Abstract
BackgroundStaphylococcus epidermidis has emerged as an often encountered pathogen responsible for hospital-acquired infections. The aim of present study is to investigate the microbiological characteristic of S. epidermidis isolates isolated from sterile specimens and skin in a Chinese tertiary hospital.MethodsA total of 223 non-duplicate S. epidermidis were collected from various sterile specimens of inpatients among 10 years in Wenzhou, China. 106 S. epidermidis obtained from the skin (urethral orifices) of healthy volunteers. All isolates were tested for antimicrobial susceptibility. PCR was used to detect the virulence- and resistance-associated genes and 7 housekeeping genes to determine the sequence types (STs) of selected isolates.ResultsThe resistance rates to antimicrobials tested except linezolid and vancomycin and the prevalence of methicillin-resistant S. epidermidis (MRSE) of S. epidermidis clinical isolates were significantly higher than those among colonized isolates (P < 0.05). The positive rates of virulence-associated genes including aap, sesI, ACME-arcA, IS256, bhp, altE, aae and gehD for S. epidermidis clinical isolates were significantly higher than those for colonized isolate (P < 0.05). A total of 60 STs including 28 from clinical isolates and 32 from colonized isolates were identified by MLST. A novel, rarely encountered clone, ST466, was found to be the second prevalent clone among clinical isolates. The great majority of the S. epidermidis isolates tested (73.86%) belonged to clone complex 2 (CC2). Compared with ST2, ST130, ST20 and ST59 clones, ST466 clone had the highest resistance rate to tetracycline (50.00%), the second highest prevalence of ACME-arcA (65.00%), bhp (30.00%) and qacA/B (65.00%), very low prevalence of carriage of icaA (0.00%) and biofilm formation (0.00%), the lack of sesI and high prevalence of aap, altE and aae (> 90%), which was similar to the characteristics of ST59 clone with one locus difference from ST466. ST466 clone competence with Staphylococcus aureus was relatively stronger, relative to ST2, ST20, ST130 and ST59 clones.ConclusionTaken together, a high-level of genetic diversity was found between clinical and colonized S. epidermidis isolates. A novel ST466 clone with distinct and similar characteristics relative to other prevalent clones, emerging as a prevalent clone in China, should be of major concern.
Highlights
Staphylococcus epidermidis has emerged as an often encountered pathogen responsible for hospitalacquired infections
In addition to polysaccharide intercellular adhesin (PIA), many components have been found to be associated with biofilm formation, such as accumulationassociated protein (Aap), biofilm-associated protein (Bap) and IS256
Methicillin resistance in Staphylococci, which is associated with the presence of the mecA gene carried by a genetic mobile element called the staphylococcal chromosomal cassette mec (SCCmec), is the other very important factor in the establishment of S. epidermidis as a nosocomial pathogen [1, 4]
Summary
Staphylococcus epidermidis has emerged as an often encountered pathogen responsible for hospitalacquired infections. Staphylococcus epidermidis is a common commensal bacterium, which belongs to coagulase-negative Staphylococci (CoNS). It is recognized as a relevant opportunistic pathogen and isolated prevalently from human epithelia and colonizes predominantly the axillae, head and nares [1]. In recent decades, as the S. epidermidis is one of the often encountered biofilm-producing bacteria, it has emerged as a common cause of hospitalacquired infections associated with the use of indwelling or implanted foreign bodies [1]. Methicillin resistance in Staphylococci, which is associated with the presence of the mecA gene carried by a genetic mobile element called the staphylococcal chromosomal cassette mec (SCCmec), is the other very important factor in the establishment of S. epidermidis as a nosocomial pathogen [1, 4]. The aim is to investigate the antimicrobial resistance profiles, virulence determinants profiles and molecular characteristics of S. epidermidis isolates
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