Diversity and antimicrobial susceptibility of cultivable commensal bacteria from 18 to 22 year-old healthy people's nose and skin / 中华检验医学杂志

ABSTRACT

Objective To investigate the diversity and antimicrobial susceptibility of cultivable commesal bacteria from 18 to 22 year-old healthy people′s nose and skin. Methods From June to August 2017,18 to 22 year-old healthy people (n=210) were swabbed on skin and nose and cultured with blood plates at Renji Hospital, School of Medicine, Shanghai Jiao Tong University; Species determination was performed using matrix assisted laser desorption Lonization-time of flight-mass spectrometry(MALDI-TOF-MS);Susceptibility testing was performed on the major species by the disc diffusion method; Genomic characteristics of methicillin resistant Staphylococcus epidermidis(MRSE) were determined by pulsed field gel electrophoresis (PFGE) method;SCCmec typing was tested by polymerase chain reaction(PCR);Statistical analysis was performed using SPSS software and association statistics were tested using Chi-Square tests. Results In total, 25 genera were identified of cultivable bacteria from 210 healthy people′s nose (1497 isolates) and skin (941 isolates).Staphylococcus isolates from nose and skin accounted for 82.03% and 80.23% respectively.Eleven species were identified of all Staphylococcus isolates and coagulase-negative Staphylococci(CoNS)from nose and skin accounted for 90.72% and 99.21% respectively.Furthermore, a variety of other species and differences between men and women were observed. Susceptibility testing was done on 631 Staphylococcus isolates, which were sensitive to most antibiotics but show high prevalence of resistance towards penicillin (76.55%), erythromycin (41.20%), clindamycin (10.77%) and trimethoprim/sulfamethoxazole(10.14%). Methicillin Resistant Staphylococcus (MRS) (45 isolates) showed higher prevalence of resistance towards penicillin (χ2=12.17,P<0.001), erythromycin (χ2=10.80,P=0.001), levofloxacin (χ2=20.24, P<0.001) and trimethoprim/sulfamethoxazole (χ2=58.57,P<0.001) compared to methicillin sensitive Staphylococcus (MSS)(586 isolates). Moreover, multidrug resistance (MDR) was observed in 42.16% of 631 isolates and MRS showed a significantly higher proportion than MSS(100.00% vs 37.71%,χ2=66.49,P<0.001).PFGE generated 23 groups out of 33 MRSE isolates. SCCmec genotyping of MRSE showed the most prevalent type was SCCmecⅣ (66.67%). Conclusions Obvious genus and species diversity and genetic diversity were observed on cultivable bacteria from 18 to 22 year-old healthy people′s nose and skin,and CoNS was in the majority. Staphylococcus isolates from healthy people′s nose and skin were sensitive to most antibiotics,but show high prevalence of resistance towards penicillin, erythromycin, clindamycin and trimethoprim/sulfamethoxazole. In addition, MDR was serious especially in MRS. Commensal bacteria may act as reservoir for resistance genes facilitating bacteria infection.