Prevalence of Nasal Carriage of Staphylococcus aureus and its Antibiotic Susceptibility among Healthcare Workers (HCWs) in Ukraine

BACKGROUND. Nasal carriage of Staphylococcus aureus among hospital personnel is a common cause of hospital acquired infections. Emergence of drug resistant strains especially methicillin resistant S. aureus (MRSA) is a serious problem in hospital environment. Therefore, the aim of this study was to determine the prevalence of nasal carriage of Staphylococcus aureus its antibiotic susceptibility among healthcare workers (HCWs) in Ukraine. METHODS. This cross-sectional study was conducted from January to December 2017. The study included medical workers from 19 hospitals in different Ukrainian regions. Nasal swabs were taken from 755 randomly selected HCWs. The mean age of participants was 32.41 ± 8.29 years (range 19—74 years) with a male-to- female ratio of 0.47. The isolates were identified as S. aureus based on morphology, Gram stain, catalase test, coagulase test, and mannitol salt agar fermentation. The sensitivity patterns of S. aureus strains were determined by disk diffusion method (Kirby — Bauer). The panel of antibiotics used in sensitivity tests included: penicillin, oxacillin, cefoxitin, amoxicillin/clavulanic acid, gentamicin, tobramicin, ciprofloxacin, levofloxacin, moxifloxacin, mupirocin, nitrofurantoin, vancomycin, teicoplanin, fosfomycin, clindamycin, erythromycin, rifampicin, linezolid, tetracycline, tigecycline, trimethoprim/sulphamethoxazole, and fusidic acid. Interpretative criteria were those suggested by the CLSI (Clinical and Laboratory Standards Institute). MRSA were confirmed by detection of the mecA gene by polymerase chain reaction. RESULTS. Nasal screening identified 31.1 % (235/755) S. aureus carriers. Of the 235 nasal carriers of S. aureus, 4 % (196/755) carried MSSA (methicillin-sensitive S. aureus) and 39/755 (16.6 %) carried MRSA. The frequency of MRSA and MSSA carriage also varied according to the department/ward. The highest prevalence of nasal carriage of MRSA was in the surgical wards. The staff of the general, pediatric, cardiovascular, neuro and orthopedic surgery wards together with the emergency department accounted for 56.4 % of all MRSA carriers. There was no significant difference between the sexes (p = 0.247), age (p = 0.817), and years of healthcare service (p = 0.15) with regard to the nasal carriage of MRSA and MSSA. In univariate analysis we divided the hospital departments into: emergency, internal medicine, pediatrics, ICUs, surgery, and non-medical units and found no significant difference between MSSA and MRSA carriers (p = 0.224). In the multivariate analysis, the occupation «nurse» was independently associated with MRSA carriage (p = 0.012, odds ratio 3.6, 95 % confidence interval 1.3—9.7). All the S. aureus isolates recovered from nasal carriers, were susceptible to linezolid, tigecycline, vancomycin, teicoplanin, and mupirocin. Susceptibility to the other antimicrobials was also on a high level: 98.3 % of strains were found susceptible to trimethoprim/sulphamethoxazole, 96.2 % — to nitrofurantoin, 95.3 % — to fusidic acid, 92.3 % — to fosfomicin, 88.5 % — to amoxicillin/clavulanic acid, 87.2 % — to tobramycin, 86.8 % — to clindamycin. Resistance to oxacyllin came up to 16.6 %. CONCLUSIONS. Nasal carriage of S. aureus appears to play a key role in the epidemiology and pathogenesis of infection. HCWs who are at interface between the hospital and the community may serve as agents of cross contamination of hospital acquired and community acquired MRSA. It is of importance to follow the evolution of resistance to antibiotics in this species, especially to β-lactams.