Emergence of staphylococcal cassette chromosome mec type Ⅰ with high-level mupirocin resistance among methicillin-resistant Staphylococcus aureus

Objective: To investigate the molecular epidemiology and antimicrobial resistance patterns of methicillin-resistant Staphylococcus aureus(MRSA) among healthcare workers and patients.Methods: MRSA isolates were recovered from nasal swabs collected at a tertiary care hospital of Nepal and confirmed on the basis of Gram staining, conventional biochemical tests, and PCR amplification of mec A gene. PCRs were also used for detection of the different resistance genes and staphylococcal cassette chromosome(SCC) mec types.Antibiotic susceptibility patterns of isolates were assessed by disc diffusion method and minimum inhibitory concentrations were determined by E-test.Results: A total of 29 MRSA were isolated from 536 nasal swabs(5.4%) of health care workers and patients at a tertiary care hospital in Nepal. All isolates were susceptible to amikacin, gentamicin, vancomycin(minimal inhibitory concentrations < 2 mg/m L), tigecycline, tetracycline, nitrofurantoin, rifampicin, quinupristin-dalfopristin, and linezolid. Among the 29 MRSA isolates, resistance to erythromycin(72%), ciprofloxacin(75%), co-trimoxazole(62%), clindamycin(10%), and chloramphenicol(10%) was found, and fifteen isolates(51%)exhibited high-level mupirocin resistance(minimal inhibitory concentrations > 1 024 mg/m L).Fourteen isolates were found harboring the mup A gene and one isolate was found carrying the novel mup B gene. High prevalence(68%) of SCCmec I type was found, followed by SCCmec V(13%) and SCCmec III(3%) among all the MRSA isolates.Conclusions: We found the emergence of SCCmec type I with high-level mupirocin resistance among MRSA in Nepal. Data also suggest that MRSA SCCmec type V strain has spread from the community to the hospital.

Molecular Diversity of <i>Staphylococcus aureus</i>from the Nares of Hospital Personnel, HIV-Positive and Diabetes Mellitus Patients in Yaounde Cameroon

Nasal carriage of Staphylococcus aureus has been identified as a risk factor for the development of staphylococcal infections caused by endogenous colonizing strains. Information on the genotypic diversity of Staphylococcus aureus is relevant for managing epidemiological and clinical challenges resulting from the evolutionary differences of this bacterium. The objective of this study was to determine and compare the molecular diversity of Staphylococcus aureus isolates from three high-risk populations in Yaounde, Cameroon. Molecular analysis confirmed that 95% of 100 tested isolates were S. aureus. The mecA and Panton Valentine-Leukocidin (PVL) genes (lukS/F-PV) were detected in 37% (35/95) and 43% (41/95) of isolates respectively and 18% (17/95) of the isolates harboured both the mecA and lukS/F-PV genes. A mixed distribution of both methicillin sensitive S. aureus (MSSA)/PVL and methicillin resistant S. aureus (MRSA)/PVL strains were detected within the study population. Community associated MRSA accounted for 94% (33/35) of the isolates, further classified into allotypes SCCmec type IV 54% (19/35) and SCCmec type V 40% (14/35), while two isolates were hospital associated SCCmec type II strains. A majority of the isolates harboured a single aggressive gene regulator allele agr type I. Pulsed Field Gel Electrophoresis (PFGE) generated 18 pulsotypes that grouped isolates irrespective of the study population. Multilocus Sequence Typing (MLST) of 12 selected isolates was assigned to six pandemic clonal complexes (CC): CC5 (ST5), CC8 [ST8, (n = 3)], CC15 (ST 15), CC25 (ST 25), CC72 [ST72 (n = 2)] and CC121 [ST 121 (n = 2)] and three atypical sequence types ST 508, ST 699 (CC45) and ST 1289 (CC 88). The study population represents an important reservoir for MRSA, MRSA-PVL and MSSA-PVL which could serve as focal point for further dissemination bringing about significant clinical and epidemiological implications. The predominance of SCCmec IV and agr types in this setting warrants further investigation. Isolates were genetically diverse with MLST indicating that pandemic ST8 was predominant. Detection of atypical STs has provided an insight into the necessity for constant monitoring.