Original article http://dx.doi.org/10.1016/j.apjtb.2016.12.002 Emergence of staphylococcal cassette chromosome mec type I with high-level mupirocin resistance among methicillin-resistant Staphylococcus aureus
Authors: Prabhu Raj Joshi, Mahesh Acharya, Rajan Aryal, Kamal Thapa, Trishna Kakshapati, Rathanin Seng, Anjana Singh, Sutthirat Sitthisak
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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 mecA 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/mL), 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/mL).
Fourteen isolates were found harboring the mupA gene and one isolate was found carrying the
novel mupB 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.