title: Growing Resistance to Vancomycin among Methicillin Resistant Staphylococcus Aureus Isolates from Different Clinical Samples.
abstract: BACKGROUND
  Methicillin resistant Staphylococcus aureus (MRSA), majorly associated with nosocomial and community infections worldwide, are emerging as resistant strains to many antibiotics narrowing down the efficacy of antimicrobial therapy. In order to investigate the changing resistant pattern of MRSA to empirical drugs, the study was carried out at KIST Medical College and Hospital, Nepal. It also aims to determine the minimum inhibitory concentration (MIC) of vancomycin among MRSA.
  
  
  METHODS
  Altogether 3500 clinical samples including 1303 blood, 1489 urine and 708 body fluids were collected and processed. Isolated S. aureus were further screened for methicillin resistance by Kirby-Bauer disk diffusion technique using cefoxitin (30µg) disk. All MRSA were subjected to in vitro determination of MIC of vancomycin by agar dilution method as recommended by CLSI guidelines.
  
  
  RESULTS
  Total 287 S. aureus were isolated from the different clinical samples. Altogether 248 (86.41%) were found to be multidrug resistance (MDR) while 42 (14.63%) of the isolates were methicillin resistance with the highest prevalence in the age group of 16-30. All 42 (100%) MRSA isolates were resistant to ampicillin and penicillin followed by 41 (97.62%), 32 (76.19%), 31(73.81%), 29 (69.05%), 9 (21.43%) and seven (16.67%) to cefotaxime, gentamycin, cotrimoxazole, erythromycin, tetracycline and ciprofloxacin respectively. Although all MRSA strains were sensitive to vancomycin on disc diffusion, four isolates were intermediates in vitro determination of MIC of vancomycin. The break point for vancomycin was found to be 15mm.
  
  
  CONCLUSIONS
  The increment in vancomycin MIC among MRSA is alarming. Strict control measures to prevent MRSA spread and a routine surveillance for VRSA must be incorporated in hospitals.
authors.affiliation: Department of Microbiology, Kantipur College of Medical Science, Kathmandu, Nepal.
authors.forename: P C
authors.initials: PC
authors.lastname: Pahadi
authors.affiliation: Department of Microbiology, Kantipur College of Medical Science, Kathmandu, Nepal.
authors.forename: U T
authors.initials: UT
authors.lastname: Shrestha
authors.affiliation: Department of Microbiology, Kantipur College of Medical Science, Kathmandu, Nepal.
authors.forename: N
authors.initials: N
authors.lastname: Adhikari
authors.affiliation: Department of Microbiology, Tri-Chandra Multiple Campus, Kathmandu, Nepal.
authors.forename: P K
authors.initials: PK
authors.lastname: Shah
authors.affiliation: Department of Microbiology, Nepal Medical College, Kathmandu, Nepal.
authors.forename: R
authors.initials: R
authors.lastname: Amatya
mesh_terms: D000293:Adolescent; D000328:Adult; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D003428:Cross Infection / Q000453:epidemiology / Q000382:microbiology*; D003430:Cross-Sectional Studies; D024881:Drug Resistance, Bacterial; D005260:Female; D006801:Humans; D008297:Male; D008712:Methicillin / Q000494:pharmacology; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects* / Q000302:isolation & purification; D008826:Microbial Sensitivity Tests / Q000379:methods; D009390:Nepal / Q000453:epidemiology; D015995:Prevalence; D013203:Staphylococcal Infections / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000302:isolation & purification; D014640:Vancomycin / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D014640:Vancomycin; D008712:Methicillin
keywords: mdr; mrsa; mic; visa; vrsa.