Incidence of Vancomycin Resistant Phenotype of the Methicillin Resistant Staphylococcus aureus Isolated from a Tertiary Care Hospital in Lahore

Staphylococcus aureus (S. aureus) associated infections are one of the major threats to public health. The aim of the present study was to determine the antibiotic resistance pattern as well as the genetic characterization of methicillin and vancomycin resistant S. aureus (VRSA) isolated from a tertiary care hospital in Lahore. The S. aureus were isolated from different clinical samples, identified by biochemical testing, and subjected to antibiotic susceptibility testing by disc diffusion method or broth microdilution method. Methicillin resistance gene (mecA) and vancomycin resistance gene (vanA) were amplified by polymerase chain reaction. The S. aureus isolates showed high incidence of resistance against methicillin (76%) and moderate incidence of resistance to vancomycin (44%). Isolates were also resistant to several other drugs such as cefoxitin (76%), ertapenem (83%), ampicillin (81%), tobramycin (78%), moxifloxacin (76%), and tetracycline (74%). An encouraging finding was that 98% of isolates were susceptible to tigecycline, indicating its possible role in the treatment of MRSA, VRSA, as well as multi-drug resistant S. aureus. The mecA gene was detected from 33.3% (10/30) while vanA gene was detected from 46.6% (14/30) of the tested isolates. In conclusion, frequent presence of methicillin and vancomycin resistance in S. aureus appraises the cautious use of these antibiotics in clinical practices. Furthermore, it is suggested that there should be continuous monitoring of tigecycline treatments in clinical setups in order to delay the development of resistance against it.