Antibiotic resistance pattern of methicillin-resistance and coagulase-negative Staphylococcus isolates among hospitalized patients at a tertiary hospital in Gansu, North-western China

This study aimed at determining the prevalence and antibiotic resistance pattern of methicillin resistant Staphylococcus aureus (MRSA) and methicillin resistant coagulase negative staphylocci (MRCoNS) isolated from various clinical specimens obtained from hospitalized patients in a Tertiary Hospital in Gansu, North-western, China from 2008-2011. Bacterial isolates were identified morphologically and biochemically using the standard laboratory operation procedures. A total of 1002 isolates were obtained from 986 clinical specimens. The frequency of MRSA 690 (68.9%) isolates were identified as Staphylococcus aureus and 312 (31.1%) were coagulase negative staphylococci. The frequency of MRSA by the Cefoxitin disk diffusion test was 56.7% (391/690) and 73.3% (229/312) were MRCoNS. The rate of multidrug resistance observed was 61.8% (242 /391) for MRSA and 71.2% (163 /229) for MRCoNS. The antibiotc susceptibility test was determined by Kirby-Bauer disc diffusion method with zones of inhibition evaluated according to the latest Clinical and Laboratory Standard Institute (CLSI) guidelines recommendations. Mueller-Hinton agar was utilized for antimicrobial susceptibility testing. All MRSA and MRCoNS were 100% resistant to penicillin and oxacilin, MRSA isolates showed high resistance to erythromycin (98.7%), clidamycin (93.1%), and ciprofloxacin (89.2%) as compared to other drugs while MRCoNS isolates showed high resistance to erythromycin (96.7%), trimetoprim/sulphametoxazole (86.7%), and clidamycin (72.4%). However, all MRSA and MRCoNS isolates were sensitive to vancomycin, Linezolid and Teicoplanin. These finding indicate that MRSA and MRCoNS were common infections among hospitalized patients at Gansu Provincial People’s Hospital (GPPH). The isolates showed high level of resistance to routinely used antimicrobial agents. This calls for strict antibiotic policy, continuous monitoring of antibiotic susceptibility pattern of all S. aureus and coagulase negative staphylococci. Further molecular study on MRSA epidemiology in future is desirable, to know the mechanism of resistance, find new antimicrobial agents and study the treatment strategies.   Key words:  Antibiotic susceptibility pattern, methicillin resistant Staphylococcus aureus (MRSA), methicillin resistant coagulase negative staphylocci (MRCoNS), multidrug resistance.