[Surveillance on gram-positive bacteria isolated from patients with hospital acquired infections or community acquired infections]

Abstract

Objective: To determine the drug-resistance rates of gram-positive cocci isolated from patients with hospital acquired infection (HAI) or community acquired infection (CAI) in 34 study wards of 13 hospitals located at different areas in China.

Methods: According to the previous protocol, from July 1(st) 2000 to June 30(th) 2001, a total of 2401 pathogenic strains were isolated from 13 hospitals. Among them, 805 strains of gram-positive cocci were collected for in vitro susceptibility test using international standard plate dilution method. According to the criteria of guidelines of NCCLS (2001), MIC(50) and MIC(90) were detected to represent the antibacterial activity of antimicrobial agents and R%, I%, and S%, were calculated to show the resistant, intermediate and susceptible rates of the bacteria to the compounds tested.

Results: The detectable rates of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus epidermidis (MRSE) were 37.4% (89/238) and 33.8% (51/151) respectively. Among a total of 238 strains of S. aureus, 139 were isolated from patients with CAI and 37 were from HAI patients, the rate of MRSA from HAI patients (89.2%, 33/37) was significantly higher than that of MRSA from CAI patients (30.2%, 42/139) (P < 0.01). The total resistant rate of penicillin resistant Streptococcus pneumoniae (PRSP) was 26.7% (8/30), including a R% of 3.3% (1/30) and an I% of 23.3% (7/30). 331 strains of Enterococcus were isolated, including 178 strains from the study wards and 153 strains from other wards. The ratio of number of strains of E. faecalis to E. faecium was 6.8:1 (286/42). The rate of ampicillin resistant E. faecium (AREF) was 73.8% (31/42), significantly higher than the rate of ampicillin resistant E. faecalis (16.4%, 47/286). Neither strains of S. aureus nor strains of coagulase negative Staphylococcus were found resistant to vancomycin. No strains of Enterococcus were found resistant to vancomycin, the intermediate rates of E. faecalis and E. faecium to vancomycin were 3.5% (10/286) and 9.5% (4/42) respectively. All strains of Enterococcus were found 100% susceptible to teicoplanin.

Conclusion: The resistance patterns of Gram-positive cocci including MRSA, PRSP, and AREF are similar to the results of the 1998 - 1999 surveillance. No strain of vancomycin-resistant Staphylococcus aureus, including VRSA and VISA or vancomycin resistant enterococcus, VRE is found in this study.