[Mupirocin resistance in methicillin-resistant Staphylococcus aureus strains isolated from wound infections]. / Yaralardan izole edilen metisiline dirençli Staphylococcus aureus suslarinda mupirosin direncinin arastirilmasi.

Methicillin-resistant Staphylococcus aureus (MRSA) has emerged as an important pathogen in community-acquired and nosocomial infections. The unique bactericidal action of mupirocin makes it one of the few antibiotics still effective against MRSA. The purpose of this study was to investigate the mupirocin resistance in MRSA strains isolated from wound infections of in- and out-patients of two distinct hospitals located in Ankara and Istanbul. A total of 143 MRSA strains were included in the study. Mupirocin resistance was investigated by Kirby-Bauer disk diffusion method and the results were confirmed by determination of the MIC values by E-test strips. Among 143 MRSA isolates, mupirocin resistance was detected by none of the methods, and overall mupirocin sensitivity was detected as 100 percent. The majority of mupirocin resistant MRSA is isolated from wound infections. The aetiology mostly depends on the increased topical use of the agent. The method used in the detection of mupirocin resistance and interpretation of the results are important parameters in the determination of mupirocin resistance in MRSA strains. Since there was no resistant strain among 143 clinical isolates obtained from two different hospitals, it was concluded that, mupirocin resistance is not an important problem in these regions currently, and mupirocin may be safely used in treating wound infections.

PCR evaluation of false-positive signals from two automated blood-culture systems.

Rapid detection of micro-organisms from blood is one of the most critical functions of a diagnostic microbiology laboratory. Automated blood-culture systems reduce the time needed to detect positive cultures, and reduce specimen handling. The false-positive rate of such systems is 1-10%. In this study, the presence of pathogens in 'false-positive' bottles obtained from BACTEC 9050 (Becton Dickinson) and BacT/Alert (Biomérieux) systems was investigated by eubacterial and fungal PCR. A total of 169 subculture-negative aerobic blood-culture bottles (104 BacT/Alert and 65 BACTEC) were evaluated. Both fungal and eubacterial PCRs were negative for all BACTEC bottles. Fungal PCR was also negative for the BacT/Alert system, but 10 bottles (9.6%) gave positive results by eubacterial PCR. Sequence analysis of the positive PCR amplicons indicated the presence of the following bacteria (number of isolates in parentheses): Pasteurella multocida (1), Staphylococcus epidermidis (2), Staphylococcus hominis (1), Micrococcus sp. (1), Streptococcus pneumoniae (1), Corynebacterium spp. (2), Brachibacterium sp. (1) and Arthrobacter/Rothia sp. (1). Antibiotic usage by the patients may be responsible for the inability of the laboratory to grow these bacteria on subcultures. For patients with more than one false-positive bottle, molecular methods can be used to evaluate the microbial DNA in these bottles. False positives from the BACTEC system may be due to elevated patient leukocyte counts or the high sensitivity of the system to background increases in CO(2) concentration.