Isolation, identification and antimicrobial susceptibility of brucella blood culture isolates.

UNLABELLED: Isolation of slowly growing and fastidious Brucella spp strains from clinical specimens is difficult, because of varying factors, including species specificities, stadium of disease, and previous antibiotic treatment of the patients. The use of automated blood culture systems has overcome some cultivation problems. The automated identification system such as VITEK 2 compact allows more precise identification, as well. AIM: To present our own experience in the isolation of Brucella species from blood cultures, by the Bact/Alert automated system, identification by the VITEK 2 compact system and antimicrobial susceptibility of isolated strains. MATERIAL AND METHODS: Patients from various regions of Macedonia hospitalized in the University Infectious Diseases and Febrile Condition Clinic in Skopje. FAN blood culture bottles (aerobic and anaerobic) of the Bact/Alert system were used, inoculated with 5-10 ml of blood, incubated under continuous agitation and monitored for up to 5 days or until they became positive (in our cases for 2-3 days). Confirmations of all isolates were made by the VITEK 2 automated system on GN cards. RESULTS: During a period of three years, 113 blood cultures from patients with diagnosis of brucellosis hospitalized at the above-mentioned clinic were examined. A total of 16 blood cultures from different patients were positive (14.2%), showing Gram negative bacilli, oxidase positive small colonies on Columbia agar media. The isolates were identified as four biochemically different types of B. mellitensis, mainly within 8 hours. Susceptibility testing by the disk diffusion method on Muller Hinton agar showed sensitivity of all strains to cephalosporin, tetracycline, aminoglycoside and quinolone antibiotic groups. CONCLUSION: With the BacT/Alert system Brucella spp. were isolated in 14.2% of suspected cases of brucellosis. Isolation was done within 2-3 days. Only B. melitensis from the Brucella genus could be identified by the VITEK 2 system and some biochemical differences could be detected. The VITEK 2 system is not able to determine the susceptibility of B. melitensis. The Disk-diffusion method used in this study showed sensitivity to all tested antibiotics, although not recommended by CLSI for the Brucella genus.

Quantitative differences in antibiotic resistance between methicillin-resistant and methicillin-susceptible Staphylococcus aureus strains isolated in Hungary, Austria and Macedonia.

The aim of this study was to compare the quantitative susceptibility of methicillin-resistant and -susceptible Staphylococcus aureus (MRSA and MSSA) strains from three European countries to nine antistaphylococcal agents. The antibiotic susceptibility of 274 MRSA and 284 MSSA strains from Hungary, Austria and macedonia was tested by the broth microdilution method. The clonal relationship of strains was determined by pulsed-field gel electrophoresis. Intermediate susceptibility to vancomycin appeared in Macedonian MRSA strains. Macedonian MRSA strains had high-level amikacin and gentamicin resistance. MSSA strains generally were susceptible to all drugs at minimum inhibitory concentrations (MIC(50)) except for gentamicin resistance in Macedonian strains. In Hungary and Austria a common antibiotic resistance phenotype of MRSA predominated, while in macedonia three other phenotypes were also prevalent. Geographical differences in the resistance of S. aureus are still high. Since resistance levels of MRSA and MSSA strains differ extensively, they should be considered separately for antibiotic resistance analysis.

Methicillin-resistant Staphylococcus aureus: comparison of susceptibility test methods with mecA gene analysis for determining oxacillin (methicillin) resistance in our clinical isolates.

The aim of the study was to determine which of the following susceptibility test methods, using recommended or modified NCCLS, best detects oxacillin resistance: disk diffusion, agar screen, and broth dilution. PCR for mecA was used as "gold standard". We studied 120 Staphylococcus aureus isolates received from different patients hospitalized at the Clinical center in Skopje from May 2001 to November 2003. There were no two isolates from the same patient. Methicillin resistance in Staphylococcus aureus strains was performed according to the recommendations of the National Committee for Clinical Laboratory Standards (NCCLS). PCR appears to be promising. Since variations among the methods exist and no acceptable guidelines are formulated, a combination of conventional methods, including either 3 microg of oxacillin/ml. in Mueller Hinton broth or one of the screen agar plates (6 microg/ml), alone or with PCR should be the method of choice for the detection of MRSA. (Tab. 4, Ref. 12.)