The need to assay the real MIC when making the decision to eradicate Staphylococcus aureus with vancomycin

PURPOSE

The aim of the study was a comparison of the MIC (minimal inhibitory concentration) evaluated in the automatic system Vitek 2 and the real MIC of vancomycin by the Etest method for S. aureus strains isolated from clinical materials.

MATERIAL AND METHODS

Over a twelve-month study period we compared the results obtained with two commercial methods - the automatic system VITEK 2 and the real MIC by Etest - for 359 strains of S. aureus isolated from clinical materials.

RESULTS

Most of the strains of S. aureus were cultured from wounds (84), the ear (60) and nose (42). MSSA (methicillin-sensitive Staphylococcus aureus) was isolated in 342 cases and MRSA (methicillin-resistant Staphylococcus aureus) in 17 cases. The test with the Vitek automatic method showed that vancomycin had MIC values of ≤1.0 μg/ml in more than 96% and 2.0 μg/ml in over 3% of cases. Using the Etest technique MIC ≤ 1.0 μg/ml was obtained in only 16.4% of cases and values of >1.0 μg/ml in 83.6% of cases.

DISCUSSION

In view of such big differences between the MIC values obtained with the two methods the authors suggest that the Etest method of assaying the real MIC is more useful than the automatic method.

[Problem of increasing resistance of pseudomonas aeruginosa in patients at ENT Clinic of Poznan University of Medical Sciences in the years 2005-2007]

INTRODUCTION Species and resistance rate of current pathogens is important for determining the appropriate treatment. P. aeruginosa is an essential issue in the group of patients with ear problems. The number of infections and relapses caused by this pathogen has been increasing with high percentage of antibiotic resistant strains responsible for treatment failure. Aim. The purpose of this work was to present the problem of increasing resistance of Pseudomonas aeruginosa in patients of ENT Department of Poznan University of Medical Sciences between 2005-2007.

MATERIAL AND METHODS

During that time at our Clinic 644 biological samples were taken to carry out a bacteriological examination. All materials were analyzed to assess the prevalence of Pseudomonas aeruginosa as an etiologic factor of infections. The groups of patients treated operatively and in outpatient clinic were taken into consideration.

RESULTS

Pseudomonas aeruginosa was found in 89 samples; most cases in 2007 (53 strains), which constitutes 18% of all samples analyzed. Predominatingly (in 54 samples) that pathological culture was found in materials coming from ears. There was noticed a 20%--rowth in the number of P. aeruginoso infections in 2007 in relation to 2005. Most of the strains (93%) were susceptible to imipenem, piperacilin and tazobactam, 83% of the strains--to ciprofloxacin, 86%--to ceftazidim.

CONCLUSIONS

Overuse of cotrimoxazol, doxycyclin and cefuroxim in empiric treatment, Pseudomonas aeruginosa strains are naturally resistant to which, is responsible for the . aeruginosa resistance to most commonly used antibiotics.