In-Vitro Efficacy of Synergistic Antibiotic Combinations in Multidrug Resistant Pseudomonas Aeruginosa Strains

PURPOSE: Combination antibiotic treatment is preferred in nosocomial infections caused by Pseudomonas aeruginosa (P. aeruginosa). In vitro synergism tests were used to choose the combinations which might be used in clinic. The aim of this study was to investigate the synergistic efficacy of synergistic antibiotic combinations in multidrug resistant P. aeruginosa strains. MATERIALS AND METHODS: Synergistic efficacies of ceftazidime-tobramycin, piperacillin/tazobactam-tobramycin, imipenem-tobramycin, imipenem-isepamycin, imipenem-ciprofloxacin and ciprofloxacin-tobramycin combinations were investigated by checkerboard technique in 12 multiple-resistant and 13 susceptible P. aeruginosa strains. RESULTS: The ratios of synergy were observed in ceftazidime-tobramycin and piperacillin/tazobactam-tobramycin combinations as 67%, and 50%, respectively, in resistant strains, whereas synergy was not detected in other combinations. The ratios of synergy were observed in ceftazidime-tobramycin, piperacillin/tazobactam-tobramycin, imipenem-tobramycin, imipenem-ciprofloxacin and imipenem-isepamycin combinations as 31%, 46%, 15%, 8%, 8%, and respectively, in susceptible strains, whereas synergy was not detected in ciprofloxacin-tobramycin combination. Antagonism was not observed in any of the combinations. CONCLUSION: Although the synergistic ratios were high in combinations with ceftazidime or piperacillin/tazobactam and tobramycin, the concentrations in these combinations could not usually reach clinically available levels. Thus, the solution of the problems caused by multiple resistant P. aeruginosa should be based on the prevention of the development of resistance and spread of the causative agent between patients.

An Outbreak of Tularemia in Western Black Sea Region of Turkey

The aim of this study was to investigate the source and the size of a tularemia outbreak in a village located in a non-endemic area. Five patients from the same village were admitted to hospital with the same complaints all within one week of September 2001. Tularemia was suspected and a diagnosis was made after physical and anamnesis examinations. The village was visited the same week that the patients were admitted to the hospital, in the January and April 2002. The villagers were examined and screened serologically by microagglutination method and the water sources were investigated bacteriologically. A total of 14 people were found to be infected from the outbreak and the oropharyngeal form was the only clinical presentation. Antibody titers ranged between 1 : 80 and 1 : 640. The patients responded well to the aminoglycoside plus tetracycline therapy. Examination of the pipewater and three springs revealed that all the water sources were contaminated by coliforms, however, Francisella tularensis could not be isolated in glucose-cystine medium. Antibody levels stayed stable or decreased seven months after. Tularemia had not been reported in this area before, so the first patients were misdiagnosed. In conclusion tularemia should be considered in differential diagnosis of patients with fever, sore throat and cervical lymphadenopaties.

A Food-Borne Outbreak Caused by Salmonella Enteritidis

This study was designed to define the epidemiology of a food-borne outbreak caused by Salmonella enteritidis that affected only one squadron of a military battalion located in the vicinity of the city of Edirne in Turkey. The outbreak was analyzed by a standard surveillance form of the Centers for Disease Control and Prevention. The relationship between the eaten foods and cases was analyzed by Fisher's exact chi-square test, and odds ratios were calculated by a case-control study. The outbreak affected 60 of 168 soldiers in the squadron, 16 of whom were hospitalized. S.enteritidis was cultured in stools from 13 of the hospitalized soldiers and from 3 soldiers who had prepared the food. All strains were completely susceptible to antibiotics; their plasmid profiles were also identical. The highest attack rate detected was 55.7% in an omelet eaten 24 hours before (p < 0.001). Furthermore, it was the riskiest food according to the case-control study (OR=7.88; 95% CI=3.68-16.89). The food samples were unobtainable because they had been discarded. All of the hospitalized cases recovered, and none of the control cultures of stools yielded the pathogen after three weeks. In conclusion, although our results didn't indicate the exact source of the outbreak microbiologically, the omelet was considered to be the source based on the epidemiological proofs.