In vitro synergistic effect of colistin and ampicillin/sulbactam with several antibiotics against clinical strains of multi-drug resistant Acinetobacter baumannii.

PURPOSE: Nowadays, Acinetobacter baumannii is resistant to almost all available antibiotics. The evaluation of synergistic effects between the antibiotics against this pathogen is among the efforts to counteract its antimicrobial resistance. This study aimed to evaluate possible synergistic effect of colistin and ampicillin/sulbactam (separately) with several antibiotics against clinical isolates of multi-drug resistant (MDR) A. baumannii. METHODS: Acinetobacter baumannii strains were isolated from biological samples of hospitalized patients with any type of nosocomial infection related to this pathogen. Only MDR strains (resistance to at least three classes of antibiotics including cephalosporins, fluoroquinolones, and aminoglycosides) were included in the study. After determining the minimum inhibitory concentration (MIC) of antibiotics against the isolates by broth microdilution test, the checkerboard method was used for evaluation of any possible synergistic effect of both colistin and ampicillin/sulbactam with several other antibiotics. RESULTS: Twenty isolates underwent synergy test for colistin and 20 isolates for ampicillin/sulbacatam. Doxycycline (55%), azithromycin (35%), and co-trimoxazole (35%) had the most frequency of synergistic effect with colistin. On the other hand, amikacin and gentamicin (55%), doxycycline (50%), co-trimoxazole (45%), azithromycin (40%), and cefepime (40%) had the most frequency of synergistic effect with ampicillin/sulbactam. No antagonistic effect was observed for both antibiotics. CONCLUSION: Colistin and ampicillin/sulbactam have substantial synergistic effect with several antibiotics especially doxycycline, co-trimoxazole, azithromycin, and amikacin (with ampicillin/sulbactam) against MDR strains of Acinetobacter baumannii.

Meropenem Utilization Evaluation in a Referral Teaching Hospital in Iran.

OBJECTIVE: Inappropriate use of antibiotics is associated with detrimental effects including emergence of antibiotic resistance. This study aimed to evaluate the use of meropenem, an extended-spectrum antibiotic, in a referral teaching hospital to detect different types of errors in its prescription. METHODS: In a cross-sectional study performed over a 6-month period (2014-2015), hospitalized adult patients who received meropenem for any indication were randomly selected. The collected data included the indication for prescription and its correctness, the basis of prescription (empirical or culture based), administered dose, duration of treatment, the status of demanding sample culture in the case of empirical prescription, the status of dose adjustment in the case of renal impairment, and the treatment outcome. FINDINGS: Over the study period, 123 patients were evaluated. The most frequent indication for prescription of meropenem was pneumonia (31.7%) and soft-tissue infections (18.7%). Out of these prescriptions, 62.6% (77 prescriptions) were incorrect. All meropenem prescriptions were initially empirical. Furthermore, sample culture and antibiotic susceptibility test were requested for only 52% of patients (n = 66). Treatment duration was correct for 53.7% of patients. Seventeen patients (13.8%) received an inappropriate dose of the antibiotic. Furthermore, of 51 patients who needed meropenem dose adjustment because of renal impairment, 17 patients (33.33%) received unadjusted dose. CONCLUSION: High rate of errors exists in the utilization of meropenem in our hospital, especially in the rank order of selection for treatment (indication), dose adjustment, and treatment duration. Therefore, modification strategies are necessary to promote the rational use of meropenem in this center.