Objectives: To characterize the OMP profile and to study the possible interference with other resistance determinants.
Material and methods: 16 non-typhoidic Salmonella strains, isolated in 1999 from stools of pediatric patients, were selected according to their resistance phenotype: resistance to Ampicillin (AMP), Amoxycillin/Clavulanic Acid (AMC), and third generation cephalosporins: Ceftriaxone (CRO) and Ceftazidime (CAZ). Identification and sensitivity testing were done by DADE MicroScan System. beta-Lactamases were characterized by isoelectric focusing (IEF) with preformed minigelss. OMPs were studied on membrane preparations on SDS-urea gels.
Results: Isoelectric points: Majority of the isolates had the association 5.4 +/- 7.6 (3/16) or 5.4 + 8.2 (6/16). The second beta-lactamase has the capacity to hydrolyse CAZ. We found three different patterns of OMPs: I: 30, 29 and 25 kDa; II: 30, 26 and 24 kDa; III: 30 and 25 kDa. We couldn't find any correlation between the OMPs profile and resistance phenotype, showing that the beta-lactamase production is the only resistant determinant.
Conclusions: The study shows the high frequency of extended-spectrum beta-lactamases (ES beta LA) amongst the non-typhoidic Salmonella; association of TEM type and ES beta LA enzymes diminishes considerably the therapeutic resources: inhibitor associated combinations are non effective. In non-typhoidic Salmonella, porins seems to have no influence in co-modulation of resistance.