Study of outer membrane proteins (OMPS) and their role in co-modulation of resistance in non typhoidic Salmonella strains isolated in Iaşi.

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.