Resistance mechanism for a number of non-typhoidic Salmonella strains isolated in Iaşi, Romania.

The aim of this study was to find a possible explanation for the resistance pattern of the selected strains and to evaluate the impact in case of isolating such strains. During the period February-March 1998, in the Pediatric Hospital "Sf. Maria" from Iasi, Romania, 12 non-typhoidic Salmonella strains, non-duplicates were isolated from stools of newborns and, in one case, from mother as well. Identification was done by standard methods, and sensitivity testing by disk diffusion method, against the following antimicrobials: Ampicillin (A), Amoxycilin/Clavulanic Acid (AMC), Tetracycline (T), Streptomycin (S), Cloramphenicol (C), Nalidixic Acid (NA), Ciprofloxacin (CIP), Cephalotin (KF), Cefuroxime (CXM), Ceftriaxone (CRO), Cefotaxime (CTX), Ceftazidime (CAZ), Aztreonam (AZT), Imipenem (IPM), Amikacin (AK). All strains showed resistance to: A, AMC, T, S, C, NA, CRO, CAZ, CXM, CTX, KF except one strain, CTX and CRO sensitive. The possible explanation is the production of an extended-spectrum beta-lactamase (ESbLA), detected by microbiological methods (Masuda and clover-leaf). Resistance transfer was realised by using the previously described method. In conjugation experiments we have obtained only one transconjugant, identified as E. coli, that has acquired all resistance determinants. This report highlights on the isolation of multiresistant non-typhoidic Salmonella strains in hospitalised patients without previous antibiotic treatment and possibility of detecting such strains by being aware of the correlation: resistance phenotype-resistance mechanism.