Molecular epidemiology and mechanisms of resistance to several antimicrobial agents in sporadic Salmonella spp. strains causing acute gastroenteritis in Cuba

Abstract number: 1134_03_33

Cabrera R., Ruiz J., Ramírez M., Bravo L., Fernández A., Aladueña A., Echeíta A., Gascón J., Alonso P., Vila J.

Objective:  

Determine the antimicrobial susceptibility and the molecular mechanisms of resistance of Salmonella spp. strains causing acute gastroenteritis in Cuba and determine the potential dissemination of a resistant clone.

Methods:  

A total of 34 Salmonella strains isolated from feces of patients with acute gastroenteritis isolated from different regions of Cuba in 2002 were received and processed in the laboratory of Clinical Microbiology of Clínic Hospital in Barcelona. The antimicrobial susceptibility to 9 antibiotics: ampicillin, amoxicillin/clavulanic acid, nalidixic acid, tetracycline, trimethoprim/sulphametoxazole, chloramphenicol, gentamicin, ciprofloxacin and spectinomycin, was determined using the agar dilution method. The molecular mechanisms of resistance to several antimicrobial agents were detected by PCR and the chloramphenicol acetyl transferase activity by a colorimetric assay. Analysis of molecular epidemiology was performed by pulsed field gel electrophoresis using the low frequency restriction enzyme XbaI.

Results:  

Twenty-two strains presented resistance, 64% was multirresistant. The serotype Typhimurium phagetype 104 was the most frequent and presented similar genetic profiles of PFGE. High levels of resistance to tetracycline (53%), spectinomycin (50%), ampicillin (44%) and chloramphenicol (41%) were found. Resistance to tetracycline was associated with the tet G and tet A genes. Resistance to ampicillin was due to the presence of b-lactamases, mainly the CARB type. The floR gene was the main mechanism of resistance to chloramphenicol. Among the susceptible strains, six belong to the serotype Agona were epidemiologically related.

Conclusions:  

The presence of two main clones was detected in Cuba, with the widespread dissemination of a multiresistant clone of Salmonella enterica serotype Typhimurium DT 104 and an antimicrobial susceptible clone of Salmonella enterica serotype Agona in two separate regions in the country.