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Molecular mechanisms of antimicrobial resistance in Salmonella typhimurium isolates, causing bacteraemia in children under 5 years of age in southern Mozambique

Abstract number: p1615

Ruiz  J., Mandomando  I., Esquivel  P., Vila  J., Gascon  J., Alonso  P.L.

Objectives: 

To analyse the molecular mechanisms of resistance to 7 antimicrobial agents in 85 Salmonella typhimurium causing bacteremia in children under 5 years of age in Mozambique.

Methods: 

The isolates were identified by biochemical tests and specific serotyping. Antimicrobial susceptibility to ampicilllin (Amp), amoxicillin plus clavulanic acid (AUC), cloramphenicol (Cm), gentamicin (Gm), cotrimoxazole (Sxt), nalidíxic acid (Nal) and tetracycline (Tc) were established by the method of Kirby Bauer. The presence of beta-lactamases encoding genes (tem, carb, oxa2-like) as well as the tetA, tetB, tetC, tetG, cmlA and floR genes, and integrons type 1 was established by PCR, while the presence of plasmid-mediated DHFR was determined by PCR-RFLP and the CAT activity by a colorimetric assay.

Results: 

Seven different resistance patterns were identified: I. Susceptible (38 strains); II. Amp, Sxt, Gm, A/C (37); III. Amp, Tc, Cm (2); IV. Amp, Tc, Sxt, Cm (2); V. Amp, A/C (4); VI. Amp, Sxt, A/C (1); VII (1). – Sxt. No isolate resistant to nalidixic acid was detected. Resistance to beta-lactam agents was due to the presence of beta-lactamases type TEM-like (pattern V), CARB-2 (III) and TEM-like plus OXA-30 (II, V, VI). Meanwhile resistance to cloranphenicol and tetracycline was associated to CAT activity (III, IV) and floR (III), and tetB (IV) and tetG (III) respectively. No mechanism of cotrimoxazole resistance was detected in the isolates of the patterns II, VI and VII, while dfrA1 was detected in the isolates of the group IV. Resistance to Gm was associated to the presence of the gene aadB, detected in the analysis of integrons type 1. Type 1 integrons were detected in isolates belonging toi the pattern II (750 bp – aadB; 2000 bp – oxa30, aadA1), III (900 bp – carb2, 1100 – aadA1), IV (1500 bp – dfrA1, aadA1), V and VI (2000 bp – oxa30, aadA1).

Conclusions: 

A great diversity of resistance mechanisms has been detected. Those mechanisms might spread among microorganisms resulting in a serious health problem due to the limited number of antibiotic treatments available in the area.

Session Details

Date: 01/08/2007
Time: 00:00-00:00
Session name: XXIst ISTH Congress
Subject:
Location: Oxford, UK
Presentation type:
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