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Antibiotic resistance mechanisms in Salmonella species causing bacteraemia in Malawi and Kenya

T M Leegaard1, M H van Gestel, P L Petit

  • 1Department of Medical Microbiology, Leiden University Hospital, The Netherlands.

APMIS : Acta Pathologica, Microbiologica, Et Immunologica Scandinavica
|April 1, 1996
PubMed

Insights

In Malawi and Kenya, 14 Salmonella strains showed resistance to common antibiotics like amoxicillin. Mechanisms included TEM-1 and OXA-1 beta-lactamases and ANT(2") enzymes, indicating a growing challenge in treating Salmonella infections.

Area of Science:

  • Microbiology
  • Infectious Diseases
  • Antimicrobial Resistance

Background:

  • Bacteraemia remains a significant health concern in low-income countries.
  • Salmonella species are common causative agents of bacteraemia.
  • Antibiotic resistance in Salmonella complicates treatment and increases mortality.

Purpose of the Study:

  • To investigate the prevalence and mechanisms of antibiotic resistance in Salmonella strains isolated from Malawi and Kenya.
  • To compare current resistance patterns with historical data.

Main Methods:

  • Isolation and identification of 33 Salmonella strains from blood cultures in Malawi and Kenya.
  • Antimicrobial susceptibility testing against amoxicillin, amoxicillin/clavulanic acid, cotrimoxazole, and aminoglycosides.
  • Characterization of resistance mechanisms, including beta-lactamase detection (TEM-1, OXA-1) and aminoglycoside-modifying enzyme analysis (ANT(2")).
  • Confirmation of gene presence using Polymerase Chain Reaction (PCR).
  • Retrospective analysis of 73 Salmonella strains from hospital records over 14 years.

Main Results:

  • Fourteen out of 33 (42%) Salmonella strains exhibited resistance to amoxicillin, amoxicillin/clavulanic acid, and cotrimoxazole.
  • Decreased susceptibility to several aminoglycosides was observed in resistant strains.
  • TEM-1 beta-lactamase was detected in 12 strains, and OXA-1 beta-lactamase in two S. typhimurium strains from Kenya.
  • The aminoglycoside-modifying enzyme ANT(2") was identified in 10 strains.
  • Historical data revealed only one amoxicillin-resistant strain over 14 years, acquired during therapy.

Conclusions:

  • A high prevalence of multidrug-resistant Salmonella strains, particularly Salmonella typhimurium and Salmonella enteritidis, was found in Malawi and Kenya.
  • Beta-lactamase enzymes (TEM-1, OXA-1) and aminoglycoside-modifying enzymes (ANT(2")) are key mechanisms conferring resistance.
  • The emergence of resistance highlights the urgent need for enhanced surveillance and antimicrobial stewardship programs to combat antimicrobial resistance in Salmonella infections.

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