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Isolation and Identification of Waterborne Antibiotic-Resistant Bacteria and Molecular Characterization of their Antibiotic Resistance Genes
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Chromosomally mediated high-level gentamicin resistance in Streptococcus mitis

A Kaufhold1, E Potgieter

  • 1Institute of Medical Microbiology, Technical University (RWTH) Aachen, Germany.

Antimicrobial Agents and Chemotherapy
|December 1, 1993
PubMed

Insights

Four Streptococcus mitis strains exhibit resistance to penicillin and gentamicin. Genetic analysis revealed the presence of a high-level gentamicin resistance gene, likely integrated into the bacterial chromosome.

Area of Science:

  • Microbiology
  • Genetics
  • Infectious Diseases

Background:

  • Streptococcus mitis is a common bacterium, part of the normal oral flora.
  • Antibiotic resistance in bacteria poses a significant global health threat.
  • Penicillin and gentamicin are commonly used antibiotics for bacterial infections.

Purpose of the Study:

  • To investigate the antibiotic resistance profiles of Streptococcus mitis blood culture isolates.
  • To identify the genetic basis for penicillin and gentamicin resistance in these strains.
  • To determine the in vitro synergy between penicillin and gentamicin against resistant S. mitis.

Main Methods:

  • Antibiotic susceptibility testing (MIC determination) for penicillin and gentamicin.
  • Polymerase chain reaction (PCR) assays to detect specific resistance genes.
  • Oligonucleotide probing and DNA hybridization to analyze gene location.

Main Results:

  • Four S. mitis isolates showed high-level resistance to both penicillin and gentamicin.
  • The gene encoding high-level gentamicin resistance, typically found in other bacteria, was present in all resistant S. mitis strains.
  • No in vitro synergy was observed between penicillin and gentamicin.
  • Resistance genes appear to be chromosomally integrated, as plasmid isolation was unsuccessful.

Conclusions:

  • Certain Streptococcus mitis strains can acquire and harbor genes for high-level antibiotic resistance.
  • The genetic mechanisms of resistance in these S. mitis strains may involve chromosomal integration.
  • Understanding resistance mechanisms is crucial for effective treatment strategies against S. mitis infections.

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