Related Experiment Videos
Resistance mechanisms of multiply resistant pneumococci: antibiotic degradation studies
Abstract:
Strains of Streptococcus pneumoniae resistant to penicillin have been reported from several countries around the world. Many South African isolates, in addition, exhibit resistance to tetracycline, chloramphenicol, erythromycin, clindamycin, and cotrimoxazole in varying patterns. A qualitative test of the ability of antibiotic-resistant pneumococci to inactivate penicillin, oxacillin, cephalothin, cefoxitin, chloramphenicol, tetracycline, minocycline, erythromycin, clindamycin, streptomycin, gentamicin, and cotrimoxazole revealed that only chloramphenicol was degraded. This finding was confirmed in a quantitative test in which the residual antimicrobial activity of broth containing chloramphenicol in subinhibitory concentrations was determined after incubation with antibiotic-resistant bacteria. Chloramphenicol resistance was shown to be associated with the production of inducible chloramphenicol acetyltransferase. No beta-lactamase activity was demonstrated. Plasmid deoxyribonucleic acid was not demonstrable in partially purified lysates of antibiotic-resistant strains of S. pneumoniae.
Insights
Antibiotic-resistant Streptococcus pneumoniae strains in South Africa degrade chloramphenicol via inducible chloramphenicol acetyltransferase. This study investigates resistance mechanisms in pneumococci, finding no beta-lactamase activity.
Area of Science:
- Microbiology
- Molecular Biology
- Pharmacology
Background:
- Antibiotic resistance in Streptococcus pneumoniae is a growing global health concern.
- Many South African isolates display resistance to multiple antibiotics, including penicillin, tetracycline, chloramphenicol, erythromycin, clindamycin, and cotrimoxazole.
Purpose of the Study:
- To investigate the mechanisms of antibiotic resistance in Streptococcus pneumoniae strains from South Africa.
- To determine if antibiotic-resistant pneumococci can inactivate specific antimicrobial agents.
- To identify the specific enzymes or genetic elements responsible for observed resistance patterns.
Main Methods:
- Qualitative and quantitative assays were performed to assess the degradation of various antibiotics by resistant pneumococcal strains.
- Incubation of subinhibitory concentrations of chloramphenicol with resistant bacteria was used to measure residual antimicrobial activity.
- Tests for beta-lactamase activity and analysis of plasmid deoxyribonucleic acid were conducted.
Main Results:
- Only chloramphenicol was found to be degraded by the antibiotic-resistant pneumococcal isolates.
- Chloramphenicol resistance was directly correlated with the production of inducible chloramphenicol acetyltransferase.
- No evidence of beta-lactamase activity or the presence of plasmid DNA was detected in the resistant strains.
Conclusions:
- Inducible chloramphenicol acetyltransferase is the primary mechanism conferring chloramphenicol resistance in these South African Streptococcus pneumoniae strains.
- The absence of beta-lactamase activity suggests alternative mechanisms for penicillin resistance.
- Further research is needed to elucidate the genetic basis of resistance to other tested antibiotics.