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Characteristics and localization of a determinant conferring partial macrolide resistance in Staphylococcus aureus
1Division of Microbiology, Hokkaido Institute of Pharmaceutical Sciences, Japan.
Abstract:
Staphylococcus aureus TPR-27, a clinically isolated strain, showed constitutive resistance to some macrolide antibiotics (erythromycin, oleandomycin, spiramycin, and josamycin), but susceptibility to the other macrolide (tylosin, rokitamycin, and mycinamicin), lincosamide, and streptogramin type B antibiotics (PM-resistance). The PM-resistant strain TPR-27 has carried for visible plasmids. Attempts to eliminate the resistant determinant in terms of ethidium bromide (about 3 micrograms/ml) did not succeed, and every trial to transduce the PM-resistant determinant into rec- mutant ISP105 using phage 80L2 propagated on strain TPR-27 also failed at the frequency of less than 1.1 x 10(-10) transductants per plaque-forming unit. These results suggest that the PM-resistance determinant is localized in chromosomal DNA.
Insights
This study investigated Staphylococcus aureus strain TPR-27's resistance to macrolide, lincosamide, and streptogramin B antibiotics. Results indicate the resistance determinant is located in the chromosomal DNA, not plasmids.
Area of Science:
- Microbiology
- Antibiotic Resistance Research
- Bacterial Genetics
Background:
- Staphylococcus aureus is a significant human pathogen.
- Antibiotic resistance in S. aureus poses a major public health threat.
- Understanding the genetic basis of resistance is crucial for developing new treatments.
Purpose of the Study:
- To characterize the resistance profile of the clinical isolate Staphylococcus aureus TPR-27.
- To determine the genetic location of the plasmid-mediated resistance (PM-resistance) determinant.
- To investigate the role of plasmids and chromosomal DNA in conferring antibiotic resistance.
Main Methods:
- Phenotypic antibiotic susceptibility testing against various macrolide, lincosamide, and streptogramin B antibiotics.
- Attempts to eliminate the resistance determinant using ethidium bromide treatment.
- Bacteriophage-mediated transduction experiments to transfer the resistance determinant to a recipient strain.
Main Results:
- Staphylococcus aureus TPR-27 exhibited constitutive resistance to specific macrolides (erythromycin, oleandomycin, spiramycin, josamycin) but remained susceptible to others (tylosin, rokitamycin, mycinamicin).
- The strain was also resistant to lincosamide and streptogramin B antibiotics.
- Ethidium bromide treatment and phage transduction experiments failed to transfer the resistance determinant, suggesting it is not plasmid-borne.
Conclusions:
- The PM-resistance determinant in Staphylococcus aureus TPR-27 is likely located in the bacterial chromosome.
- The absence of plasmid involvement suggests a chromosomal mechanism for this specific antibiotic resistance pattern.
- Further investigation is needed to identify the specific genes and mechanisms responsible for chromosomal PM-resistance in S. aureus.