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In vitro activity of various antimicrobial agents against Staphylococcus aureus isolates including fluoroquinolone-
K E Aldridge1, R N Jones, A L Barry
1Louisiana State University Medical Center, New Orleans 70112.
Abstract:
To determine susceptibility to 31 old and new antimicrobials, 44 strains of Staphylococcus aureus, most resistant to oxacillin and ciprofloxacin and isolated in a community hospital, were tested in vitro. For the peptide/peptide-derivative compounds, with the exception of mersacidin, all strains were inhibited by less than or equal to 2 micrograms/ml. Minimum inhibitory concentration (MIC)90 values indicated mupirocin, teicoplanin, and MDL 62211 to be fourfold more active than vancomycin, ramoplanin, and decaplanin. For fluoroquinolones, ciprofloxacin-resistant S. aureus exhibited high-level cross-resistance to ofloxacin, norfloxacin, fleroxacin, enoxacin, and Ro 23-9424. WIN 57253, a new fluorinated naphthyridine, showed good activity against these strains. Among the beta-lactams, the penem-derivative compounds (imipenem, meropenem, FCE 22101, and HRE 664) had the greatest activity, although resistance to each compound was detected among oxacillin-resistant S. aureus. The presence of tazobactam reduced the piperacillin MIC90 fourfold. Oxacillin-susceptible strains were susceptible to cephalosporins/cephamycins, whereas most oxacillin-resistant strains exhibited resistance. This study has shown that certain old and new quinolones and peptide-derivative compounds have good in vitro activity against multiply resistant strains of S. aureus.
Insights
This study evaluated 31 antimicrobials against resistant Staphylococcus aureus strains. New quinolones and peptide derivatives showed promising in vitro activity against these challenging bacteria.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Staphylococcus aureus is a significant pathogen, frequently developing resistance to multiple antibiotics.
- Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) poses a growing public health concern.
- Limited treatment options exist for infections caused by multidrug-resistant S. aureus.
Purpose of the Study:
- To assess the in vitro susceptibility of clinical Staphylococcus aureus isolates to a broad spectrum of 31 antimicrobial agents.
- To identify novel antimicrobial agents with potential efficacy against oxacillin- and ciprofloxacin-resistant S. aureus strains.
- To compare the activity of new antimicrobial compounds with established drugs.
Main Methods:
- In vitro susceptibility testing of 44 Staphylococcus aureus strains against 31 antimicrobials.
- Determination of Minimum Inhibitory Concentration (MIC)90 values for various antibiotic classes.
- Evaluation of cross-resistance patterns among fluoroquinolones and beta-lactams.
Main Results:
- Peptide/peptide-derivative compounds (except mersacidin) inhibited all strains at ≤2 µg/ml, with mupirocin, teicoplanin, and MDL 62211 showing superior activity over vancomycin and related compounds.
- Ciprofloxacin-resistant S. aureus exhibited high cross-resistance to older fluoroquinolones, but WIN 57253 demonstrated good activity.
- Penem derivatives showed the greatest activity among beta-lactams, though resistance was observed. Tazobactam reduced piperacillin MIC90 fourfold.
- Oxacillin-susceptible strains were sensitive to cephalosporins/cephamycins, while resistant strains showed resistance.
Conclusions:
- Certain novel quinolones and peptide-derivative compounds exhibit significant in vitro activity against multidrug-resistant Staphylococcus aureus.
- These findings suggest potential therapeutic options for infections caused by challenging S. aureus strains.
- Further investigation into these agents is warranted for the treatment of resistant S. aureus infections.