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Comparative activity of the 4-quinolones
1Department of Microbiology, United Medical School, Guy's Hospital, London, United Kingdom.
Abstract:
Minimal inhibitory concentrations (MICs) of the 4-quinolones ciprofloxacin, enoxacin, norfloxacin, ofloxacin, pefloxacin, difloxacin, A-56620, and CI-934 are consistent world-wide, with allowances for differences in acquired resistance. MICs of these drugs for Enterobacteriaceae correlate with those of nalidixic acid, but resistance to the quinolones is rare if a breakpoint of greater than 2 mg/L is accepted. Most intestinal pathogens are sensitive. Acinetobacter, Pseudomonas aeruginosa, and other Pseudomonas species except Pseudomonas maltophilia are usually sensitive. Ciprofloxacin is generally the most active of the 4-quinolones against these organisms. All of the new agents have antistaphylococcal activity, but that of norfloxacin and ofloxacin is borderline. Against streptococci, including enterococci and pneumococci, the drugs' activity is moderate or poor. Haemophilus influenzae and Branhamella catarrhalis are very sensitive. Gonococci and meningococci are also highly sensitive to the new agents, but activity against Chlamydia trachomatis and the mycoplasmas is borderline. The organisms associated with nonspecific vaginal infection are not very sensitive. Anaerobes except Bacteroides ureolyticus and Clostridium perfringens are mostly resistant.
Insights
The 4-quinolone antibiotics show consistent minimal inhibitory concentrations (MICs) globally. Most common pathogens are susceptible, with variations mainly due to acquired resistance, making them effective antimicrobial agents.
Area of Science:
- Microbiology
- Pharmacology
- Infectious Diseases
Background:
- The 4-quinolone class of antibiotics, including ciprofloxacin and ofloxacin, are widely used antimicrobials.
- Understanding their spectrum of activity and resistance patterns is crucial for effective clinical application.
Purpose of the Study:
- To determine the global minimal inhibitory concentrations (MICs) of several 4-quinolones against a range of clinically relevant bacteria.
- To assess the susceptibility patterns of various pathogens to these agents, considering acquired resistance.
Main Methods:
- Determination of MICs for ciprofloxacin, enoxacin, norfloxacin, ofloxacin, pefloxacin, difloxacin, A-56620, and CI-934.
- Testing against a broad spectrum of bacterial species, including Enterobacteriaceae, Pseudomonas, Staphylococcus, Streptococcus, Haemophilus, Neisseria, Chlamydia, Mycoplasma, and anaerobes.
Main Results:
- MICs for 4-quinolones are globally consistent, with variations linked to acquired resistance.
- Enterobacteriaceae and most intestinal pathogens are sensitive; ciprofloxacin shows high activity against Pseudomonas aeruginosa.
- Haemophilus influenzae, Branhamella catarrhalis, Neisseria species are highly sensitive, while activity against Chlamydia, Mycoplasma, and anaerobes is variable or poor.
Conclusions:
- 4-quinolones exhibit broad-spectrum activity, with notable efficacy against Gram-negative bacteria and some Gram-positive organisms.
- Resistance patterns, particularly in Pseudomonas and anaerobes, require consideration for optimal therapeutic use.
- The study confirms the reliable antimicrobial profiles of these 4-quinolones worldwide.