Daniel L. Shungu

In vitro antibacterial activity of norfloxacin (MK-0366, AM-715) and other agents against gastrointestinal tract pathogens.

A comparison was made of the in vitro activities of norfloxacin and of nine other orally administered antibacterial agents against 180 clinical isolates representing the bacterial species most frequently implicated in infections of the gastrointestinal tract in humans. The 90% minimal inhibitory concentrations showed norfloxacin to be 4, 15, 4, 17, 17, 17, and 33 times more active than the next best compound tested against Campylobacter fetus subsp. jejuni, Escherichia coli, Salmonella spp., Shigella spp., Vibrio cholerae, Vibrio parahaemolyticus, and Yersinia enterocolitica, respectively, with an overall 90% minimal inhibitory concentration of less than or equal to 0.5 micrograms/ml. Norfloxacin was least active against Clostridium difficile (90% minimal inhibitory concentration, 128 micrograms/ml). These results should encourage further evaluation of norfloxacin as a potential chemotherapeutic agent in the treatment of enteric bacterial infections for which antibiotic therapy is indicated.

Comparison of the antibacterial activity of norfloxacin (MK 0366, AM 715), a new organic acid, with that of other orally absorbed chemotherapeutic agents

Summary425 randomly selected, fresh clinical isolates were tested for susceptibility to norfloxacin and other orally absorbed agents, i. e. amoxicillin, ampicillin, carbenicillin (available commercially as the indanyl ester), cefaclor, cinoxacin, erythromycin, nalidixic acid, penicillin G, tetracycline, trimethoprim and co-trimoxazole. The results have shown norfloxacin to be the most potent agentin vitro against representative members of the familyEnterobacteriaceae, Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter spp.,Neisseria gonorrhoeae andHaemophilus influenzae. Ninety percent of the isolates in these groups of bacteria were inhibited by less than 1 mg/l, 2 mg/l, 8 mg/l, 32 mg/l, 0.06 mg/l and 0.25 mg/l of norfloxacin, respectively. Although norfloxacin inhibited most streptococci andUreaplasma at a concentration of 8 mg/l or less, penicillin G proved to be the most active againstStreptococcus pygenes andStreptococcus pneumoniae; trimethoprim was the most active againstStreptococcus faecalis, and tetracycline the most active againstUreaplasma.Zusammenfassung425 zufallsgemäß ausgewählte, frische klinische Isolate wurden auf ihre Empfindlichkeit gegenüber Norfloxacin und anderen nach oraler Gabe resorbierbaren Substanzen, wie Amoxicillin, Ampicillin, Carbenicillin (kommerziell als Indanylester erhältlich), Cefaclor, Cinoxacin, Erythromycin, Nalidixinsäure, Penicillin G, Tetracyclin, Trimethoprim und Co-Trimoxazol, getestet. Die Ergebnisse zeigten, daß Norfloxacinin vitro die wirksamste Substanz gegen repräsentative Mitglieder der FamilieEnterobacteriaceae, Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter spp.,Neisseria gonorrhoeae undHaemophilus influenzae ist; 90% der Isolate dieser Gruppen von Bakterien wurden durch Norfloxacin in Konzentrationen von weniger als 1 mg/l; 2 mg/l; 8 mg/l; 32 mg/l; 0,06 mg/l und 0,25 mg/l gehemmt. Norfloxacin hemmte zwar die meisten Streptokokken undUreaplasma Stämme bei einer Konzentration von 8 mg/l oder weniger, doch erwies sich Penicillin G als die wirksamste Substanz gegenüberStreptococcus pyogenes undStreptococcus pneumoniae, Trimethoprim war am aktivsten gegenStreptococcus faecalis und Tetracyclin wies die stärkste Aktivität gegenUreaplasma auf.

In vitro Antibacterial Activity of Norfloxacin and Other Agents against Ocular Pathogens

302 clinical isolates representing 16 bacterial species most often implicated in ocular infections were tested in vitro against norfloxacin and a panel of antibacterial agents. On the basis of the 90% minimal inhibitory concentration (MIC90) data, norfloxacin was 4-32 times more active than the next best antimicrobial tested against Citrobacter freundii, Escherichia coli, Morganella morganii, Proteus mirabilis, Proteus vulgaris, Haemophilus influenzae, Neisseria gonorrhoeae and Staphylococcus epidermidis, with overall MIC90 less than or equal to 1 mg/l. Norfloxacin was equal in activity to polymyxin B against Klebsiella pneumoniae (MIC90 = 1 mg/l), and it ranked second to both polymyxin B against Pseudomonas aeruginosa and cotrimoxazole against Staphylococcus aureus, (MIC90 = 2 mg/l in each case). Along with neomycin and cotrimoxazole, norfloxacin (MIC90 = 1 mg/l) ranked second to gentamicin and tetracycline against Moraxella species. Compared to erythromycin (MIC90 less than or equal to 0.125 mg/l), norfloxacin (MIC90 less than or equal to 16 mg/l) was considerably less active against streptococci. Overall, norfloxacin was the most active agent in both potency and antibacterial spectrum against the test organisms. These results suggest the potential use of norfloxacin in the treatment of superficial bacterial infections of the eye.

Comparative susceptibilities of Campylobacter pylori to norfloxacin and other agents.

Twenty-one strains of Campylobacter pylori (Campylobacter pyloridis) were tested for susceptibility to norfloxacin and other agents by the serial agar dilution method. Ampicillin (MIC for 90% of isolates [MIC90], 0.016 micrograms/ml) and famotidine (MIC90, greater than 1,024 micrograms/ml) were, respectively, the most and the least active of the agents tested. Norfloxacin (MIC90, 1 microgram/ml) and imipenem (MIC90, 0.125 micrograms/ml) were substantially active against this organism.

Norfloxacin, the first of a new class of fluoroquinolone antimicrobials, revisited

Norfloxacin is the first in a series of new 4-quinolones that have been introduced into medical practice for the treatment of bacterial infections. This totally synthetic compound is a broad spectrum, bactericidal agent that is much more potent than the earlier analogs, i.e. nalixidic acid, pipemidic acid, cinoxacin, rosoxacin, and flumequine, is less likely to select for resistant mutants. While the compound has been used most widely in the treatment of urinary tract infections including pyelonephritis and prostatitis, utility has also been demonstrated in gastrointestinal and ophthalmological infections, gonorrhea, typhoid fever, the typhoid carrier state, as well as in the prophylaxis of travelers diarrhea, biliary tract infections prior to surgery, and gram-negative bacillary infections in profoundly neutropenic patients.

Comparative in vitro activity of norfloxacin against resistantNeisseria gonorrhoeae

The in vitro activity of seven antibiotics against 52 isolates ofNeisseria gonorrhoeae was determined. Against penicillinase-producingNeisseria gonorrhoeae, ceftriaxone was the most active agent (MIC90 0.015 µg/ml), followed by ceftizoxime and norfloxacin (MIC90 0.03–0.125 µg/ml). Against spectinomycin-resistantNeisseria gonorrhoeae, the most active agents were ceftizoxime, ceftriaxone and norfloxacin (MIC90 0.015–0.125 µg/ml). Ceftizoxime, ceftriaxone and norfloxacin were also the most active agents against tetracycline-resistantNeisseria gonorrhoeae (MIC90 0.06–0.125 µg/ml). Overall, the rank order of activity from the most to the least active agent was as follows: ceftizoxime (MIC90 0.015 µg/ml); ceftriaxone (MIC90 0.06 µg/ml); norfloxacin (MIC90 0.125 µg/ml); cefoxitin (MIC90 2 µg/ml); tetracycline (MIC90 8 µg/ml); penicillin (MIC90 > 8 µg/ml); and spectinomycin (MIC90 > 128 µg/ml).

Comparative in vitro antimicrobial susceptibilities of a special panel of 74 Bacteroides fragilis group isolates in Wilkins-Chalgren agar with and without sheep blood.

Seventy-four cefoxitin-resistant Bacteroides fragilis group isolates were tested by the serial twofold agar dilution method for susceptibility to imipenem and other agents in medium with and without 5% sheep blood. Imipenem (MIC for 90% of strains tested, 1 microgram/ml) and metronidazole (MIC for 90% of strains tested, 2 micrograms/ml) were the two most active agents. The addition of 5% sheep blood to the medium had little or no effect on the activity of the antibiotics tested.