title: Activity of 16 antimicrobial agents against drug-resistant strains of Mycobacterium tuberculosis.
abstract: The in vitro activity of 16 antimicrobial agents against 46 drug-resistant strains of Mycobacterium tuberculosis recently isolated from Italian patients was determined. As for first-line antituberculosis drugs, while isoniazid was ineffective against all the strains tested, resistance to streptomycin, rifampicin, pyrazinamide, and ethambutol was 80.4%, 71.7%, 39.1%, and 8.7%, respectively. Among second-line antituberculous drugs, resistance to ciprofloxacin, ofloxacin, and sparfloxacin and to amikacin and kanamycin was around 20%. About 10% of the strains were resistant to capreomycin and cycloserine and 4.3% were resistant to ethionamide; no strain was found to be resistant to thiacetazone, para-aminosalicylic acid, and viomycin. Although all strains displayed a rather continuous distribution of minimal inhibitory concentrations (MICs), a bimodal distribution was observed for rifampicin, amikacin, and kanamicin, with very high MIC values for resistant strains; relatively low MICs were found for fluoroquinolone-resistant strains. Among the small number of strains resistant to second-line agents, low resistant levels were observed. Restriction fragment length polymorphism analysis showed few strain clusters with resistance to first-line antituberculous drugs and aminoglycosides, fluoroquinolones, or both. Altogether, these results showed that second-line agents were still active against the isoniazid-resistant and multiply first-line resistant strains tested, with none or low resistance levels; these observations can be of importance for the treatment of multidrug-resistant tuberculosis in Italy.
authors.affiliation: Laboratory of Bacteriology and Medical Mycology, Istituto Superiore di Sanità, Rome, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Fattorini
authors.forename: E
authors.initials: E
authors.lastname: Iona
authors.forename: M L
authors.initials: ML
authors.lastname: Ricci
authors.forename: O F
authors.initials: OF
authors.lastname: Thoresen
authors.forename: G
authors.initials: G
authors.lastname: Orrù
authors.forename: M R
authors.initials: MR
authors.lastname: Oggioni
authors.forename: E
authors.initials: E
authors.lastname: Tortoli
authors.forename: C
authors.initials: C
authors.lastname: Piersimoni
authors.forename: P
authors.initials: P
authors.lastname: Chiaradonna
authors.forename: M
authors.initials: M
authors.lastname: Tronci
authors.forename: G
authors.initials: G
authors.lastname: Pozzi
authors.forename: G
authors.initials: G
authors.lastname: Orefici
mesh_terms: D000995:Antitubercular Agents / Q000494:pharmacology*; D004352:Drug Resistance, Microbial / Q000235:genetics; D006801:Humans; D008826:Microbial Sensitivity Tests; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000235:genetics; D012150:Polymorphism, Restriction Fragment Length
chemical_list: D000995:Antitubercular Agents