To evaluate the incidence and the significance of resistance to erythromycin among clinical isolates of Streptococcus pneumoniae, we identified and prospectively followed all hospitalized patients in a 27-month period who had the organism isolated from any clinical sample. Patients who had an infection caused by pneumococci resistant to erythromycin (minimum inhibitory concentration, > 1 microgram/mL) were compared to those with infections caused by erythromycin-susceptible organisms. The incidence of erythromycin resistance among pneumococci doubled over the study period (from 7.6% in 1988 to 15.2% in 1992). Most strains (94%) showed resistance to multiple antibiotics, including other macrolides. By multivariate analysis, an age of < 5 years and nosocomial acquisition of the infection were independent risk factors for erythromycin resistance. Among patients with pneumococcal pneumonia caused by erythromycin-resistant organisms, 9 patients treated with third-generation cephalosporins were cured, while therapy with erythromycin failed for 2 of the 6 patients to whom it was administered. The rapid and significant increase of erythromycin resistance among clinical isolates of S. pneumoniae points to the need for routine surveillance of pneumococcal resistance.
Erythromycin, new macrolides, and quinolones are alternatives for the treatment of Campylobacter infections. Concerns related to the emergence of resistance to both groups of drugs have been raised. We studied the evolution of antimicrobial susceptibilities of 275 clinical isolates of microorganisms of the genus Campylobacter isolated in our institution during a 5-year period (1988 to 1992). The microorganisms studied were C. jejuni (n = 230), C. coli (n = 42), and C. fetus (n = 3). The overall resistance rates (determined by the agar dilution method and the recommendations of the National Committee for Clinical Laboratory Standards) were as follows: erythromycin, 2.3%; clarithromycin, 2.3%; azithromycin, 1.9%o; ciprofloxacin, 28.5%; norfloxacin, 31%; ofloxacin, 26.3%; and nalidixic acid, 36.8%. The evolution of resistance (percent resistance in 1988 versus percent resistance in 1992) was as follows: erythromycin, 2.6 versus 3.1; clarithromycin, 2.6 versus 3.1; azithromycin, 2.6 versus 3.1; ciprofloxacin, 0 versus 49.5; norfloxacin, 2.6 versus 55.5; ofloxacin, 0 versus 45.6; nalidixic acid, 2.6 versus 56.8. Our data show stable macrolide activity against Campylobacter spp. and the rapid development of quinolone resistance over the last 5 years.
Two hundred fifty isolates of Mycobacterium tuberculosis were evaluated for susceptibility to ciprofloxacin, ofloxacin, levofloxacin, grepafloxacin, trovafloxacin, and gemifloxacin (SB-265805). Levofloxacin, ciprofloxacin, and grepafloxacin showed the greatest activity (MIC for 90% of strains tested [MIC 90 ] 1 g/ml), although ofloxacin also showed good activity, with an MIC 90 of 2 g/ml. Trovafloxacin and gemifloxacin showed lower in vitro activity, with MIC 90 s of 64 and 8 g/ml, respectively.The increase in drug-resistant Mycobacterium tuberculosis isolates during recent years presents a therapeutic challenge to physicians selecting antimicrobial agents (2,3,4,10,12). Fluoroquinolones may have a useful role in the treatment of these infections not only because some of their derivatives, e.g., ofloxacin (11), have already been used for the treatment of pulmonary tuberculosis but also because newer derivatives are continually being developed. However, comparative in vitro susceptibility data for classic and new agents of this class against a representative number of M. tuberculosis isolates are scarce (5,13,14).In our study, we compared the activities of the fluoroquinolones ciprofloxacin, ofloxacin, levofloxacin, grepafloxacin, trovafloxacin, and the novel compound gemifloxacin (SB-265805) against 250 clinical isolates of M. tuberculosis with different levels of susceptibility to first-line antituberculosis drugs.(Part of this study was presented as a poster at the 39th Interscience Conference on Antimicrobial Agents and Chemotherapy, 1999.) The active substances of the assayed antimycobacterial agents were kindly provided as reference powders by SmithKline Beecham (Worthing, United Kingdom). Ofloxacin was obtained from Sigma Chemical Co. (St. Louis, Mo.). Agent corrections were made for purity of antimicrobials. Stock solutions of all of the fluoroquinolones were prepared at 10,000 g/ml in distilled water by adding a 0.1 M NaOH solution for dilution when necessary. Aliquots of the antituberculosis agents were frozen at Ϫ70°C until use. Staphylococcus aureus strain ATCC 29213 was used for quality control to ensure the potency of the fluoroquinolones tested.Two hundred fifty clinical isolates of M. tuberculosis from 250 tuberculosis patients were selected from our laboratory collection (1988 to 1999). Of the samples tested, 197 were of respiratory origin and 53 were of nonrespiratory origin. Testing of susceptibility to first-line antituberculosis drugs (isoniazid, rifampin, ethambutol, and streptomycin) was performed by the agar proportion method in a reference laboratory. Of the strains tested, 44 (18%) were resistant to at least one first-line antituberculosis drug (R-MTB group; 24 monodrug-resistant and 20 multidrug-resistant strains) while the rest were fully susceptible (S-MTB group). The agar proportion method was performed as recommended by the National Committee for Clinical Laboratory Standards (9). Briefly, 7H10 agar medium (Difco) was prepared from a dehydrated base as recommended by the manufact...
Over a period of 5 years we have recovered 32 clinical isolates of coagulase-negative staphylococci (CoNS) exhibiting either decreased levels of susceptibility or true resistance to teicoplanin (MICs, 16 to 128 g/ml); these isolates make up 0.55% of the total CoNS isolated by us. Twenty-nine of the strains were also methicillin resistant, and all were susceptible to vancomycin. Fourteen of the strains were Staphylococcus epidermidis, fourteen were Staphylococcus haemolyticus, and four were Staphylococcus hominis. In one case, a strain of S. haemolyticus was isolated with a vancomycin-resistant, teicoplanin-resistant Enterococcus faecalis strain. All strains were nosocomially acquired and were isolated from 17 different wards. Teicoplanin resistance occurred as a sporadic phenomenon, and none of the isolates were epidemiologically related. The isolates were from 30 patients, 13 of whom presented with true infections (43%). Five (38%) of the 13 patients with true infections had been previously treated with vancomycin. None of the infected patients were previously treated with teicoplanin. The in vivo development of resistance to teicoplanin among CoNS strains limits the therapy of infections by these microorganisms. There is a need for surveillance of nosocomial isolates of CoNS to determine resistance to glycopeptides.
We studied 961 clinical Salmonella isolates (one per patient) seen in one Spanish hospital from 1988 to 1991. The incidence of non-Salmonella typhi SalmoneUla infections per 100,000 admissions increased from 3.93 to 5.98. Overall rates of resistance to ampicillin, chloramphenicol, and co-trimoxazole were 32, 11, and 2%, respectively. Resistance to chloramphenicol increased from 9 to 16% during the study period, while resistance to each of the other drugs remained stable. Variations related to serogroups were observed.
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