In vitro effect of moxifloxacin and rifampicin on biofilm formation by clinical MRSA isolates.

OBJECTIVE: In this study, it was aimed to investigate in vitro activity of moxifloxacin and rifampicin on biofilm formation by clinical MRSA isolates. BACKGROUND: Methicillin resistant Staphylococcus aureus (MRSA) strains could be the causative agent in chronical and medical device associated infections by biofilm formation. METHODS: Moxifloxacin and rifampicin MIC values of 98 MRSA clinical isolates were determined by microdilution method. Biofilm formation of all isolates was determined in 96-well microplates by using spectrophotometric method. Effects of MIC and sub-inhibitory concentrations (1/2 and 1/4 MIC) of antibiotics on biofilm formation were examined in 46 strong biofilm producer strains. RESULTS: Biofilm production decreased in 37 and 44 isolates at all studied concentrations of moxifloxacin and rifampicin, respectively. Biofilm production increased in six isolates with moxifloxacin and in two isolates with rifampicin. CONCLUSION: Biofilm inhibitory effect of rifampicin was found to be stronger than moxifloxacin in the examined strains. The studied antimicrobials also induced biofilm formation in some strains. Results of this study may help to evaluate the effects of these antibiotics on biofilm formation of clinical MRSA strains and to control the antibiotic resistance in clinical settings (Tab. 2, Ref. 25).

Activity of amikacin, ertapenem, ciprofloxacin and levofloxacin alone and in combination against resistant nosocomial pathogens by time-kill / Actividad letalidad-tiempo de la amicacina, la ertapenema, la ciprofloxacina y la levofloxacina, solas o en combinación, frente a los patógenos nosocomiales

OBJECTIVE: The purpose of this study was to determine the synergistic activity of amikacin/ertapenem, fluoroquinolones (ciprofloxacin and levofloxacin)/ertapenem and amikacin/fluoroquinolones combinations against resistant nosocomial pathogens. METHODS: Time-kill studies were performed over 24 hours using an inoculum of 5 x 106 - 1 x 107 cfu/mL. Antibiotics were tested at the 1 x MIC and 4 x MIC concentrations. RESULTS: At MIC and/or 4 x MIC concentrations, the antibiotic combinations showed additive or synergistic activity against Acinetobacter strains and extended spectrum beta-lactamase producing Klebsiella pneumoniae. In Escherichia coli strains, synergy was seen when amikacin was combined with ertapenem, ciprofloxacin and levofloxacin; ertapenem in combination with fluoroquinolones demonstrated antagonism. In Pseudomonas aeruginosa strains, synergistic effect was exhibited by ertapenem plus amikacin and ertapenem plus fluoroquinolones. The antibiotic combinations showed antagonistic interaction in methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecalis. CONCLUSION: The antibiotic combinations showed additive or synergistic activity against many gram-negative pathogens.

OBJETIVO: El propósito del presente estudio fue determinar la actividad sinérgica de la amicacina/ ertapenema/fluoroquinolonas (ciprofloxacina y levofloxacina)/ertapenema y amicacina/y combinaciones de fluoroquinolonas frente a patógenos nosocomiales resistentes. MÉTODOS: Se realizaron estudios de letalidad-tiempo por 24 horas, usando un inóculo de 5 x 106 - 1 x 107 cfu/mL. Se probaron antibióticos en concentraciones de 1xCIM y 4xCIM. RESULTADOS: En concentraciones de CIM y/o 4 x CIM, las combinaciones de antibióticos mostraron actividad aditiva o sinergésica frente a las cepas Acinetobacter y Klebsiella pneumoniae productoras de la beta-lactamasa de espectro extendido. En las cepas de Escherichia coli, se observó sinergia cuando se combinó la amicacina con la ertapenema, la ciprofloxacina y la levofloxacina; la ertapenema en combinación con las fluoroquinolonas demostró antagonismo. En las cepas de Pseudomonas aeruginosa, se puso de manifiesto un efecto sinergésico al sumar la ertapenema con amicacina y la ertapenema con fluoroquinolonas. Las combinaciones antibióticas mostraron interacción antagonística en Staphylococcus aureus resistente a la meticilina y Enterococcus faecalis resistente a la vancomicina. CONCLUSIÓN: Las combinaciones antibióticas mostraron actividad aditiva o sinergésica frente a muchos patógenos gram-negativos.

Activity of amikacin, ertapenem, ciprofloxacin and levofloxacin alone and in combination against resistant nosocomial pathogens by time-kill.

OBJECTIVE: The purpose of this study was to determine the synergistic activity of amikacin/ertapenem, fluoroquinolones (ciprofloxacin and levofloxacin)/ertapenem and amikacin/fluoroquinolones combinations against resistant nosocomial pathogens. METHODS: Time-kill studies were performed over 24 hours using an inoculum of 5 x 10(6) - 1 x 10(7) cfu/mL. Antibiotics were tested at the 1 x MIC and 4 x MIC concentrations. RESULTS: At MIC and/or 4 x MIC concentrations, the antibiotic combinations showed additive or synergistic activity against Acinetobacter strains and extended spectrum beta-lactamase producing Klebsiella pneumoniae. In Escherichia coli strains, synergy was seen when amikacin was combined with ertapenem, ciprofloxacin and levofloxacin; ertapenem in combination with fluoroquinolones demonstrated antagonism. In Pseudomonas aeruginosa strains, synergistic effect was exhibited by ertapenem plus amikacin and ertapenem plus fluoroquinolones. The antibiotic combinations showed antagonistic interaction in methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecalis. CONCLUSION: The antibiotic combinations showed additive or synergistic activity against many gram-negative pathogens.

Investigation of synergism of meropenem and ciprofloxacin against Pseudomonas aeruginosa and Acinetobacter strains isolated from intensive care unit infections.

The aim of this study was to determine synergistic effects of meropenem and ciprofloxacin against Pseudomonas aeruginosa and Acinetobacter strains isolated from intensive care unit (ICU) infections. A total of 18 P. aeruginosa and 17 Acinetobacter strains were tested. MICs were determined using the broth microdilution method. The synergy of meropenem and ciprofloxacin was investigated in glass tubes using time-kill methodology. The synergistic effect of meropenem and ciprofloxacin in combination was found to be 22% at 0.5 x the MIC and 61% at 1 x the MIC in P. aeruginosa strains. Two strains (11%) showed synergy at both 0.5 and 1 x the MIC. Of the 18 P. aeruginosa strains, 1 strain (6%) did not show a synergistic effect at either 0.5 or 1 x the MIC. In Acinetobacter strains, the synergistic effect of meropenem and ciprofloxacin in combination was found to be 29% at 0.5 x the MIC and 18% at 1 x the MIC. One strain (6%) showed synergy at both 0.5 and 1 x the MIC. Of the 17 Acinetobacter strains, 8 strains (47%) did not show a synergistic effect at either 0.5 or 1 x the MIC. According to the results of this study, the combination of meropenem and ciprofloxacin is more effective than either antibiotic alone in ICU infections due to P. aeruginosa strains.

Use of nucleic acid probes for identification of Mycobacterium tuberculosis directly from MB/BacT bottles.

The feasibility of using nucleic acid probes directly from positive MB/BacT broth to identify mycobacteria was determined in this study. A total number of 2,727 specimens were cultured into the MB/BacT (Organon Teknika) automated system and on conventional Loweinstein-Jensen (LJ) slants. The Gen-Probe AccuProbe culture identification tests (DNA probes) were used on samples from bottles which were identified as positive for mycobacteria by MB/BacT. Samples of positive MB/BacT broth (0.1 ml) were used directly in the broth culture method for the DNA probes as published by Gen-Probe. Centrifugation of the contents of the bottle was not done prior to probe testing. The number of mycobacteria detected by MB/BacT and LJ was 253 (221 isolates of M. tuberculosis and 32 isolates of mycobacteria other than M. tuberculosis [MOTT]). A total of 96.4% (213 of 221) of the bottles growing M. tuberculosis produced a positive direct DNA probe result for M. tuberculosis complex. One hundred percent (16 of 16) of the bottles growing M. gordonae produced a positive direct DNA probe result for M. gordonae. A total of 3.6% (8 of 221) of the bottles growing M. tuberculosis did not yield a positive direct DNA probe result for M. tuberculosis complex. The testing of subcultures made onto solid media from the positive bottles by AccuProbe identified six of these eight M. tuberculosis isolates. Two (0.9%) M. tuberculosis isolates gave a negative result for the M. tuberculosis probe test applied on the MB/BacT broth and its subculture. The rest of the positive MB/BacT bottles growing MOTT (16 of 32) were negative for M. gordonae, M. avium, M. intracellulare, and M. kansasii probes. The sensitivity and specificity of AccuProbe for the identification of M. tuberculosis and M. gordonae directly from MB/BacT broth were 96.4 and 100% for M. tuberculosis and 100 and 100% for M. gordonae, respectively. The direct testing of positive MB/BacT broth by AccuProbe, without prior centrifugation, allows for the accurate and rapid identification of M. tuberculosis and M. gordonae.