[Class 1 integrons in Enterobacteriaceae and its association with multidrug resistance and conjugative plasmids]. / Asociación entre integrones de clase 1 con resistencia a múltiples antimicrobianos y plásmidos conjugativos en Enterobacteriaceae.

The prevalence of antimicrobial resistance genes is a cause of concern. The combination of antimicrobial resistance genes and mobile genetic elements leads to their widespread presence in different bacterial species, in which integrons are a new and important element. We studied the presence of integrons in 123 unrelated enterobacteria and identified them in 20.3% of the strains. The combination of integrons and multidrug resistance was shown to be statistically significant (p <0.001). Integron-positive isolates were statistically (p <0.05) more likely to be resistant to amoxicillin-clavulanic acid, quinolones and trimethoprim-sulfamethoxazole. All the integrons were identified in conjugative plasmids. The prevalence of integrons increased from 21.2% in 1992-1994 to 72% in 1995-1997 (p <0.001). The aacC1 and aacC2 genes were identified in 80% of the integrons. The relationship between integrons and conjugative plasmids is a matter of concern because it could contribute to the dissemination of antimicrobial resistance genes among different bacterial populations.

In vitro activity of telithromycin against mefA and ermB erythromycin-resistant viridans streptococci isolated from bacteremia of oral origin in Spain.

Erythromycin-resistant viridans streptococci are often responsible of bacteremias following dental manipulations. The aim of this study was to evaluate the in vitro activity of telithromycin against erythromycin-susceptible and erythromycin-resistant viridans streptococci. Venous blood samples were collected from 84 patients, 30 s after dental extractions. Viridans streptococci were identified by conventional microbiological techniques. A set of 36 viridans streptococci were selected to investigate the in vitro activity of telithromycin by the agar dilution method. Macrolide resistance genes were amplified with specific primers for the mefA and ermB genes and visualized by electrophoresis. For erythromycin-susceptible viridans streptococci, telithromycin minimal inhibitory concentration90 (MIC90) was <0.008 microg/ml. For erythromycin-resistant viridans streptococci, telithromycin MIC90 was 1 microg/ml. The MIC90 to telithromycin of the mefA-positive and ermB-negative viridans streptococci was lower than that of the mefA-negative and ermB-positive viridans streptococci (0.128 microg/ml versus 1 microg/ml). The in vitro activity of telithromycin was high, irrespective of the erythromycin susceptibility and the mechanism of erythromycin resistance identified.

In vitro activity of moxifloxacin compared to other antimicrobials against streptococci isolated from iatrogenic oral bacteremia in Spain.

BACKGROUND/AIMS: Systemic dissemination of oral bacteria to distant body sites may be the cause of focal infections. The unsuitable use and overexposure to antimicrobial therapy in clinical dental practice may contribute to the worldwide problem of antimicrobial resistance. The aim of this study was to determine the susceptibilities of streptococci isolated from the bloodstream after dental extractions against penicillin, ampicillin, amoxicillin, erythromycin, clindamycin, and a new fluoroquinolone, moxifloxacin. PATIENTS AND METHODS: Eighty-four patients who required dental extractions were studied. Venous blood samples were collected from each patient at baseline (before dental manipulation) and 30 s after dental extractions. The samples were processed in the Bactec 9240. The isolated bacteria were identified by conventional microbiological techniques. The antimicrobial susceptibility of 81 streptococci was determined by the E-test method. The NCCLS performance standards were followed. RESULTS: 88.9-92.5% of the streptococci were sensitive to beta-lactam agents tested with a minimum inhibitory concentration (MIC)(90s) ranging from 0.094 to 0.19 mg/l. The resistance to erythromycin and clindamycin was 40.8% (MIC(90HR) = 256 mg/l) and 21% (MIC(90HR) = 256 mg/l), respectively. The MIC(90) to moxifloxacin was 0.125 mg/l. CONCLUSION: Most of the streptococci isolated from the bloodstream after dental extractions were susceptible in vitro to penicillin, ampicillin, and amoxicillin. The high percentage of streptococci resistant to erythromycin and clindamycin could restrict their usefulness as prophylactic drugs. All the isolates showed a low MIC of moxifloxacin in vitro, making it a promising antimicrobial alternative for the prevention of streptococcal focal infections associated with certain dental manipulations, when the administration of beta-lactam agents is not indicated.

Asociación entre integrones de clase 1 con resistencia a múltiples antimicrobianos y plásmidos conjugativos en Enterobacteriaceae / Class 1 integrons in Enterobacteriaceae and its association with multidrug resistance and conjugative plasmids

La amplia diseminación de genes de resistencia a antimicrobianos es motivo de preocupación. La asociación de los genes de resistencia con elementos génicos móviles favorece su presencia en distintas especies de bacterias, siendo los integrones un elemento importante. En este trabajo se estudia en 123 enterobacterias la presencia de integrones, identificándose éstos en el 20,3 por ciento de las cepas. La asociación entre integrones y resistencia múltiple a antimicrobianos fue estadísticamente significativa (p <0.001). Los aislamientos con integrones fueron con mayor frecuencia, estadísticamente significativa (p <0.05), resistentes a amoxicilina-ácido clavulánico, quinolonas y trimetoprima-sulfametoxazol. Todos los integrones formaban parte de plásmidos conjugativos. La prevalencia de integrones se incrementó del 21,2 por ciento en 1992-1994 al 72 por ciento en 1995-1997 (p <0.001). Los genes aacC1 y aacC2 se identificaron en el 80 por ciento de los integrones. La relación entre integrones y plásmidos conjugativos debe preocuparnos, ya que podría contribuir a la diseminación de los genes de resistencia a antimicrobianos entre diferentes poblaciones bacterianas (AU)