Caracterización fenotípica y genotípica de la resistencia a meticilina de cepas de Staphylococcus aureus aisladas en Antofagasta / Phenotypic and genotypic characterization of methicillin resistance in strains of Staphylococcus aureus isolated in Antofagasta

Staphylococcus aureus resistant to methicillin (SARM) has been associated with nosocomial infections due to its capacity to develop resistance to multiple antibiotics. There is little information about the SARM which are found in the hospital services of Antofagasta. We studied the phenotypic and genotypic characteristics of methicillin resistance in 38 strains of S. aureus isolated in Antofagasta, identified by coagulase and API Staph tests and by a biochemical test (Ph-system). The susceptibility to antibiotics was studied using the agar dilution technique, identifying SARM strains with discs of oxacillin. Beta-lactamase with nitrocephine, and the gene mecA by means of PCR. Eighty nine percent (34 strains) were SARM with a high resistance to ampicillin, penicillin, erythromycin, claritromycin. gentiamycin, amikacine and ciprofloxacine. All isolates were susceptible to vancomycin and rifampicin. Beta-lactamase was demonstrated in 79% of the SARM strains. Strain typing and resistance patterns revealed a great diversity of PhP-types and antibiotypes in the isolates. Ninety seven percent of the SARM strains had the gene mecA. One PhP-type (C6) was dominant (5 SARM strains) all had the mecA gene, produced beta lactamase and had the same pattern of antibiotic resistance. We conclude that the dominant phenotypes of SARM strains which have the mecA gene and multiple resistance to antibiotics are present in the hospitals of Antofagasta, and sound the alert on the risk of nosocomial transmission of epidemic clones of SARM.

Staphylococcus aureus resistentes a meticilina (SARM) han sido asociados con infecciones nosocomiales por su capacidad para desarrollar resistencia a múltiple antibióticos, existiendo escasa información acerca de SARM que están circulando en los servicios hospitalarios de Antofagasta. Se estudió características fenotIpicas y genotípicas de la resistencia a meticilina en 38 cepas de S. aureus aisladas en Antofagasta, identificadas por tests de coagulasa y API Staph y por tipificación bioquímica (Ph-Sistem). La susceptibilidad a antibióticos se realizo por técnica de dilución en agar, las cepas SARM fueron identificadas con discos de oxacilina, beta-lactamasa por nitrocefina y gen mecA fue detectado pot PCR. El 89% (34 cepas), fueron SARM con una alta resistencia a ampicilina, penicilina, eritromicina, gentamicina, amikacina y ciprofloxacino. Todos los aislados fueron susceptibles a vancomocina y rifampicina. Beta lactamasa fue demostrada en 79% de las cepas SARM. La tipificación y los patrones de resistencia revelaron una alta diversidad de PhP tipos y antibioticos en los aislamientos. El 97% de las cepas SARM albergaban el gen mecA. Un PhP tipo (C6) fue dominante. (5 cepas SARM), todos presentando el gen mecA, produciendo beta lactamasa y mostrando el mismo patrón de resistencia antibiótica. Se concluye que los fenotipos dominantes de cepas SARM que albergan el gen mecA y resistencia múltiples alos antibióticos están circulando en los hospitales de Antofagasta, alertando sobre el riesgo de transmisión intranosocomial de clones epidémicos de SARM.

Resistencia a antimicrobianos en cepas de Enterococcus sp aisladas en hospitales del norte de Chile / Resistance to antimicrobial drugs in Enterococcus sp strains isolated in hospitals of Northern Chile

Se estudió la prevalencia de diferentes especies de Enterococcus y su resistencia a antimicrobianos en cepas aisladas en 5 hospitales del norte de Chile. Un total de 249 cepas de Enterococcus spp fueron incluidas en el estudio. Las principales fuentes de obtención fueron muestras de orinas y heridas operatorias. Se identificaron 5 especies de Enterococcus, siendo E. faecalis y E. faecium las especies aisladas con mayor frecuencia en todos los hospitales. Se observó una alta susceptibilidad a los antimicrobianos β-lactámicos, resistencia moderada a tetracilina, ciprofloxacina y eritromicina, y resistencia elevada a cloranfenicol. No se detectó resistencia a vancomicina y aproximadamente, 12% de las cepas de Enterococcus sp presentó resistencia a altas concentraciones de gentamicina. En 30% del total de las cepas de Enterococcus estudiadas se observó resistencia a 3 y más antimicrobianos.

[Resistance to antimicrobial drugs in Enterococcus sp. strains isolated in hospitals of Northern Chile]. / Resistencia a antimicrobianos en cepas de Enterococcus sp aisladas en hospitales del norte de Chile.

The prevalence of different species of Enterococcus and the resistance to antimicrobial drugs was studied in strains isolated in 5 hospitals of Northern Chile. A total of 249 of Enterococcus spp strains were included in this study. Enterococci were mostly isolated from urine and wounds. Among five species identified, E. faecalis and E. faecium were most frequently isolated in the all hospitals. High susceptibility to beta-lactam antibiotics, moderate resistance to tetracycline, ciprofloxacin and erythromycin, and high resistance to chloramphenicol was observed. Vancomycin resistance was absent. Approximately 12% of Enterococcus spp strains presented high level of gentamicin resistance. Multiresistance to 3 or more antimicrobial agents was detected in 30% of total Enterococcus strains studied.

Prevalencia de Enterococos resistentes a antibióticos en aguas servidas en el norte de Chile / Prevalence of antibiotic resistant Enterococcus spp in waste waters in the north of Chile

Background: There is little information available in Chile on the distribution of Enterococcus spp in waste water and its implications in transmission of antibiotic resistance through the water cycle. Enterococcus spp are common in nosocomial infections and may spread antibiotic resistance through the food chain. Aim: To determine the presence of antibiotic resistant Enterococcus spp in the sewage of Antofagasta, Chile. Material and Methods: Samples of sewage from two sewage treatment plants and from the Public Hospital of Antofagasta collector were obtained. Enterococcus spp were isolated on m-Enterococcus agar containing ampicillin, vancomycin and streptomycin. The isolates were identified and subjected to biochemical typing (PhPlate). Minimal inhibitory concentration determination was performed by agar dilution technique. Results: High counts of resistant Enterococcus spp were found on the streptomycin plates, lower on ampicillin and very low on vancomycin plates. A total of 63 Enterococcus spp strains were typed and the identification showed 5 different species; E faecalis (65%), E faecium (14%), E hirae (13%), E durans (6%) and E gallinarum (2%). The typing revealed a high diversity among the isolates. Two biochemical phenotypes were predominant, C1 (21 strains) and C6 (7 strains). Both were highly resistant to gentamycin and streptomycin; moderately resistant to ampicillin, cloramphenicol, tetracycline and ciprofloxacin, and with intermediate susceptibility to vancomycin. Both phenotypes were found in the sewage of the hospital collector and in the treatment plants. Conclusions: In the sewage of Antofagasta we found dominating phenotypes of multiresistant Enterococcus spp. Sewage could be an important way of transmission of these microorganisms.

Resistencia a antimicrobianos en diferentes biotipos de acinetobacter baumannii aislados en el norte de Chile / Antimicrobial resistance of different acinetobacter baumannii biotypes isolated in the northern region of Chile

Background: Acinetobacter baumannii nosocomial outbreaks are common and the microorganism is frequently resistant to multiple antimicrobials. There is little information about Acinetobacter baumannii antimicrobial susceptibility in the northern region of Chile. Aim: To identify different Acinetobacter baumannii biotypes isolated from clinical samples and to determine their antimicrobial susceptibility. Material and methods: One hundred twenty three Acinetobacter baumannii isolates were studied. The identification and typing of Acinetobacter baumannii was based on phenotypic characteristics. Antimicrobial susceptibility was investigated using agar dilution techniques. Results: Most Acinetohacter baumannii strains were isolated from wounds, urinary and respiratory infections. Seven biotypes were isolated, being biotype 9 the most frequent. lmipenem was the antimicrobial with the higher activity against the microorganism. Amikacin, cefoperazonesulbactam, ampicillinsulbactam and ceftazidime had a moderate activity. There were high resistance levels to ampicillin and older cephalosporins. Conclusions: Acinetobacter baumannii is emerging as a significant nosocomial pathogen in Chile and shows high resistance rates to multiple antibiotics