Resistencia bacteriana a antibióticos en el Hospital San Juan de Dios, 1995-1999

Justificación: La resistencia a antibióticos por parte de bacterias patógenas es un grave problema mundial. Su control ha sido difícil pero deben hacerse todos los esfuerzos por realizarlo. Conocer la epidemiología en las diferentes regiones y países se constituye en parte importante de este control. Este estudio se llevó a cabo con el fin de analizar el comportamiento de la resistencia en el hospital San Juan de Dios, centro de atención nacional de adultos de aproximadamente 700 camas.

Materiales y métodos: El estudio se basó en los datos obtenidos en los años 1995-1999 ya que en 1995 se inició el empleo de equipo automatizado VITEK® en este hospital. Se analizaron 2817 aislamientos de cocos Gram positivos (CGP) y 7626 de bacilos Gram negativos (BGN) obtenidos de todos los sitios anatómicos y fluidos corporales. Por ser un estudio retrospectivo, no se pudo definir cuáles aislamientos provenían de infecciones intra o extrahospitalarias.

Resultados: Staphylococcus aureus fue el CGP más frecuentemente aislado, mientras que el BGN más frecuente fue Escherichia coli. En más de 90% de los estafilococos aislados se demostró resistencia a la penicilina. La resistencia a la oxacilina en S.aureus se incrementó de 35% en 1995 a 52% en 1999 mientras que en los estafilococos coagulasa negativa, pasó de 70 a 77% en el mismo periodo. La resistencia a la cefalotina en S.aureus pasó de 35 a 50% mientras que en los estafilococos coagulasa negativa pasó de 65 a 76%. La resistencia a la clindamicina en ambos grupos bacterianos se mantuvo relativamente estable. No se demostró resistencia a la vancomicina.

La mayoría de los enterococos aislados correspondieron a E. faecalis, 75% de ellos fueron sensibles a la penicilina y 50% no mostraron sinergismo de la gentamicina con los antibióticos que actúan sobre la pared. No se encontraron enterococos vancomicina resistentes. En las enterobacterias se observó un aumento importante de la resistencia a cefalosporinas de tercera generación. E. coli mostró un aumento de la resistencia a ceftazidima de 10% en 1995 a 35% en 1999, mientras que Klebsiella pmeumoniae pasó de 0% a 52% para el mismo antibiótico en ese periodo. Con respecto a cefotaxima, mientras que en E.coli se incrementó la resistencia de 5 a 12%, en K. pneumoniae se modificó de 5 a 24%. Esto podría deberse a la presencia de ß-lactamasas de espectro ampliado. La sensibilidad a ciprofloxacina en E. coli al igual que en K. pneumoniae se mantuvo estable. En cuanto a amicacina, E.coli pasó de 0% de resistencia en 1995 a 15% en 1999 y K. pneumoniae de 20 a 32%. En Enterobacter cloacae se demostró aumento importante de la resistencia a cefalosporinas de tercera generación y a amicacina no así a la ciprofloxacina. En todas las enterobacterias se mantuvo una baja resistencia al imipenem.

En cuanto a BGN no fermentadores, se demostró en Pseudomonas aeruginosa un aumento de la resistencia a la mayoría de los antibióticos con excepción del imipenem y ceftazidima. No obstante Acinetobacter calcoaceticus presentó un incremento importante de la resistencia a amicacina (de 20 a 72%), a cefalosporinas de tercera generación (de 0 a 61%) y ciprofloxacina (57%), manteniendo alta sensibilidad sólo a imipenem (95%).

Background and aim: Antimicrobial resistance results in increased morbidity, mortality and costs of health care. Therefore, surveillance of antimicrobial resistance in hospitals must be part of infection control programs.

The Hospital San Juan de Dios is a tertiary health care center in Costa Rica with 700 beds for adults. Since 1995, an automatized system (VITEK®) is used in our bacteriology laboratory allowing an adequate control of the resistance patterns of bacterias isolated from different sites.

The aim of this report is to describe the susceptibility to some antibiotics found in bacterias isolated from different sites from 1995 to 1999 and to determine their changes in resistance.

Materials and Methods: Were reviewed. The files of the bacteriology laboratory of the hospital was done. We analized bacterial strains from 1995 to 1999. Data from 1996 were incomplete and were not studied. All isolates were analized in the automatized system VITEK®. Streptococcus pneumoniae strains from blood or sputum were studied by the E-test method and their sensitivity ranges met the NCCLS criteria.

Results: We studied 2817 Gram positive cocci (GPC) strains and 7626 isolates of Gram negative bacteria (GNB). Staphylococcus aureus was the most frequently GPC specie found and Escherichia coli was the most common GNB.

More than 90% of staphylococcal species produced ß-lactamase and were resistant to penicillin.

Resistance to oxacillin (methicillin) in Staphylococcus aureus increased from 35% to 52% in this period. In coagulase negative staphylococci the resistance to this antibiotic was very high (70-77%).

Susceptibility to cephalotin and clindamycin in Staphylococcus aureus was similarly high (50-60%) in the years studied and in coagulase negative staphylococci (Staphylococcus epidermidis) the resistance stayed in high levels (65-70%). There were not resistance to vancomycin in the staphylococci analyzed.

Ninety eight per cent of the 61 isolates of Streptococcus pneumoniae were susceptible to penicillin.

Susceptibility to penicillin was observed in 80% of 483 isolates of Enterococcus faecalis. Fifty percent of the enterococci showed synergism between gentamicin and cell-wall active agents.

Only a few isolates of Enterococcus faecuim were analized and no resistance to vancomycin was found. Resistance to aminoglycosides was demonstrated in 50% of enterococci isolates.

Regarding enterobacterias, Escherichia coli strains presented high resistance to ampicillin (60%), sulfa trimetoprin (60%) and a decrease in the susceptibility to ceftazidime from 90% in 1995 to 65% in 1999, to cefotaxime from 95% to 88%, from 67% to 57% to cephalotin and from 100% to 85% to amikacin in the same period. Resistance to ciprofloxacin was 10% in 1995 and 20% in 1999.

Regarding Klebsiella pneumoniae, resistance to amikacin increase from 20% to 32%, to ceftazidime from 0% to 52%, to cefotaxime from 5% to 24% but susceptibility to ciprofloxacin was high in the period (80-90%). Resistance to ampicillin was present in more than 90% of the K.pneumoniae isolates and to cephalotin in more than 50% of this bacteria.

Enterobacter cloacae showed high resistance patterns to ampicillin (>95%),cephalotin (> 90%) and ceftazidime (25-50%).

In non-fermenting Gram negative bacilli, resistance to amikacin (20%-72%) ceftazidime (42%-61%) and ciprofloxacin(58%) was documented in Acinetobacter calcoaceticus. In Pseudomonas aeruginosa an increase in the resistance to amikacin (15%-30%) and ciprofloxacin(20%-37%) were noted.

In all BGN strains studied, a high susceptibility pattern to imipenem (from 88% in Ps. aeruginosa and 95% in Ac. calcoaceticus to 100% in enterobacterias) were observed.

Discussion: We analized these findings and compared them with those found in the medical literature. High resistance patterns to penicillin and oxacillin in staphylococci strains were documented. High resistance in GNB to ampicillin, cephalotin, ceftazidime and ciprofloxacin was observed. High susceptibility patterns to imipenem in GNB were found.