Resistencia a los β -lactámicos en enterococos / Resistance to β-lactams in enterococci

Enterococci are intrinsically resistant to several antimicrobial classes and show a great ability to acquire new mechanisms of resistance. Resistance to β-lactam antibiotics is a major concern because these drugs either alone or in combination are commonly used for the treatment of enterococcal infections. Ampicillin resistance, which is rare in Enterococcus faecium occurs in most of the hospital-associated Enterococcus faecium isolates. High-level resistance to ampicillin in E. faecium is mainly due to the enhanced production of PBP5 and/or by polymorphisms in the beta subunit of this protein. The dissemination of high-level ampicillin resistance can be the result of both clonal spread of strains with mutated pbp5 genes and resistance horizontal gene transfer.

Los enterococos son intrínsecamente resistentes a varias clases de antimicrobianos y presentan una gran capacidad para adquirir mecanismos de resistencia. La resistencia a los antibióticos p-lactámicos es preocupante porque estos fármacos solos o combinados se usan comúnmente para el tratamiento de las infecciones enterocócicas. La mayoría de los aislamientos hospitalarios de Enterococcus faecium presentan resistencia a la ampicilina, la cual es rara en Enterococcus faecalis. El alto nivel de resistencia a la ampicilina en E. faecium se debe principalmente a la hiperproducción de PBP5 y/o a polimorfismos en la subunidad beta de esta proteína. La propagación de esta resistencia puede deberse tanto a la diseminación clonal de cepas con genes pbp5 mutados como a la transferencia horizontal de genes.

Resistencia a drogas antimicrobianas, en cepas de Haemophilus influenzae tipo b, aisladas de pacientes con síndrome neurológico infeccioso / Antimicrobial drug resistance in Haemophilus influenzae type b strains isolated from patients with infectious neurologic syndrome

Se estudió por primera vez la sensibilidad de 92 cepas de Haemophilus influenzae tipo b, a diferentes antimicrobianos : ampicillina, cloranfenicol, rifampicina, ceftriaxone (rocephin) y cefotaxime (claforán), por el método de dilución en placas de agar. Se encontró una mayor resistencia de las cepas estudiadas frente al ampicillina (42,39 por ciento ) y al cloranfenicol (58,69 por ciento ) y una alta sesibilidad frente a la rifampicina (100 por ciento ), Ceftriaxone (100 por ciento ) y Cefotaxime (100 por ciento )

Plasmid mediated multidrug resistance in Salmonella typhi.

Between September 1989 and February 1991, strains of S. typhi showing multiple drug resistance were isolated from blood cultures of patients with typhoid fever. A total of 283 isolates were obtained over a period of 18 months. Forty four (11%) of these isolates were resistant to chloramphenicol, ampicillin, co-trimoxazole and tetracycline, the first three being drugs currently used in treating typhoid fever. Forty of the 44 multi-resistant strains tested showed transfer of resistance 'en block' to recipient Escherichia coli K 12 (J62-2). All 44 multi-resistant strains were sensitive to ciprofloxacin and ofloxacin. Since the resistance is plasmid-mediated, the problem is likely to get aggravated.