[Clinical relevance of gram-negative bacteria having inducible chromosomic beta-lactamase at an intensive care unit].
BACKGROUND
The aim of the study was to determine the frequency of third-generation cephalosporins and aztreonam resistance in gram-negative bacteria with inducible chromosomal beta-lactamase (beta Lac-ind) after beta-lactam therapy in the medical-surgical intensive care unit (ICU) at a university-affiliated hospital.


METHODS
We studied 34 infections in 29 patients admitted to the ICU. All were infected by strains with beta Lac-ind and all were treated with beta-lactam antibiotics. Susceptibility was determined by disc-diffusion. The beta-lactamase activity of those strains showing constitutive beta-lactamase overproduction were characterized by isoelectrofocusing. When this derepression occurred during the therapy, the strains were compared by genomic macrorestriction (PGFE).


RESULTS
In 29 out of 34 infections the initial strains was susceptible. In 11 cases, the culture were not negativized in spite of their susceptible pattern. In 4 cases there was derepression during therapy. In 5 cases the initial strains were derepressed. The microorganisms isolated more frequently were Pseudomonas aeruginosa (22 cases) and Enterobacter cloacae (5 cases). The beta-lactamase activity detected correspond well with a betaLac-ind. In those cases with derepression during therapy, the initial susceptible strain and the resistant strain were identical by PGFE.
Navarro
F
F
Servicio de Microbiología, Hospital de la Santa Creu i Sant Pau, Universitat Autònoma de Barcelona.
Alonso
C
C
Ballús
J
J
Miró
E
E
March
F
F
Coll
P
P
Mirelis
B
B
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001398:Aztreonam / Q000494:pharmacology*; D018550:Cephalosporin Resistance; D002648:Child; D002675:Child, Preschool; D005260:Female; D005500:Follow-Up Studies; D006090:Gram-Negative Bacteria / Q000187:drug effects / Q000235:genetics*; D016905:Gram-Negative Bacterial Infections / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D008997:Monobactams / Q000494:pharmacology*; D011446:Prospective Studies; D001618:beta-Lactamases / Q000235:genetics*
D008997:Monobactams; D001618:beta-Lactamases; D001398:Aztreonam
Relevancia clínica de las bacterias gramnegativas que poseen betalactamasa cromosómica inducible en una unidad de cuidados intensivos.