RESUMO
Administration of either gentamicin or amikacin induced an increase in the number of amikacin-resistant (AR) isolates of certain Enterobacteriaceae and Acinetobacter species in a hospital in Buenos Aires. A total of 127 AR isolates was selected to study the molecular mechanisms of resistance involved. The aac(6')-Ic gene was found by dot-blot hybridisation in every Serratia marcescens isolate. A gene different from aac(6')-Ia, aac(6')-Ib and aac(6')-Ic encoding the AAC(6')-I activity was found in a 15.5-kb plasmid in Acinetobacter spp. Plasmids from 27 Enterobacteriaceae contained and aac(6')-Ib gene and 26 of these carried sequences related to the Tn1331 transposon, whereas one Escherichia coli plasmid showed homology in another fragment of the Tn1331 transposase. Because plasmids bearing the aac(6')-Ib gene were heterogeneous, dissemination of the aac(6')-Ib gene may have been due to transposition of Tn1331 rather than the spread of an epidemic plasmid. The rate of AR isolates varied within each species in spite of the presence of Tn1331, and it is likely, therefore, that this transposon may not be the sole factor responsible for the observed variation. The aph(3')-VIa gene (originally described in Acinetobacter spp.) was found with high frequency (80%) in this Acinetobacter population. Furthermore, this gene was found also in plasmids from 20% of other gram-negative organisms commonly involved in nosocomial infections in this hospital.
Assuntos
Amicacina/farmacologia , Infecção Hospitalar/microbiologia , Bactérias Gram-Negativas/efeitos dos fármacos , Infecções por Bactérias Gram-Negativas/microbiologia , Acinetobacter/efeitos dos fármacos , Acinetobacter/genética , Amicacina/uso terapêutico , Argentina , Infecção Hospitalar/tratamento farmacológico , DNA Bacteriano/análise , Resistência Microbiana a Medicamentos/genética , Enterobacteriaceae/efeitos dos fármacos , Enterobacteriaceae/genética , Gentamicinas/farmacologia , Gentamicinas/uso terapêutico , Bactérias Gram-Negativas/genética , Infecções por Bactérias Gram-Negativas/tratamento farmacológico , Humanos , Fatores RRESUMO
From January, 1990, to December 31, 1990, 75 children with multiply resistant Salmonella gastroenteritis were studied at the Children's Hospital "Ricardo Gutierrez" of Buenos Aires. These children ranged from 1 month to 15 years of age. Infection was community-acquired in 20 (26.6%), nosocomially acquired in 50 (66.7%) and undetermined in 5. Thirty-nine (52%) had grossly bloody stools. Fever occurred at some point in the clinical course in 61 children (81.3%) with a duration of 1 to 33 days (mean, 6.7 days). The duration of diarrhea (1 to 69 days) was longer in those who developed complications (P < 0.001). Six (8%) developed enterocolitis (2 with bowel perforation), 1 had a pulmonary abscess and 8 (11.4%) had bacteremia; 4 children died (5.3%). Salmonella typhimurium was the most common serovar (85.3%). Ninety percent minimum inhibitory concentration studies demonstrated that all strains were resistant to ampicillin (> 128 micrograms/ml), cephalothin (> 128 micrograms/ml), cefuroxime (> 128 micrograms/ml), nalidixic acid (> 256 micrograms/ml), rifampin (> 256 micrograms/ml), gentamicin (> 256 micrograms/ml) and tobramycin (256 micrograms/ml); 77.3% of strains were resistant to ceftazidime (32 micrograms/ml), 97.6% to netilmicin (> 256 micrograms/ml), 92.8% to amikacin (256 micrograms/ml), 24.4% to isepamicin (32 micrograms/ml), 5.3% to chloramphenicol (4 micrograms/ml) and 2.7% to cefoxitin (2 micrograms/ml). The 90% minimum inhibitory concentration of cefotaxime and ceftazidime was reduced by the addition of clavulanate. Aggressive multiply resistant Salmonella strains are a major pediatric problem in Buenos Aires.