The AdeABC pump of Acinetobacter spp. confers resistance to various antibiotic classes. This pump is composed of the AdeA, AdeB, and AdeC proteins where AdeB is a member of the resistance-nodulation-division efflux pump superfamily. The adeA, adeB, and adeC genes are contiguous and adjacent to adeS and adeR, which are transcribed in the opposite direction and which specify proteins homologous to sensors and regulators of two-component systems, respectively. In this study, an attempt is made to elucidate the role of the AdeABC efflux pump in carbapenem resistance in Acinetobacter spp.
Acinetobacter spp is a known nosocomial pathogen causing a wide range of clinical diseases such as pneumonia, wound infection and bloodstream infections (BSI). The clinical outcomes of acinetobacter BSI were determined by a 1:1 case control study involving 58 confirmed cases of acinetobacter BSI who were compared to other gram-negative infections. The crude mortality of acinetobacter BSI was 47.2%, which was significantly greater than other gram-negative BSI (OR 1.89, 95% CI 1.10-3.24) but there were no significant differences in attributed mortality between the two groups. We found that patients treated in intensive care units (ICU), who had longer ICU stays, who presented with shock or coagulopathy, had prior exposure to carbapenems, had mechanical ventilation, were on a ventilator for longer periods, had a nasogastric tube, had an arterial catheter or had parenteral nutrition at a significantly greater risk of mortality due to acinetobacter BSI. Patients presenting with septic shock (OR 17.95, 95% CI 3.36-95.84) or having a central venous catheter (OR 12.48, 95% CI 1.09-142.68) were independently at higher risk for mortality. Appropriateness of therapy reduced the mortality attributes of acinetobacter BSI (OR 0.197, 95% CI 0.040-0.967) but did not significantly reduce crude mortality in acinetobacter BSI patients. This study shows the importance of preventing acinetobacter BSI and the appropriate use of antimicrobial agents to reduce mortality.
Fluorescent in situ hybridization (FISH) was carried out using two different oligonucleotide probes specific for Pseudomonas spp. and Acinetobacter spp. These probes were tested against different organisms and were found to be highly specific. Sensitivity testing showed that the probes were able to detect as low as 10 3 CFU/mL. In addition, FISH was carried out directly on positive blood culture samples and the detection of microorganisms took less than 2 h. We believe that FISH is a rapid method that can be used as a routine laboratory diagnostic technique for the detection of Acinetobacter spp. and Pseudomonas spp. in clinical samples.
The antibiotic susceptibility profiles and the repetitive extragenic palindromic sequence-based polymerase chain reaction (REP-PCR)-determined genotypes of 109 Acinetobacter strains collected from the University Malaya Medical Center (UMMC), Kuala Lumpur, Malaysia, in 1987 (N=21) and 1996-1998 (N=88) were established. Twelve antibiotic susceptibility profiles of antibiotics used at the UMMC were obtained. In descending order of effectiveness, imipenem, amikacin and ciprofloxacin were the most effective against the Acinetobacter strains. Compared with 1987 isolates, the isolates obtained in 1996-1998 had decreased susceptibility to these antibiotics and were tolerant to the antibiotics up to an MIC90 of > or =256 mg/L. REP-PCR DNA fingerprints of all the isolates revealed the presence of four Acinetobacter spp. lineages; 92% of all the isolates belonged to two dominant lineages (genotypes 1 and 4). Genotype 4 isolates predominant in 1987 showed increased resistance and antibiotic tolerance to imipenem, amikacin and ciprofloxacin compared with the 1996-1998 isolates. In contrast, genotype 1 isolates from 1996-1998 were mainly sensitive to these antibiotics. These findings demonstrate the presence of at least two independent Acinetobacter spp. lineages in the same hospital, and suggest the possibility that genotype 4 Acinetobacter spp. acquired the resistance phenotype in situ, whereas most of the genotype 1 isolates were probably introduced to the hospital in recent years.
Acinetobacter calcoaceticus, a gram-negative bacterium ubiquitous in soil, water and sewage, is a rare cause of endocarditis in children. The first case of Acinetobacter endocarditis in an infant is described. This patient had underlying tetralogy of Fallot with absent pulmonary valve. A review of the literature in English revealed only four other cases of Acinetobacter endocarditis in children; three of whom had underlying congenital heart disease. Like the other reported cases, this patient responded well to antibiotic treatment. Subsequently this patient underwent corrective cardiac surgery but died of post-operative complications.