Evaluation of Acinetobacter baumannii Infection and Colonization, and Antimicrobial Treatment Patterns in an Urban Teaching Hospital

Abstract

In 1990 there was a sudden increase in the incidence of colonization and infection due to Acinetobacter baumannii (AB) in our intensive care units (ICUs). The isolates were multiply resistant to beta-lactam and aminoglycoside antibiotics, but remained susceptible to imipenem, amikacin, and ampicillin-sulbactam. We examined the frequency of infection and colonization with AB and the effects of increased imipenem and amikacin therapy on Pseudomonas aeruginosa. We also used disease-matched controls to determine the clinical and financial impacts of treating colonization. All patients with at least one AB isolate from January-December 1992 were identified retrospectively and classified as infected or colonized based on published Centers for Disease Control criteria; the control group was selected from a computerized medical records data base matching primary diagnostic codes (102 patients both groups). The 102 patients yielded 140 isolates, 124 resistant AB and 16 sensitive AB. Thirty three patients were infected, 69 colonized. Mortality correlated with APACHE II scores. Patients acquired the organism approximately 2 weeks after admission; they had a mean ICU stay of 27.35 days, compared with 5.53 days for controls. Patients with positive AB cultures required significantly more use of ventilators than those with negative AB cultures. They also had significantly longer hospital stay, more bed transfers, greater duration and number of antibiotics, and higher hospital and pharmacy charges. Unnecessary treatment for colonization with either imipenem or amikacin resulted in a substantial decrease of P. aeruginosa susceptibility to each agent. The financial impact of treating colonization was significant and is a potential area for cost avoidance. Our results emphasize the need to extubate and move patients to non-ICU beds as soon as possible to decrease the risk of nosocomial infection. It also highlights the need to avoid treating colonization, thus avoiding unnecessary antibiotic therapy.

Antimicrobial treatment and clinical outcome for infections with carbapenem- and multiply-resistant Acinetobacter baumannii around London

“…A small excess mortality in bacteraemia is compatible with our results. Four studies [20][21][22][23] pooled infected and colonised ICU patients as 'cases', matching these to Acinetobacter-free ICU controls and finding 16-30% excess mortality (P < 0.001 to 0.046) in the colonised/infected group. Strikingly, 138/241 (57%) of the 'cases' in these studies were classed as colonised, not infected, and since true colonisation cannot be harmful, the excess mortality can only be rationalised if: (i) infection has a very high excess mortality, which seems unlikely; (ii) the distinction between infection and colonisation is unreliable; or (iii) some factor not identified in the matching increased both mortality risk and vulnerability to colonisation by A. baumannii.…”

Extensively drug-resistant Acinetobacter baumannii: risk factors for acquisition and prevalent OXA-type carbapenemases—a multicentre study

“…This pathogen affects severely ill patients and causes a wide spectrum of problems, from skin and wound infections to sepsis [19]. Acinetobacter baumannii was previously considered an opportunistic pathogen of relatively low virulence [20]. However, recent reports from various locations around the world suggest that A. baumannii is now frequently isolated and is associated with severe infections and adverse outcomes [21][22][23].…”

Impact of rapid identification of Acinetobacter Baumannii via matrix-assisted laser desorption ionization time-of-flight mass spectrometry combined with antimicrobial stewardship in patients with pneumonia and/or bacteremia

“…excess costs of treatment ranging from $8,480-$168,648 [2,3]. Currently approximately 63% of AB in the U.S. is considered MDR, making the administration of timely, effective antimicrobial therapy challenging [1].…”