Acinetobacter baumannii: An Emerging Multidrug-resistant Threat

Thomas D Gootz; Andrea Marra

Disclosures

Expert Rev Anti Infect Ther. 2008;6(3):309-325. 

In This Article

Recent Surveillance Studies that Define the Problem of Antibiotic Resistance

Many studies have documented the rise of antibiotic resistance in clinical isolates of A. baumannii on a global scale. As an example, ongoing surveillance studies from hospitals in New York City (NY, USA)[62] indicate that the percentages of A. baumannii remaining susceptible to piperacillin-tazobactam, ceftazidime, cefepime, imipenem, meropenem and ciprofloxacin have decreased between 1999 and 2006. In the case of imipenem, the percentage of susceptible isolates determined in 1999, 2001 and 2006 decreased from 67, to 63 and 37%, respectively. By 2006, only 9% of A. baumannii tested were susceptible to ciprofloxacin.[62] In another recent surveillance study from the USA including 1026 A. baumannii, 27.5% were resistant to three or more classes of antibiotics.[63] Resistant strains were collected from 27 states across the USA, with the most common phenotype observed being resistance to cefepime, ceftriaxone, ceftazidime, piperacillin-tazobactam and levofloxacin. Studies from hospitals in Greece monitoring resistance from 1996 to 2006 found significant increases in the percentages of imipenem-resistant strains isolated from ICUs, medical wards and surgical wards from 0-91, 8-71 and 5-71%, respectively.[64] Two studies from Spain found that outbreaks of carbapenem-resistant A. baumannii strains had become endemic through the rapid dissemination of the original clone in many hospitals, followed by the introduction of new MDR strains.[65,66] A study from China found that, between 1996 and 2002, the prevalence of MDR isolates of this species increased from 17.6 to 39.5%.[67]

Associated with the rise in global antibiotic resistance in A. baumannii has been an increase in the prevalence of human infections in some regions. A large study conducted in ICUs in the USA over 12 years indicated that, out of 74,394 Gram-negative bacilli collected, A. baumannii ranked fifth in frequency, at 6.2%.[68] Over this study period, mean rates of resistance increased in this species to nine out of 12 antibiotics tested. Rates of resistance steadily increased to ciprofloxacin, amikacin, piperacillin-tazobactam and ceftazidime from 1995 to 2004.

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