We may soon be facing the end of the "antibiotic era." The initial and seemingly unstoppable success of antibiotics, the fruit of human ingenuity, has been countered by an escalation of resistance mechanisms in bacteria. This crisis has been described as an "unwinnable war" (www.wellcome.org). The statistics compiled as a result of surveillance efforts illustrate the emergence of many genera of bacteria that are resistant to all antibiotics (57, 60). The genus Acinetobacter epitomizes this trend and deserves close attention. Acinetobacter spp. display mechanisms of resistance to all existing antibiotic classes as well as a prodigious capacity to acquire new determinants of resistance (7). The increasing recovery in the clinic of multidrug-resistant (MDR) Acinetobacter baumannii is a frightening reality (112). This review summarizes the worldwide emergence of antibiotic-resistant A. baumannii as a nosocomial pathogen and focuses on its mechanisms of resistance against selected antibiotics. It concludes with a summary of current strategies in the treatment of MDR A. baumannii and offers perspectives on the control of this global public health threat. GLOBAL EPIDEMIOLOGY A. baumannii is a nonfermentative, gram-negative, nonmotile, oxidase-negative bacillus, whose natural reservoir still remains to be determined. Nevertheless, it is found in many health care environments and is a very effective human colonizer in the hospital (www.cdc.gov). The combination of its environmental resilience and its wide range of resistance determinants renders it a successful nosocomial pathogen (137). As such, A. baumannii is emerging as a cause of numerous global outbreaks (213), displaying ever-increasing rates of resistance (Tables 1 and 2; Fig. 1). There are reports of MDR A.

In this outbreak of carbapenem-resistant A. baumannii and K. pneumoniae across a healthcare system, we illustrate the important role post-acute care facilities play in the dissemination of multidrug-resistant phenotypes.

Data are needed from outpatient settings to better inform antimicrobial stewardship. In this study, a random sample of outpatient antibiotic prescriptions by primary care providers (PCPs) at our health care system was reviewed and compared to consensus guidelines. Over 12 months, 3,880 acute antibiotic prescriptions were written by 76 PCPs caring for 40,734 patients (median panel, 600 patients; range, 33 to 1,547). PCPs ordered a median of 84 antibiotic prescriptions per 1,000 patients per year. Azithromycin (25.8%), amoxicillin-clavulanate (13.3%), doxycycline (12.4%), amoxicillin (11%), fluoroquinolones (11%), and trimethoprim-sulfamethoxazole (10.6%) were prescribed most commonly. Medical records corresponding to 300 prescriptions from 59 PCPs were analyzed in depth. The most common indications for these prescriptions were acute respiratory tract infection (28.3%), urinary tract infection (23%), skin and soft tissue infection (15.7%), and chronic obstructive pulmonary disease (COPD) exacerbation (6.3%). In 5.7% of cases, no reason for the prescription was listed. No antibiotic was indicated in 49.7% of cases. In 12.3% of cases, an antibiotic was indicated, but the prescribed agent was guideline discordant. In another 14% of cases, a guideline-concordant antibiotic was given for a guideline-discordant duration. Therefore, 76% of reviewed prescriptions were inappropriate. Ciprofloxacin and azithromycin were most likely to be prescribed inappropriately. A non-face-to-face encounter prompted 34% of prescriptions. The condition for which an antibiotic was prescribed was not listed in primary or secondary diagnosis codes in 54.5% of clinic visits. In conclusion, there is an enormous opportunity to reduce inappropriate outpatient antibiotic prescriptions.