BACKGROUND/OBJECTIVES: A hospital-wide increase of ACBA colonization and infection was noted. The mean rate significantly changed from period 1(January to October 2003) to period 2 (November 2003 to May 2004), with an increase from 0.79 per 1000 patient days (k-pd) to 1.04 /k-pd (p=0.05). The greatest ACBA incidence was in the adult ICU (7.8 in ICU/5.4 in the non-ICU; RR=10) and was most frequently cultured from respiratory specimens (0.75 and 0.19 in the non-ICU; RR=27). The housewide crude mortality rate was 28%; for patients with ACBA in respiratory secretions it was 46%. Along with traditional control methods to increase attention to contact precautions, a program of microbiologic surveillance for ACBA was conducted.

METHODS: Weekly prevalence ACBA cultures were obtained from all patients in adult ICUs. Sputum was the preferred source, and the anterior nares site was the alternative. Previously positive ACBA cultures were noted at the time of collection. Sensitivity and negative predictive value (NPV) were calculated using the any positive cultures for ACBA as the “gold standard” for comparison.

RESULTS: During the program, 649 cultures were obtained, with 558 negative (86%) and 91 positive 14%). Among the positive results, 73 (80.2%) were from patients with previous ACBA. Of the 18 with newly recognized ACBA (19.8% of positives/ 2.7% of all cultures), 12 (67%) had surveillance cultures preceding clinical cultures, and 6 (33%) had only positive surveillance cultures. For the entire program, the sensitivity was 69% and the NPV was 93%; for sputum specimens, the results were 78% sensitivity and 93% NPV; for nasal cultures, the results were 51% sensitivity and 93% NPV. Specificity and positive predictive value could not be calculated because of the use of cultures as the “gold standard.”

CONCLUSIONS: An aggressive program aimed at early identification of ACBA, with the goal of decreased transmission, was logistically complicated and demanded extensive attention from nursing, laboratory, and infection control personnel. Because only 2.7% of all obtained cultures represented an otherwise unrecognized opportunity for potential transmission control, the program was discontinued until a more extensive cost benefit analysis can conducted. Results demonstrated that sputum cultures are superior to nasal cultures for ACBA surveillance.
Any Evidence of ACBASurveillance CulturesYesNoTotalPositive91091Negative40518558Total131518649