Identification of acinetobacters on blood agar in presence of D-glucose by unique browning effect

Polymicrobial Outbreak of Intermittent Peritoneal Dialysis Peritonitis during External Wall Renovation at a Dialysis Center

Objective

To investigate an outbreak of peritonitis in intermittent peritoneal dialysis (IPD) patients.

Design

An outbreak investigation was performed to identify the etiology of the polymicrobial outbreak, and a retrospective case-control study was conducted to assess the risk factors for development of peritonitis.

Setting

Renal dialysis center.

Patients

Ten episodes of peritonitis occurred in 8 of 61 patients over a 6-month period in which 669 IPD procedures were analyzed.

Interventions

Field visit to renal dialysis center to examine the entire IPD procedure, inspect the hospital environment, and perform air bacterial count.

Main Outcome Measures

The environmental factors and risk factors contributing to the polymicrobial peritonitis outbreak in IPD patients. The incidence of IPD peritonitis was determined before and after interventions.

Results

The causative organisms included Acinetobacter baumanii ( 6 ), Stenotrophomonas maltophilia ( 2 ), Pseudomonas aeruginosa ( 1 ), Candida albicans ( 1 ), C. tropicalis ( 1 ), Enterococcus ( 3 ), and Enterobacteriaceae ( 2 ). Four episodes of peritonitis involved infection by more than one organism. Air sampling of the environment detected a median of 110 colony forming units of bacteria per cubic meter of air, 10% of which were found to be Acinetobacter baumanii. The source of this polymicrobial outbreak was attributed to the bamboo scaffolding structure covering the external wall of the hospital during renovation. A retrospective case-control study indicated that the absence of the flush-before-fill step was a risk factor for development of peritonitis.

Conclusion

In addition to invasive aspergillosis in transplant or oncology patients, Acinetobacter peritonitis in dialysis patients should be considered another microbial cause of outbreak associated with hospital renovation.

Epidemiology and clonality of multidrug-resistant Acinetobacter baumannii from a healthcare region in Hong Kong

We assessed the risk factors and molecular epidemiology of multidrug-resistant Acinetobacter baumannii (MDR-AB) in Hong Kong. The patients were treated in five hospitals in a healthcare region during 2005-2006. We performed genomic identification by amplified rRNA gene restriction analysis (ARDRA) and investigated the existence of metallo-beta-lactamases and the clonality of representative MDR-AB strains by phenotypic and molecular methods. Forty-five subjects with MDR-AB were compared with 135 controls (patients with no MDR-AB). In the logistic regression, chronic wound (odds ratio: 29.5, 95% confidence interval: 8.1-107.2; P<0.001) was the only factor independently associated with MDR-AB colonisation or infection. ARDRA identified all 45 MDR-AB as genomic species 2TU. Pulsed-field gel electrophoresis clustered all except two isolates into two clonal types, designated HKU1 and HKU2 with 24 and 19 isolates, respectively. The main features of HKU1 strains were ST26, adeB type XII, positivity for bla(OxA-23-like) and bla(OxA-51-like) genes and high level resistance to carbapenems. Most HKU1 strains retained susceptibility to gentamicin, cotrimoxazole and minocycline. By contrast, HKU2 strains exhibited ST22, adeB type II, and were usually positive only for the bla(OxA-51-like) gene and resistant to gentamicin, cotrimoxazole and minocycline. Both clones were found to have disseminated widely. In conclusion, clonal expansion is playing major roles in the increase of MDR-AB in these hospitals in Hong Kong. The findings highlight the need to enhance infection control measures.