Epidemiology and infection control implications of Acinetobacter spp. in Hong Kong

Abstract

In a previous study, we showed that Acinetobacter genomic DNA group 3 was the most common species among blood culture isolates and was commonly found on superficial carriage sites of the healthy and the sick, which are different findings from those reported in Europe and North America. We used amplified ribosomal DNA restriction analysis and pulsed-field gel electrophoresis to study further the molecular epidemiology of acinetobacters in our region. Over a study period of 6 weeks with 136 consecutive routine clinical isolates (1.33% of all specimens), genomic DNA groups 2 (Acinetobacter baumannii), 3, and 13TU were obtained from 59 of 69 positive patients. There is a significant difference in the specimen sources of the three genomic DNA groups, with group 13TU being significantly associated with the respiratory tract (chi-square exact test, P = 0.0064). Settle plates showed a significantly heavier environmental load from the intensive care unit (ICU) than from the four surgical wards examined (22 of 70 versus 76 of 120 plates with <5 colonies; chi-square test, P < 0. 0001). Genomic group 3 accounted for 6 of 12 clusters of possibly related strains among patients, between patients and the ICU environment, and in the ICU environment. Genomic groups 2 and 3 accounted for 21% of the 132 genomically identified isolates recovered from 21 of 41 local vegetables, 53 of 74 fish and meat samples, and 22 of 60 soil samples. Group 13TU was present only in patients' immediate surroundings. The role played by the environment and by human carriage should be evaluated in order to devise a cost-effective infection control program pertinent to our situation of acinetobacter endemicity.

FIG. 1

Dendrogram and fingerprints of 15 isolates of genomic DNA group 13TU obtained by PFGE, showing two clusters of clinical isolates (SLC, SCL, and WC; SA and CKN) and one cluster of two clinical isolates (FY and SA) with one environmental isolate (E6A), with a Dice coefficient of similarity of ≥70%. First column, isolate identification; second column, date of isolation (year-month-day); third column, source of isolate. E4B, E6, E6A, environmental isolates; TA, tracheal aspirate; CIV, central intravenous catheter; SP, sputum.