Abstract:
Acinetobacter baumannii is an opportunistic pathogen that is increasingly responsible
for hospital-acquired infections. The increasing prevalence of carbapenem resistant
A. baumannii has left clinicians with limited treatment options. Last line antimicrobials
(i.e., polymyxins and glycylcyclines) are often used as treatment options. The aim
of this study was to determine the prevalence of selected b-lactamase genes from
A. baumannii isolates obtained from patients with hospital-acquired infections and
to determine the genetic relationship and epidemiological profiles among clinical
A. baumannii isolates collected from two tertiary academic hospitals in the Tshwane
region, South Africa (SA). Multiplex-PCR (M-PCR) assays were performed to detect
selected resistance genes. The collected isolates’ genetic relatedness was determined
by using pulsed field gel electrophoresis (PFGE) and multilocus sequence typing (MLST).
The acquired oxacillinase (OXA) genes, notably blaOXA-23-like were prevalent in the
A. baumannii isolates. The M-PCR assays showed that the isolates collected from
hospital A contained the OXA-23-like (96%; n = 69/72) genes and the isolates collected
from hospital B contained the OXA-23-like (91%; n = 63/69) and OXA-58-like (4%;
n = 3/69) genes. Colistin resistance was found in 1% of the isolates (n = 2/141) and
tigecycline intermediate resistance was found in 6% of the isolates (n = 8/141). The
A. baumannii isolates were genetically diverse. Molecular epidemiological data showed
that specific sequence types (STs) (ST106, ST229, ST258 and ST208) were established
in both hospitals, while ST848 was established in hospital A and ST502, ST339 and
the novel ST1552 were established in hospital B. ST848 (established in hospital A) was
predominately detected in ICU wards whereas ST208, ST339 and the novel ST1552 (established in hospital B) were detected in ICUs and the general wards. The origin of the
A. baumannii isolates in the hospitals may be due to the dissemination and adaptation
of a diverse group of successful clones. Poor infection control and prevention strategies
and possibly the overuse of antimicrobials contributed to the establishment of these
A. baumannii clones in the studied hospitals.
