Acinetobacter baumannii is an opportunistic pathogen and causes
various infections in patients. This study aimed to describe the clinical,
epidemiological and molecular characteristics of A. baumannii isolated
from BCs in patients at a tertiary-level hospital in South Africa. Ninety-six
isolates from bloodstream infections were collected. Clinical characteristics
of patients were recorded from patient files. Organism identification and
AST was performed using automated systems. PCR screening for the mcr-1
to mcr-5 genes was done. To infer genetic relatedness, a dendrogram
was constructed using MALDI-TOF MS. All colistin-resistant isolates (n = 9)
were selected for WGS. The patients were divided into three groups, infants
(<1 year; n = 54), paediatrics (1–18 years; n = 6) and adults (≥19 years;
n = 36) with a median age of 13 days, 1 and 41 years respectively. Of the 96
A. baumannii bacteraemia cases, 96.9% (93/96) were healthcare-associated.
The crude mortality rate at 30 days was 52.2% (48/92). The majority of the
isolates were multidrug-resistant (MDR). All isolates were PCR-negative for
the mcr-1 to mcr-5 genes. The majority of the isolates belonged to cluster
1 (62/96) according to the MALDI-TOF MS dendrogram. Colistin resistance
was confirmed in nine A. baumannii isolates (9.4%). The colistin-resistant
isolates belonged to sequence type (ST) 1 (5/6) and ST2 (1/6). The majority
of ST1 isolates showed low SNP diversity (≤4 SNPs). All the colistin-resistant
isolates were resistant to carbapenems, exhibited an XDR phenotype and
harboured the blaOXA−23 gene. The blaNDM gene was only detected in ST1 colistin-resistant isolates (n = 5). The lpsB gene was detected in all colistinresistant isolates as well as various efflux pump genes belonging to the RND,
the MFS and the SMR families. The lipooligosaccharide OCL1 was detected in
all colistin-resistant ST1 and ST2 isolates and the capsular polysaccharide KL3
and KL17 were detected in ST2 and ST1 respectively. This study demonstrated
a 9.4% prevalence of colistin-resistant ST1 and ST2 A. baumannii in BC isolates.
The detection of the lpsB gene indicates a potential threat and requires close
prospective monitoring.National Health Laboratory Service (NHLS) Research Trust.https://www.frontiersin.org/journals/microbiologydm2022BiochemistryForestry and Agricultural Biotechnology Institute (FABI)GeneticsMicrobiology and Plant Patholog