Molecular Epidemiology and Clone Transmission of Carbapenem-Resistant Acinetobacter baumannii in ICU Rooms

Abstract

Carbapenem-resistant Acinetobacter baumannii (CRAB) is a major cause of nosocomial infections and hospital outbreaks worldwide, remaining a critical clinical concern. Here we characterized and investigated the phylogenetic relationships of 105 CRAB isolates from an intensive care unit from one hospital in China collected over six years. All strains carried blaOXA-23, blaOXA-66 genes for carbapenem resistance, also had high resistance gene, virulence factor, and insertion sequence burdens. Whole-genome sequencing revealed all strains belonged to ST2, the global clone CC2. The phylogenetic analysis based on the core genome showed all isolates were dominated by a single lineage of three clusters and eight different clones. Two clones were popular during the collection time. Using chi-square test to identify the epidemiologically meaningful groupings, we found the significant difference in community structure only existed in strains from separation time. The haplotype and median-joining network analysis revealed genetic differences appeared among clusters and changes occurred overtime in the dominating cluster. Our results highlighted substantial multidrug-resistant CRAB burden in the hospital ICU environment demonstrating potential clone outbreak in the hospital.

Bacterial Community and Genomic Analysis of Carbapenem-Resistant Acinetobacter baumannii Isolates from the Environment of a Health Care Facility in the Western Region of Saudi Arabia

“…The results are consistent with previous studies showing that bla OXA-23 is the most widely reported gene, while bla OXA66 is the most common OXA variant in A. baumanni i [ 9 , 24 , 50 ]. In A. baumannii , the augmented antibiotic resistance is largely attributed to the actions of MGEs and the activation of intrinsic resistance mechanisms, such as chromosomal β-lactamases, bla ADC , and efflux pump activity [ 3 , 14 , 52 ]. In addition, diverse MGEs were found in the Ab27-HEnv isolate.…”

“…It is noteworthy that insertion sequences, such as IS 26 , IS Vsa3 , IS Aba24 , and IS Aba26 , and a composite transposon were retrieved in the A. baumannii genome. The AdeFGH RND efflux pumps were previously identified in isolates with carbapenem resistance [ 52 ]. According to other reports, these genetic structures could facilitate the spread of antibiotic resistance determinants among pathogens, potentially compromising the effectiveness of many antibiotic treatments, including those prescribed to patients [ 3 , 52 ].…”

“…The AdeFGH RND efflux pumps were previously identified in isolates with carbapenem resistance [ 52 ]. According to other reports, these genetic structures could facilitate the spread of antibiotic resistance determinants among pathogens, potentially compromising the effectiveness of many antibiotic treatments, including those prescribed to patients [ 3 , 52 ]. Furthermore, the carbapenem-resistant isolates were also phenotypically resistant to several antibiotics often used in clinical practice.…”

“…Virulence factors, in conjunction with drug resistance, are widely believed to be responsible for the ability of A. baumannii to grow in unfavorable conditions, particularly in the hospital environment [ 52 , 53 ]. Interestingly, the genes associated with virulence factors, such as biofilm formation, immune evasion, iron uptake, phospholipases, and adherence, were conserved in most of the genomes analyzed in this study.…”

“…Interestingly, the genes associated with virulence factors, such as biofilm formation, immune evasion, iron uptake, phospholipases, and adherence, were conserved in most of the genomes analyzed in this study. The presence of the virulence genes csu ABCD, bfmR /S, entE , ompA , and plcD suggests the infectious nature of these strains [ 52 , 53 ]. Csu pili ( csuA /BABCDE, which are regulated by the bfmR / S two-component system), biofilm-associated proteins (BAP), and poly-N-acetylglucosamine production ( pga ABCD) are all involved in biofilm formation, maintenance, and maturation [ 11 ].…”