Acinetobacter baumannii Virulence Traits: A Comparative Study of a Novel Sequence Type with Other Italian Endemic International Clones

Abstract

Carbapenem-resistant Acinetobacter baumannii (CRAb) have emerged in recent decades as major causes of nosocomial infections. Resistance is mainly due to overexpression of intrinsic and/or acquired carbapenemases, especially oxacillinases (OXA). In Italy, although the sequence type (ST) 2 and the ST78 are the most frequently detected, we recently reported ST632, a single locus variant of ST2. Therefore, this study was aimed at unraveling common bacterial surface virulence factors involved in pathogenesis and antibiotic resistance in representative CRAb of these ST genotypes. Outer membrane protein (OMP) composition together with motility, biofilm formation, in vitro adherence to, invasion of, and survival within pneumocytes were analyzed. Differently from the carbapenem-susceptible reference strain ATCC 17978, either overexpressed OXA-51 or both OXA-23 and OXA-51 co-purified with OMPs in CRAb. This tight association ensures their maximal concentration on the inner surface of the outer membrane to provide the best protection against carbapenems. These findings led us to propose for the first time a common behavior of OXA enzymes in CRAb. Despite the presence of both OmpA and phosphorylcholine-porinD and the ability of all the strains to adhere to cells, invasion, and survival within pneumocytes was shown only by ST2 and ST78 isolates, sharing the highest number of identified OMPs. Conversely, notwithstanding genetic and OMPs similarities with ST2, ST632 was unable to invade and survive within epithelial cells. Overall, our study shows that different STs share a specific OMP composition, also shaped by overexpressed OXA, that is needed for invasiveness and survival of CRAb.

Occurrence, distribution and virulence factors of clinically important Acinetobacter species recovered from selected freshwater resources in the Eastern Cape Province, South Africa

“…The OmpA gene is the main outer membrane protein (OMP) located on the A. baumannii membrane [39,40], which [36]. These observations corroborate the findings of this current study which reports that the virulence profiles of an individual isolate varied greatly and OmpA gene was mostly detected [36].…”

“…The virulence traits of A. baumannii and A. nosocomialis have been a major research focus in recent times [17,36]. This is due to the nature of A. baumannii infections as well as the role virulence genes play in the pathogenicity of the emerging waterborne pathogen.…”

“…This is due to the nature of A. baumannii infections as well as the role virulence genes play in the pathogenicity of the emerging waterborne pathogen. Virulence genes are the mechanisms through which A. baumannii initiates pathogenesis [36,37], most especially in the clinical settings.…”

“…Generally, the outer membranes of Gram-negative bacteria are made up of the OMPs, lipopolysaccharides and phospholipids layer [37]. The presence of outer membrane protein A gene (OmpA) in the A. baumanni isolated from the freshwater source is of a major concern based on its role in pathogenesis [36]. Besides, studies have shown that A. baumannii uses OmpA for adhesion to the lung epithelial cell by interacting with a cell cytoskeleton such as fibronectin on the cell surface and thereby inducing pneumonia [41,42].…”

Occurrence, distribution and virulence factors of clinically important Acinetobacter species recovered from selected freshwater resources in the Eastern Cape Province, South Africa

“…All isolates that were positive for the recA (425 bp) ( Figure 1 nosocomialis have been a major research focus in recent times [17,39]. This is due to the nature of A.…”