1e - Acinetobacter baumannii PCR-based replicon typing and resistance genes among isolates from pneumonia and skin and soft tissue infections from patients in southern Poland.

Background : Acinetobacter baumannii (AB) is an opportunistic pathogen, dominant in Central/Southern Europe in healthcare-associated infections. In Polish hospitals, especially in intensive care units, there is a predominance of carbapenem-resistant AB, which in 2021 reached over 80% according to ECDC. The present study investigated AB resistance genes and the type of plasmids on which they are carried.

Methods : In 2019-2020, 40 strains were collected from pneumonia (PNEU) and 40 strains from soft and skin tissue infections (SSTI) from patients from hospitals in the southern Poland. The antimicrobial susceptibility to 14 agents was studied and interpreted according EUCAST or CLSI criteria (cefiderocol and ampicillin/sulbactam). Resistance plasmids were typed by AB PCR-based replicon typing method which groups them into 19 homology groups (GRs). Screening for carbapenem resistance genes was performed by multiplex PCR. 

Results : All AB strains were resistant to carbapenems, fluoroquinolones, piperacillin/tazobactam, and tripetoprim/sulfamethoxazole. They showed the highest susceptibility to colistin (100%), cefiderocol (100%) and gentamicin (40%). No significant differences were found between the susceptibility of strains isolated from PNEU and SSTI.The presence of plasmids from the GR2 group was confirmed in 75 strains. Most strains with this type of plasmid (85.3%) carried the blaOXA24/40-like gene, 24% had blaOXA23-like, 4% had the blaNDM and 1.3% had the blaOXA58-like.

Conclusions The susceptibility of carbapenems resistant strains to cefiderocol indicates its promising role but its place in the treatment of AB infections remains debated in the literature.The present study revealed that most strains carry GR2 plasmids with the blaOXA24/40-like gene, highlighting the epidemic nature of carbapenem-resistant AB and emphasizing the need for comprehensive genomic surveillance and targeted infection control strategies to identify multidrug-resistant pathogens.Founded by the National Science Centre, no.2020/39/O/NZ7/00145