Phenotypic and Molecular Characterization of a Hospital Outbreak Clonal Lineage of Salmonella enterica Subspecies enterica serovar Mikawasima Containing blaTEM-1B and blaSHV-2 That Emerged on a Neonatal Ward, During the COVID-19 Pandemic.

Nontyphoid salmonella can cause severe infections in newborns and is therefore declared a pathogen of major health significance at this age. The aim of the study was molecular and antimicrobial characterization of ß-lactamase-producing Salmonella Mikawasima outbreak clone on a Neonatal ward, University Hospital of Split (UHS), Croatia during the COVID-19 pandemic. From April 2020, until April 2023, 75 nonrepetitive strains of Salmonella Mikawasima were isolated from stool specimens and tested for antimicrobial resistance. All 75 isolates were resistant to ampicillin and gentamicin, while 98% of isolates were resistant to amoxicillin/clavulanic acid. A high level of resistance was observed to third-generation cephalosporins (36% to ceftriaxone and 47% to ceftazidime). Extended-spectrum ß-lactamase production was phenotypically detected by double-disk synergy test in 40% of isolates. Moderate resistance to quinolones was detected; 7% of isolates were resistant to pefloxacin and ciprofloxacin. All isolates were susceptible to carbapenems, chloramphenicol, and co-trimoxazole. Fourteen representative isolates, from 2020, 2021, 2022, and 2023, were analyzed with PFGE and all of them belong to the same clone. Whole-genome sequencing (WGS) analysis of three outbreak-related strains (SM1 and SM2 from 2020 and SM3 from 2023) confirmed that these strains share the same serotype (Mikawasima), multilocus sequence typing profile (ST2030), resistance genes [blaTEM-1B, aac(6')-Iaa, aac(6')-Im, and aph(2'')-Ib)] and carry incompatibility group C (IncC) plasmid. Furthermore, the gene blaSHV-2 was detected in SM1 and SM2. In summary, WGS analysis of three representative strains clearly demonstrates the persistence of ß-lactamase-producing Salmonella Mikawasima in UHS during the 4-year period.

Molecular Characterization and Survival of Carbapenem-Resistant Acinetobacter baumannii Isolated from Hospitalized Patients in Mostar, Bosnia and Herzegovina.

Increasingly difficult treatment of multidrug-resistant (MDR) bacteria has become a global problem of the 21st century. Within a group of multiresistant bacteria, the Acinetobacter baumannii convincingly occupies the position at the top of the group designated as ESKAPE pathogens. In this study, 61 isolates of A. baumannii were recovered from different samples originating from various departments of the University Clinical Hospital Mostar during 2018. All of the isolates were identified using conventional phenotypic methods and the VITEK® 2 Compact System, and were confirmed by MALDI-TOF mass spectrometry. The minimum inhibitory concentrations (MICs) were determined by the microbroth dilution method using MICRONAUT-S MDR MRGN-Screening and VITEK 2 Compact System. All strains were resistant to carbapenems and classified in eight different resistotypes according to their antibiotic resistance and macrorestriction pulsed-field gel electrophoresis profiles, with all belonging to IC II. One isolate displayed resistance to colistin (MIC ≥16 mg/L). The presence of blaOXA genes encoding OXA-type carbapenemases was investigated by multiplex PCR and the Eazyplex® SuperBugAcineto system and showed 100% compatibility with the detection of acquired oxacillinases. Molecular characterization of the isolates tested in this study revealed the OXA-23- and OXA-40-like groups of acquired oxacillinases. Sequencing of two PCR products of the OXA-40-like group confirmed the presence of OXA-72. Survival assays with two selected isolates of A. baumannii encoding different mechanisms of carbapenem resistance revealed that one isolate was able to survive on a fragment of white laboratory coat during 90 days of monitoring. To the best of our knowledge, this is the first article to present the results of a comprehensive phenotypic, genotypic, and molecular analysis of A. baumannii isolates from the leading clinical hospital center in the southwestern part of Bosnia and Herzegovina, including data for the survival of this pathogen on the white laboratory coats used as compulsory medical clothing.