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During November to December 2020, a high rate of COVID-19-associated pneumonia with bacterial superinfections due to multidrug-resistant (MDR) pathogens was recorded in a COVID-19 hospital in Zagreb. This study analyzed the causative agents of bacterial superinfections among patients with serious forms of COVID-19. In total, 118 patients were hospitalized in the intensive care unit (ICU) of the COVID-19 hospital. Forty-six out of 118 patients (39%) developed serious bacterial infection (VAP or BSI or both) during their stay in ICU. The total mortality rate was 83/118 (70%). The mortality rate due to bacterial infection or a combination of ARDS with bacterial superinfection was 33% (40/118). Six patients had MDR organisms and 34 had XDR (extensively drug-resistant). The dominant species was Acinetobacter baumannii with all isolates (34) being carbapenem-resistant (CRAB) and positive for carbapenem-hydrolyzing oxacillinases (CHDL). One Escherichia coli causing pneumonia harboured the blaCTX-M-15 gene. It appears that the dominant resistance determinants of causative agents depend on the local epidemiology in the particular COVID center. Acinetobacter baumannii seems to easily spread in overcrowded ICUs. Croatia belongs to the 15 countries in the world with the highest mortality rate among COVID-19 patients, which could be in part attributable to the high prevalence of bacterial infections in local ICUs. [ABSTRACT FROM AUTHOR]

In the previous studies OXA-23-like and OXA-24-like β-lactamase were reported among Acinetobacter baumannii in both hospitals and long-term care facilities (LTCF) in Croatia. The aim of this study was to analyze clinical and sewage A. baumannii isolates from two nursing homes in Zagreb, with regard to antibiotic susceptibility and resistance mechanisms, to determine the route of spread of carbapenem-resistant isolates. Nine clinical isolates were collected from February to May 2017 whereas in April 2017, ten A. baumannii isolates were collected from sewage of two nursing homes in Zagreb. Antibiotics susceptibility was determined by broth microdilution method. The presence of carbapenemase and extended spectrum β-lactamases (ESBL) encoding genes was explored by PCR. Conjugation and transformation experiments were performed as previously described. Genotyping was performed by SG determination, PFGE and MLST. Seven clinical isolates were positive for blaOXA24-like whereas two clinical and environmental carbapenem-resistant isolates, respectively, were found to possess blaOXA-23-like genes. Attempts to transfer imipenem resistance were unsuccessful indicating chromosomal location of blaOXA-23 gene. All carbapenem-resistant isolates belonged to SG- 1 (IC-2) whereas the rest of the isolates susceptible to carbapenems were allocated to SG- 2 (IC-1). PFGE analysis revealed low degree of genetic variability within both IC- I and IC- II. MLST corroborated that two environmental OXA-23 isolates belong to the ST-195. This study showed dissemination of OXA-23 producing A. baumannii from the nursing home into the urban sewage. Disinfection of nursing home sewage should be recommended in order to prevent the spread of resistance genes into the community sewage. [ABSTRACT FROM AUTHOR]

Introduction: Carbapenem resistance in Acinetobacter baumannii can be mediated by carbapenemases of class A, class B metallo-β-lactamases (MBLs), and class D carbapenem-hydrolyzing oxacillinases (CHDL). The aim of the study was to investigate the antimicrobial susceptibility and β-lactamase production of carbapenem-resistant A. baumannii isolates (CRAB) from the Children's Hospital Zagreb, Croatia. Methods: A total of 12 A. baumannii isolates collected between August 2016 and March 2018 were analyzed. Antibiotic susceptibility was determined by the broth microdilution method. The presence of MBLs was explored by combined disk test with EDTA. The presence of carbapenemases of class A, B, and D was explored by PCR. The occurrence of the ISAba1 upstream of the blaOXA-51-like or blaOXA-23-like was determined by PCR mapping. Epidemiological typing was performed by determination of sequence groups (SG). Genotyping was performed by SG determination, rep-PCR, and MLST. Results: All CRAB were resistant to piperacillin/tazobactam, ceftazidime, cefotaxime, ceftriaxone, cefepime, imipenem, meropenem, gentamicin, and ciprofloxacin. Moderate resistance rates were observed for ampicillin/sulbactam (67%) and tigecycline (42%). The isolates were uniformly susceptible to colistin. PCR revealed the presence of genes encoding OXA-24-like CHDL in nine and OXA-23-like CHDL in three isolates. blaOXA-51 genes were preceded by ISAba1. PCR for the common MBLs in Acinetobacter was negative. All isolates belonged to SG 1 corresponding to ICL (International Clonal Lineage) II. Rep-PCR identified four major clones. Conclusions: The study found OXA-24-like β-lactamase to be the dominant CHDL among children'sCRAB. The predominant spread of OXA-24-like is in contrast with the recent global dissemination of OXA-23 reported all over the world. In contrast to the previous studies in which emergency of OXA-24-like positive isolates was monoclonal, we found considerable genetic diversity of the isolates. [ABSTRACT FROM AUTHOR]