Multidrug-resistant (MDR) bacteria of the utmost importance are extended-spectrum β-lactamase (ESBL) and carbapenemase-producing Enterobacterales (CRE), carbapenem-resistant Acinetobacter baumannii (CRAB), carbapenem-resistant Pseudomonas aeruginosa (CRPA), methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus spp. (VRE). In this study, an evaluation of MDR bacteria in surgical intensive care units in a tertiary referral hospital was conducted. The study aimed to characterize β-lactamases and other resistance traits of Gram-negative bacteria isolated in surgical intensive care units (ICUs). Disk diffusion and the broth dilution method were used for antibiotic susceptibility testing, whereas ESBL screening was performed through a double disk synergy test and an inhibitor-based test with clavulanic acid. A total of 119 MDR bacterial isolates were analysed. ESBL production was observed in half of the Proteus mirabilis, 90% of the Klebsiella pneumoniae and all of the Enterobacter cloacae and Escherichia coli isolates. OXA-48 carbapenemase, carried by the L plasmid, was detected in 34 K. pneumoniae and one E. coli and Enterobacter cloacae complex isolates, whereas NDM occurred sporadically and was identified in three K. pneumoniae isolates. OXA-48 positive isolates coharboured ESBLs belonging to the CTX-M family in all but one isolate. OXA-23 carbapenemase was confirmed in all A. baumannii isolates. The findings of this study provide valuable insight of resistance determinants of Enterobacterales and A. baumannii which will enhance surveillance and intervention strategies that are necessary to curb the ever-growing carbapenem resistance rates.

K. pneumoniae harbors various antibiotic resistance determinants like extended-spectrum and plasmid-mediated AmpC β-lactamases and carbapenemases. In the last three years, in the period of intense population aging, migrations and climate changes in Europe and Croatia as well, we observed changes in antibiotic resistance patters of carbapenem-resistant K. pneumoniae (CRKP) isolates obtained routinely in community and inpatient setting. The aim was to compare and subsequently analyze CRKP hospital and community isolates resistance mechanisms, traits and molecular epidemiology, in order to analyze the dynamic of resistance trends, carbapenemase types and plasmid epidemiology. Disk diffusion and broth dilution method were the methods of choice to determine antibiotic susceptibility. β-lactamases were screened by phenotypic methods and confirmed with PCR. In total 113 isolates were analysed. Resistance to amoxicillin-clavulanate and ertapenem was confirmed in all strains. High resistance rates (over 90%) were observed for extended-spectrum cephalosporins, and ciprofloxacin. OKNV (OXA-48, KPC, NDM, VIM) testing and PCR detected OXA-48 in 106, NDM in 7 and KPC in only one isolate. ESBLs accompanied carbapenemases in 103 isolates. IncL, associated with OXA-48, was the dominant plasmid type. No significant differences in the resistance profile and resistance determinants were found between hospital and community isolates plasmid type. The predominance of OXA-48 carbapenemase is in line with the reports from the neigbouring countries.

Background/Objectives: Proteus mirabilis is a frequent causative agent of urinary tract and wound infections in community and hospital settings. It develops resistance to expanded-spectrum cephalosporins (ESC) due to the production of extended-spectrum β-lactamases (ESBLs) or plasmid-mediated AmpC β-lactamases (p-AmpC). Here, we report the characteristics of ESBLs and p-AmpC β-lactamases encountered among hospital and community isolates of P. mirabilis in two hospitals and the community settings in Zagreb, Croatia. Methods: Antibiotic susceptibility testing was performed using disk-diffusion and broth dilution methods. The double-disk-synergy test (DDST) and inhibitor-based test with clavulanic and cloxacillin were applied to screen for ESBLs and p-AmpC, respectively. PCR investigated the nature of ESBL, carbapenemases, and fluoroquinolone resistance determinants. Selected strains were subjected to molecular analysis of resistance traits by the Inter-Array CarbaResist Kit and whole-genome sequencing (WGS). Results: In total, 39 isolates were analyzed. Twenty-two isolates phenotypically tested positive for p-AmpC and seventeen for ESBLs. AmpC-producing organisms exhibited uniform resistance to amoxicillin-clavulanate, ESC, ciprofloxacin, and sulphamethoxazole-trimethoprim, and uniform susceptibility to carbapenems and piperacillin-tazobactam and all harbored bla_CMY-16 genes. ESBL-positive isolates demonstrated resistance to amoxicillin-clavulanate, cefuroxime, cefotaxime, ceftriaxone, and ciprofloxacin but variable susceptibility to cefepime and aminoglycosides. They possessed bla_CTX-M genes that belong to cluster 1 (n = 5) or 9 (n = 12), with CTX-M-14 and CTX-M-65 as the dominant allelic variants. Conclusions: The study demonstrated the presence of CTX-M ESBL and CMY-16 p-AmpC among hospital and community-acquired isolates. AmpC-producing isolates showed uniform resistance patterns, whereas ESBL-positive strains had variable degrees of susceptibility/resistance to non-β-lactam antibiotics, resulting in more diverse susceptibility patterns. The study found an accumulation of various resistance determinants among hospital and outpatient isolates, mandating improvement in detecting β-lactamases during routine laboratory work.

During the COVID-19 pandemic carbapenem-resistant Acinetobacter baumannii (CRAB) was found to be the major pathogen associated with ventilator-associated pneumonia in mechanically ventilated patients. This prompted us to analyze the post-pandemic mechanisms of carbapenem resistance, antibiotic resistance trends, and molecular epidemiology of CRAB in Croatia. In total, 94 CRAB isolates from two hospital centers, including outpatient settings, were investigated. Antimicrobial susceptibility testing was performed by broth microdilution. PCR was used to detect genes encoding carbapenemases of group A, B and D and extended-spectrum β-lactamases (ESBL). Randomly selected isolates were subjected to whole resistome analysis by Inter-array CarbaResist Kit and whole-genome sequencing (WGS). Phylogenetic tree and sequence types (STs) were retrieved from WGS. Plasmid incompatibility groups were determined by PCR-based replicon typing (PBRT). All isolates were extensively drug resistant (XDR), showing resistance to ceftazidime, cefepime, piperacillin–tazobactam, imipenem, meropenem, gentamicin, amikacin and ciprofloxacin, and 13% (n = 12) were also resistant to colistin. The Hodge and CIM test exhibited poor sensitivity with only 32 and 30% of isolates being identified as carbapenemase producers, respectively. PCR identified bla_OXA-23 as the dominant carbapenemase gene in both hospitals, found in 71% of the isolates (67/94). In an outpatient setting, bla_OXA-24/40 was dominant. bla_OXA-23 and bla_OXA-72 were the only allelic variants. The Inter-array CarbaResist Kit and whole-genome sequencing (WGS) identified a variety of aminoglycoside (armA, ant(3″)-IIa, aph(3″)-Ib, aph(6)-Id) and sulphonamide resistance (sul1 and sul2) genes. The representative bla_OXA-23-positive isolates belonged to ST2, while bla_OXA-72-positive isolates were allocated to ST492. These data show that there are different populations of XDR A. baumannii between hospital and outpatients.

Background: The primary aim of this study was to evaluate the performance of four burn prognostic scores—Abbreviated Burn Severity Index (ABSI), Ryan, Belgium Outcome Burn Injury (BOBI), and revised Baux score (rBaux) in a Croatian burn center. A secondary aim was to compare patient outcomes before and after the organizational and protocol changes. Methods: A retrospective study and comparison of four prediction scores was conducted over a nine-year period in burn patients with ≥20% total body surface area (TBSA) burned. Additionally, outcomes before and after organizational changes were compared. Results: A total of 149 patients were included, with the mean patient age of 54.62 ± 19.38 years, the mean of TBSA of 42.98 ± 19.90, and an overall mortality rate of 48.99%. The area under the ROC curve (AUROC) was 0.79 for the rBaux and ABSI score, 0.77 for the BOBI score, and 0.76 for the Ryan score. The duration of mechanical ventilation and length of stay (LOS) in burn intensive care units (BICU) decreased after the organizational changes, though survival rates remained similar. Conclusions: Prognostic scores are good predictors of mortality but with moderate predictive accuracy. Continuity of care in intensive care could be important for better outcomes.

The COVID-19 pandemic has underscored the intricate interplay between viral infections and opportunistic bacterial pathogens such as Klebsiella pneumoniae. K. pneumoniae harbors various antibiotic resistance determinants like extended-spectrum and plasmid-mediated AmpC β-lactamases and carbapenemases. In the two years following the pandemic, carbapenemase producing K. pneumoniae isolates obtained routinely in outpatient and inpatient setting demonstrated similar resistance patterns which prompted research. The aim was to compare and subsequently analyze carbapenem-resistant hospital and outpatient’s K. pneumoniae isolates’ resistance mechanisms, traits and molecular epidemiology, following the COVID-19 pandemic. Disk diffusion and broth dilution method were the methods of choice to determine antibiotic susceptibility. β-lactamases were screened by phenotypic methods and confirmed with PCR. In total 113 isolates were analysed. Resistance to amoxicillin-clavulanate and ertapenem was confirmed in all strains. High resistance rates (over 90%) were observed for extended-spectrum cephalosporins, and ciprofloxacin. OKNV testing and PCR detected OXA-48 in 106, NDM in 7 and KPC in only one isolate. ESBLs accompanied carbapenemases in 103 isolates. Carbapenem resistance in K. pneumoniae is becoming a global problem, hence careful monitoring of its resistance traits is of utmost importance in order to combat the arising threat. OXA-48 seems to continue predominating in the turbulent period after pandemic.