SARS-CoV-2 Seroprevalence and Neutralizing Antibody Response after the First and Second COVID-19 Pandemic Wave in Croatia.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a novel coronavirus with a pandemic spread. So far, a total of 349,910 SARS-CoV-2 cases and 7687 deaths were reported in Croatia. We analyzed the seroprevalence and neutralizing (NT) antibody response in the Croatian general population after the first (May-July 2020) and second (December 2020-February 2021) pandemic wave. Initial serological testing was performed using a commercial ELISA, with confirmation of reactive samples by a virus neutralization test (VNT). A significant difference in the overall seroprevalence rate was found after the first (ELISA 2.2%, VNT 0.2%) and second waves (ELISA 25.1%, VNT 18.7%). Seropositive individuals were detected in all age groups, with significant differences according to age. The lowest prevalence of NT antibodies was documented in the youngest (<10 years; 16.1%) and the oldest (60-69/70+ years; 16.0% and 12.8%, respectively) age groups. However, these age groups showed the highest median NT titers (32-64). In other groups, seropositivity varied from 19.3% to 21.5%. A significant weak positive correlation between binding antibody level as detected by ELISA and VNT titer (rho = 0.439, p < 0.001) was observed. SARS-CoV-2 NT antibody titers seem to be age-related, with the highest NT activity in children under 10 years and individuals above 50 years.

Characterization of Isolates Associated with Emergence of OXA-48-Producing Klebsiella pneumoniae in Croatia.

Here, we report a retrospective study conducted to elucidate emergence, epidemiology, and molecular mechanisms of resistance underlying the early spread of OXA-48 carbapenemase-producing Enterobacteriaceae in Croatia. Retrospective screening for OXA-48 producers was performed on a collection of 296 nonrepetitive, carbapenem-nonsusceptible enterobacterial isolates collected from January 2011 to December 2012 from 40 participating centers in Croatia. Antimicrobial susceptibility profiles and production of carbapenemases were assessed phenotypically. Pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing were used for epidemiological analysis. Resistance genes were characterized by polymerase chain reaction (PCR) and sequencing. Plasmid localization of blaOXA-48 in isolates and transconjugants was investigated by S1-PFGE and Southern hybridization. PCR mapping was used for identification of genetic platform surrounding blaOXA-48. Out of 296 carbapenem-nonsusceptible isolates, blaOXA-48 gene was detected in 12 Klebsiella pneumoniae isolates. All OXA-48-producing isolates showed varying resistance to carbapenems and 11 were multidrug resistant. All coproduced additional beta-lactamases, including CTX-M-15, which was detected in eight isolates. Isolates were delineated in five clonal types by PFGE corresponding to five sequence types (STs) assigned ST15, ST16, ST37, ST528, and ST1418. All OXA-48 isolates conjugated successfully and other resistance determinants were not cotransferred. blaOXA-48 was carried on a ∼60 kb IncL/M plasmid and was detected within Tn1999.2 composite transposon. OXA-48, a class D carbapenemase, is emerging as a potentially significant contributor among carbapenem-resistant Enterobacteriaceae in Croatia, alongside class A and B carbapenemases. Polyclonal genetic background of K. pneumoniae isolates carrying ∼60 kb incL/M plasmid indicates that dissemination of the blaOXA48 gene is not driven exclusively by the spread of a single clone.

KPC-Producing Klebsiella pneumoniae Isolates in Croatia: A Nationwide Survey.

BACKGROUND: In the last few years, Klebsiella pneumoniae strains producing K. pneumoniae carbapenemase (KPC) enzymes have emerged as important multidrug-resistant pathogens in hospitalized patients. This report describes KPC-producing isolates collected through the Croatian antimicrobial resistance surveillance program in the early stage of their dissemination in Croatia. MATERIALS AND METHODS: Forty-eight KPC-producing K. pneumoniae isolates, collected during a period from February 2011 to August 2013, were analyzed in this study. Antimicrobial susceptibility profiles were determined using disk diffusion and E-test. Pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) were used for epidemiological analysis. Identification of ß-lactamase genes and associated antibiotic resistance mechanisms was performed by polymerase chain reaction and positive products were sequenced. Localization of blaKPC was investigated by S1 PFGE and Southern hybridization. RESULTS: Of 40 participating centers in Croatia, KPC isolates were recorded in 9 of them. They all had multidrug-resistant phenotype, but showed varying levels of resistance to carbapenems. All isolates displayed ST258, and PFGE showed that all but one were closely related. All isolates harbored blaKPC-2. Isolate with a unique PFGE pattern produced TEM-1, while others produced TEM-116. All isolates harbored blaSHV-11, but were negative for blaCTX-M and blaAmpC genes. All isolates contain one KPC-harboring plasmid, ranging in size from ∼60 to ∼210 kb, characterized as FIIs and IncR. CONCLUSION: This report describes that the early stage of KPC-producing K. pneumoniae dissemination in Croatia is associated with a prolific PFGE type belonging to ST258. So far, the spread of an outbreak strain is limited to the northwest region of the country.

Sequence types 235, 111, and 132 predominate among multidrug-resistant pseudomonas aeruginosa clinical isolates in Croatia.

A population analysis of 103 multidrug-resistant Pseudomonas aeruginosa isolates from Croatian hospitals was performed. Twelve sequence types (STs) were identified, with a predominance of international clones ST235 (serotype O11 [41%]), ST111 (serotype O12 [15%]), and ST132 (serotype O6 [11%]). Overexpression of the natural AmpC cephalosporinase was common (42%), but only a few ST235 or ST111 isolates produced VIM-1 or VIM-2 metallo-ß-lactamases or PER-1 or GES-7 extended-spectrum ß-lactamases.