Background/Objectives: Intestinal colonization by multidrug-resistant (MDR) bacteria is considered one of the main risk factors for invasive infections in the hematopoietic stem-cell transplant (HSCT) setting, associated with hard-to-eradicate microorganisms. The aim of this study was to assess the rate of intestinal colonization by MDR bacteria and their microbial spectrum in a group of post-HSCT patients to study the genetic determinants of beta-lactam and glycopeptide resistance in the recovered isolates, as well as to determine the epidemiological relation between them. Methods: The intestinal colonization status of 74 patients admitted to the transplantation center of University Hospital “St. Marina”—Varna in the period January 2019 to December 2021 was investigated. Stool samples/rectal swabs were screened for third-generation cephalosporin and/or carbapenem-resistant Gram-negative bacteria, methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE), and Stenotrophomonas maltophilia. Identification and antimicrobial susceptibility testing were performed by Phoenix (BD, Sparks, MD, USA) and MALDI Biotyper sirius (Bruker, Bremen, Germany). Molecular genetic methods (PCR, DNA sequencing) were used to study the mechanisms of beta-lactam and glycopeptide resistance in the collected isolates, as well as the epidemiological relationship between them. Results: A total of 28 patients (37.8%) were detected with intestinal colonization by MDR bacteria. Forty-eight non-duplicate MDR bacteria were isolated from their stool samples. Amongst them, the Gram-negative bacteria prevailed (68.8%), dominated by ESBL-producing Escherichia coli (30.3%), and followed by carbapenem-resistant Pseudomonas sp. (24.2%). The Gram-positive bacteria were represented exclusively by Enterococcus faecium (31.2%). The main beta-lactam resistance mechanisms were associated with CTX-M and VIM production. VanA was detected in all vancomycin-resistant enterococci. A clonal relationship was observed among Enterobacter cloacae complex and among E. faecium isolates. Conclusions: To the best of our knowledge, this is the first Bulgarian study that presents detailed information about the prevalence, resistance genetic determinants, and molecular epidemiology of MDR gut-colonizing bacteria in HSCT patients.

The aim of this study was to investigate the prevalence of intestinal colonization by major multidrug-resistant (MDR) bacteria and fungi in patients with hematological malignancies (HM) and its relationship with subsequent bloodstream infections (BSIs). The study was performed between December 2023 and June 2024 at the University Hospital “Saint Marina”, Varna, Bulgaria. A total of 180 HM patients were screened for intestinal colonization by 3rd generation cephalosporin-resistant (3rdGCephR) and carbapenem-resistant (CR) Enterobacterales , Pseudomonas aeruginosa , Stenotrophomonas maltophilia , Vancomycin-Resistant Enterococci (VRE) and Candida sp. according to our own protocol. Blood cultures were taken according to clinical indications. Multiplex PCR was used to detect beta-lactamase genes in all invasive Enterobacterales isolates. A total of 100 patients (55.6%) were colonized by one or more of the screened agents. Among these, 88 patients were MDR carriers (48.9%, 88/180) and the highest colonization rates were found for CR Klebsiella pneumoniae (CRKP) (42%), Candida sp. (34%), VRE (25%) and 3rdGCephR Escherichia coli (23%). A total of 29 patients (16.1%; 29/180) developed BSIs, with K. pneumoniae responsible for 44.8%. Of these, 76.9% (10/13) were CR and bla _NDM positive isolates. Related BSIs were diagnosed in 57.9% of the MDR carriers with BSIs (11/19). The related BSIs percentage according to the colonizing agent was 21.4% for CRKP (9/42), 7.1% for 3rdGCephR K. pneumoniae (1/14) and 25% for P. aeruginosa (1/4). CRKP colonization was significantly higher among patients with CRKP BSIs than those with non-CRKP BSIs ( P < 0.001). The MDR intestinal colonization, specifically by CRKP is an important source for subsequent BSIs in this high-risk patient population.

Many studies report an increase in antimicrobial resistance of Gram – negative bacteria during the COVID-19 pandemic. Our aim was to evaluate the epidemiological relationship between carbapenem-resistant (CR) Enterobacteriaceae isolates from patients in COVID-19 wards and to investigate the main mechanisms of carbapenem resistance in these isolates during the period April 2020–July 2021. A total of 45 isolates were studied: Klebsiella pneumoniae (n = 37), Klebsiella oxytoca (n = 2), Enterobacter cloacae complex (n = 4) and Escherichia coli (n = 2). Multiplex PCR was used for detection of genes encoding carbapenemases from different classes (bla_KPC, bla_IMP, bla_VIM, bla_NDM, bla_OXA-48). For epidemiological typing and analysis, ERIC PCR was performed. Two clinical isolates of E. cloacae, previously identified as representatives of two dominant hospital clones from the period 2014–2017, were included in the study for comparison. In the CR K. pneumoniae group, 23 (62.2%) carried bla_KPC, 13 (35.1%) bla_NDM, 10 (27.0%) bla_VIM, and 9 (24.3%) were positive for both bla_KPC and bla_VIM. The bla_KPC was identified also in the two isolates of K. oxytoca and bla_VIM in all E. cloacae complex isolates. The two CR isolates of E. coli possessed bla_KPC and bla_OXA-48 genes. Epidemiological typing identified 18 ERIC profiles among K. pneumoniae, some presented as clusters of identical and/or closely related isolates. The carbapenem resistance in the studied collection of isolates is mediated mainly by bla_KPC. During the COVID-19 pandemic intrahospital dissemination of CR K. pneumoniae, producing carbapenemases of different molecular classes, as well as continuing circulation of dominant hospital clones of multidrug-resistant E. cloacae complex was documented.

Objectives: The aim of the current report is to present three cases of necrotizing fasciitis and sepsis caused by Vibrio vulnificus on the Bulgarian Black Sea coast. Materials and Methods: Two of the patients are males, 70 and 86 years of age, respectively, and one is an 86-year-old female. Data were collected from the patients’ examination records. V. vulnificus was isolated on 5% sheep blood agar from wound and blood samples and identified by the automated system Phoenix M50 (BD, Franklin Lakes, NJ, USA). Antimicrobial susceptibility was tested with two well-known methods (disk diffusion and broth microdilution). Results: All of the patients were admitted to our hospital due to pain, swelling, ulceration, and bullae on the legs and were febrile. They underwent surgery and received intensive care support. One of the patients developed septicemia and septic shock; one of his legs was amputated, but the outcome was fatal. The other patient received immediate approptiate antibiotic and surgical treatment, and the outcome was favorable. The third patient underwent emergency fasciotomy but died a few hours after admission. Conclusions: Global climate change is affecting the distribution of Vibrio spp., and their incidence is expected to increase. It is important to highlight the need for awareness among immunocompromised and elderly patients of the potential threat posed by V. vulnificus infections.

The aim of this study is to evaluate the antimicrobial susceptibility of invasive isolates of Serratia marcescens, associated with blood stream infections (BSIs) in patients hospitalized in Varna University Hospital, Bulgaria, as well as to identify the genetic mechanisms responsible for 3rd generation cephalosporin and carbapenem-resistance among these isolates. A total of 45 consecutive S. marcescens isolates, obtained from blood cultures of 45 patients with BSIs, hospitalized during an 8-year period (2016–2023) were included. Species identification and antimicrobial susceptibility testing were done by Phoenix (BD, USA) and Vitek 2 (BioMerieux, France) systems and the results were interpreted according to EUCAST guidelines. The genetic mechanisms of beta-lactam resistance were studied by PCR. During the study period, a total of 45 patients were diagnosed with S. marcescens-associated BSIs. All infections were defined as nosocomial, predominantly intensive care unit-acquired (42.2%) and 28.8% were central venous catheter-associated. The following antimicrobial resistance rates were found: ceftriaxone, piperacillin/tazobactam, 57.8%; ceftazidime, 55.6%; cefepime, trimethoprime/sulfamethoxazole, 53.3%; gentamicin, 48.8%; ciprofloxacin, 44.5%; amikacin, 15.6%; carbapenems, 2.2%. The bla_CTX-M was identified in 88.9% of the tested 3rd generation cephalosporin resistant isolates. Among these, 50% were also bla_TEM positive. The single carbapenem-resistant isolate harboured bla_KPC, bla_CTX-M1/9, bla_CMY-2 and bla_TEM. This study demonstrates S. marcescens as a problematic nosocomial pathogen and we report a KPC-producing S. marcescens clinical isolate from a BSI in Bulgaria.