Search Results (204)

Background: Pseudomonas aeruginosa is one of the leading agents causing healthcare-associated infections (HAIs) due to its intrinsic resistance, its capacity to acquire resistance mechanisms, and its persistence in hospital environments. In Mexico, it ranks among the most frequently reported pathogens in national surveillance systems. The aim of this study was to characterize antimicrobial resistance profiles and the genetic determinants associated with MDR/XDR phenotypes in P. aeruginosa strains from HAIs at Hospital Juárez de México (HJM). Methods: Sixty-three strains from patients with HAIs were analyzed. Identification was confirmed by 16S rRNA gene sequencing. Antimicrobial susceptibility testing followed CLSI guidelines. MDR/XDR phenotypes were classified according to the Latin American consensus for categorizing MDR, XDR, and PDR pathogens. Screening for resistance mechanisms was carried out by PCR for the main β-lactamases circulating at HJM. Finally, mutations in the oprD gene were detected in imipenem-resistant isolates through amino acid sequence alignment. Results: Resistant phenotypes allowed the identification of MDR and XDR profiles. Only the metallo-β-lactamase bla_VIM was detected. Analysis of oprD porin sequences revealed recurrent mutations (S103T, T115K, L170F, G186P, and T189V) associated with imipenem resistance. Conclusions: In P. aeruginosa, the presence of bla_VIM and structural alterations in OprD confirms the multifactorial nature of carbapenem resistance. These findings underscore the need to strengthen microbiological surveillance programs and antimicrobial stewardship strategies to mitigate the impact and spread of MDR/XDR isolates. Full article

Background: Libya, a conflict-affected North African country, has a fragile health system and poor surveillance, leaving it largely underrepresented in global estimates. Earlier Libyan reviews were descriptive, lacking breakpoint standardization, isolate-level pooling, or AMR-attributable mortality and DALY estimates. To our knowledge, this study represents the first comprehensive report that integrates phenotypic and genotypic data to estimate deaths and DALYs attributable to AMR-induced mortality and morbidity, describe spatiotemporal patterns, and model future trajectories. Methods: We performed a meta-analysis according to the PRISMA 2020 guideline of Libyan studies reporting phenotypic or genotypic resistance among clinical bacterial isolates (1970–2024), combined with microbiology records from hospitals and national surveillance systems (preregistered in PROSPERO ID: CRD420251066018). Susceptibility results were standardized to CLSI/EUCAST and deduplicated using WHO GLASS first-isolate rules. We used random-effects meta-regression to estimate pooled resistance, and the counterfactual approach of Global Burden of Disease (GBD) was applied to estimate AMR-attributable DALYs. Molecular data on resistance genes, sequence types, and tuberculosis mutations were systematically collected. Results: We included 62 eligible studies together with national and facility-level surveillance datasets, providing isolate-level susceptibility data for 31,439 clinical isolates from Libya. In 2024, we estimated 2183 deaths (95% UI 1752–2614) attributable to AMR, representing 9.7% (95% UI 7.8–11.6) of total deaths with a mortality rate of 15.2 per 100,000 (12.2–18.2). DALYs attributable to AMR increased from 14,628 (95% UI 11,702–17,554) in 1970 to 96,715 (95% UI 77,372–116,058). The highest pooled resistance involved carbapenem-resistant/MDR A. baumannii, third-generation cephalosporin- and fluoroquinolone-resistant Enterobacterales, and carbapenem-resistant P. aeruginosa. Molecular data showed widespread ESBLs, OXA-/NDM-type carbapenemases, plasmid-mediated colistin resistance, high-risk E. coli ST131 and K. pneumoniae ST147 lineages, and canonical drug-resistant M. tuberculosis mutations. Conclusions: Combined with global and regional evidence, our findings suggest a high and increasing burden of AMR in Libya. These findings emphasize the need for rapid expansion of data collection systems, GLASS-aligned surveillance, diagnostic capacities, and infection control measures. Full article

Antimicrobial resistance in urinary tract infections (UTIs) poses a critical public health challenge, yet comparative data between outpatient and inpatient settings remain limited, particularly in Latin America. This study characterized the epidemiology, microbiology, and resistance patterns of UTIs in northwestern Mexico. A retrospective analysis of 1041 patients with UTI (May–November 2024) was conducted. Microorganism identification and antimicrobial susceptibility were determined using the MicroScan WalkAway system in accordance with CLSI guidelines. Results: Outpatients accounted for 80.5% of cases and inpatients for 19.4%, with a 3.1% mortality rate. Escherichia coli predominated (62.9%), with a significant association with outpatients (p = 0.02), whereas Enterobacter cloacae, Acinetobacter spp., Candida tropicalis, and C. albicans were associated with inpatients (p < 0.05). Pediatric patients exhibited distinctive microbiological profiles: Pseudomonas aeruginosa (9.7% vs. 2.1%, p = 0.032), Enterococcus faecalis (33.3% vs. 16.2%, p = 0.001), and Staphylococcus epidermidis (26.6% vs. 6.5%, p = 0.027) were significantly more prevalent than in adults. Multidrug resistance (MDR) was detected in 27.1% of isolates, and extensive drug resistance (XDR) in 3.2%. XDR was associated with Gram-positive bacteria (12.2% vs. 1.4%, p < 0.001). Carbapenem-resistant Enterobacteriaceae (CRE) were identified in 0.9% (7/772) of cases, with 42.9% occurring in outpatients. Hospitalization (OR: 2.01; 95% CI: 1.43–2.83), surgical services (OR: 1.41; 95% CI: 1.02–1.97), and recent surgery (OR: 2.37; 95% CI: 1.04–5.39) were independent predictors of MDR/XDR infections. Conclusions: These findings demonstrate the emergence of CRE within the community and distinctive pediatric resistance patterns, underscoring the need for tailored antimicrobial stewardship strategies in this region. Full article

Background: Rapid antimicrobial susceptibility testing (RAST) allows early detection of resistance directly from positive blood cultures, potentially improving outcomes in bloodstream infections (BSIs). We evaluated the performance of EUCAST RAST for Gram-negative ESKAPEEc pathogens and characterized carbapenemase genes in carbapenem-resistant Klebsiella pneumoniae (CRKP). Methods: A total of 354 positive blood cultures were screened, including 51 monomicrobial Gram-negative ESKAPEEc isolates. RAST results at 4, 6, 8, and 16–20 h were compared with standard antimicrobial susceptibility testing (AST) obtained using the BD Phoenix™ system. Categorical agreement (CA) and error frequency were calculated. Multiplex PCR and Sanger sequencing were performed on 15 CRKP isolates to identify carbapenemase genes and allelic variants. Results: 51 Gram-negative ESKAPEEc isolates met the inclusion criteria for RAST (15 E. coli, 19 K. pneumoniae, 11 A. baumannii, and 6 P. aeruginosa). Overall performance varied markedly by species and antibiotic. E. coli showed frequent unreadable or ATU zones at early timepoints and wide CA variability (50–100%), with high very major error (VME) rates for AMP, TZP, and CAZ, particularly at 6–8 h. K. pneumoniae displayed consistently high CA (mostly 100%) for carbapenems, CAZ, and TZP. A. baumannii demonstrated excellent agreement (100% for most agents), except for GEN at 6–8 h. P. aeruginosa could be evaluated only at 16–20 h, showing high CA for AMK, CAZ, and CIP; lower CA for MEM (83%); non-calculable CA for IMI due to universal ATU readings; and a CA value of 0% for TZP due to the predominance of the ATU results. VMEs ranged from 0% to 26.1% across species and reading times, but carbapenems did not generate VMEs. Molecular analysis revealed bla_KPC in 66.7%, bla_NDM in 46.7%, and bla_OXA-48 in 33.3% of isolates, with co-occurrence in several strains. Sequencing identified bla_KPC-2 and bla_NDM-1 as the predominant variants, with one isolate harboring bla_NDM-5. Conclusions: EUCAST RAST markedly accelerates susceptibility reporting from positive blood cultures, but its accuracy is species- and time-dependent. Performance was excellent for K. pneumoniae (including CRKP) and A. baumannii and acceptable for P. aeruginosa at 16–20 h. In contrast, E. coli showed frequent ATU results at early timepoints and high ME/VME rates, making readings before 8 h unreliable for clinical decisions. Overall, RAST can effectively support rapid antimicrobial stewardship when species-specific limitations are recognized, and early-timepoint results are interpreted with caution. Full article

Background/Objectives: Metallo-β-lactamase (MBL)-producing Gram-negative bacteria represent a growing global health threat due to their broad resistance to β-lactam antibiotics, including carbapenems, which severely limits treatment options. This study aimed to evaluate the in vitro synergistic activity of fosfomycin (FOS) in combination with selected older and newer antimicrobials against MBL-producing Klebsiella pneumoniae and Pseudomonas aeruginosa. Methods: Synergistic interactions were assessed using agar dilution checkerboard on 42 MBL-producing clinical isolates (22 K. pneumoniae, 20 P. aeruginosa) and confirmed using time-kill assays with selected isolates. FOS was tested in combination with colistin (COL), ceftazidime–avibactam (CAZ-AVI), meropenem (MER), amikacin (AMI), aztreonam (AZT), aztreonam–avibactam (AZT-AVI), or cefiderocol (FDC). Results: Most FOS combinations exhibited additive or synergistic effects against clinical isolates. Synergy rates reached 72.7% for the FOS+CAZ-AVI combination (K. pneumoniae) and 65.0% for the FOS+COL combination (P. aeruginosa). An asymmetric synergistic interaction was identified for FOS+CAZ-AVI, with FOS enhancing the activity of CAZ-AVI more markedly than vice versa, especially in K. pneumoniae. Time-kill assays on selected isolates confirmed synergistic and bactericidal activity of FOS+CAZ-AVI and FOS+COL, and showed that bacterial regrowth observed with FOS, CAZ-AVI, and COL alone was suppressed in combination therapy. Conclusions: FOS-based combinations, particularly with CAZ-AVI and COL, demonstrated potent synergistic activity against MBL-producing K. pneumoniae and P. aeruginosa, supporting their potential utility in rational combination therapies for infections due to MBL-producing bacteria. Full article

Antimicrobial resistance (AMR) is a global health threat, increasing morbidity, mortality, and healthcare costs. Multi-drug resistant ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter cloacae) cause most hospital-acquired infections. Local data on their resistance profiles remain limited in low-income settings. This study assessed the prevalence and resistance patterns of ESKAPE pathogens isolated from clinical specimens at Rwanda Military Referral and Teaching Hospital. A descriptive cross-sectional study was conducted from June 2022 to January 2023. ESKAPE isolates were identified and tested for antimicrobial susceptibility using the BD Phoenix M50 System. Data on sample type, ward, and demographics were analyzed. Of 744 bacterial findings, 207 (30%) were ESKAPE isolates. After excluding duplicates and non-recovered isolates, 156 were identified as ESKAPE. K. pneumoniae was most common (41%), followed by S. aureus (27%), A. baumannii (13%), P. aeruginosa (11%), and E. cloacae (8%); no E. faecium was detected. Among Gram-negatives, 63% were resistant to third-generation cephalosporins and 32% to carbapenems, with A. baumannii showing highest resistance (85% and 75%). Methicillin-Resistance in Staphylococcus aureus (MRSA) was 7%. This first hospital-based study in Rwanda shows high cephalosporin and carbapenem resistance, highlighting the need to strengthen diagnostics and stewardship. Full article

Multi-drug-resistant Pseudomonas aeruginosa (P. aeruginosa) commonly causes infections that are difficult to treat, necessitating the development of new therapeutics. The search for more effective ways to combat the emergence of bacterial resistance has also led to research into phage-antibiotic synergy (PAS) as a potential therapeutic strategy. The aim of this study was to isolate and characterize virulent phages from water sources that are active against clinical carbapenem-resistant P. aeruginosa isolates, and to evaluate their in vivo efficacy using a Galleria mellonella larvae infection model. The biological and genomic characteristics of the isolated phages were determined using host range analysis, one-step growth curve analysis, transmission electron microscopy analysis and whole-genome sequencing. Two phages (vB_PaMB13 and vB_PaMB17) that demonstrated in vitro synergistic and bactericidal interactions with antipseudomonal antibiotics (tobramycin and ceftazidime) were selected for further investigation using the checkerboard method. The study revealed synergy between all phages and either antibiotic, tobramycin or ceftazidime, against P. aeruginosa. Similarly, the percentage survival rates increased in the in vivo model when both phages and antibiotics were used in combination. Overall, our study provides further support for the idea that phage-antibiotic synergy could be an effective strategy for improving treatment outcomes. Full article

Background: Carbapenem-resistant Enterobacterales and difficult-to-treat resistance (DTR) Pseudomonas aeruginosa are a growing public health issue. Cefiderocol demonstrated activity against β-lactamase-producing Gram-negative bacteria (GNB). However, bone PharmacoKinetics (PK) data is lacking. Here, we report a case of post-traumatic chronic osteomyelitis caused by extensively drug-resistant (XDR) Pseudomonas aeruginosa which was successfully treated with cefiderocol. Moreover, we conducted a non-systematic review of the available literature. Case Report: We described the case of a 64-year-old man who was admitted to a traumatology ward after a work accident caused crushing of his left foot. Microbiological tests on intraoperative biopsies demonstrated XDR P. aeruginosa and K. oxytoca. Despite the administrations of different antibiotics regimens and multiple surgical revisions, the patient developed chronic osteomyelitis. To prevent amputation, cefiderocol was prescribed for six weeks, resulting in a complete clinical resolution of osteomyelitis. Review of the Literature: We performed a non-systematic review of the literature searching the public databases PubMed and Google Scholar. We identified nine case reports. In most patients (60%) the cause of osteomyelitis was post-surgical, and all the reported cases were healthcare associated. Osteomyelitis treatment required both antimicrobial therapy and surgery in all the cases described. Cefiderocol was often prescribed in association with other antibiotics (70%). Clinical cure was described in all the reported cases. Conclusions: This study highlights that cefiderocol is safe and efficacious to treat osteomyelitis caused by carbapenem-resistant GNB. However, evidence is limited to a few case reports. Full article

Neutropenic patients with acute myeloid leukemia (AML) are at high risk for severe, multidrug-resistant infections. Sepsis due to carbapenem-resistant Pseudomonas aeruginosa (CRPA) in this population often leads to septic shock and acute respiratory distress syndrome (ARDS), with historically poor outcomes. CytoSorb™ hemoadsorption has been proposed as an adjunctive therapy for refractory septic shock, but evidence in hematologic malignancies remains limited. This report describes a 29-year-old male with newly diagnosed AML complicated by neutropenic fever, bacteremia due to CRPA, and subsequent hospital-acquired pneumonia progressing to ARDS. Despite multiple antibiotic regimens and aggressive intensive care management, including mechanical ventilation, prone positioning, and continuous renal replacement therapy (CRRT), the patient developed refractory septic shock with persistent lactic acidosis and elevated inflammatory markers. Early adjunctive CytoSorb hemoadsorption was initiated, guided by maximal CytoScore criteria, as part of a comprehensive supportive strategy. Following CytoSorb therapy, the patient demonstrated transient hemodynamic and biochemical improvement; however, profound neutropenia and multi-organ failure persisted. Microbiological clearance of CRPA was not achieved; given confirmed colistin susceptibility and unknown carbapenemase mechanism, a salvage combination of colistin plus ceftazidime–avibactam was employed. Transient hemodynamic improvement was observed after CytoSorb initiation; however, cytokine assays were not performed, and microbiological clearance was not achieved, precluding any mechanistic attribution to CytoSorb. This case highlights the complexity of managing CRPA sepsis and ARDS in neutropenic AML patients, and the challenges in attributing observed clinical improvement to CytoSorb therapy in the context of multiple simultaneous interventions. The absence of cytokine assays (e.g., IL-6, TNF-α) precludes any mechanistic attribution of observed changes to cytokine adsorption, and interpretation should remain descriptive rather than causal. Observed transient changes occurred amid simultaneous interventions (broad-spectrum antibiotics, CRRT, prone ventilation, corticosteroids, and filgrastim), precluding attribution to any single therapy, including CytoSorb. Given the fatal outcome and persistent CRPA positivity, the clinical impact of this observation is limited, and the generalizability of a single-case report is restricted. Cautious interpretation is warranted, and CytoSorb may be considered as part of a comprehensive care bundle rather than as a standalone solution. Alternative tetracycline-based combinations were reviewed but not adopted under our center’s salvage protocol for this XDR presentation. Future studies are warranted to clarify its clinical benefit and optimal timing in this population. Full article

Background/Objectives: The COVID-19 pandemic accelerated the inappropriate use of antibiotics, amplifying the global threat of antimicrobial resistance (AMR), particularly in resource-limited healthcare settings. This study investigated AMR patterns in a tertiary care hospital, focusing on the impact of the COVID-19 pandemic on invasive bacterial pathogens. Methods: This retrospective observational study was conducted at the University Clinical Centre of the Republic of Srpska, analyzing AMR data from invasive bacterial isolates collected between 2015 and 2024, and assessing correlations between antibiotic utilization and resistance patterns during the study periods. Results: Among 4718 invasive bacterial isolates, Acinetobacter spp. (26.7%) and K. pneumoniae (20.8%) were the most prevalent. A significant increase in invasive isolates was observed during the COVID-19 period, particularly for K. pneumoniae (p = 0.003), P. aeruginosa (p = 0.017), Acinetobacter spp. (p = 0.013), and E. faecium (p = 0.028). The highest multidrug-resistant (MDR) rates were observed in Acinetobacter spp. (97% during COVID-19) and K. pneumoniae (>80% post-COVID-19). Resistance increased significantly in K. pneumoniae to cephalosporins, fluoroquinolones, and carbapenems, and in P. aeruginosa and Acinetobacter spp. to carbapenems, while P. aeruginosa resistance to aminoglycosides declined. Strong correlations were found between carbapenems use and Acinetobacter spp. resistance (r = 0.861, p = 0.001), and vancomycin use and E. faecalis resistance (r = 0.798, p = 0.006). Moderate correlations were also observed between carbapenems use and resistance of K. pneumoniae and P. aeruginosa. Conclusions: These findings highlight the profound impact of the COVID-19 pandemic on AMR dynamics, particularly among Gram-negative pathogens, and underscore the urgent need for strengthened antimicrobial stewardship and targeted surveillance to curb the spread of MDR pathogens, especially in resource-limited hospitals. Full article

Canine otitis externa is a common and recurrent ear infection in dogs, often caused by bacterial pathogens, and complicated by increasing antimicrobial resistance. The analysis of bacterial isolates from dogs with otitis externa revealed a predominance of Staphylococcus pseudintermedius, representing 41% of all cases, followed by Staphylococcus aureus (23%), and Pseudomonas aeruginosa (19%). Other less frequently isolated organisms included Escherichia coli, Streptococcus canis, and Proteus mirabilis. These results highlight the significant role of S. pseudintermedius in the pathogenesis of otitis externa in dogs, as well as the relevance of Gram-negative opportunistic pathogens like P. aeruginosa, which exhibits the highest recurrence rate, with 90% of the cases associated with highly resistant to β-lactams (93% for amoxicillin–clavulanic acid; >70% for third-generation cephalosporins). P. mirabilis showed complete resistance to tetracycline, partial resistance to doxycycline, and reduced susceptibility to carbapenems, nitrofurantoin, and polymyxin B. S. canis exhibited limited resistance to erythromycin and clindamycin, while S. epidermidis displayed extensive multidrug resistance, including β-lactams, fluoroquinolones, sulfonamides, and polymyxins. These findings highlight the high prevalence of multidrug-resistant pathogens in canine otitis externa, emphasizing the need for culture-guided therapy and raising concerns regarding One Health, due to potential zoonotic transmission and dissemination of genetic determinants of antimicrobial resistance. Full article

Background: The COVID-19 pandemic profoundly affected healthcare delivery and antibiotic prescribing, raising concerns about increasing antimicrobial resistance. This study investigated seven-year trends in bacterial resistance, underlying resistance mechanisms, and antibiotic consumption in COVID-19 and non-COVID-19 units at a tertiary hospital in Slovakia. Methods: A retrospective cohort analysis (2018–2024) was conducted using clinical isolates of Klebsiella sp., Acinetobacter sp., and P. aeruginosa. Data on hospitalizations, resistance profiles, resistance mechanisms, and standardized antibiotic use were compared between COVID-19 and non-COVID-19 departments. Results: Hospitalizations markedly decreased in COVID-19 units, while pathogen occurrence—particularly of Acinetobacter sp.—was substantially higher compared with non-COVID-19 units. Resistance in Klebsiella sp. shifted from extended-spectrum beta-lactamase production to carbapenemase production. Acinetobacter sp. remained highly resistant, although some declines were observed in ceftazidime and gentamicin resistance. P. aeruginosa showed a gradual reduction in resistance, notably to piperacillin/tazobactam and imipenem. Antibiotic consumption was consistently higher in COVID-19 units, particularly for broad-spectrum beta-lactams and carbapenems, whereas fluoroquinolone use decreased over time. Clinically effective treatment options were considerably fewer in COVID-19 units, often limited to colistin. Conclusions: COVID-19 units experienced greater pathogen burden, higher broad-spectrum antibiotic exposure, and increased prevalence of critical resistance mechanisms. Tailored antimicrobial stewardship and infection prevention, and control are essential to reduce selective pressure and preserve last-line antibiotics. Full article

Background and Objectives: Odontogenic infections are common emergencies in oral and maxillofacial surgery. They are typically polymicrobial, with aerobes guiding initial empirical therapy. However, regional data on their microbiology and resistance patterns in Romania are limited. This study aimed to characterize the aerobic microbial profile of odontogenic infections in Southwestern Romania and assess the antimicrobial susceptibility of isolated pathogens. Materials and Methods: A prospective observational study was conducted over 12 months at a tertiary referral hospital. Pus samples collected intraoperatively were cultured aerobically. Bacterial identification used biochemical methods and the VITEK 2 system. Antimicrobial susceptibility was determined by disk diffusion and automated MIC testing, interpreted according to EUCAST v13.0 (2023). Results: Of 110 patients, 96 (87.3%) yielded positive aerobic cultures, producing 97 isolates. Streptococcus spp. were predominant (49.5%), followed by coagulase-negative staphylococci (24.7%), Staphylococcus aureus (14.4%), Enterobacterales (7.2%), and Pseudomonas aeruginosa (3.1%). Streptococcus spp. remained susceptible to penicillin G (82.3%), amoxicillin–clavulanate (76.4%), and clindamycin (70.5%), but only 55.0% to erythromycin. Most S. aureus isolates were methicillin-susceptible (92.9%), while coagulase-negative staphylococci showed high methicillin resistance (59.3%) yet full susceptibility to linezolid, vancomycin, and teicoplanin. Enterobacterales were resistant to ampicillin (90%) and amoxicillin–clavulanate (65%) but remained susceptible to ceftriaxone (80%) and ciprofloxacin (85%). P. aeruginosa isolates were fully susceptible to piperacillin–tazobactam, ceftazidime, cefepime, and meropenem. Conclusions: This study provides regional data on aerobic pathogens in odontogenic infections. High resistance to penicillin and macrolides limits empirical use. Amoxicillin–clavulanate and clindamycin retain moderate activity, while glycopeptides, linezolid, and carbapenems preserved full efficacy. Surgical drainage remains central to management, and antibiotic therapy should be guided by local susceptibility patterns. These data provide baseline information to inform empirical therapy and stewardship efforts and highlight the need for multicenter studies including anaerobic and molecular analyses. Full article

Background/Objectives: Gram-negative bacteria with acquired carbapenem resistance have become increasingly common in serious infections. This study aimed to evaluate the in vitro activity of cefiderocol against multidrug-resistant Gram-negative clinical isolates collected from a tertiary care hospital in Romania. Methods: A retrospective study (November 2024–February 2025) involving 89 consecutive Multi-Drug Resistant (MDR) Gram-negative isolates, 66 Enterobacterales and 23 non-fermenters (P. aeruginosa, S. maltophilia, A. baumannii), was conducted. Results: Overall, 52.8% of Enterobacterales and P. aeruginosa isolates were susceptible to cefiderocol, with higher susceptibility among Enterobacterales alone (63.6%). Using disk diffusion, 66.3% of all isolates were classified as susceptible to the antibiotic. K. pneumoniae isolates co-harboring NDM and OXA-48 were susceptible in 65.3% of cases, while NDM-only producers were resistant. All P. aeruginosa isolates tested were susceptible to the antibiotic. Susceptibility rates in A. baumannii were lower (68.8%), with variability between testing methods. Conclusions: The presence of NDM-producing isolates with complete resistance to cefiderocol in our study highlights the risk that resistance may spread rapidly once the drug becomes widely used. Cefiderocol may be an effective option for treating MDR bacterial infections, but strict microbiological monitoring remains essential. Full article

Background: Urinary tract infections (UTIs) are among the most common hospital- and community-acquired infections, creating a substantial healthcare burden due to recurrence, complications, and rising antimicrobial resistance. Accurate diagnosis and timely antimicrobial therapy are essential. This study aimed to identify trends in the etiology, treatment, and resistance patterns of UTIs through a retrospective analysis of urine isolates processed at the Laboratory of Microbiology at University Hospital St. George in Plovdiv, the largest tertiary care and reference microbiology center in Bulgaria, between 2017 and 2022. Materials and Methods: A retrospective single-center study was performed at the hospital’s Microbiology Laboratory. During the study period, 74,417 urine samples from 25,087 hospitalized patients were screened with the HB&L UROQUATTRO system. Positive specimens were cultured on blood agar, Eosin-Methylene Blue, and chromogenic media. Identification was performed using biochemical assays, MALDI-TOF MS, and the Vitek 2 Compact system. Antimicrobial susceptibility testing included disk diffusion, MIC determination, broth microdilution (for colistin), and Vitek 2 Compact, interpreted according to EUCAST standards. Descriptive analysis and temporal resistance trends were evaluated with regression models, and interrupted time-series analysis was applied to assess COVID-19-related effects. Results: Out of 10,177 isolates, Gram-negative bacteria predominated (73%), with Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis as the leading pathogens. Among Gram-positives, Enterococcus faecalis was the most frequent. In the post-COVID-19 period, ESBL production increased in E. coli (34–38%), K. pneumoniae (66–77%), and P. mirabilis (13.5–24%). Carbapenem resistance rose in K. pneumoniae (to 40.6%) and P. aeruginosa (to 24%), while none was detected in E. coli. Colistin resistance increased in K. pneumoniae but remained absent in E. coli and P. aeruginosa. High-level aminoglycoside resistance in E. faecalis was stable (~70%), and vancomycin resistance in E. faecium rose from 4.6% to 8.9%. Conclusions: Both community- and hospital-acquired UTIs in Southeastern Bulgaria are increasingly linked to multidrug-resistant pathogens, particularly ESBL-producing and carbapenem-resistant Enterobacterales. Findings from the region’s largest referral center highlight the urgent need for continuous surveillance, rational antibiotic use, and novel therapeutic approaches. Full article