Background/Objectives: Carbapenem-resistant Klebsiella pneumoniae (CRKP) infections present a significant clinical challenge due to limited therapeutic options and high transmission potential. This study aimed to identify the resistance genes associated with carbapenemase production in CRKP isolates and evaluate the in vitro activity of ceftazidime/avibactam (CZA) and meropenem/vaborbactam (MEV), among other β-lactam/β-lactamase inhibitor combinations. Methods: Between October 2021 and June 2022, a total of 504 CRKP isolates were grown from patient samples in intensive care units. When duplicate patient samples were removed, the remaining 89 isolates were included in the study. Bacterial identification and antimicrobial susceptibility testing were per-formed using MALDI-TOF, Phoenix M50, and disk diffusion methods, following EUCAST guidelines. PCR analyses identified carbapenemase genes such as OXA-48, NDM, and KPC. Results: The most prevalent carbapenemase gene was OXA-48 (79.8%), followed by NDM (21.4%) and KPC (17.9%). The susceptibility rate to CZA was 82.0%, significantly higher than MEV (10.1%). All isolates were resistant to piperacillin/tazobactam and ceftolozane/tazobactam. Among MEV-resistant isolates, most carried the OXA-48 gene, while NDM was common in CZA-resistant isolates. Conclusions: CZA demonstrates high efficacy against OXA-48-producing CRKP, making it a viable treatment option in settings where OXA-48 predominates. The limited activity of MEV in this study underscores the need for molecular surveillance of resistance mechanisms to guide empirical therapy.

Objective: Invasive candidiasis is defined as an important infection that increases the duration of patients’ hospital stay, costs, mortality and morbidity. In this study, we aimed to investigate the frequency of candidiasis in blood cultures of pediatric hematology patients, Candida species, antifungal susceptibilities, and their effects on mortality. Materials and Methods: Patients with Candida growth in their blood cultures at follow-up in the pediatric hematology clinic of our hospital between 2020 and 2024 were included in the study. Age, gender, primary diseases and risk levels, subtypes and antifungal susceptibilities of Candida grown in blood cultures, the presence of neutropenia in patients, the antifungals used for prophylaxis and treatment, the duration of infection, other bacteria grown additionally during the fungal infection period, the local infection source and the patients’ discharge status were obtained from medical records. These constituted the study data. Results: Blood cultures were requested for 594 patients from the Pediatric hematology Clinic, and Candida was grown in only 37 (6.7%) of them. A total of 43.2% of them were the Candida parapsilosis complex, 29.7% were Candida albicans and 8.1% were the Candida haemulonii complex. Antifungal susceptibilities were over 90% for anidulafungin, micafungin, caspofungin, posaconazole, itraconazole and amphotericin B, followed by 86.7% for fluconazole and 84.4% for voriconazole. The mean age of the patient group was 6.8 years, 50.5% of whom were female and 40.5% of whom were male. The Candida infections developed on the 12.1th day of the neutropenia process on average. The mean invasive Candida infection period was 7 days. A total of 18.9% had a second bacterial infection and 13.5% had a local infection. A total of 51.4% had a single antifungal, 18.9% had two antifungals and 2.1% had more than two antifungals. A total of 35.1% of the patients with invasive candidiasis died. The primary diagnosis of the disease, Patient risk level, and the female gender were important factors affetting mortality. Conclusions: In a pediatric hematology clinic, the non-albicans group in invasive candidiasis infections was notable, with the C. parapsilosis complex occurring most frequently. There was still a high sensitivity to echinocandin antifungals and a decreased sensitivity to triazoles. It was found that the factor of the clinical diagnosis, being in the high-risk group and being female had significant effects on the survival rate of patients with candidiasis infections.

In this study, we aimed to determine the antibiotic resistance status of Campylobacter spp. isolated from human infections in our region, including the role of mechanisms involved in erythromycin resistance. Standard methods were used for the isolation, identification and antibiotic susceptibility testing of Campylobacter spp. isolates. Erythromycin-resistant mutants were selected from erythromycin-susceptible clinical isolates, and the erythromycin resistance mechanisms were investigated phenotypically by determining the erythromycin MICs of isolates in the presence and absence of the resistance nodulation cell division (RND) type efflux pump inhibitor, phenylalanine-arginine beta-naphthylamide dihydrochloride (PA beta N), and genotypically by determining ribosomal and cmeABC alterations using PCR and DNA sequence analysis. Campylobacter spp., including 184 C. jejuni and 20 C. coli in a two-year period, were the most frequently isolated gastrointestinal bacterial pathogens in our region. However, in both C. jejuni and C. coli, resistance to tetracycline and ciprofloxacin were found to be high, erythromycin resistance was especially high (20%) in C. coli. With a ribosomal alteration, A2075G, which was found to be associated with high-level erythromycin resistance in clinical isolates, PA beta N significantly reduced the erythromycin MICs in both clinical isolates and mutants. An important finding of this study, while considering cmeABC operon, is the explanation of why erythromycin resistance is more common among C. coli than C. jejuni, bearing in mind the specific deletions and alterations in the intergenic region of the operon in all erythromycin-resistant C. coli isolates. Ultimately, these findings revealed the significant role of RND-type efflux activity in increased erythromycin MICs of the isolates.

Objective: To evaluate demographic, laboratory, biopsy, and imaging variables as potential predictors of microbial identification in patients with suspected vertebral osteomyelitis, aiming to enhance diagnostic accuracy and optimize patient care. Methods: This retrospective cohort study analyzed 83 patients who underwent image-guided percutaneous disc-space sampling between June 2020 and December 2023. Inclusion criteria were adults aged ≥18 years with imaging-based evidence of vertebral osteomyelitis and clinical suspicion of infection. Exclusion criteria were presence of known malignancy and non-infective causes. Demographics, clinical history, imaging, biopsy, and microbiology data were collected. Logistic regression analysis was used to identify predictors of positive microbiological yield. Results: Microorganisms were identified in 32 of 83 cases (38.6%), with Mycobacterium tuberculosis being the most common pathogen identified (21.9%). Elevated C-reactive protein (CRP) levels, erythrocyte sedimentation rate (ESR), and paravertebral signal changes on MRI were associated with a positive culture yield. Multivariate analysis identified CRP as an independent predictor of positive microbiological results. CT-guided percutaneous biopsy was found to be safe, with no major complications reported. Conclusion: CT-guided percutaneous biopsy is a reliable and safe diagnostic tool for identifying the causative pathogens in vertebral osteomyelitis. Elevated CRP levels were independently associated with positive microbiological yield, highlighting its role as a crucial predictor in clinical practice. These findings underscore the importance of incorporating CRP levels into the diagnostic process, potentially guiding the selection of patients for biopsy to improve the detection of infection.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is routinely used in clinical microbiology for rapid species identification; however, its potential to support early antimicrobial decision-making remains under active investigation. Rapid discrimination of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-susceptible Staphylococcus aureus (MSSA) at the time of identification could facilitate earlier optimization of antimicrobial therapy and infection control measures. In this study, MALDI-TOF MS spectral data were analyzed to evaluate supervised machine learning–based differentiation of MRSA and MSSA. A total of 91 S. aureus isolates (37 MRSA and 54 MSSA) were included, with methicillin susceptibility determined by the cefoxitin disk diffusion test according to EUCAST guidelines and used as the reference standard. MALDI-TOF MS spectra were acquired following standard on-plate extraction, subjected to quality control, and preprocessed prior to analysis. Principal component analysis demonstrated partial but consistent separation between MRSA and MSSA isolates. A Random Forest classifier was trained and validated using stratified 10-fold cross-validation, achieving an overall classification accuracy of 81.3% and a receiver operating characteristic area under the curve of 0.916. Class-specific analysis revealed high precision for MRSA (95.5%) and excellent recall for MSSA (98.1%). These findings indicate that MALDI-TOF MS combined with machine learning can provide clinically relevant information for rapid MRSA/MSSA differentiation and may serve as a cost-free decision-support approach in routine clinical microbiology workflows, complementing standard phenotypic susceptibility testing.