Pseudomonas aeruginosa is one of the most commonly isolated bacteria from clinical specimens, with an increasing isolation frequency in nosocomial outbreaks. The hypothesis tested was whether carbapenem-resistant P. aeruginosa strains display an altered carriage of the virulence factor genes, depending on the type of carbapenem resistance. The aim of the study was to investigate, by PCR, the frequency of 10 chosen virulence factors genes (phzM, phzS, exoT, exoY, exoU, toxA, exoS, algD, pilA and pilB) and the genotype distribution in 107 non-duplicated carbapenem-resistant P. aeruginosa isolates. P. aeruginosa genes involved in phenazine dyes and exoenzyme T synthesis were noted with the highest frequency (100%). Fimbriae-encoding genes were detected with the lowest incidence: 15.9% and 4.7% for pilin A and B, respectively. The differences observed between the exoS gene prevalence amongst the carbapenemase-positive and the carbapenemase-negative strains and the pilA gene prevalence amongst the strains of different origins were statistically significant. Virulence genes’ prevalence and the genotype distribution vary amongst P. aeruginosa strains resistant to carbapenems, especially in terms of their carbapenemase synthesis ability and the strain origin.

Viral infections, or their reactivations, are one of the most important groups of transplantation complications that can occur among recipients of both hematopoietic cells and solid organ transplants. They are the most commonly caused by cytomegalovirus (CMV). Currently, the use of whole blood or plasma samples is recommended for CMV viral load monitoring. The aim of the study was to assess and compare the level of CMV DNA, depending on the type of clinical material—whole blood or plasma fraction derived from the same patient. The studies were carried out on 156 whole blood samples in which the presence of CMV genetic material was confirmed and the corresponding plasma samples from the same rounds of sampling. CMV DNA was not present in 59 (37.8%) of plasma samples compared to whole blood-positive counterparts. Of the samples positive in both types of clinical specimen, 77 (79.4%) had higher viral DNA levels in the whole blood samples. There were statistically significant differences in the detected CMV DNA load in the whole blood compared to plasma fraction counterparts (p < 0.001). The detected CMV DNA value is usually higher in whole blood compared to plasma samples of the same patient. Due to the variability in CMV viral load depending on the clinical material used for a particular patient, one type of specimen should be always used consequently for CMV viremia monitoring.

Epstein–Barr virus (EBV) is an oncogenic virus classified by the World Health Organization as a class 1 carcinogen. Post-transplant lymphoproliferative disorders are believed to be strongly related to an EBV infection. Monitoring of EBV DNAemia is recommended to assess the risk of reactivation of latent infection and to assess the effectiveness of therapy. Currently, various types of clinical specimens are used for this purpose. The aim of the study was to assess a reliable method of EBV viral load investigation depending on the clinical material used: whole blood or plasma samples. We found that of 134 EBV-DNA-positive whole-blood samples derived from 51 patients (mostly hemato-oncology or post-transplantation), only 43 (32.1%) were plasma-positive. Of these, 37 (86.0%) had lower plasma DNAemia compared to the corresponding whole-blood samples. We conclude that whole-blood samples have a higher sensitivity than plasma samples in EBV DNA detection. The clinical utility of the tests is unclear, but our results suggest that either whole blood or plasma should be used consistently for EBV viral load monitoring.

Pseudomonas aeruginosa is a Gram-negative rod and an etiological factor of opportunistic infections. The infections of this etiology appear mostly among hospitalized patients and are relatively hard to treat due to widespread antimicrobial resistance. Many virulence factors are involved in the pathogenesis of P. aeruginosa infection, the coexistence of which have a significant impact on the course of an infection with a particular localization. The aim of this study was to assess the antimicrobial susceptibility profiles and the frequency of genes encoding selected virulence factors in clinical P. aeruginosa strains isolated from bloodstream infections (BSIs). The following genes encoding virulence factors of enzymatic activity were assessed: lasB, plC H, plC N, nan1, nan2, aprA and phzM. The frequency of the genes encoding the type III secretion system effector proteins (exoU and exoS) and the genes encoding pilin structural subunits (pilA and pilB) were also investigated. The occurrence of virulence-factor genes was assessed using polymerase chain reactions, each in a separate reaction. Seventy-one P. aeruginosa strains, isolated from blood samples of patients with confirmed bacteremia hospitalized at the University Hospital No. 1 of Dr. Antoni Jurasz in Bydgoszcz, Poland, were included in the study. All the investigated strains were susceptible to colistin, while the majority of the strains presented resistance to ticarcillin/clavulanate (71.8%), piperacillin (60.6 %), imipenem (57.7%) and piperacillin/tazobactam (52.1%). The presence of the lasB and plC H genes was noted in all the tested strains, while the plC N, nan2, aprA, phzM and nan1 genes were identified in 68 (95.8%), 66 (93.0%), 63 (88.7%), 55 (77.5%) and 34 (47.9%) isolates, respectively. In 44 (62.0%) and 41 (57.7%) strains, the presence of the exoU and exoS genes was confirmed, while the pilA and pilB genes were noted only in 14 (19.7%) and 3 (4.2%) isolates, respectively. This may be due to the diverse roles of these proteins in the development and maintenance of BSIs. Statistically significant correlations were observed between particular gene pairs’ coexistence (e.g., alkaline protease and neuraminidase 2). Altogether, twenty-seven distinctive genotypes were observed among the studied strains, indicating the vast variety of genetic compositions of P. aeruginosa strains causing BSIs.

Bacterial infection of the lower respiratory tract frequently occurs in mechanically ventilated patients and may develop into life-threatening conditions. Yet, existing diagnostic methods have moderate sensitivity and specificity, which results in the overuse of broad-spectrum antibiotics administered prophylactically. This study aims to evaluate the suitability of volatile bacterial metabolites for the breath-based test, which is used for diagnosing Ventilator-Associated Pneumonia (VAP). The in vitro experiments with pathogenic bacteria most prevalent in VAP etiology (i.e., Acinetobacter baumannii, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa) were performed to identify bacteria-derived metabolites using a specially designed cultivation system enabling headspace sampling for GC-MS analysis. Thirty-nine compounds were found to be significantly metabolized by tested species and, therefore, selected for monitoring in the exhaled breath of critically ill, mechanically ventilated (MV) patients. The emission of volatiles from medical respiratory devices was investigated to estimate the risk of spoiling breath results with exogenous pollutants. Bacterial metabolites were then evaluated to differentiate VAP patients from non-infected MV controls using Receiver Operating Characteristic (ROC) analysis, with AUC, sensitivity, and specificity calculated. Nine bacterial metabolites that passed verification through a non-parametric ANOVA test for significance and LASSO penalization were identified as key discriminators between VAP and non-VAP patients. The diagnostic model achieved an AUC of 0.893, with sensitivity and specificity values of 87% and 82.4%, respectively, being competitive with traditional methods. Further validation could solidify its clinical utility in critical care settings.

Healthcare-associated infections caused by multidrug-resistant Acinetobacter baumannii strains are a serious global threat. Therefore, it is important to expand the knowledge on the mechanisms of pathogenicity of these particular bacteria. The aim of this study was to assess the distribution of selected virulence factor genes (bap, surA1, omp33-36, bauA, bauS, and pld) among carbapenem-non-susceptible clinical A. baumannii isolates and to evaluate their potential usefulness as genetic markers for rapid diagnostics of A. baumannii infections. Moreover, we aimed to compare the virulence genes prevalence with the occurrence of carbapenemases genes. A total of 100 carbapenem-non-susceptible A. baumannii clinical isolates were included in the study. The presence of virulence factors and bla_OXA genes was evaluated by real-time PCR. The occurrence of virulence factors genes was as follows: 100.0% for the bap and surA1 genes, 99.0% for the basD and pld genes. The bauA and omp33-36 genes were absent among the studied strains. The predominant genes (bap and surA1) are involved in biofilm formation and their presence among all clinical strains can be applied as a genetic marker to recognize A. baumannii infection. High frequencies of the basD gene—involved in siderophore biosynthesis and the gene encoding phospholipase D (pld)—were also noted among bla_OXA-positive strains, showing their potential role in a pathogenicity of bla_OXA-positive A. baumannii clinical strains.