Staphylococcus aureus nasal carriage contributes to asymptomatic transmission in both community and healthcare settings. This study aimed to characterize S. aureus strains isolated from students of the Pomeranian Medical University in Szczecin, Poland, using phenotypic and genotypic methods. A total of 175 S. aureus strains were isolated from the nasal vestibules of 800 students between 2014 and 2015. Species identification and antimicrobial susceptibility testing were performed using standard microbiological methods, while virulence-associated genes and agr groups were analyzed using Single-PCR and Multiplex-PCR assays. Genotypic diversity was assessed by pulsed-field gel electrophoresis (PFGE). The prevalence of S. aureus nasal carriage among students was 21.9% and did not differ according to faculty or year of study. Most isolates (84.0%) were susceptible to all tested antibiotics, and no methicillin-resistant S. aureus (MRSA) strains were detected. All strains carried the hla gene, whereas hld and hlg were identified in 93.7% and 93.1% of isolates, respectively. In addition, the tst gene was detected in 22.3% of strains, while the lukS-PV/lukF-PV genes were identified in only one isolate (0.6%). The most prevalent enterotoxin genes were sep (17.1%) and sea (13.7%), whereas genes of the egc cluster, including seg, sei, and seo, were detected in 53.7% of isolates. Significant associations were observed between specific egc gene combinations and superantigen gene profiles, including increased frequencies of sec, sel, and tst genes (p < 0.001). The predominant agr type was agr-1 (49.7%), followed by agr-3 (28.6%) and agr-2 (20.0%). Strains carrying agr-1 more frequently harbored the g i m n o cluster as well as the sec, sel, and sep genes, whereas agr-3-positive isolates were significantly associated with the g i m o u and g i o u clusters and with the presence of tst, sea, and seh genes (p < 0.05). PFGE analysis demonstrated substantial genetic heterogeneity among the isolates, with no evidence of a predominant clonal lineage. These findings indicate a heterogeneous, non-epidemic population structure of S. aureus strains circulating among university students and highlight the considerable diversity and interrelationships of virulence-associated genetic profiles within this population.

Wound infections pose a significant challenge in modern medicine, driven by multimorbidity, weakened immunity, microbial virulence factors, and resistance to antibiotics and antiseptics. This study aims to evaluate the antibacterial properties of carvacrol (CAR), its impact on biofilm formation, and its capacity to trigger oxidative stress in clinical strains of Pseudomonas aeruginosa, Klebsiella pneumoniae, and Enterobacter cloacae. Carbapenemases in the studied bacteria were detected using culture on CarbaId agar. The presence of genes encoding bacterial virulence factors and carbapenemase production was confirmed using the PCR method. The antimicrobial activity of carvacrol was evaluated using the broth microdilution method. The ability of strains to form biofilm was determined using a modified crystal violet assay. Oxidative stress levels in bacterial cells in response to carvacrol treatment were measured using 2′,7′-dichlorofluorescein diacetate. Real-TimePCR was used to confirm the presence of NDM family carbapenemase genes in K. pneumoniae strains, KPC genes in E. cloacae strains, and VIM genes in P. aeruginosa strains. CAR exhibited a broad spectrum of antibacterial activity against the tested bacteria, with MIC values ranging from 125 to 1000 μg/mL. Treatment with 1/2 MIC of CAR did not significantly influence biofilm formation, except in a K. pneumoniae isolate. At 1/2 MIC, CAR induced an increase in intracellular ROS in most tested strains, with the exception of P. aeruginosa 25521221. This study provides insights into the antimicrobial efficacy of carvacrol against carbapenemase-producing pathogens isolated from wound infections—specifically P. aeruginosa, K. pneumoniae, and E. cloacae. CAR demonstrated promising bactericidal properties, likely mediated through the induction of oxidative stress, as evidenced by increased ROS generation in most studied isolates.

Klebsiella pneumoniae, due to its capacity to produce numerous virulence factors and form biofilms, is one of the most significant etiological agents of nosocomial infections. The extensive and often unwarranted use of antibiotic therapy has driven the emergence of various mutations, adaptive mechanisms, and horizontal gene transfer among K. pneumoniae strains, resulting in resistance to most beta-lactam antibiotics, carbapenems, and the last-resort drug—colistin. A promising alternative or adjunctive treatment is the application of rotating magnetic fields (RMFs). The present study aimed to evaluate changes in colistin susceptibility among 20 extended-spectrum beta-lactamases (ESBLs) and 20 K. pneumoniae carbapenemase (KPC)-positive K. pneumoniae strains isolated from hospital infections following exposure to RMF at frequencies of 5 and 50 Hz. Exposure to RMF at 5 Hz resulted in decreased colistin minimum inhibitory concentration (MIC) values in over half of the tested (ESBLs) and (KPC)-positive strains. Additionally, RMF at 50 Hz reduced colistin MIC values in 30% of (ESBL)-positive and 40% of (KPC)-positive strains. Therefore, in the future, RMF may be developed as a supportive therapeutic strategy to improve the efficacy of antibiotics in the treatment of infections caused by multidrug-resistant (MDR) pathogens, including colistin-resistant K. pneumoniae.

Klebsiella pneumoniae is a typical opportunistic pathogen that exhibits multiple virulence factors and antibiotic resistance conditioning mechanisms. Carbapenemases are enzymes that help bacteria to exhibit the strongest resistance against antibiotics. Therefore, in routine microbiological diagnoses, it is crucial to confirm antibiotic-resistant strains, including carbapenemase-producing bacteria strains, isolated from patients. Two types of tests play an important role here: phenotypicand molecular diagnostic methods. The latter complement phenotypic tests and a mandatory procedure to confirm the detection of carbapenemases. This study aimed to evaluate the usefulness and effectiveness of tests and methods used to identify and confirm the ability of clinical K. pneumoniae strains to produce carbapenemases. The production of carbapenemases was assessed using phenotypic and genetic methods. The strains tested showed complete resistance to most beta-lactams and varying sensitivity to drugs from the quinolone carbapenem group and aminoglycosides. Among the most commonly produced carbapenemases were the metallo-beta-lactamase (NDM) family. The most accurate phenotypic method for detecting carbapenemases was the NG CARBA-5 assay, and the PCR method confirmed these results. Notably, a few inconclusive results were obtained for NDM-positive and VIM-positive strains when the disk diffusion method and CIM test were used. Further, the Carba tube assay and the RAPIDEC CARBA NP assay produced questionable results for the OXA-48 strain group. This group also generated false-negative results on Carba's CHROM ID medium.

The COVID-19 pandemic made the medical community realize how large a problem it would face. The epidemiological situation forced the opening of additional wards, the so-called “COVID wards”, where an increase in the rate of coexisting bacterial infections was observed. We report a hospital outbreak due to New Delhi carbapenemases producing K. pneumoniae clones. Twenty-eight K. pneumoniae strains were analyzed from patients with primary COVID-19 infection. The drug susceptibility of the strains was determined by the diffusion–circulation method and E-test. Phenotypic and PCR methods confirmed the production of carbapenemases. The phylogenetic similarity of the obtained strains was examined using pulsed-field electrophoresis. Most strains were isolated from bronchoalveolar lavage. All isolates obtained were resistant to β-lactams and fluoroquinolones. All strains produced New Delhi carbapenemases and were classified into two genetic clusters, A and B. Eight risk factors for secondary bacterial infection were analyzed. Following an intervention involving hand hygiene, strict contact prevention, and cleaning of the hospital environment and medical devices, this outbreak was successfully brought under control.

Infections caused by Acinetobacter baumannii are increasing worldwide. We evaluated the antibiotic resistance profile, biofilm production, and the frequency of 12 genes encoding carbapenemases and 13 virulence factors in 90 isolates from patients of three hospitals in various regions of Poland. Antibiotic resistance survey was performed using the disc-diffusion method, genes encoding resistance to carbapenems and virulence factors were detected with PCR, and biofilm formation was tested using microtiter plates. A total of 52.2% of isolates were resistant to all tested antibiotic groups (penicillins with β-lactamase inhibitors, cephalosporins, carbapenems, aminoglycosides, fluoroquinolones, and trimethoprim plus sulfamethoxazole). Among the genes encoding carbapenem resistance, the blaOXA-23 (68.9%), blaOXA-40 (83.3%), and ISAba-blaOXA-51 (18.9%) were detected. The ompA, ata, and recA genes responsible for biofilm formation, adhesion, and stress response, respectively, occurred in all isolates. Genes responsible for the production of other adhesins (bap—94.4%, espA—4.4%, chop—37.7%), biofilm formation (pbpG—90.0%), production of siderophore (basD—97.7%), toxins (lipA—92.2%, cpaA—1.1%), glycoconjugates (bfmR—84.4%), and inducing host cell death (fhaB—71.1%, abeD—93.3%) were also found. A total of 68.8% of isolates produced biofilm. The isolates from Masovia had more virulence genes than isolates from the other regions; moreover, all isolates from Masovia and West Pomerania were multidrug-resistant (MDR), including resistance to carbapenems.

Staphylococcus aureus, being one of the most common human pathogens, is responsible for infections in both hospital and community settings. Its virulence is attributed to its ability to evade the immune system by producing immune evasion (IE) proteins. The aim of this study was to detect the frequency of selected IE genes (spin, sbi, sea, sak, chp, scin, sep, ecb), belonging to the immune evasion cluster (IEC), and IEC types in 86 methicillin-susceptible S. aureus (MSSA) strains isolated from unrelated outpatients. In order to determine the diversity of analyzed strains, the phylogenetic relatedness was also determined. All strains were examined for the presence of IE genes using polymerase chain reaction assay. To analyze the clonal relatedness of S. aureus, pulsed-field gel electrophoresis (PFGE) was performed. All analyzed strains harbored the scn gene, followed by sbi (95.4%), ecb (91.7%), spin (89.5%), sak (83.7%), chp (67.4%), sep (67.4%) and sea (5.8%). Seventy-three (84.9%) S. aureus strains were classified into IEC types, of which, IEC type F was most commonly observed. IEC type A was not detected. PFGE results showed no association between clonal relatedness and the presence of IE genes/IEC types. In conclusion, the abundant and so diverse repertoire of genes determining invasion in analyzed strains may prove the fact that these strains are highly advanced and adapted to evade the host immune response.

Background: This in vitro study set out to find out how well oral cavity-dwelling bacteria can form biofilms and adhere on the surfaces of zirconium oxide samples created by 3D printing and milling technologies. Methods: 5 strains of microorganisms were used for the study, and 40 zirconium oxide samples were prepared, which were divided into two groups (n = 20)—20 samples produced using removal technology comprised the control group, while 20 samples produced by 3D printing technology comprised the test group. The prepared samples were placed in culture media of bacteria and fungi that naturally occur in the oral cavity. Then, the intensity of biofilm build-up on the samples was determined using qualitative and quantitative methods. The results for both materials were compared with each other. Results: No variations in the degree of biofilm deposition on zirconium oxide samples were found for the microorganisms Streptococcus mutans, Pseudomonas aeruginosa, Enterococcus faecalis, and Staphylococcus aureus. For Candida albicans fungi, more intense biofilm deposition was observed on samples made using 3D printing technology, but these differences were not statistically significant. Conclusion: The biofilm accumulation intensity of ceramics produced by additive technology is comparable to that of milled zirconium oxide, which supports the material’s broader use in clinical practice from a microbiological perspective. This ceramic has demonstrated its ability to compete with zirconium oxide produced by milling techniques in in vitro experiments, but sadly, no in vivo tests have yet been found to determine how this material will function in a patient’s oral cavity.

Introduction: Surgical site infections (SSIs) are at the forefront of healthcare-associated infections and the second most common cause of hospital readmission. The etiology of these infections is generally monobacterial with a predominance of Staphylococcus aureus. Although it is a preventable infection it significantly increases the cost of hospitalization and doubles the mortality rate.The aim of the present study was to evaluate the prevalence of SSIs and antimicrobial susceptibility of S. aureus isolated from SSIs in patients hospitalized at the Clinical Hospital No. 1 of the Pomeranian Medical University in Szczecin (Poland) – CH-1 – during the period 2019–2021, in the course of the COVID-19 pandemic.Materials and methods: Analysed specimens were collected from patients with diagnosed skin and soft tissue infections (SSTIs) caused by S. aureus, collected in 2019–2021, and then examined during routine microbiological diagnostics. The collection included specimens from patients hospitalized at CH-1, as well as consulted at the Emergency Department (ED) of CH-1, patients from healthcare facility of the Ministry of Internal Affairs and Administration in Szczecin, and from detainees of the Szczecin Detention Centre (Poland). Out of the total of 1140 results, 232 were classified as SSIs caused by S. aureus and then analysed. All the data were systemically entered into a spreadsheet (Excel 2019) and later subjected to several statistical tests (using StatSoft Statistica 13 package).Results: From the collection of results, 20.4% (232/1140) were considered as SSIs of S. aureus etiology. In the following years 2019, 2020, and 2021, the SSIs of S. aureus etiology were 17.1% (72/421), 19.5% (66/339), and 24.7% (94/380), respectively. Methicillin- -resistant S. aureus (MRSA) was the cause of 7% of analysed SSIs. The highest incidence of SSIs was observed mainly in patients admitted to the trauma and orthopaedic wards and in patients seen in the ED. The majority of SSIs were mono-etiologic, caused by S. aureus only (93%). Mixed etiology was determined in 7% of SSIs with a significant share of beta hemolytic streptococci, enterobacteria, and non-fermentative Gram-negative rods. A slight increase in the prevalence of SSIs was observed during the analysed period. The overall antimicrobial susceptibility of all examined strains was noted, with a low rate of MRSA. The obtained results demonstrate the good practice of both strategies of hospital infection control, as well as the coherent and rational antibiotic policy in the CH-1 in the West Pomeranian region in Poland. The 2017–2018 data on the incidence of SSTIs and the percentage of SSIs among patients hospitalized in CH-1 show that in 2017, SSIs represented 17.9% of all cases classified as SSTIs (57/318), followed by SSIs in 2018, which represented 19.5% of all SSTIs analysed in CH-1 (68/348). The percentage of SSIs among the total SSTIs confirmed during the 2-year pre-pandemic period did not indicate significant changes in the number of SSIs among CH-1 patients hospitalized during the period of analysis. Therefore, it can be concluded that pandemic restrictions did not significantly affect the trend in the predominant proportion of S. aureus among SSIs during the study period.

This study aimed to analyze the chemotactic response of differentiated HL-60 neutrophil-like (dHL-60) cells to trans-anethole (TA)-treated Staphylococcus aureus strains. Special attention was paid to evaluate the influence of TA on the chp gene expression level, as well as molecular docking and molecular dynamics (MD) simulation studies on interactions of TA with chemotaxis inhibitory protein of S. aureus (CHIPS). The following parameters were studied: susceptibility to TA using the agar diffusion method, the chp gene detection and its expression under TA influence, and clonal diversity of S. aureus strains using molecular techniques. Furthermore, a chemotactic response of dHL-60 cells to TA-treated S. aureus using Boyden chamber assay was detected and molecular modeling using both the docking methodology and unbiased MD simulations was conducted. It was found that TA showed antibacterial activity against all strains. Three genotypes and one unique pattern were distinguished among the strains. 50% of the isolates were chp-positive. It was observed that TA reduced/inhibited chp gene expression in most S. aureus strains. Enhanced chemotactic response of dHL-60 cells to TA-treated S. aureus strains was also noted. This correlation was similar for both chp-positive and chp-negative strains. Both molecular docking and MD simulations studies confirmed that TA is preferentially bound in the complement component 5a/CHIPS interface interaction region and can interfere with any processes exploiting this binding cavity. It has been proven that dHL-60 cells exhibited a higher chemotactic response to TA-treated S. aureus strains in comparison to non-treated bacteria, regardless of the achieved expression of the chp gene or its lack. Nevertheless, further analyses are required to understand this mechanism better.

Klebsiella pneumoniae is an important opportunistic pathogen responsible for severe infections, mainly urinary tract infections (UTIs) and pneumonia. Hospital epidemic infections caused by multiresistant strains of carbapenemase-producing K. pneumoniae are the most concerning. NDM-producing strains are resistant to a wide range of antibiotics and have become the most significant threat. Determining the natural reservoirs and routes of infections is essential to end hospital outbreaks. Understanding the relatedness of K. pneumoniae strains is essential to determine the range and nature of the infection. The study compared phylogenetic relatedness between multiresistant K. pneumoniae strains isolated from hospitalized patients. Susceptibility to drugs and mechanisms of resistance were confirmed using phenotypic methods. PFGE was used to analyze the relatedness between strains. We analyzed 69 K. pneumoniae strains from various healthcare units. The isolates were mainly identified from urine. Strains were resistant to β-lactam antibiotics with β-lactamase inhibitors, cephalosporins, and quinolones. Their susceptibility to aminoglycosides and carbapenem antibiotics was diverse. Most of the isolated strains produced New Delhi metallo-ß-lactamase (NDM). Although K. pneumoniae strains were classified into several genotype clusters, closely related isolates were confirmed in the same hospital's wards, and in two hospitals in the same province.

INTRODUCTION AND OBJECTIVE:Candidiasis is a fungal infection caused by yeasts from the Ogenus Candida. Considering increasing antifungal resistance rates the activity was analyzed of natural compounds to eradicate Candida spp. The aim of the study was to check the antifungal activity of selected essential oil compounds (EOCs; thymol, menthol, eugenol [E], carvacrol, trans-anethole [TA]) alone, and in combination with octenidine dihydrochloride (OCT) against C. albicans and C. parapsilosis reference, and clinical strains.MATERIAL AND METHODS:Investigated clinical isolates were obtained from skin wounds of patients treated for superficial wounds candidiasis. The following parameters were studied: antifungal susceptibility testing using the VITEK system, antifungal activity of EOCs alone and in combination with OCT using microdilution and checkerboard assays, antifungal efficacy of selected chemicals using time-kill curve assay, and changes in cell permeability in the presence of selected chemicals using crystal violet assay.RESULTS:Clinical isolates of C. albicans and C. parapsilosis were resistant to fluconazole and voriconazole. The highest inhibition activity against Candida isolates was observed for E. The OCT - TA and OCT - E combinations showed synergistic and additive activities against all strains, respectively. These combinations also appeared to affect the rate of yeast cell killing and increasing the permeability of Candida cells.CONCLUSIONS:The study indicates that E and TA potentially used in formulation with OCT might eradicate pathogenic yeasts; however, microbiological and clinical studies are still required.

In our former studies based on a human whole-blood model infected with trans-anethole (TA)-treated Staphylococcus aureus Newman strain, we have observed that selected parameters/mechanisms of innate and acquired immune response were more enhanced in comparison to samples infected with non-treated bacteria. Due to this observation, the current study aimed to evaluate the concentration of selected proteins involved in both types of responses (IL-1α, IL-1β, IL-2, IL-6, IL-12, IL-17, TNF-α, IFN-γ, G-CSF, C5a, CCL1-CCL5, CXCL1, CXCL2, CXCL9-CXCL11, MMP-8, TLR2, and PGLYRP1) in healthy participants' plasma after blood stimulation of TA-treated S. aureus Newman strain. Determination of analyzed protein concentration was conducted using Luminex and ELISA assays. Based on the results, it has been proven that the immunomodulatory potential of TA-treated S. aureus Newman strain on increasing IL-1β, IL-6, TNF-α, IL-12, G-CSF, C5a, CCL2-CCL4, CXCL1, CXCL2, MMP-8 and PGLYRP1 levels in plasma. Moreover, it has been also demonstrated an association between TNF-α and CCL4 in a blood model infected with TA-treated cells. More research is warranted to find more underlying mechanisms involved in the effects of TA-treated S. aureus Newman in human blood, mainly whether the observed "immunity boost" can be regulated after bacteria elimination. Therefore, the potential of TA should be further explored to understand under which conditions it might help treat or prevent infections caused by S. aureus.

The reduction of staphyloxanthin (STX) production in Staphylococcus aureus under trans-anethole (TA) influence was proven in former studies. However, no tests concerning the impact of TA on a biosynthetic pathway of this carotenoid pigment have been published so far. Thus, for the first time, the present preliminary study evaluated the influence of TA on the expression level of genes (crtOPQMN operon and aldH) encoding STX pathway enzymes. Additional attention was paid to the identification of STX and its intermediates. Gene expression and identification of extracted compounds were conducted using quantitative real-time PCR and HPLC-MS techniques, respectively. The analyzes showed no difference in crtM, crtN, crtO, crtP, crtQ, and aldH gene expression between bacterial samples isolated from the non-stimulated (control) medium and the stimulated one with TA. Compared to the control group that showed the presence of all metabolic intermediates and STX, the TA-treated bacteria were characterized by a lack or a significant reduction of the majority of compounds, except 4,4'-diaponeurosporenoate, the content of which was elevated in the TA-treated sample. Moreover, in silico molecular docking analysis revealed that TA is capable to create relatively strong interactions with both 4,4'-diapophytoene synthase and 4,4'-diapophytoene desaturase. The preliminary findings indicate that the previously observed TA effect reducing the number of S. aureus colonies pigmentation is probably not associated with the expression levels of genes encoding STX pathway enzymes. It has been proven that adding TA to the medium can interfere with the formation of STX at different levels of its biosynthetic pathway.

Introduction: Klebsiella pneumoniae is one of the etiological factors of nosocomial infections. Recently, infections caused by these bacteria have become more dangerous due to the acquired resistance to many antibiotics, severely limiting therapeutic options. The most common mechanism of resistance in K. pneumoniae rods is the production of extended-spectrum β-lactamases (ESBL). However, a more perilous mechanism is the production of carbapenemases. The course of the infection process is also influenced by various virulence characteristics, primarily enabling adhesion and aiding in avoiding host immune responses. Most genes encoding mechanisms of resistance and virulence are located on plasmids, facilitating their spread. The aim of the study was to detect selected virulence genes among clinical multidrug-resistant strains of K. pneumoniae. Materials and methods: We determined the drug susceptibility of strains and confirmed the presence of antibiotic resistance mechanisms using phenotypic methods. Additionally, we assessed the presence of genes encoding selected resistance mechanisms and genes determining selected virulence factors. A total of 134 strains from various hospital units were used for the study. Results: The highest percentage of strains was isolated from urine (46%). Among the isolates, 72% were from male patients. Fifty-seven percent of K. pneumoniae produced ESBL (KpESBL), while the remaining 43% carried the New Delhi metallo-β-lactamase (NDM) mechanism. The drug susceptibility of the KpESBL varied, with full sensitivity observed only in the case of antibiotics from the carbapenem group. New Delhi metallo-β-lactamase-producing K. pneumoniae showed sensitivity only to amikacin and gentamicin. In KpESBL strains, genes from the TEM family were most observed (74/76). Most of the strains had all 4 β-lactamase-encoding genes (61/76). In the group of strains producing carbapenemases, only the bla NDM gene was detected. Regardless of the resistance mechanisms, the tested strains most often had virulence genes related to the adhesion ability (fimH) and the structure of LPS (wabG).

INTRODUCTION AND OBJECTIVE:Klebsiella pneumoniae is an essential component of the human gut microflora. However, it can pose a threat by causing opportunistic infections, especially in hospitalised or immunocompromised patients. It is a serious problem for health medicine, primarily because of increasing resistance to previously used antibiotics. Infections with multidrug-resistant strains are difficult to treat, creating a challenge for clinicians. Also of growing concern is the increasing resistance to the drug of last resort - colistin (CL). The aim of the study is to determine the prevalence of resistance to CL among clinical K. pneumoniae strains.MATERIAL AND METHODS:The study was conducted on 200 clinical strains of K. pneumoniae. Drug susceptibility, production of resistance mechanisms, and determination of the minimum inhibitory concentration of CL were evaluated.RESULTS:Of all isolates, 73.0% produced carbapenemases, while the remainder produced an extended substrate spectrum - β-lactamases (ESBLs). All strains showed a diverse antibiotic resistance profile. Resistance to CL was noted among 14.5% of carbapenemase-producing strains, particularly MBL and OXA-48. ESBL-positive strains showed full susceptibility to CL.CONCLUSIONS:Although a low rate of CL resistance was observed, this was true for strains simultaneously producing carbapenemases. Such strains should be under special epidemiological surveillance due to their potential to cause epidemic outbreaks. Monitoring the prevalence of clinical CL-resistant strains would allow for more effective counteraction against pathogens in various fields, including medicine, agriculture, veterinary medicine and industry.

The study aimed to examine the influence of a rotating magnetic field (RMF) of two different frequencies (5 and 50 Hz) on the expression of regulatory (agrA, hld, rot) and staphylococcal enterotoxin (SE-sea, sec, sel) genes as well as the production of SEs (SEA, SEC, SEL) by the Staphylococcus aureus FRI913 strain cultured on a medium supplemented with a subinhibitory concentration of trans-anethole (TA). Furthermore, a theoretical model of interactions between the bacterial medium and bacterial cells exposed to RMF was proposed. Gene expression and SEs production were measured using quantitative real-time PCR and ELISA techniques, respectively. Based on the obtained results, it was found that there were no significant differences in the expression of regulatory and SE genes in bacteria simultaneously cultured on a medium supplemented with TA and exposed to RMF at the same time in comparison to the control (unexposed to TA and RMF). In contrast, when the bacteria were cultured on a medium supplemented with TA but were not exposed to RMF or when they were exposed to RMF of 50 Hz (but not to TA), a significant increase in agrA and sea transcripts as compared to the unexposed control was found. Moreover, the decreased level of sec transcripts in bacteria cultured without TA but exposed to RMF of 50 Hz was also revealed. In turn, a significant increase in SEA and decrease in SEC and SEL production was observed in bacteria cultured on a medium supplemented with TA and simultaneously exposed to RMFs. It can be concluded, that depending on SE and regulatory genes expression as well as production of SEs, the effect exerted by the RMF and TA may be positive (i.e., manifests as the increase in SEs and/or regulatory gene expression of SEs production) or negative (i.e., manifests as the reduction in both aforementioned features) or none.

The World Health Organization points out that the opportunistic pathogen Klebsiella pneumoniae that causes various infections among others, urinary tract infections (UTIs), is one of the high-priority species due to a global problem of antimicrobial resistance. The aim of this study was to investigate antibacterial and anti-biofilm activities of chosen constituents of essential oils against NDM-1-producing, uropathogenic K. pneumoniae strains. The genes encoding lipopolysaccharide (uge, wabG), adhesin gene fimH (type I fimbriae) and gene encoding carbapenemase (blaNDM-1) for all tested strains were detected by PCR amplification. The K. pneumoniae ATCC BAA-2473 reference strain was uge- and blaNDM-1-positive. The effectiveness of fifteen essential oil compounds (EOCs) (linalool, β-citronellol, linalyl acetate, menthone, (−)-menthol, (+)-menthol, geraniol, eugenol, thymol, trans-anethole, farnesol, β-caryophyllene, (R)-(+)-limonene, 1,8-cineole, and carvacrol) was assessed by determining the MIC, MBC, MBC/MIC ratio against K. pneumoniae strains by the microdilution method. Anti-biofilm properties of these compounds were also investigated. Thymol, carvacrol and geraniol exhibited the best antibacterial and anti-biofilm activities against uropathogenic NDM-1-producing K. pneumoniae isolates. Results of our investigations provide a basis for more detailed studies of these phytochemicals on their application against uropathogenic K. pneumoniae.

The aim of the study was to evaluate the clonal relatedness and antimicrobial susceptibility in 52 Staphylococcus aureus strains isolated from cut wound infections in non-related community patients and to determine the presence of selected virulence genes. To analyse the clonal relatedness of investigated strains, pulsed-field gel electrophoresis (PFGE) of macrorestricted DNA fragments was conducted. Antimicrobial susceptibility testing was performed using the AST-P644 card in the VITEK 2 Compact system. All strains were tested for the presence of selected virulence genes using Single and Multiplex PCR. All isolates were classified into 15 PFGE genotypes and seven unique patterns. The vast majority of investigated S. aureus strains were susceptible to all tested antimicrobial agents. Among examined S. aureus strains, 24 combinations of virulence factors were identified. 62.5% of S. aureus strains contained various egc types, alone or together with other staphylococcal enterotoxin genes. A high percentage (86.5%) of isolates harboured superantigen genes. The most frequent enterotoxin gene identified was encoding for sep. All S. aureus strains were classified as agr-positive, and the most frequent agr gene was agr-1. Our results indicate that all examined strains isolated from cut wound infections demonstrated high clonal diversity, diversified gene distribution and good susceptibility to antimicrobial agents.

Klebsiella pneumoniae is one of the most common etiological agents isolated from epidemic outbreaks in neonatal wards. We describe how an extended-spectrum β-lactamase-producing K. pneumoniae (ESBL-KP) outbreak in a neonatal ward was extinguished. During the outbreak, which lasted over two months, 26 neonates were tested for K. pneumoniae, and 42 environmental swabs were taken. Drug susceptibility was determined for the isolated strains, and their virulence and phylogenetic similarity were checked. ESBL-KP colonization was confirmed in 18 neonates, and six were also confirmed to be infected. All strains isolated from patients represented one clonal type, K. pneumoniae. One strain isolated from an environmental source was determined to be a unique pulsed-field gel electrophoresis pattern. Gestational age and Apgar score were assessed as statistically significant for neonates with ESBL-KP infection. The epidemiological measures taken have been successful, and no further cases appeared. Immediate tightening of hospital hygiene rules, screening of all hospitalized neonates, and cohorting ESBL-KP-positive patients proved effective in controlling and ending the outbreak. The lack of ESBL-KP in the environment suggests that the outbreak was transmitted by colonized hospital staff. This theory could be confirmed by introducing mandatory screening for medical personnel.