Quorum sensing (QS) is a mechanism that enables microbial communication. It is based on the constant secretion of signaling molecules to the environment. The main role of QS is the regulation of vital processes in the cell such as virulence factor production or biofilm formation. Due to still growing bacterial resistance to antibiotics that have been overused, it is necessary to search for alternative antimicrobial therapies. One of them is quorum quenching (QQ) that disrupts microbial communication. QQ-driving molecules can decrease or even completely inhibit the production of virulence factors (including biofilm formation). There are few QQ strategies that comprise the use of the structural analogues of QS receptor autoinductors (AI). They may be found in nature or be designed and synthesized via chemical engineering. Many of the characterized QQ molecules are enzymes with the ability to degrade signaling molecules. They can also impede cellular signaling cascades. There are different techniques used for testing QS/QQ, including chromatography-mass spectroscopy, bioluminescence, chemiluminescence, fluorescence, electrochemistry, and colorimetry. They all enable qualitative and quantitative measurements of QS/QQ molecules. This article gathers the information about the mechanisms of QS and QQ, and their effect on microbial biofilm formation. Basic methods used to study QS/QQ, as well as the medical and biotechnological applications of QQ, are also described. Basis research methods are also described as well as medical and biotechnological application.

Clostridium difficile infection (CDI) is one of the most common causes of nosocomial infectious diarrhea in children during anticancer therapy or undergoing hematopoietic stem cell transplantation (HSCT) in Europe. Immunosuppression in these patients is a risk factor for CDI. Malignant diseases, age, acute graft-versus-host disease (aGVHD), HLA mismatch, or use of total body irradiation may play an important role in CDI course. The aim of this study was to evaluate the incidence, course, and outcome of CDI in children treated for malignancy or undergoing HSCT. Between 2012 and 2015, a total number of 1846 patients were treated for malignancy in Polish pediatric oncological centers (PHO group) and 342 underwent transplantation (HSCT group). In PHO group, episodes of CDI occurred in 210 patients (14%). The incidence of CDI was higher in patients with hematological malignancies in comparison to that with solid tumors. Patients with acute myeloblastic leukemia had shorter time to episode of CDI than those with acute lymphoblastic leukemia. Patients over 5 years and treated for acute leukemia had more severe clinical course of disease in PHO group. In HSCT group, CDI occurred in 29 (8%) patients. The incidence of CDI was higher in patients transplanted for acute leukemia. The recurrence rate was 14.7% in PHO and 20.7% in HSCT patients. CDI incidence was highest in patients with hematological malignancies. Most of patients experienced mild CDI. Age < 5 years and diagnosis other than acute leukemia were the positive prognostic factors influencing clinical CDI course.

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Increased numbers of faecal Enterobacteriaceae are observed among patients with irritable bowel syndrome. Escherichia coli strains are present in the lower intestine of humans, and may include several potentially pathogenic adhesive pathotypes. The aim of this study was to determine whether there were differences between the adhesive pathotypes of E. coli strains recovered from stool specimens of patients with irritable bowel syndrome and those recovered from healthy controls. The ability of E. coli isolates to adhere to cultured epithelial cells was assessed in an in-vitro adherence assay with HEp-2 cells. Enteroaggregative E. coli (EAEC) strains were isolated significantly more frequently (p <0.00001) from patients with irritable bowel syndrome (81.8%) than from healthy controls (32.3%). However, despite this association, the precise role of the EAEC pathotype in irritable bowel syndrome remains to be determined.

New antimicrobial agents are needed to address infections caused by multidrug-resistant bacteria. Here, we are reporting novel O-alkyl derivatives of naringenin and their oximes, including novel compounds with a naringenin core and O-hexyl chains, showing activity against clinical strains of clarithromycin-resistant Helicobacter pylori, vancomycin-resistant Enterococcus faecalis, methicillin-resistant Staphylococcus aureus, and beta-lactam-resistant Acinetobacter baumannii and Klebsiella pneumoniae. The minimum inhibitory concentrations (MICs), which provide a quantitative measure of antimicrobial activity, were in the low microgram range for the selected compounds. Checkerboard assays for the most active compounds in combination with antibiotics revealed interactions that varied from synergistic to neutral.

ObjectiveThe aim of this cross-sectional in vitro study was to evaluate the mucosal surfaces of healthy maxillary sinuses, explore different forms of bacterial microorganism colonies present on the mucous membrane, and determine a mucosal surface area they occupy.MethodsSamples of the maxillary sinus mucosa were collected from 30 healthy patients (M = 11; F = 19). The material was obtained during the Le Fort I osteotomy performed during corrective jaw surgery. The morphological and morphometric analysis of sinus mucosa and bacterial film that was grown on it was performed using scanning electron microscopy (SEM) as well as imaging software.ResultsScanning electron microscopy analysis showed the presence of different bacterium and bacteria-like structures in all the analyzed samples. In most cases, the bacterial film was mostly composed of diplococci-like and streptococci-like structures on the mucosa of the paranasal sinus. In any case, the mucous layer did not cover the whole lining of the evaluated sample. Each colony consists of more than 20 single bacterial cells, which has grown in aggregates.ConclusionsUnder the conditions of normal homeostasis of the body, the maxillary sinuses present diverse bacterial colonization. The bacteria are dispersed or concentrated in single microcolonies of the biofilm on the border of the mucous covering the ciliary epithelium. There is no uniform layer of the biofilm covering the mucosa of the maxillary sinuses. Because the biofilm is detected on healthy individuals sinus mucosa, the clinical question if it may become pathogenic is unclear and require an explanation.

Pseudomonas aeruginosa is one of the pathogenic bacteria which utilize binding of the host plasminogen (Plg) to promote their invasion throughout the host tissues. In the present study, we confirmed that P. aeruginosa exhibits binding affinity for human plasminogen. Furthermore, we showed that the protein detected on the cell wall of P. aeruginosa and binding human plasminogen is an enolase-like protein. The hypothesis that alpha-enolase, a cytoplasmatic glycolytic enzyme, resides also on the cell surface of the bacterium was supported by electron microscopy analysis. The plasminogen-binding activity of bacterial cell wall outer membrane enolase-like protein was examined by immunoblotting assay.

Background. Urinary tract infections (UTis) represent 10-20% of all community-acquired infections. Escherichia coli remains the most commonly isolated microorganism. Because of the dominance of these bacteria, routine laboratory tests are not recommended in making the first UTi diagnosis. However, careful monitoring of all etiological agents of uncomplicated UTis should be an important strategy for empirical therapy. Objectives. a determination of the incidence of UTi bacterial etiological agents in outpatients. Material and methods. The results of urine cultures were analyzed. The samples were obtained in the period from 01.2011 to 03.2013 from outpatients of all age groups. Results. The rods of Escherichia coli were the most frequently identified microorganisms responsible for uncomplicated UTis. They were isolated from 52% of infected patients. every fourth case of UTi indicated the participation of Enterococcus spp. and Streptococcus agalactiae. The next 21% of infections were caused by gram-negative bacteria other than E. coli. The role of coagulase-negative staphylococci was insignificant and equaled less than 2%. Conclusions. despite the dominant role of E. coli in urinary tract infections, there has been a decrease in the frequency of its isolation. However, the natural resistance of Enterococcus spp. to antibiotics increases the number of urinary tract infections caused by these bacteria. Streptococcus agalactiae is a UTi cause with similar frequency in women of reproductive age and postmenopausal women. Monitoring of the incidence of uncomplicated infections facilitates empirical treatment and prevents UTi recurrence. Key words: Streptococcus agalactiae, Enterococcus spp., uncomplicated urinary tract infection. Material and methodsThe urine culture results were analyzed in dysuric outpatients with symptoms of varying severity over 26 months (from 01.2011 to 03.2013). The most common UTi symptoms reported by patients were: urinary frequency, pain during urination, abdominal pain, pain in the lower abdomen and/or lumbar region, changed color and/or odor of urine. less frequently patients reported fever, weakness and decreased appetite. all subjects provided urine for culture to the specialist Microbiological laboratory of the Medical University Foundation microFaM in wroclaw. The tests were performed by a quantitative method (calibrated loops) on columbia agar medium with 5% sheep blood, Macconkey agar and sabouraud agar (Becton dickinson). The identification of pathogens was performed in an automatic BBl crystal system (Becton dickinson) based on the biochemical activity of microorganisms in accordance with the recommendations of the national consultant for clinical Microbi-