Slobodanka Djukic

Quantification of biofilm in microtiter plates: overview of testing conditions and practical recommendations for assessment of biofilm production by staphylococci

The details of all steps involved in the quantification of biofilm formation in microtiter plates are described. The presented protocol incorporates information on assessment of biofilm production by staphylococci, gained both by direct experience as well as by analysis of methods for assaying biofilm production. The obtained results should simplify quantification of biofilm formation in microtiter plates, and make it more reliable and comparable among different laboratories.

Surgical Wound Infection Associated with Staphylococcus sciuri

We describe a case of surgical wound infection due to Staphylococcus sciuri. The isolated strain was susceptible to trimethoprim–sulfamethoxazole, erythromycin, chloramphenicol, ciprofloxacin and vancomycin and resistant to gentamicin, clindamycin, rifampicin, methicillin, ampicillin and ceftriaxone. The multiresistance of the strain had a serious impact on the prolonged course of the infection. Although this bacterium is principally found in animals, our strain was probably of nosocomial origin.

Association between pet‐keeping and asthma in school children

The role of pet exposure in childhood asthma and allergy is still controversial. The aim of this study was to investigate the association between pet‐keeping during different periods of childhood and asthma and sensitization in school children.

Intra-amniotic Chlamydia trachomatis infection.

Chlamydia trachomatis is one of the most prevalent genital pathogens in pregnant women. Ascending, transcervical infection may reach fetal membranes creating chorioamnionitis or amniotic fluid infection. The aim of this study was to examine amniotic fluids obtained during cesarean section for the presence of chlamydial IgM- and IgG-specific antibodies, and for the presence of C. trachomatis antigen. Five of 52 (9.6%) amniotic fluid samples were seropositive. Two of 52 (3.8%) amniotic fluid samples had C. trachomatis antigen in the epithelial cells of the amnion. In conclusion, our data indicate that there is a high rate of transmission of C. trachomatis from mother to infant and that the pathogen can be identified in the amniotic fluid.

Licheniocin 50.2 and Bacteriocins from Lactococcus lactis subsp. lactis biovar. diacetylactis BGBU1-4 Inhibit Biofilms of Coagulase Negative Staphylococci and Listeria monocytogenes Clinical Isolates.

Background Coagulase negative staphylococci (CoNS) and Listeria monocytogenes have important roles in pathogenesis of various genital tract infections and fatal foetomaternal infections, respectively. The aim of our study was to investigate the inhibitory effects of two novel bacteriocins on biofilms of CoNS and L. monocytogenes genital isolates. Methods The effects of licheniocin 50.2 from Bacillus licheniformis VPS50.2 and crude extract of bacteriocins produced by Lactococcus lactis subsp. lactis biovar. diacetylactis BGBU1-4 (BGBU1-4 crude extract) were evaluated on biofilm formation and formed biofilms of eight CoNS (four S. epidermidis, two S. hominis, one S. lugdunensis and one S. haemolyticus) and 12 L. monocytogenes genital isolates. Results Licheniocin 50.2 and BGBU1-4 crude extract inhibited the growth of both CoNS and L. monocytogenes isolates, with MIC values in the range between 200–400 AU/ml for licheniocin 50.2 and 400–3200 AU/ml for BGBU1-4 crude extract. Subinhibitory concentrations (1/2 × and 1/4 × MIC) of licheniocin 50.2 inhibited biofilm formation by all CoNS isolates (p < 0.05, respectively), while BGBU1-4 crude extract inhibited biofilm formation by all L. monocytogenes isolates (p < 0.01 and p < 0.05, respectively). Both bacteriocins in concentrations of 100 AU/mL and 200 AU/mL reduced the amount of 24 h old CoNS and L. monocytogenes biofilms (p < 0.05, p < 0.01, p < 0.001). Conclusions This study suggests that novel bacteriocins have potential to be used for genital application, to prevent biofilm formation and/or to eradicate formed biofilms, and consequently reduce genital and neonatal infections by CoNS and L. monocytogenes.

Emergence of VIM-2 metallo-β-lactamase-producing Pseudomonas aeruginosa isolates in a paediatric hospital in Serbia

Molecular detection and surveillance of the resistance genes harboured by Pseudomonas aeruginosa are becoming increasingly important in assessing and controlling spread and colonization in hospitals, and in guiding the antibiotic treatment of infections. Metallo-blactamase (MBL)-producing P. aeruginosa strains are slowly but steadily increasing within hospitals, causing outbreaks and/or hyperendemic situations in some centres, mostly in the Far East and the south of Europe (Queenan & Bush, 2007). The global dissemination of MBL-producing P. aeruginosa strains has also reached the Balkan region (Lepsanovic et al., 2008; Sardelic et al., 2003). The objective of our study was to detect and characterize P. aeruginosa isolates producing MBLs from the 400-bed paediatric tertiary care hospital Mother and Child Health Institute of Serbia ‘Dr Vukan Cupic’.

Antimicrobial Activity of Human Follicular Fluids

The aim of this study was to explore the antimicrobial activity of human follicular fluid (HFF), to test the hypothesis that different strains of the same bacterial species could display different patterns of susceptibility to antimicrobial action of HFF, and to preliminarily investigate the possible mechanism of antimicrobial action of this fluid. Antimicrobial activity of 60 samples of HFF toward 30 Streptococcus agalactiae strains was determined by the agar diffusion method and broth dilution method. To explore the mechanism of antimicrobial activity, biochemical analyses were performed with selected fluid samples. The obtained results indicate that 38.3% fluid samples did not inhibit bacterial growth, 53.3% showed moderate and 8.3% high antimicrobial activity. The tested effect of HFF on S. agalactiae strains was bactericidal and was not strain dependent. Lysozyme activity was detected in HFF exhibiting antimicrobial activity. There were no statistically significant differences in concentrations of estradiol, progesterone, transferrin, iron, total protein and albumin levels among tested samples regardless of the different rate of antimicrobial activity. The obtained results indicate that lysozyme is most probably a crucial antibacterial agent in this fluid; however, some other still unidentified factors may contribute to it.

Diagnosis of bacterial vaginosis

Bacterial vaginosis is a common, complex clinical syndrome characterized by alterations in the normal vaginal flora. When symptomatic, it is associated with a malodorous vaginal discharge and on occasion vaginal burning or itching. Under normal conditions, lactobacilli constitute 95% of the bacteria in the vagina. Bacterial vaginosis is associated with severe reduction or absence of the normal H2O2-producing lactobacilli and overgrowth of anaerobic bacteria and Gardnerella vaginalis, Atopobium vaginae, Mycoplasma hominis and Mobiluncus species. Most types of infectious disease are diagnosed by culture, by isolating an antigen or RNA/DNA from the microbe, or by serodiagnosis to determine the presence of antibodies to the microbe. Therefore, demonstration of the presence of an infectious agent is often a necessary criterion for the diagnosis of the disease. This is not the case for bacterial vaginosis, since the ultimate cause of the disease is not yet known. There are a variety of methods for the diagnosis of bacterial vaginosis but no method can at present be regarded as the best. Diagnosing bacterial vaginosis has long been based on the clinical criteria of Amsel, whereby three of four defined criteria must be satisfied. Nugents scoring system has been further developed and includes validation of the categories of observable bacteria structures. Up-to-date molecular tests are introduced, and better understanding of vaginal microbiome, a clear definition for bacterial vaginosis, and short-term and long-term fluctuations in vaginal microflora will help to better define molecular tests within the broader clinical context.

Ground red hot pepper agar in the isolation of yeasts of Candida spp.

The purpose of this study was to investigate and determine the value of a novel, simple and inexpensive selective medium for isolation of yeasts of Candida spp. - ground red hot pepper agar (GRHP). The study compared GRHP and Sabouraud dextrose agar (SDA), an insufficiently selective medium routinely used for primary isolation of yeasts. The comparison was based on qualitative and quantitative characterisation of growth of 25 bacterial strains, measurement of growth of 22 yeast strains and testing on clinical specimens. Qualitative tests on bacteria showed either significantly less growth on GRHP than on SDA, or no growth on GRHP. Quantitative tests confirmed these results; the number of colonies of all tested bacterial species and strains on GRHP was significantly lower than on SDA. With regard to the isolation of Candida spp., GRHP had the same properties as SDA. Statistical analysis showed no significant differences in the growth of Candida spp. and strains on the two media. All these results were confirmed by tests on clinical material. The results clearly show that GRHP agar is an economical medium for the isolation of yeasts of Candida spp., with excellent selectivity.

Quantification of biofilm formation on silicone intranasal splints: An in vitro study

OBJECTIVES Biofilms are associated with persistent infections and resistant to conventional therapeutic strategies. The aim of this study was to investigate the quantity of biofilm produced on silicone intranasal splints. METHODS Quantity of biofilm formation on silicone splints (SS) was tested on 15 strains of Staphylococcus aureus and Moraxella catarrhalis, respectively. Antimicrobial susceptibility testing was performed in accordance with European Committee on Antimicrobial Susceptibility Testing recommendations. RESULTS All tested strains formed different amounts of biofilm on SS: 66.7% S. aureus and 93.3% M. catarrhalis were weak biofilm producers and 33.3% S. aureus and 6.7% M. catarrhalis were moderate biofilm producers. S. aureus formed significantly higher quantity of biofilm compared with M. catarrhalis (p < 0.05). Multidrug resistant S. aureus produced significantly higher amount of biofilm compared with non-multidrug resistant strains (p < 0.05). CONCLUSION Quantity of biofilm on SS is highly dependent on bacterial species and their resistance patterns. Future studies are needed to ascertain another therapeutic option for prophylaxis prior to SS placement.