Microbiologie médicale et diagnostic

Background: Chlamydia trachomatis is the most common cause of chronic follicular conjunctivitis. As a rapid diagnosis is important in the reducing the long-term squeal of the diseases, the objective of this study was to compare the three methods, direct immunofluorescence (DIF), staining and PCR, for detection of Chlamydia trachomatis in patients with follicular conjunctivitis.

Material and methods: Overall 90 patients with conjunctival were enrolled in this study smears were prepared for DIF and Giemsa staining. PCR amplification after Extraction performed using CT1 and CT5 primers designed from Omp1 gene.

Results: Of the 90 patients, 28 (31.1%) were positive by DIF and 13 (14.4%) by Giemsa staining; and 35 patients (38.8%) showed positive results in PCR. Sensitivity, specificity, predictive positive value, and negative predictive value of DIF in comparison to PCR respectively were calculated as 88.33, 100, 100 and 88.70. Sensitivity, specificity, predictive positive value and negative predictive value of DIF in comparison to PCR respectively were calculated as 61.40, 100, 100 and 71.42. Therefore, sensitivity and negative predictive value of DIF are significantly higher than Giemsa staining.

Conclusion: DIF is more sensitive and more reliable than Giemsa staining for detection of Chlamydia trachomatis in the conjunctiva samples of patients with follicular conjunctivitis.

Background:Atmospheric pressure non-thermal plasma (APNTP) is a promising, relatively novel method for destroying microorganisms either in planktonic or biofilm form, alternative to “conventional” methods which have numerous drawbacks.

Aim of the work: To assess the microbicidal activity of atmospheric pressure non-thermal plasma (APNTP) on planktonic and biofilm forms.

Subjects and methods: This study was performed on Staphylococcus aureus (S. aureus), coagulase negative staphylococci (CoNS), Pseudomonas (P.) aeruginosa and Escherichia (E.) coli isolates from patients with indwelling medical devices associated infections in different intensive care units (ICUs), Zagazig University Hospitals. Detection of biofilm forming ability of these isolates was done by tube method (TM). Planktonic and biofilm counterpart of selected biofilm forming isolates were exposed to APNTP for different durations to assess the biocidal efficacy of plasma on both microbial forms by colony forming unit (CFU) count and/or 2,3-Bis-(2-Methoxy-4-Nitro-5- Sulfophenyl)-2H-Tetrazolium-5-Carboxanilide (XTT), assay. APNTP morphological changes in E. coli and S. aureus were assessed by transmission electron microscopic (TEM) imaging.

Results: APNTP treatment of S. aureus, E. coli suspensions caused progressive reduction in surviving bacterial count and metabolic activity with increasing treatment duration and at 180 seconds of exposure complete sterilization achieved. Similar but more prolonged effect was detected on CoNS and P. aeruginosa suspensions. Its exposure for 240 seconds was needed for their complete sterilization. There was no difference between bacterial percentage reduction calculated by CFU count and XTT assay except in P. aeruginosa suspension for 60 seconds. No observed difference between APNTP effect on planktonic gram positive (GP) and gram negative (GN) bacteria. On the other hand, GN bacterial biofilm was more resistant to APNTP than GP bacterial biofilm. TEM showed that in both S. aureus and E. coli there were significant morphological changes after exposure to plasma.

Conclusion: The efficacy of APNTP was proved for in vitro decontamination of planktonic and biofilm forms of S. aureus, CoNS, P. aeruginosa and E. coli that are responsible for many healthcare-acquired infections (HCAIs).

GXM (glucuronoxylomannan) is the major component surrounding the capsule of Cryptococcus neoformans having multiple biological functions, one of them and most important, the reduction in production of inflammatory cytokines. They were evaluated in this study the correlation of the production GXM with TNF, IL-6, IL-10, as well, as survival in murine model (BALB-c) and severe combined immunodeficiency (SCID). The animals were infected intravenously with 0.1 ml of a suspension containing 3.0 × 106 model, BALB-c compared to the model. The high production GXM as well as the induction of viable cells of C. neoformans. There was an increase in the production of GXM, as well as a decrease in survival in (SCID) a severe inflammatory response in this model may be due to a compromised immune system.

Bacteria have evolved multiple protein secretion systems to survive and cope with surrounding environmental stresses. So far, there are seven secretion systems (type I to type VII), which have been identified and demonstrated the structural and molecular mechanisms. Among them, type three secretion system (T3SS), hallmark of acute infection, is considered as the most complicated system and can translocate effector proteins directly into host cell through a needle-like apparatus. Type six secretion system (T6SS) targets both prokaryotic and eukaryotic cells using a bacteriophage-like structure and plays a role in pathogenesis and bacterial competition. This review is based on our understanding of comparison of the structure, regulation, function and application between T3SS and T6SS. Understanding the structural and functional mechanisms, as well as the difference and relationship between these two secretion systems will help our understanding of bacterial pathogenesis and interspecies interaction.

Background: Pseudomonas aeruginosa, is a Gram-negative opportunistic bacterium which establishes itself in vulnerable patients, such as those with cystic fibrosis or hospitalized in intensive care units.

Methods: Forty-five P. aeruginosa strains isolated from 26 cystic fibrosis patients were obtained. Both qualitative and quantitative assays were conducted to determine a number of virulence factors such as elastase, alkaline proteases and pyocyanin. Elastase gene expression profiling was conducted using RT-PCR. Spirometry was used to measure lung function and this was correlated to the severity of P. aeruginosa infection. Spirometry measurements i.e. forced expiratory volume (FEV) and forced vital capacity (FVC) were made to measure lung function and to see if there was any correlation with the production of virulence factors.

Results: Virulence factors profiling revealed that about 30% of the isolates were of clinical significance having expressed a number of virulence factors, in particular elastase (lasB).

Conclusion: Some strains of P. aeruginosa produce greater quantities of virulence factors and are more damaging to the lungs of patients with cystic fibrosis, although statistical analysis revealed no correlation between the virulence factors tested and the level of lung function. In addition, other factors such as biofilm formation may play a larger role for CF lung infections.

The study was a cross-sectional study of indoor hospital surfaces within paediatric wards to determine the pattern of pathogenic aerobic bacterial contaminants on non-critical surfaces within paediatric wards of UITH, Ilorin. A total of 201 surface swab samples were collected, using sterile ethylene oxide sterilized swab sticks premoistened with sterile normal saline, from selected non-critical surfaces and were aseptically cultured on media and incubated aerobically at 35°C to 37°C for 18 to 24 hours. Identification of bacterial isolates was carried out using standard microbiological procedure. Non-critical surfaces within paediatric wards: emergency paediatrics-unit 1 (EPU 1), emergency paediatric-unit 2 (EPU 2), paediatric medical-ward (PMW), paediatric surgical-ward (PSU) and neonatal intensive care unit (NICU). A prevalence of 67.7% was recorded for surface contamination; Staphylococcus aureus was the predominant isolate 39.4% and Pseudomonas aeruginosa 1.3% was the least contaminant isolated from this study. Wash sinks were the most commonly contaminated site amongst surfaces studied with a proportion of 123.5%, medical tables were the least contaminated with 33.33%. Among the wards sampled, EPU2 has the highest contamination level with 87.5% while NICU has the least contamination with 67.6%. This study showed that most of the sites sampled had bacterial contaminants indicating potential sources of cross contamination from surfaces to hands of healthcare workers, patients and vice-versa. It is pertinent to understand that non-critical hospital surfaces are important in the passive transmission of healthcare associated infectious pathogens. Thorough cleaning, disinfection of these surfaces and proper hand washing practices will break the chain of transmission.