Microbiologie médicale et diagnostic

Human cytomegalovirus (HCMV) can be transmitted through blood transfusion and organ transplantation and could be cause of some complication in solid-organ transplant recipients. Current study is aimed to compare the sensitivity and Specificity of ELISA, Antigenemia assay and nested PCR methods to detection of Cytomegalovirus infection in renal transplantation patients.

In this study blood samples were collected from 200 renal transplant recipients’ patients.

DNA was extracted by commercial kit and Nested PCR was done by 2 pairs of internal and external primers. Anti CMV antibodies (IgM and IgG) were detected by ELISA and CMV-pp65 antigenemia assay (Ag) was used to detect CMV antigens. The sensitivity and Specificity of each test and all the methods together were evaluated, and SPSS software was used to analysis of data.

From 200 patients, 193 (96.5%) were positive for CMV antibodies with the Specificity of 100 and sensitivity of 97.76%. 120 (60%) and 25 (12.5) samples were positive by nested PCR and Ag assay with the Specificity of 94.49 and 78.12 and sensitivity of 94.49 and 78.12, respectively.

In the case of early diagnosis of the disease, nested PCR diagnose the infection 14 years earlier than Ag assay and was consistently positive, whereas false negative results were frequently observed with the pp65 Ag assay. The sensitivity and specificity of the two methods combined detection for CMV infection were 96.76% and 99.89%. ELISA can be used as a screening reliable detection test for CMV infection in recipient especially when PCR is unavailable.

Combination of ELISA and CMV-PCR methods, provide a more effective method to monitor CMV infection.

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most dangerous antibiotic resistant pathogens and a common cause of most health-care acquired infections. MRSA causes skin, wound and bloodstream infections that can cause sepsis and ultimately lead to death. CDC and WHO have listed MRSA as a serious threat infection and included in The National Action Plan for Combating Antibiotic-resistant Bacteria. Early, reliable, and accurate diagnosis of MRSA in a clinical setting is critical for the treatment and control of infection in hospitals and the community. We comparatively evaluated the efficacy of two commercial diagnostic systems, Biomed InTray® Colorex and BDTM ESwab Regular Collection Kit/ BBL™ CHROMagar® (ESwab + CHROMagar®) to recover 51 MRSA clinical isolates. The percentage recovery of MRSA clinical isolates in InTray® and in ESwab + CHROMagar® was 99% and 75%, respectively. Our findings suggest that InTray® was more efficient than ESwab + CHROMagar® in recovering MRSA clinical isolates.

Staphylococci can cause many nosocomial and community acquired infections with high rates of morbidity and mortality. The large scale of spread of resistance to vancomycin and other antibiotics has been perceived as a fearsome threat to the already challenging therapy of Staphylococci. A total of 982 clinical samples were obtained from different departments of Tanta university hospital. Microscopical examination and standard biochemical tests revealed that 437 isolates were Staphylococci.

Resistance to vancomycin was determined using disk diffusion and agar dilution methods which revealed that 89 were vancomycin resistant Staphylococci (VRS). The susceptibility of VRS isolates to 15 different antimicrobial agents was performed using agar dilution method. All VRS isolates were multidrug resistant (MDR).

Polymerase chain reaction (PCR) studies were performed on selected Staphylococci isolates with different vancomycin MICs ranging from 2 to 512 μg/ml for detection of vancomycin resistance genes (van genes). The vanA gene was detected in VRS isolates only with vancomycin MICs from 32 to 512 μg/ml. Neither vanB nor vanC gene was detected.

β-Lactamase production by VRS isolates was investigated. A total of 88.7% of isolates produced β-lactamase enzyme. Disk approximation test was performed on all VRS isolates that were resistant to erythromycin and sensitive to clindamycin. Out of the 29 isolates on which the test was performed, 24 (82.8%) tested positive. Ciprofloxacin resistant VRS isolates were selected to study the presence of efflux mechanism of resistance. All the tested isolates were efflux positive.

The VRS isolates in hospitals as well as in community are alarming to the clinicians and multi drug resistance in these isolates is very dangerous. In this study we tried to investigate the prevalence of VRS isolates in Tanta and to determine their antibiotic susceptibility.

Cryptococcosis is a subacute or chronic disease caused through the inhalation of infectious particles from the opportunistic yeast Cryptococcus neoformans spp. The objective of the present study was to evaluate cryptococcosis in a murine model Immunocompetent (BALB/c), as well as in a model with combined immunodeficiency (SCID) through histopathological analyzes of pulmonary and cerebral tissues. After intravenous inoculation with 3.0 × 105 viable yeast cells the animals were euthanized daily for evaluation. The study period was 15 days. There were no significant changes in lung tissue in immunocompetent murine model (BALB/c). While in brain tissue, it was observed: congested vessel, evolving when C. neoformans was visualized in the meningeal area, and a large area of ischemia, which evolved throughout the studied period culminating on the 15th day of inoculation with visualization of the yeast in the meningeal and parenchyma. In SCID model, twenty-four hours after inoculation were observed in the lung tissue, hemorrhagic areas and a discrete neutrophilic inflammatory infiltrate, presence of discrete congestion in the lung, diffuse hemorrhage, edema and intense quantity of yeast were observed on the wall of the capillary at 11 days after inoculation. In brain tissue discrete area necrosis liquefaction was observed, focal well as the presence of C. neoformans, interspersed with fragments of necrotic cells was observed. On day 11 after inoculation were large areas of liquefaction necrosis associated with the formation of cavities in the parenchyma and an intense quantify of the yeast. Histopathological examination is one of the techniques usually used in the definitive diagnosis of cryptococcosis.

Study background: The purpose of this study was to evaluate recent strategies for anti-infective treatment in patients suffering from ventilator-associated respiratory infections caused by P. aeruginosa and to assess the riskbenefit profile of inhaled tobramycin.
Methods: Electronic health records of patients suffering from respiratory infections caused by P. aeruginosa from 2011-2014 were retrospectively screened.
Results: In 81 patients, P. aeruginosa was found in respiratory secretions, of which 26 patients suffered from ventilator-associated pneumonia (VAP), whereas 55 patients only fulfilled criteria of ventilator-associated tracheitis (VAT). Inhaled tobramycin was used in 14 patients with VAP and 31 patients with VAT. In this context, inhaled tobramycin was shown to be safe (e.g. no bronchoconstriction or systemic toxicity) and did not result in an increase of tobramycin resistant strains in respiratory secretions at 90 days following study inclusion. However, a clear clinical benefit (e.g. reduced need for i.v. antibiotics) could not be shown.\
Conclusion: Inhaled tobramycin was shown to be a suitable approach with a favorable risk profile to treat patients suffering from respiratory infections (VAP, VAT) caused by P. aeruginosa. The clinical benefit needs to be reevaluated in a larger prospective investigation.

Background: Campylobacteriosis is the leading zoonotic disease in developed countries with C. jejuni and C. coli being the two predominant causative pathogens. It has been shown that quinolone consumption in livestock is associated with increased quinolone resistance of Campylobacter isolates from food producing animals and infected patients. However, susceptibility testing of clinical isolates is not commonly performed and, consequently, resistance rates of human C. jejuni and C. coli isolates in areas of high consumption of antimicrobials in livestock may be undervalued. A strong association between C. jejuni infections and patients` age and gender has been highlighted by several authors. However, there is still little information on the demographic pattern in C. coli infections.
Methods: 1135 C. jejuni and 156 C. coli human isolates were obtained within a rural region of Germany. The study area was characterised by intensive swine and poultry farming involving high consumption of clinically important antimicrobials. Isolates were analysed for susceptibility to amoxicillin, ciprofloxacin, tetracycline and erythromycin using the EUCAST disc diffusion method. Furthermore, data were stratified with respect to patients age and gender.
Results: Contrary to male-biased distribution in C. jejuni isolates, C. coli was the predominant species in female patients with a maximum female surplus in young children and middle-aged adults. Resistance rates of C. coli vs. C. jejuni to amoxicillin, ciprofloxacin, tetracycline and erythromycin were 46.2% vs. 48.3%, 62.8% vs. 64.5%, 68.6% vs. 35.2% and 14.7 vs. 0.6%, respectively. Resistance rates were found to correlate with usage of these antimicrobials in livestock.
Conclusion: The high prevalence of C. coli in female patients may point to sex-specific behavioural or physiological aspects. The observed high to moderate resistance rates of Campylobacter isolates warrant prudent use of antimicrobials in livestock as well as routine susceptibility testing of human isolates to ensure efficacy of antimicrobial therapy.