Browsing by Author "Yassin A.S."

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Biofilm formation in enterococci: Genotype-phenotype correlations and inhibition by vancomycin
(Nature Publishing Group, 2017) Hashem Y.A.; Amin H.M.; Essam T.M.; Yassin A.S.; Aziz R.K.; Department of Microbiology and Immunology; Faculty of Pharmacy; British University in Egypt (BUE); Shorouk City; Egypt; Department of Microbiology and Immunology; Faculty of Pharmacy; October University for Modern Sciences and Arts; 6 October City; Egypt; Department of Microbiology and Immunology; Faculty of Pharmacy; Cairo University; Cairo; Egypt
Enterococci are nosocomial pathogens that can form biofilms, which contribute to their virulence and antibiotic resistance. Although many genes involved in biofilm formation have been defined, their distribution among enterococci has not been comprehensively studied on a genome scale, and their diagnostic ability to predict biofilm phenotypes is not fully established. Here, we assessed the biofilm-forming ability of 90 enterococcal clinical isolates. Major patterns of virulence gene distribution in enterococcal genomes were identified, and the differentiating virulence genes were screened by polymerase chain reaction (PCR) in 31 of the clinical isolates. We found that detection of gelE in Enterococcus faecalis is not sufficient to predict gelatinase activity unless fsrAB, or fsrB alone, is PCR-positive (P = 0.0026 and 0.0012, respectively). We also found that agg is significantly enriched in isolates with medium and strong biofilm formation ability (P = 0.0026). Additionally, vancomycin, applied at sub minimal inhibitory concentrations, inhibited biofilm in four out of five strong biofilm-forming isolates. In conclusion, we suggest using agg and fsrB genes, together with the previously established gelE, for better prediction of biofilm strength and gelatinase activity, respectively. Future studies should explore the mechanism of biofilm inhibition by vancomycin and its possible use for antivirulence therapy. � 2017 The Author(s).
Molecular characterization of Enterococcus spp. clinical isolates from Cairo, Egypt
(Medknow Publications, 2015) Hashem Y.A.; Yassin A.S.; Amin M.A.; Department of Microbiology and Immunology; Faculty of Pharmacy; Modern Sciences and Arts University; Giza; Egypt; Cairo University; Cairo; Egypt
Purpose: Enterococci are responsible for serious diseases such as bacteraemia, endocarditis and urinary tract infections. The ability of enterococci to cause such diseases is due to acquisition of certain virulence factors such as haemolysin, gelatinase and enterococcus surface protein. This study has been conducted to investigate the occurrence of virulence factors and resistance to various antibiotics with emphasis on vancomycin in the Enterococcus spp. Materials and Methods: Clinical specimens were collected and isolates were identified by proper microscopic, culture and biochemical tests. Susceptibility and degree of resistance of the isolates to various antibiotics were determined. Virulence factors were examined by phenotypic tests followed by molecular methods. Bioinformatics analysis was used to detect regions in the genomes that might have originated from horizontal gene transfer. Result: The presence or absence of virulence genes did not affect the pattern of antimicrobial resistance in Enterococcus isolates; consequently, no relationship was found between virulence factors and resistance to different antibiotics used. Bioinformatics analysis showed that the virulence genes were mainly transferred by transposons. Conclusion: Among the enterococci, environmental factors may interfere in the expression of virulence factors. Horizontal gene transfer plays an important role in the spread of resistance and virulence genes.
The Nile River Microbiome Reveals a Remarkably Stable Community between Wet and Dry Seasons, and Sampling Sites, in a Large Urban Metropolis (Cairo, Egypt)
(Mary Ann Liebert Inc., 2018) Eraqi W.A.; Elrakaiby M.T.; Megahed S.A.; Yousef N.H.; Elshahed M.S.; Yassin A.S.; Department of Microbiology and Immunology; Faculty of Pharmacy; Cairo University; Cairo; Egypt; Department of Microbiology and Immunology; Faculty of Pharmacy; October University for Modern Sciences and Arts (MSA); 6th of October; Giza; Egypt; Department of Microbiology and Molecular Genetics; Oklahoma State University; Stillwater; OK; United States
World freshwater supplies are in need of microbiome diversity analyses as a first step to future ecological studies, and to monitor water safety and quality. The Nile is a major north-flowing river in Africa that displays both spatial and temporal variations in its water quality. Here, we present the first microbiome analysis of the Nile River water in two seasons: (1) summer representing the wet season, and (2) winter representing the dry season, as sampled around Cairo, the capital of Egypt. Surface river water samples were collected from selected locations along the path of river, and the microbial composition was analyzed by next-generation sequencing of the 16S rRNA gene. We found a striking stability in the Nile microbiome community structure along the examined geographical urban sites and between the wet and dry seasons as evidenced by the high proportion of shared operational taxonomic unit values among all samples. The community was dominated by the Cyanobacteria (mainly Synechococcus), Actinobacteria candidate family (ACK-M1), and Proteobacteria (mainly family Comamonadaceae). Among these dominant taxa, Synechococcus exhibited seasonal driven variation in relative abundance. Other taxa were predominantly rare across all seasons and locations, including genera members of which have been implicated as pathogens such as Acinetobacter, Aeromonas, and Legionella. In addition, comparisons with data on freshwater microbiome in other world regions suggest that surface water communities in large rivers exhibit limited variation. Our results offer the first insights on microbial composition in one of the most notable rivers near a large metropolis. � 2018, Mary Ann Liebert, Inc.
Seroprevalence of occult hepatitis B among Egyptian paediatric hepatitis C cancer patients
(Blackwell Publishing Ltd, 2015) Raouf H.E.; Yassin A.S.; Megahed S.A.; Ashour M.S.; Mansour T.M.; Department of Microbiology and Immunology; Faculty of Pharmacy; Modern Sciences and Arts University; Giza; Egypt; Department of Microbiology and Immunology; Faculty of Pharmacy; Cairo University; Kasr El-Aini St.; Cairo; 11562; Egypt; Cancer Biology Department; National Cancer Institute; Cairo University; Cairo; Egypt
Occult hepatitis B infection is characterized by the presence of hepatitis B virus (HBV) DNA in the serum in the absence of hepatitis B surface antigen (HBsAg). Prevalence of hepatitis C virus (HCV) infections in Egypt is among the highest in the world. In this study, we aim at analysing the rates of occult HBV infections among HCV paediatric cancer patients in Egypt. The prevalence of occult HBV was assessed in two groups of paediatric cancer patients (HCV positive and HCV negative), in addition to a third group of paediatric noncancer patients, which was used as a general control. All groups were negative for HBsAg and positive for HCV antibody. HBV DNA was detected by nested PCR and real-time PCR. HCV was detected by real-time PCR. Sequencing was carried out in order to determine HBV genotypes to all HBV patients as well as to detect any mutation that might be responsible for the occult phenotype. Occult hepatitis B infection was observed in neither the non-HCV paediatric cancer patients nor the paediatric noncancer patients but was found in 31% of the HCV-positive paediatric cancer patients. All the detected HBV patients belonged to HBV genotype D, and mutations were found in the surface genome of HBV leading to occult HBV. Occult HBV infection seems to be relatively frequent in HCV-positive paediatric cancer patients, indicating that HBsAg negativity is not sufficient to completely exclude HBV infection. These findings emphasize the importance of considering occult HBV infection in HCV-positive paediatric cancer patients especially in endemic areas as Egypt. � 2014 John Wiley & Sons Ltd.