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Search Results: 1 - 10 of 401379 matches for " Ghassan M Matar "
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Detection of a highly prevalent and potentially virulent strain of Pseudomonas aeruginosa from nosocomial infections in a medical center
Ghassan M Matar, Mira H Chaar, George F Araj, Zaher Srour, Ghassan Jamaleddine, Usamah Hadi
BMC Microbiology , 2005, DOI: 10.1186/1471-2180-5-29
Abstract: Data showed that most of the clinical and environmental isolates were susceptible to tested antimicrobial agents. RAPD analysis determined the presence of 31 genotypes, with genotype 1 detected in 42% of the clinical isolates and 43% of the environmental isolates. Enzymatic activity testing showed that genotype 1 produced all virulence factors tested for.In conclusion, our data demonstrated the predominant prevalence of a potentially virulent P. aeruginosa genotype, circulating in a number of units of the medical center and emphasize the need to reinforce infection control measures.Despite the advances in hospital care and the introduction of a wide variety of antimicrobial agents, Pseudomonas aeruginosa continues to be a major nosocomial pathogen particularly in patients who suffer from immunosuppression [1]. P. aeruginosa is a ubiquitous pathogen prevalent in the hospital environments, and can cause severe nosocomial infections [2]. The latter involve a broad spectrum of infections including the respiratory, gastrointestinal, and urinary tracts as well as wound infections, sepsis and others [3]. Various possible sources of P. aeruginosa infection in hospitals have been identified; such as tap water, medical equipment, hospital personnel and other patients [2,4]. P. aeruginosa accounts for 10% of all hospital acquired infections, a site specific prevalence which may vary from one unit to another and from study to study [5]. Among data on site-specific infections, P. aeruginosa appears to be the major cause of ventilator-associated pneumonia with a high rate of attributable mortality [6]. Moreover this organism can contaminate a number of other medical equipment such as respirators, endoscopes, bronchoscopes, transvenous pacemakers, urinary catheters, and dialysis equipment, leading to site-related infections [7,8]. During the last year, the average prevalence of P. aeruginosa nosocomial infections in our medical center was 18%. Such a high rate prompted us to study
Decrease in Shiga toxin expression using a minimal inhibitory concentration of rifampicin followed by bactericidal gentamicin treatment enhances survival of Escherichia coli O157:H7-infected BALB/c mice
Elias A Rahal, Natalie Kazzi, Ahmad Sabra, Alexander M Abdelnoor, Ghassan M Matar
Annals of Clinical Microbiology and Antimicrobials , 2011, DOI: 10.1186/1476-0711-10-34
Abstract: The utility of decreasing Shiga toxin gene expression in E. coli O157:H7 with rifampicin prior to bacterial eradication with gentamicin was evaluated in vitro using real-time reverse-transcription polymerase chain reaction. Toxin release from treated bacterial cells was assayed for with reverse passive latex agglutination. The effect of this treatment on the survival of E. coli O157:H7-infected BALB/c mice was also monitored.Transcription of Shiga toxin-encoding genes was considerably decreased as an effect of treating E. coli O157:H7 in vitro with the minimum inhibitory concentration (MIC) of rifampicin followed by the minimum bactericidal concentration (MBC) of gentamicin (> 99% decrease) compared to treatment with gentamicin alone (50-75% decrease). The release of Shiga toxins from E. coli O157:H7 incubated with the MIC of rifampicin followed by addition of the MBC of gentamicin was decreased as well. On the other hand, the highest survival rate in BALB/c mice infected with E. coli O157:H7 was observed in those treated with the in vivo MIC equivalent dose of rifampicin followed by the in vivo MBC equivalent dose of gentamicin compared to mice treated with gentamicin or rifampicin alone.The use of non-lethal expression-inhibitory doses of antimicrobial agents prior to bactericidal ones in treating E. coli O157:H7 infection is effective and may be potentially useful in human infections with this agent in addition to other Shiga toxin producing E. coli strains.Escherichia coli O157:H7 is the most commonly encountered member of the Enterohemorrhagic Escherichia coli (EHEC) group. Infection with this agent typically results in bloody diarrhea with low-grade or absence of fever with no leukocytes in the stools [1]. Symptoms may progress, culminating in potentially fatal complications such as the hemolytic uremic syndrome (HUS) [2-4] and thrombotic thrombocytopenia purpura (TTP) in the elderly and the young [3]. This organism causes about 73,000 illnesses annually in th
Frequency of conjugative transfer of plasmid-encoded ISEcp1 - blaCTX-M-15 and aac(6')-lb-cr genes in Enterobacteriaceae at a tertiary care center in Lebanon - role of transferases
Mohamad Harajly, Marie-Therese Khairallah, John E Corkill, George F Araj, Ghassan M Matar
Annals of Clinical Microbiology and Antimicrobials , 2010, DOI: 10.1186/1476-0711-9-19
Abstract: Conjugation experiments were done on 53 ESBL-producing and/or fluoroquinolone resistant E. coli and K. pneumoniae and ESBL-producing S. sonnei isolates. Antimicrobial susceptibility testing on parent and transconjugant isolates, and PCR amplifications on plasmid extracts of the resistance-encoding genes: blaCTX-M-15 with the ISEcp1 insertion sequence, the aac(6')-lb-cr and qnrS genes, as well as tra encoding transferases genes were done. Random amplified polymorphic DNA (RAPD) analysis was performed to demonstrate whether conjugative isolates are clonal and whether they are linked epidemiologically to a particular source.Antimicrobial susceptibility testing on transconjugants revealed that 26 out of 53 (49%) ESBL-producing Enterobacteriaceae were able to transfer antimicrobial resistance to the recipients. Transfer of high-level resistance to the transconjugants encoded by the blaCTX-M-15 gene downstream the ISEcp1 insertion sequence against 3rd generation cephalosporins, and of low-level resistance against ciprofloxacin, and variable levels of resistance against aminoglycosides encoded by aac(6')-lb-cr gene, were observed in transconjugants. tra encoding transferase genes were detected exclusively in conjugative isolates.In conclusion, the frequency of transfer of antimicrobial resistance in non clonal Enterobacteriaceae at the tertiary care center by conjugation was 49%. Conjugation occurred in isolates expressing the tra encoding transferase genes. Multiple conjugative strains harboring the plasmid encoded antimicrobial resistant genes were circulating in the medical center. Molecular epidemiology analysis showed that conjugative isolates are neither clonal nor linked to a particular site and transfer of antimicrobial resistance is by horizontal transfer of plasmids.Plasmid-encoded Extended-spectrum β-lactamases (ESBL) are increasingly spreading among Enterobacteriaceae clinical isolates throughout the world due mostly to their presence on highly conjugative plas
HLA Allele Associations and V-Beta T-Lymphocyte Expansions in Patients With Psoriasis, Harboring Toxin-Producing Staphylococcus aureus
Rola Ajib,Lori Janbazian,Elias Rahal,Ghassan M. Matar,Shukrallah Zaynoun,Abdul-Ghani Kibbi,Alexander M. Abdelnoor
Journal of Biomedicine and Biotechnology , 2005, DOI: 10.1155/jbb.2005.310
Abstract: HLA alleles have been associated with psoriasis. Toxin-producing strains of Staphylococcus aureus behave as superantigens, and if present in patients, might play a role in the exacerbation of psoriatic lesions by activating certain V-beta (Vβ) T-lymphocyte subsets. Allele frequencies in 22 patients and 22 controls (alleles determined by DNA/SSP typing) were used to calculate a relative risk of 4.7 (P<.05) for HLA-Cw6. S aureus was isolated from the throat of 11 patients. Enterotoxins A and C were detected by agglutination in the culture filtrate of one isolate. The enterotoxin A and/or C genes were detected by PCR in 9 isolates, and transcripts were detected by RT-PCR in 7 of them. None of the isolates from controls harbored enterotoxin genes. Vβ expansions were detected by RT-PCR in all 22 patients. Low or no Vβ expansions were obtained in controls. The association of HLA-Cw6 with psoriasis in Lebanese concurs with that reported for other ethnic groups. Toxin-producing isolates that colonize patients might play a role in the exacerbation of psoriatic lesions.
Correlation between Group B Streptococcal Genotypes, Their Antimicrobial Resistance Profiles, and Virulence Genes among Pregnant Women in Lebanon
Antoine Hannoun,Marwa Shehab,Marie-Therese Khairallah,Ahmad Sabra,Roland Abi-Rached,Tony Bazi,Khalid A. Yunis,George F. Araj,Ghassan M. Matar
International Journal of Microbiology , 2009, DOI: 10.1155/2009/796512
Abstract: The antimicrobial susceptibility profiles of 76 Streptococcus agalactiae (Group B Streptococci [GBS]) isolates from vaginal specimens of pregnant women near term were correlated to their genotypes generated by Random Amplified Polymorphic DNA analysis and their virulence factors encoding genes cylE, lmb, scpB, rib, and bca by PCR. Based on the distribution of the susceptibility patterns, six profiles were generated. RAPD analysis detected 7 clusters of genotypes. The cylE gene was present in 99% of the isolates, the lmb in 96%, scpB in 94.7%, rib in 33%, and bca in 56.5% of isolates. The isolates demonstrated a significant correlation between antimicrobial resistance and genotype clusters denoting the distribution of particular clones with different antimicrobial resistance profiles, entailing the practice of caution in therapeutic options. All virulence factors encoding genes were detected in all seven genotypic clusters with rib and bca not coexisting in the same genome.
Genotypes and serotype distribution of macrolide resistant invasive and non- invasive Streptococcus pneumoniae isolates from Lebanon
Nedal Taha, George F Araj, Rima H Wakim, Souha S Kanj, Zeina A Kanafani, Ahmad Sabra, Marie-Therese Khairallah, Farah J Nassar, Marwa Shehab, Maysa Baroud, Ghassan Dbaibo, Ghassan M Matar
Annals of Clinical Microbiology and Antimicrobials , 2012, DOI: 10.1186/1476-0711-11-2
Abstract: Forty four macrolide resistant and 21 macrolide susceptible S. pneumoniae clinical isolates were tested for antimicrobial susceptibility according to CLSI guidelines (2008) and underwent molecular characterization. Serotyping of these isolates was performed by Multiplex PCR-based serotype deduction using CDC protocols. PCR amplification of macrolide resistant erm (encoding methylase) and mef (encoding macrolide efflux pump protein) genes was carried out.Among 44 isolates resistant to erythromycin, 35 were resistant to penicillin and 18 to ceftriaxone. Examination of 44 macrolide resistant isolates by PCR showed that 16 isolates harbored the erm(B) gene, 8 isolates harbored the mef gene, and 14 isolates harbored both the erm(B) and mef genes. There was no amplification by PCR of the erm(B) or mef genes in 6 isolates. Seven different capsular serotypes 2, 9V/9A,12F, 14,19A, 19F, and 23, were detected by multiplex PCR serotype deduction in 35 of 44 macrolide resistant isolates, with 19F being the most prevalent serotype. With the exception of serotype 2, all serotypes were invasive. Isolates belonging to the invasive serotypes 14 and 19F harbored both erm(B) and mef genes. Nine of the 44 macrolide resistant isolates were non-serotypable by our protocols.Macrolide resistance in S. pneumoniae in Lebanon is mainly through target site modification but is also mediated through efflux pumps, with serotype 19F having dual resistance and being the most prevalent and invasive.Streptococcus pneumoniae continues to be a major cause of morbidity and mortality in humans. It is one of the most significant bacterial pathogens causing community acquired infections, most notably pneumonia, otitis media, bacteremia, and meningitis [1,2]. Treatment of pneumococcal infections is becoming difficult due to the high prevalence of penicillin-resistant strains and to the rapid development of resistance to other antimicrobials including macrolides. These drugs are extensively used for the treat
Prevalence and clinical relevance of Helicobacter pylori cagA and vacA genes in Lebanese patients with gastritis and peptic ulcer disease
Aline E.Khayat,1 Assaad M. Soweid,2 Mireille M. Kattar,3 Ayman N. Tawil,3 Ihab I. El Hajj,2 Cecilio Azar,2 Benjamin D. Gold,4 and Ghassan M. Matar.1
Journal of Infection in Developing Countries , 2007,
Abstract: Background: The prevalence and clinical relevance of H. pylori cagA and vacA virulence genes in the pathogenesis of disease phenotype was assessed by a novel approach for this organism consisting of determination and comparisons of H. pylori gene transcription levels directly in gastric biopsies according to disease phenotype.Methodology: Gastric mucosal biopsies were collected from patients with peptic ulcer disease (PUD), gastritis, and normal mucosa in an academic medical center in Lebanon. H. pylori was detected in these biopsies by rapid urease (CLO ) test and PCR amplification of the ureA gene. H. pylori virulence genes, their transcription and transcription levels were determined respectively by PCR, RT-PCR and real time RT-PCR. Results: Forty-five percent of patients were H. pylori positive by PCR of the ureA gene, 37.5% of whom had cagA and 59.4% vacA.Conclusions: The cagA and vacA genes were detected more frequently in PUD patients with significantly higher transcription levels than in gastritis and normal mucosa.
Existence of solution to fractional nonlinear backward differential equations on Banach spaces
M. M. Matar
International Journal of Mathematical Analysis , 2012,
On existence of solution to some nonlinear differential equations of fractional order 2 < alpha leq 3
M. M. Matar
International Journal of Mathematical Analysis , 2012,
Existence and uniqueness of solutions to fractional semilinear mixed Volterra-Fredholm integrodifferential equations with nonlocal conditions
Mohammed M. Matar
Electronic Journal of Differential Equations , 2009,
Abstract: In this article we study the fractional semilinear mixed Volterra-Fredholm integrodifferential equation $$ frac{d^{alpha }x(t)}{dt^{alpha }} =Ax(t)+fBig(t,x(t), int_{t_0}^tk(t,s,x(s))ds,int_{t_0}^{T}h(t,s,x(s))dsBig) , $$ where $tin [t_0,T]$, $t_0geq 0$, $0
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