Tarek Na'was - Academia.edu (original) (raw)

Papers by Tarek Na'was

In vitro activities of antimicrobial agents against Proteus species from clinical specimens

PubMed, Jun 1, 1994

Two hundred clinical isolates of members of the genus Proteus were definitively identified and th... more Two hundred clinical isolates of members of the genus Proteus were definitively identified and their antimicrobial susceptibilities to 12 antimicrobials tested, 176 isolates (88%) being identified as Proteus mirabilis, 12 strains (6%) as Proteus vulgaris and 12 strains (6%) as Proteus penneri. Most strains were isolated from pus (62.5%) and urine (34%), but in general there were no significant differences in the rates of isolation of any of the species by age or sex, although it was noted that P. vulgaris was only isolated from patients belonging to the older age group (> 5 years). The Proteus spp. were notably susceptible to nalidixic acid, ceftazidime and the aminoglycosides tested, and resistant to polymyxin B and colistin. The inclination of certain Proteus species to be susceptible or resistant to certain antimicrobials was noted, but strain differences also existed. The results of the study confirm the importance of performing antimicrobials susceptibility testing of each Proteus isolate to avoid potentially misleading therapy. The noted discrepancy in the result of the susceptibility of P. penneri to chloramphenicol as tested by different standard methods merits further investigation.

Methicillin-resistant Staphylococcus aureus in clinical specimens at a North Jordan Hospital

Journal of Hospital Infection, Sep 1, 1993

Journal of Clinical Microbiology, Feb 1, 1998

Staphylococcus aureus is a major cause of nosocomial infections. During the period from March 199... more Staphylococcus aureus is a major cause of nosocomial infections. During the period from March 1992 to March 1994, the patients admitted to the intensive care unit of the University of Maryland Shock Trauma Center were monitored for the development of S. aureus infections. Among the 776 patients eligible for the study, 60 (7.7%) patients developed 65 incidents of nosocomial S. aureus infections. Of the clinical isolates, 43.1% possessed a polysaccharide type 5 capsule, 44.6% possessed a type 8 capsule, and the remaining 12.3% had capsules that were not typed by the type 5 or type 8 antibodies. Six antibiogram types were noted among the infection-related isolates, with the majority of the types being resistant only to penicillin and ampicillin. It was noted that the majority of cases of pneumonia were caused by relatively susceptible strains, while resistant strains were isolated from patients with bacteremia and other infections. Only 16 (6.3%) of the isolates were found to be methicillin-resistant S. aureus (MRSA). DNA fingerprinting by pulsed-field gel electrophoresis showed 36 different patterns, with characteristic patterns being found for MRSA strains and the strains with different capsular types. Clonal relationships were established, and the origins of the infection-related isolates in each patient were determined. We conclude that (i) nosocomial infection-related isolates from the shock trauma patients did not belong to a single clone, although the predominance of a methicillin-resistant genotype was noted, (ii) most infection-related S. aureus isolates were relatively susceptible to antibiotics, but a MRSA strain was endemic, and (iii) for practical purposes, the combination of the results of capsular and antibiogram typing can be used as a useful epidemiological marker.

Journal of Environmental Science and Natural Resources, 2012

The study aimed at examining the microbial quality of restaurant salad and the water used for sal... more The study aimed at examining the microbial quality of restaurant salad and the water used for salad preparation and their role as a source of antibiotic resistant bacteria. Samples were collected from 15 different restaurants located in Chittagong city. The range of Total Viable Count was 1.86×104 to7.28×105 CFU/g and 1.60×104 CFU/ml to 4.38×105 CFU/ml for salad and water respectively. Total colifrm and fecal coliform count > 1100 CFU/100 ml were found in 73.33% of salad and 33.33% water samples. Salmonella spp was present in 46.67% of restaurants salad and water. Vibrio spp. was present in 66.67% of salad and 53.33% of water. A total of 102 isolates belonging to genus Vibrio, Salmonella and E. coli were subjected to antibiotic sensitivity test by disc diffusion method by using nine different types of antibiotic discs. Salmonella spp. from salad and water showed resistance against Amoxicillin (75%), Cephradine and Cephalexin (68.75%). 85.71% Vibrio spp. isolated from salad and w...

Journal of Hospital Infection, Mar 1, 1991

Background The emergence of multidrug-resistant bacterial microorganisms is a particular challeng... more Background The emergence of multidrug-resistant bacterial microorganisms is a particular challenge for the health care systems. Little is known about the occurrence of methicillin-resistant Staphylococcus aureus (MRSA) and multidrug-resistant Gram-negative bacteria (MDRGNB) in patients of palliative care units (PCU). Aim The primary aim of this study was to determine the carriage of MRSA among patients of a PCU at a German University Hospital and to assess whether the positive cases would have been detected by a risk-factor-based screening-approach. Design Between February 2014 and January 2015 patients from our PCU were tested for MRSA carriage within 48 hours following admission irrespective of pre-existing risk factors. In addition, risk factors for MRSA colonization were assessed. Samples from the nostrils and, if applicable, from pre-existing wounds were analysed by standardized culture-based laboratory techniques for the presence of MRSA and of other bacteria and fungi. Results from swabs taken prior to admission were also recorded if available. Results 297 out of 317 patients (93.7%) fulfilled one or more MRSA screening criteria. Swabs from 299 patients were tested. The detection rate was 2.1% for MRSA. All MRSA cases would have been detected by a risk-factor-based screening-approach. Considering the detected cases and the results from swabs taken prior to admission, 4.1% of the patients (n = 13

Aerobic diphtheroids identification criteria and relative occurrence of different species ... human sources

International Journal of Engineering, May 28, 2018

The isolation of many potential pathogens from many sources commonly used by the public, raised a... more The isolation of many potential pathogens from many sources commonly used by the public, raised awareness on needed measures to avoid such a hidden danger. In this study another commonly used surface, namely the elevator buttons of public elevators located in the busy Ras Beirut area in Beirut, the capital of Lebanon, were studied for bacterial contamination. Eight of the 12 public elevators sampled (67%) grew more than one bacterium, the buttons of the remaining 4 elevators (33 %) grew only one bacterial organism. The isolated organisms included: coagulase-negative staphylococci isolated from the buttons of 75 % of the sampled elevators, Staphylococcus aureus from 67 %, Klebsiella pneumoniae (sub sp. pneumoniae 1) from 17 %, Enterobacter aerogenes from 8 %, and Rahnella aquatilis also from 8 %. Due to the frequency of use of public elevators, people usually do not note the threat posed by these elevators. As hands remain the major method of transmission of pathogenic bacteria, this study concludes that elevator buttons can be dangerous fomites that can harbor pathogenic bacteria from carriers as much as they can be dangerous fomites that spread serious agents of disease.

Antibiotic resistance being a major threat to public health, instigated the search for new antimi... more Antibiotic resistance being a major threat to public health, instigated the search for new antimicrobial agents especially in the recognized medicinal plants. In this study the antibacterial effect of the leaves of the plant: Eucalyptus globulus, used in herbal medicine, against clinical Gram positive and Gram negative clinical bacterial isolates was studied. This antibacterial effect was determined using the well agar diffusion and agar dilution methods. Using the well agar diffusion method, the aqueous extract of E. globulus exhibited a weak inhibitory effect evident at a volume of 200 μl against the methicillin resistant and methicillin sensitive Staphylococcus aureus isolates and 2 of the 3 Enterococcus faecalis isolates and at a volume of 300 μl for the Acinetobacter baumannii isolates. On the other hand, the methanolic extract of the plant showed a notable inhibitory activi...

Samples of the popular chicken shawarma sandwiches from ten reputed restaurants in the Hamra regi... more Samples of the popular chicken shawarma sandwiches from ten reputed restaurants in the Hamra region of Ras Beirut, were tested for contamination with Salmonella. The sandwiches tested were those regularly offered to customers, but were of two categories, with and without a garlic spread that is usually added to this type of Sandwiches. Salmonellawas isolated from sandwiches taken from 3 different restaurants (30%). Two of the three were isolated from part not containing garlic while the third was isolated from a sample that contained the garlic spread. The isolation of Aeromonashydrophila and Escherichia coli, two other major causes of gastroenteritis in man, from sandwiches from two other restaurants, is a clear indication that this type of sandwich tends to be easily contaminated due to many reasons discussed in this study. It is recommended that strict measures be taken by the health care authorities to ensure the safety of the numerous consumers of this commonly favored type of food.

As potentially pathogenic organisms were previously isolated from different inanimate objects, it... more As potentially pathogenic organisms were previously isolated from different inanimate objects, it was decided to investigate, in this study, the extent of contamination of the press buttons or touch screens of public vending machines, that have now become so diverse and distributed in almost all public areas in any community. Twelve vending machines located in different places in public areas in the Ras-Beirut area were included in the study. Standard microbiology laboratory techniques were conducted and several bacterial species were isolated from the tested sites of the machines in the following frequencies: S. aureus (67%), coagulase-negative staphylococci. (33 %), Enterobacter cloacae (25%), Klebsiella pneumoniae (17 %), Citrobacter freundii (17%), Serratia ficaria (17%), Rahnella aquatilis (17%), Escherichia vulneris (8 %), Pantoea sp. (8 %), and Serratia plymuthica(8 %). Vending machine buttons or touch screens were proved to act as vehicles of potential pathogens, unintention...

ChemInform Abstract: Synthesis of 2,3-Diarylglutaramides and Their Antibacterial Activity

ChemInform, 1990

The increasing resistance of microorganism to antibiotics in the last decades, drove microbiologi... more The increasing resistance of microorganism to antibiotics in the last decades, drove microbiologists, botanists, and natural-products chemists to search for phytochemicals that could be used for treatment of infectious diseases. Essential oils, which are derived from plants, such as thujone, have been recognized to display many biological activities many of which needed more exploration. This study was designed to test the ability of alpha thujone to inhibit the growth and biofilm formation of clinical bacterial isolates. The agar dilution method used to detect the antibacterial effect of alpha thujone, revealed that at high concentrations (30 mg/ml and 15 mg/ml) alpha thujone showed some antibacterial activity on some of the Gram-negative isolates tested. It was evident, however, and after using standard tests for detection of the inhibition of biofilm formation, that alpha thujone, at low concentrations (3.8 mg/ml) demonstrated an inhibitory effect on the biofilm formation of most...

Methods: the CNS strains isolated were identified and classified as clinically significant and co... more Methods: the CNS strains isolated were identified and classified as clinically significant and contaminant, based on a series of clinical and laboratory data obtained from patients who stayed in the Neonatal Unit. The following data were analyzed: risk factors for infections, clinical evolution, abnormal blood cell counts and/or C-reactive protein e antibiotic therapy. Results: among the 117 CNS strains isolated, 60 (51.3%) were classified as significant and 57 (48.7%) as contaminant. Among the 54 infants infected by CNS, 43 (79.6%) presented very low birthweight (< 1,500g). Most of the infants infected by CNS were submitted to two or more invasive procedures (77.8%), including use of catheter (88.9%), parenteral nutrition (64.8%) and mechanical ventilation (61.1%). Staphylococcus epidermidis was the most frequently isolated species (77.8%) and more often associated with infection (86.7%) than with contamination (68.4%). Other species of CNS, including two strains of S. haemolyticus, three strains of S. lugdunensis, one strain of S. simulans, one strain of S. warneri and one strain of S. xylosus were also isolated from infants with clinical evidence of pneumonia, necrotizing enterocolitis and sepsis Conclusions: most newborns infected by CNS presented important risk factors for infection onset, including birthweight < 1,500g, foreign body presence and previous use of antibiotics. The identification of CNS species constitutes a useful marker of infection, since S. epidermidis was the species more frequently associated with infection.

Vending machine buttons and touch screens

Computer mice in public centers

Staphylococcus aureus is a gram positive coccus that has long been associated with many serious i... more Staphylococcus aureus is a gram positive coccus that has long been associated with many serious infections amongst which foodborne illnesses are common. The enteric pathogenicity of this bacterium is mediated mainly by its production of various enterotoxins. The role of S. aureus in causing numerous types of infections and its ability to rapidly become resistant to antibacterial agents have shadowed its association with food poisoning. This study, which aimed at detecting the prevalence of S. aureus in coleslaw, a salad commonly served in the restaurants in the Ras-Beirut area, revealed alarming results. Of the 37 samples tested, 32 (86.5%) were positive for the presence of S. aureus . Although the isolated strains were not tested for enterotoxin production, yet such a high prevalence is a clear indicator of the lack of application of proper sanitary protocols in the tested food outlets.

International Journal of Advanced Research

Journal of Medicinal Plants Research

Malva neglecta, a wild plant that grows in different parts of Lebanon, was noted by residents to ... more Malva neglecta, a wild plant that grows in different parts of Lebanon, was noted by residents to have soothing effects if taken during episodes of respiratory tract infections. This study was designed to test for the ability of this plant to inhibit bacterial growth and biofilm formation of clinical bacterial isolates. The results showed that while the aqueous extract of the leaves of the plant did not show any antibacterial effect on the tested bacterial isolates, the methanol extract clearly demonstrated an ability to inhibit the growth of the isolates tested. The agar dilution method revealed that the lower concentrations of the methanol extract of M. neglecta inhibited some isolates, but the inhibition was noted to increase with an increase in the concentration of the extract until at a ratio of 0.3 (volume of extract to volume of the agar medium), the growth of all the tested organisms was completely inhibited. The methanol extract of the plant was also capable of inhibiting the formation of biofilms by many of the clinical isolates tested. The active component in the M. neglecta if identified, purified and proved safe for human consumption, may prove to be a new effective antibacterial agent.

Madridge Journal of Case Reports and Studies, Dec 18, 2018

Pyocyanin, a pigment naturally produced by most Pseudomonas aeruginosa strains and noted to have ... more Pyocyanin, a pigment naturally produced by most Pseudomonas aeruginosa strains and noted to have a role in the well being of the organism and its pathogenicity, was studied for its role as an inhibitor of bacterial growth and biofilm formation of many clinical bacterial isolates. The organisms included in the study were 33 isolates of 11 different bacterial species. The results showed that most of the Gram-positive isolates from the 3 species included in the study: Staphylococcus aureus, Staphylococcus saprophyticus and Enterococcus fecal is were inhibited at low concentrations of pyocyanin. The results varied for the Gram-negative organisms tested. Whereas the growth of the Escherichia coli, Citrobacter koseri, Enterobacter cloacae and A. baumannii isolates was clearly inhibited even by low concentrations of pyocyanin, the growth of Klebsiella pneumonia, Proteus mirabilis and Morganella morganii was not affected even by higher concentrations of pyocyanin. The methanol extract of the pigment was highly effective in preventing the biofilm forming ability of all S. saprophyticus, A. baumannii, E. cloacae and K. pneumoniae isolates, 3 of the 4 P. mirabilis isolates and 2 of the 5 E. coli isolates. All the other isolates tested, also showed a moderate antibiofilm activity This study revealed that pyocyanin has a powerful inhibitory effect on the bacterial growth and/or biofilm forming ability of the numerous clinically significant isolates tested, a characteristic that can prove valuable in developing new drugs for the treatment and prevention of different bacterial infections, once its safety for regular use has been assessed.

International Journal of Current Microbiology and Applied Sciences