PubMed Health⌕ Search

Biomedical subjects

A M Shibl

Publications and source records attributed to A M Shibl.

At least 19 recordsLinked to original sources
PubMed2004

Beta-lactam and macrolide resistance and serotype distribution among Streptococcus pneumoniae isolates from Saudi Arabia.

Three hundred thirty-six clinically significant Streptococcus pneumoniae isolates were collected from laboratories of different hospitals in Riyadh, Saudi Arabia. Most of these isolates were from pulmonary and otitis media (68.2%), and 31.8% were extrapulmonary (blood and CSF). Of the 336 isolates, 44.6% were susceptible to penicillin, and 55.4% were penicillin non-susceptible (35.7% were intermediate and 19.7% were fully resistant). The isolates showed 9.0% resistance to co-amoxiclav, 31.8% to cefuroxime and 39.4% to cefprozil. None of the isolates were resistant to ceftriaxone. Overall macrolide resistance rates were 22.6% to erythromycin, 18.5% to roxithromycin, 17.9% to azithromycin and 17.3% to clarithromycin. Most penicillin non-susceptible pneumococci were of serogroups/types 19 (21.0%), 6 (10.8%), 18 (8.6%), 23 (8.1%) and 14 (7.0%). Serogroups 9, 15, and 1 were found in 5.4%, 4.3%, and 2.2% of the isolates, respectively. Nontypeable strains constituted 6.5%. In exploring the mechanism of resistance to macrolides, 28 of 76 (36.8%) of isolates were erythromycin-resistant due to ribosomal mechanism (all were constitutive type, none were inducible), whereas 48 (63.2%) isolates were resistant due to an efflux mechanism. Good antibiotic control with periodical antibiotic surveillance and appropriate use of pneumococcal vaccine may improve current treatment of pneumococcal infections.

Anti-Bacterial Agents↗
PubMed2001

Carriage of antibiotic-resistant pneumococci among Asian children: a multinational surveillance by the Asian Network for Surveillance of Resistant Pathogens (ANSORP).

To investigate the nasal carriage of antibiotic-resistant pneumococci by children, anterior nasal swabs were done for 4963 children <5 years old in 11 countries in Asia and the Middle East. In total, 1105 pneumococci isolates (carriage rate, 22.3%) were collected, 35.8% of which were found to be nonsusceptible to penicillin. Prevalence of penicillin nonsusceptibility was highest in Taiwan (91.3%), followed by Korea (85.8%), Sri Lanka (76.5%), and Vietnam (70.4%). Penicillin resistance was related to residence in urban areas, enrollment in day care, and a history of otitis media. The most common serogroups were 6 (21.5%), 23 (16.5%), and 19 (15.7%). The most common clone, as assessed by pulsed-field gel electrophoresis, was identical to the Spanish 23F clone and to strains of invasive isolates from adult patients. Data in this study documented the high rate of penicillin or multidrug resistance among isolates of pneumococci carried nasally in children in Asia and the Middle East and showed that this is due to the spread of a few predominant clones in the region.

Anti-Bacterial Agents↗
PubMed2001

Elucidation of antibiotic effectiveness against Staphylococcus epidermidis during intraocular lens implantation.

The effect of various antimicrobial agents commonly used in irrigating solutions on the hydrophobicity and adherence of Staphylococcus epidermidis ATCC 14990 was investigated. The longest post-antibiotic effect (PAE=3.2 h) was obtained with gentamicin followed by ciprofloxacin (2.7 h), clindamycin (2.2 h), ceftazidime (1.8 h) and vancomycin (1.6 h). The post-antibiotic effect on surface hydrophobicity of cells previously treated with gentamicin, ciprofloxacin, or clindamycin for 120 min resulted in a substantial decrease in affinities to hexadecane (31.4, 28.5 and 27%, respectively) compared with control untreated cells. Less effect was noted with cells previously treated with ceftazidime or vancomycin (20.5 and 15.8%, respectively). Similar but less marked results were obtained when the cells were exposed to antibiotics for 30 or 60 min. The post-antibiotic effect on adherence of cells to both intraocular lenses and to epithelial cells showed that adherence to lenses decreased as the time of exposure to antimicrobial agents increased. Adherence was greatly diminished with cells treated with gentamicin or ciprofloxacin compared with control untreated cells. Adherence was less affected by clindamycin, ceftazidime and vancomycin. The data supported the use of antimicrobial agents in irrigating solution during intraocular surgery, since, reduced adherence (colonization) and might result in a lower incidence of endophthalmitis.

Anti-Bacterial Agents↗
PubMed2001

Antibiotic resistance in developing countries.

During the past decade there have been major changes in the susceptibility of bacteria that cause various infections. Resistance to anti-infective agents, including antibiotics, is worldwide, both in developed and developing countries. Almost all bacterial species can develop resistance to anti-infective agents and resistance can readily be transferred among bacteria by transmissible elements (plasmids). Measures to prevent the emergence of resistance must be implemented urgently. A multiplicity of factors drive antibiotic resistance and solutions require the collaboration of governmental agencies, pharmaceutical companies, healthcare providers and consumers. Knowledge of resistance patterns and of the ways by which resistance is overcome is vital to the future of antimicrobial chemotherapy.

Developing Countries↗
PubMed2000

Antibiotics in the irrigating solutions reduce Staphylococcus epidermidis adherence to intraocular lenses.

PURPOSE: To investigate the effect of antibiotics in the irrigating solutions on hydrophobicity, slime production and the adherence of Staphylococcus epidermidis to intraocular lenses (IOLs). METHODS: A standard culture of S. epidermidis was incubated with a control phosphate-buffered saline (PBS) or PBS containing vancomycin (20 micrograms/ml) or gentamicin (8 micrograms/ml) or a combination of gentamicin and vancomycin (8 and 20 micrograms/ml, respectively) for 30, 60 and 120 min at 35 degrees C. The bacteria were harvested by centrifugation, and washed with PBS before incubation with IOLs for 1 h. Adhesion of bacterial cells to IOLs was determined by counting the viable cells attached to the lenses. Slime production on IOLs was measured using safranin staining. Hydrophobicity of the control cultures and cultures treated with antibiotics was assayed on the basis of the hexadecane droplet method. RESULTS: Bacterial exposure to antibiotics produced a time-dependent significant decrease in bacterial hydrophobicity and adherence to IOLs compared with the untreated control cells (p < 0.001). Hydrophobicity showed a significant correlation with adherence (r = 0.89, p < 0.001). Gentamicin was significantly more effective than vancomycin, and the synergistic combination of gentamicin and vancomycin was the most effective in reducing bacterial adherence to IOLs, hydrophobicity and slime production. CONCLUSIONS: The use of antibiotics in the irrigating solutions during cataract surgery may be useful in reducing bacterial adherence to IOLs. Further studies are needed to determine the clinical implications of these findings in reducing the incidence of post-operative endophthalmitis associated with IOL implantation.

Anti-Bacterial Agents↗
PubMed2000

Penicillin-resistant and -intermediate Streptococcus pneumoniae in Saudi Arabia.

The antibiotic susceptibility was analyzed of approximately 400 consecutive isolates of S. pneumoniae isolated from different regions of Saudi Arabia. Most of these isolates were from respiratory (sputum, otitis, 53.8%), blood/CSF (26.3%) and ophthalmic (20%) specimens. Overall 6.2% of the isolates were penicillin-resistant (MICs > or =2 microg/ml) and 51.2% were -intermediate (MICs 0.1-1 microg/ml). The resistance rates to cefuroxime, clarithromycin and ceftriaxone were 14.9%, 14.8% and 4.5% respectively. Only 3.5% of S. pneumoniae showed resistance to amoxycillin/clavulanic acid. The MICs of all tested antibiotics increased as did the penicillin MICs. Penicillin resistance was significantly associated with resistance to cefuroxime (p<0.001) but not with the others. These data indicate the presence of penicillin and multiple-resistant pneumococci in Saudi Arabia and that these strains can spread among individuals. A greater awareness with extended indications for microbiological diagnosis, antimicrobial susceptibility testing and restrictive prescription of antibiotics are needed.

Amoxicillin↗
PubMed1998

Plasmid profile and antibiotic resistance in coagulase-negative staphylococci isolated from polluted water.

Four different species of coagulase-negative staphylococci (CNS) were isolated from polluted waters in Fez, Morocco and found to be Staphylococcus simulans, Staph. lenticus, Staph. hyicus and Staph. xylosus. Eight isolates belonging to these four species were analysed for their plasmid content. Southern blot hybridizations were performed to define the resistance determinants of the plasmids harboured by these species. These determinants were found to be carried mainly by Class I staphylococcal plasmids (1-5 kb). A plasmid (4.3 kb) carrying a tetracycline resistance gene was present in five isolates from all identified species. Plasmids carrying a chloramphenicol resistance gene were more frequently encountered and found to be of different sizes. Plasmids carrying erythromycin, neomycin, and streptomycin resistance genes were less frequent and were the same size. The results indicate that the occurrence of multi-resistant CNS in polluted waters may constitute a reservoir for disseminating antibiotic-resistance into the community.

Anti-Bacterial Agents↗
PubMed1997

Heparin and heparin-surface-modification reduce Staphylococcus epidermidis adhesion to intraocular lenses.

Bacterial adherence to intraocular lenses (IOLs) could be the cause of endophthalmitis following cataract surgery and lens implantation. The majority of cases of postoperative endophthalmitis are caused by microflora that reside on or near the eye of the patient. Staphylococcus epidermidis commonly colonizes the eyelid margin and conjunctiva and is the most common organism causing postoperative endophthalmitis. In this study, the in vitro adherence of S. epidermidis to regular poly-methyl methacrylate (PMMA) IOLs and to heparin-surface-modified (HSM) PMMA IOLs was investigated. The effects of heparin and antibiotics in solution on the adherence of bacteria to regular PMMA IOLs were evaluated. Adhesion of bacterial cells to IOLs was determined by counting the viable cells attached to the lenses. Significantly, fewer S. epidermidis attached to HSM-PMMA IOLs and to regular PMMA IOLs treated with heparin than to PMMA IOLs (p < 0.001). Furthermore, bacteria attached in significantly lower numbers to regular PMMA IOLs treated with heparin than to HSM-PMMA IOLs (p = 0.0031). Antibiotics in solution had no significant effect on bacterial adherence to PMMA IOLs. These data indicate that the use of HSM-PMMA IOLs and treatment of PMMA IOLs with heparin could diminish the incidence of postoperative endophthalmitis and intraocular inflammation associated with IOL implantation.

Anti-Bacterial Agents↗
PubMed1996

Effect of beta-lactamase inhibitors on normal immune capabilities and their interactions with staphylococcal pathogenicity.

The effects of the beta-lactamase inhibitors, clavulanic acid, sulbactam and tazobactam on normal immune responses were investigated. These agents did not interfere with either humoral or cell-mediated immune responses as measured by the hemolytic plaque assay and delayed type hypersensitivity reaction assay respectively. In addition, human polymorphonuclear leukocyte phagocytic activity was not altered by these agents. When these agents were tested for their effect on Staphylococcus aureas adherence to buccal epithelial cells we found that all inhibitors suppressed staphylococcal adherence at therapeutic serum concentrations. Among the inhibitors investigated, sulbactam was found to significantly inhibit the hemolysin production of S. aureus. These data suggest that beta-lactamase inhibitors do not exhibit immunomodulating activity, but they interfere with some of the virulence factors of S. aureus. These findings suggest the advantage of preparations containing these inhibitors.

Animals↗
PubMed1996

Efficacy and safety of once-daily amikacin in combination with ceftazidime in critically ill adults with severe gram-negative infections.

Forty critically ill adult patients with severe Gram-negative infection were treated with once-daily amikacin combined with ceftazidime. The mean age was 56.6 +/- 19 years and mean APACHE II score was 22.7 +/- 6.6. Forty percent of patients required mechanical ventilation. The mean creatinine clearance at onset of therapy was 59.4 +/- 28 ml/min. All bacterial isolates were sensitive to amikacin. Fixed doses of amikacin 15 mg/kg, 12 mg/kg, and 8 mg/kg body weight were given once daily to patients with estimated creatinine clearance of > 80 ml/min., 50-80 ml/min., and < 50 ml/min, respectively. Forty-two causative gram-negative bacteria were isolated from 40 patients. The most common bacteria were Pseudomonas aeruginosa (18), and Escherichia coli (10). Overall clinical success and bacteriological eradication occurred in 85% and 87.5% of patients; 78.9% and 79% of patients with hospital-acquired infections; 90.5% and 95.2% of patients with community-acquired infections; and 62.5% and 81.3% of patients requiring mechanical ventilation, respectively. Therapeutic failure was documented in 15% of patients. Death due to infection was scored in two patients. The remaining were all due to persistence of the initial causative bacteria in patients with hospital-acquired infections. Persistence was documented with Ps. aeruginosa (2), Serratia spp. (1), and Acinetobacter spp. (1). Overall mortality occurred in 22.5% patients. Death unrelated to infection occurred in 7 patients. There was no clinical evidence of ototoxicity in any of our patients, however, nephrotoxicity was documented in 5%. In conclusion, once-daily amikacin combined with ceftazidime is practical, efficacious and probably safe in critically ill infected patients.

APACHE↗
PubMed1995

In vitro activity of subinhibitory concentrations of quinolones on urea-splitting bacteria: effect on urease activity and on cell surface hydrophobicity.

The effect of subinhibitory concentrations of ciprofloxacin, lomefloxacin, norfloxacin, ofloxacin, and sparfloxacin on urease activity and on cell surface hydrophobicity of urea-splitting bacteria was examined. Quinolones at 0.5 MICs demonstrated variable effects on bacterial-urease activity. Norfloxacin inhibited enzyme activity in Proteus vulgaris and Proteus mirabilis, while other quinolones had no effects. In Morganella morganii, sparfloxacin and ciprofloxacin enhanced urease activity, particularly at the initial phase of growth. All quinolones tested showed no marked effect on urease activity by Providencia rettgeri. Quinolones at the same concentrations induced an increase in the cell surface hydrophobicity, which was strain-dependent. There was no correlation between urease inhibition and cell surface hydrophobicity. Inhibition of urease activity by quinolones, in addition to their antibacterial activities, may prevent the progression of urinary tissue damage and stone formation.

Anti-Infective Agents↗
PubMed1995

Post-antibiotic effect of azithromycin and erythromycin on streptococcal susceptibility to phagocytosis.

The effect of azithromycin and erythromycin on growth, cell surface hydrophobicity and the susceptibility to the bactericidal activity of human polymorphonuclear leucocytes (PMNL) was examined in four Streptococcus species. Exposure to either 10 x MIC azithromycin or erythromycin induced a post-antibiotic effect (PAE) of between 2.4 and 4.3 h. Erythromycin caused a longer PAE for S. sanguis than azithromycin under the same conditions. The cell surface charge (hydrophobic or hydrophilic) of the streptococci was altered significantly during PAE; loss of hydrophobicity was induced by both macrolides, and this effect was variable amongst the species. The decrease in hydrophobicity was not related to inhibition of growth. The effect of each drug during PAE on the interaction of opsonised suspensions of the streptococci with human PMNL revealed that erythromycin, and to a lesser extent azithromycin, increased susceptibility to the bactericidal activity of human PMNL; this effect was abolished following PAE. The present study clearly showed that PAE should not only be considered as delayed bacterial growth, but also as modulation of bacterial susceptibility to phagocytosis which may influence the outcome of the host-parasite relationship.

Azithromycin↗
PubMed1995

Determination of meropenem in plasma by high-performance liquid chromatography and a microbiological method.

A rapid and selective high-performance liquid chromatographic (HPLC) method for the quantitative determination of meropenem in plasma is described. The drug was separated from plasma after plasma protein precipitation with 15% of trichloroacetic acid. The mobile phase consisted of acetonitrile-water-glacial acetic acid (21.2, 78 and 0.8% v/v, respectively) delivered at a flow rate of 1.2 ml/min. Meropenem was quantified using ultraviolet detection at 296 nm. Meropenem and the internal standard (pheniramine) were well separated from plasma components. The drug could be assayed by the HPLC method in the presence of its analogue, imipenem. The detection limit in plasma was 25 ng/ml of meropenem. The results were compared with those of agar for a microbiological diffusion method using Escherichia coli ATCC 25922 as the test organism. The sensitivity of the microbiological assay was less than 5 ng/ml, but this decreased at higher concentrations. Both methods were applied to the determination of the drug in aqueous solutions and in plasma.

Anti-Bacterial Agents↗
PubMed1995

Antimicrobial resistance and prevalence of extended spectrum beta-lactamase among clinical isolates of gram-negative bacteria in Riyadh.

The activity of ciprofloxacin, imipenem and 12 other commonly used antibiotics was evaluated against 106 documented clinical isolates from a medical Intensive Care Unit (ICU). The resistance rates to ceftriaxone, cefotaxime, aztreonam and ceftazidime were 42, 25, 24 and 21%, respectively. Apart from Pseudomonas aeruginosa, all isolates were sensitive to ciprofloxacin and imipenem. Complete cross resistance among tested beta-lactam groups was uniformly evident in Enterobacter cloacae, Citrobacter freundii and P. aeruginosa. On the other hand, penicillins and second generation cephalosporins showed cross resistance among Escherichia coli and Klebseilla pneumoniae isolates. Induction experiments indicate that 70 and 62% of P. aeruginosa and E. cloacae or C. freundii produce class I cephalosporinase, respectively. Among all tested isolates, plasmid mediated extended spectrum beta-lactamase (ESBL) was detected in one isolate of K. pneumoniae. The plasmid mediated beta-lactamase is transferable and inhibited by beta-lactamase inhibitors. The transconjugates not only expressed resistance to extended spectrum beta-lactams and aztreonam but also toward tested aminoglycoside antibiotics, with the exception of gentamicin. The obtained transconjugates conferred high level resistance to ceftazidime and aztreonam but considerably low resistance to ceftriaxone and cefotaxime. The isoelectric point for the extended-spectrum beta-lactamase is 8.2.

Anti-Bacterial Agents↗
PubMed1994

Postantibiotic effect of roxithromycin on streptolysin O production, hydrophobicity, and bactericidal activity of PMNL by Streptococcus pyogenes.

Exposure of Streptococcus pyogenes to 5 x minimum inhibitory concentration of roxithromycin for 1 h produced a significant postantibiotic effect. More than 2.5 h was necessary for roxithromycin-treated bacteria to increase by 1 log10 in colony-forming units after drug removal, compared with the unexposed cells. After exposure to and removal of the drug, treated cells failed to exhibit normal hemolytic activity for at least 4 h. The inhibitory effect persisted for 20 h after drug removal, although the extent of growth for treated and untreated cells was almost the same. Hydrophobicity of treated cells, studied throughout the logarithmic growth phase with a water-hexadecan two-phase system, was markedly decreased by 40%, compared with untreated cells 4 h after drug removal. Cells that had been treated with roxithromycin became more susceptible to the bactericidal activity of human PMNL than untreated bacteria. The data indicate that some of the metabolic activity that contributes to the virulence of S. pyogenes is affected by postexposure to roxithromycin, and its minimum inhibitory concentration and serum level might not be the best indicators of efficacy in this class of drugs.

Bacterial Proteins↗
PubMed1994

Differential inhibition by clindamycin on slime formation, adherence to teflon catheters and hemolysin production by Staphylococcus epidermidis.

Slime formation was detected in Staphylococcus epidermidis strains isolated from either infected patients or healthy individuals. Cells of S. epidermidis, that either formed slime or not, adhered to teflon catheters. There was no correlation between adherence of bacteria to teflon catheters and slime formation. Clindamycin at subinhibitory concentration significantly inhibited slime formation without inhibiting bacterial growth. Adherence of S. epidermidis to teflon catheters was affected by the presence of clindamycin whether slime was produced or not. Clindamycin at subinhibitory concentrations markedly inhibited hemolysin production by S. epidermidis without appreciably altering the cell density, and cells grown in the presence of the drug showed very low hemolytic activity upon disruption. These results suggest that clindamycin at low concentration alters S. epidermidis virulence properties, apart from inhibiting growth.

Bacterial Adhesion↗