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Biomedical subjects

A F Cheng

Publications and source records attributed to A F Cheng.

150 records · Page 9Linked to original sources
PubMedDate not supplied

Patterns of antibiotic resistance, serotype distribution, and patient demographics of Streptococcus pneumoniae in Hong Kong.

Streptococcus pneumoniae isolates from clinical specimens during the period 1993-1997 at the Prince of Wales Hospital, Hong Kong, were analysed by the antibiotic resistance profiles, the distribution of serotypes, specimen types, and patient demographics. 1,229 non-duplicate S. pneumoniae isolates were evaluated; 84% from the respiratory tract, 11% from blood and cerebrospinal fluid and the remainder from body fluids and pus swabs. The percentage of S. pneumoniae of reduced penicillin susceptibility was 38.6%, and the percentage resistance to erythromycin, chloramphenicol, co-trimoxazole and tetracycline were 40.4, 43.2, 54.9 and 77.8%, respectively. The organism was isolated from patients of all age groups, 14.6% from children aged below 10 years, half of whom were from children aged 2 years or below. 57.0% were from elderly patients aged above 60. The male to female ratio was 2.5:1. Isolates with reduced penicillin susceptibility were seen significantly more so in children under 10 than in those aged 11 or above (52 versus 36%, p < 0.0001). A diverse range of serotypes was obtained in the penicillin-susceptible isolates whilst those of reduced susceptibility were confined to serotypes 23F, 19F, 6B, 14 and 9V.

Adolescent↗
PubMedDate not supplied

In vitro activity and post-antibiotic effect of quinupristin/dalfopristin (Synercid).

The in vitro activities of quinupristin/dalfopristin (Synercid), ampicillin, erythromycin, clarithromycin, vancomycin, teicoplanin, ciprofloxacin and tetracycline were examined and compared against 526 gram-positive bacteria. The minimal inhibitory concentrations (MICs) for quinupristin/dalfopristin against Staphylococcus aureus, including methicillin-resistant strains, were low (MIC(90) = 0.5 mg/l), and were comparable with those of vancomycin and teicoplanin. This compound was superior to the macrolides and highly active against Streptococcus pneumoniae (both penicillin-sensitive and penicillin-resistant strains), with MIC(90) = 2 mg/l. It was also active against other streptococci, with MIC(90) = 4 mg/l. However, this agent is less active against enterococci (MIC(90) = 32 mg/l). Quinupristin/dalfopristin showed high activity against gram-positive anaerobes, including Clostridium spp., Peptococcus spp. and Peptostreptococcus spp., with MIC(90) < or = 2 mg/l. Quinupristin/dalfopristin was also investigated for its post-antibiotic effect (PAE) and bactericidal kinetics against nine strains of gram-positive organisms, including staphylococci, enterococci and pneumococci. Exponentially growing (log phase) cultures were exposed to quinupristin/dalfopristin at 2 x MIC. Growth kinetics was evaluated using viable counting. The drug was uniformly bactericidal against pneumococci and staphylococci within 2 and 8 h of exposure, respectively. The killing activity against enterococci was weak; there was little or no reduction in bacterial count over 24 h of incubation. PAEs ranging from 2.13 to 3.28 h, 0.92 to 3.02 h and 1.89 to 7.07 h were produced on the tested pneumococci, staphylococci and enterococci, respectively. This study showed that quinupristin/dalfopristin is a promising agent active against gram-positive bacteria. The prolonged PAEs also suggest that the drug could be used intermittently at more widely spaced dosing intervals against gram-positive organisms.

Anti-Bacterial Agents↗
PubMedDate not supplied

Evaluation of the BD Phoenix Automated Microbiology System for identification and antimicrobial susceptibility testing of common clinical isolates.

OBJECTIVE: To evaluate the accuracy and reliability of the BD Phoenix Automated Microbiology System for identification (ID) and antimicrobial susceptibility testing (AST) of Gram-positive and Gram-negative isolates. MATERIALS AND METHODS: The ID of 291 Gram-negative and 158 Gram-positive clinical isolates were evaluated by the system. The AST of 252 Gram-negative and 151 Gram-positive isolates with correct ID were then evaluated. The results were compared with those of the API ID system and the microbroth dilution method. All discrepant results were repeated for verification. RESULTS: Over 90% Gram-negative and Gram-positive isolates were correctly identified to species or genus level by the Phoenix system. The minimum inhibitory concentration agreement rates between the Phoenix and the microbroth dilution methods within +/-1 dilution ranged from 87.3 to 97.6% for Gram-negative isolates, and from 50 to 100% for Gram-positive isolates. For Gram-positive isolates, vancomycin had significant low minimum inhibitory concentration agreement rates. CONCLUSIONS: Overall, the results indicate that the Phoenix system is a reliable system. It could provide accurate ID and AST results for routine clinical laboratories.

Anti-Bacterial Agents↗
PubMedDate not supplied

Comparison of oral ciprofloxacin and amoxycillin in treating infective exacerbations of bronchiectasis in Hong Kong.

A randomised double-blind controlled clinical trial was conducted to compare oral ciprofloxacin (500 mg b.d.) and amoxycillin (1 g t.d.s.) in the treatment of infective exacerbations of bronchiectasis. The commonest organism isolated from sputum was Pseudomonas aeruginosa, which accounted for 34% of all positive sputum cultures. Other Pseudomonas species and Haemophilus influenzae, accounted for 19%, respectively. Ciprofloxacin produced better clinical response, a higher sputum to serum antibiotic level (mean of 0.65 in the ciprofloxacin group vs. 0.18 in amoxycillin group, p = 0.0001), broader spectrum of antibacterial activity and less side-effect. It was also better tolerated by patients. The findings suggest that ciprofloxacin is an effective treatment of infective exacerbations of bronchiectasis.

Administration, Oral↗
PubMedDate not supplied

Antibiotics, biliary sepsis, and bile duct stones.

Bacteriologic studies of bile and blood cultures of 579 patients with ductal stones and infected bile revealed that 121 patients (21%) had associated bacteremia. Analysis of bile and stone cultures showed that Escherichia coli, Klebsiella sp, Enterobacter sp, Enterococcus sp, and Streptococcus sp were the most commonly isolated bacteria. Two-thirds of the patients with bacteremia had similar organisms isolated from blood and bile. Pharmacokinetic studies of the hepatic/biliary excretion profiles of ceftazidime, cefoperazone, imipenem, netilmicin, and ciprofloxacin were performed by ERCP and nasobiliary catheter drainage. The bile samples obtained immediately after cannulation from patients with complete biliary obstruction contained low or undetectable levels of the antibiotics administered--the exception being ciprofloxacin, which was present at a concentration of 20% of the serum level. In vitro determination of minimum inhibitory concentration of the aforementioned antibiotics against 199 isolates of biliary pathogens revealed imipenem and ciprofloxacin to have the highest antimicrobial activity. Based on pharmacokinetic studies and in vitro susceptibility findings, we conclude that ciprofloxacin is superior to the other tested antibiotics in prophylaxis and treatment of biliary sepsis.

Adolescent↗