Biomedical subjects

A F Cheng

Publications and source records attributed to A F Cheng.

At least 91 records · Page 5Linked to original sources

PubMed1997

Antibiotic exposure and its relationship to postantibiotic effect and bactericidal activity: constant versus exponentially decreasing tobramycin concentrations against Pseudomonas aeruginosa.

In vitro postantibiotic effects (PAEs) exhibited by a standard strain of Pseudomonas aeruginosa following exposure to tobramycin at constant concentrations were compared to those at exponentially decreasing concentrations. Exposure to a constant concentration showed more extensive bacterial killing and resulted in longer PAEs at comparable areas under the concentration-time curves above the MIC. This phenomenon suggests a significant contribution of pharmacokinetics to antimicrobial pharmacodynamics.

Anti-Bacterial Agents↗

PubMed1997

Use of CHROMagar Candida for genital specimens in the diagnostic laboratory.

OBJECTIVE: To evaluate CHROMagar Candida (CA), a new yeast differential medium, for yeast isolation in a clinical laboratory for the routine examination of high vaginal swabs. METHODS: Results of high vaginal swab cultures processed in a standard manner on plates containing equal halves of Sabouraud dextrose agar (SDA) and CA were compared. Non-Candida albicans yeast isolates were further speciated with API 20C AUX or API 32C. To assess the ease of use of CA, laboratory staff lacking in experience of the medium were asked to identify 23 unlabelled yeast cultures on CA by referring to six labelled reference plates. RESULTS: Of the 1784 swab cultures processed, yeasts were isolated from 373 SDA and 368 CA. Of the 78 non-albicans isolates further speciated, CA identified correctly all cultures of C krusei and C tropicalis, and 82% of C glabrata. All the 38 inexperienced laboratory staff achieved 100% accuracy for C albicans and over 90% for C krusei and C tropicalis. CONCLUSIONS: CA is a satisfactory isolation medium for genital specimens, allowing immediate and correct identification of the commonly encountered yeasts and easy recognition of mixed cultures.

Candida↗

PubMed1997

Respiratory Chlamydial infections in a Hong Kong teaching hospital and association with coronary heart disease.

The microimmunofluorescence antibody technique was used to determine the seroprevalence of antibodies to Chlamydia pneumoniae and Chlamydia psittaci from hospitalized patients in Hong Kong. Antibodies to C. pneumoniae were found in 54.8% of 157 patients hospitalized with respiratory disease, in 71.1% of 83 patients with cardiac disease and in 31.2% of 93 patients without either respiratory or cardiac disease. Antibodies to C. psittaci were found in 0.9% of the combined study groups. There was serological evidence of C. pneumoniae being the responsible agent in 24.8% of the severe respiratory cases. A significant correlation between antibody prevalence and coronary heart disease was identified during the study.

Adult↗

PubMed1996

Dual therapy versus triple therapy for Helicobacter pylori-associated duodenal ulcers.

We compared the ulcer healing effect and eradication of H. pylori by one-week triple therapy of bismuth, metronidazole, and tetracycline with two-week dual therapy of amoxicillin and omeprazole. One hundred twelve patients with confirmed H. pylori infection and duodenal ulcers were recruited in a prospective, randomized, single-blinded trial. Ulcer healing, eradication of H. pylori in the stomach six weeks after randomization and side effect reported by patients during the therapy. Duodenal ulcers were healed in 44 of 49 (89.8%, 95% CI, 81.3-98.3 %) patients receiving triple therapy and in 44 of 53 (83.0%, 95% CI, 72.9-93.1%) patients receiving dual therapy (P=0.32). H. pylori was successfully eradicated in 41 of 49 (83.6%, 95% CI 73.4-94%) patients and in 40 of 53 (75.5%, 95% CI 63.9-87.1%) patients in the triple therapy group and the dual therapy group respectively (P=0.31). Side effects experienced by patients who received triple therapy were significantly more frequent than those who received dual therapy (P=0.0076). In conclusion, a two-week course of omeprazole and amoxicillin achieves a comparable rate of H. pylori and ulcer healing with fewer side effect.

Adolescent↗

PubMed1996

Varicella exposure in a neonatal intensive care unit: emergency management and control measures.

We describe an exposure of varicella zoster virus in our neonatal intensive-care unit and the emergency procedures instituted to prevent an outbreak. Fifty-seven infants and 129 staff members were exposed but none developed chickenpox. The measures included rapid identification of varicella antibody status in all neonates and those staff members with uncertain history of varicella infection; cohorting of exposed infants according to immune status; and prompt administration of varicella zoster immunoglobulin to susceptible patients. The recommendation of the American Academy of Pediatrics did not accurately predict the immune status of preterm infants, as only one of the eight susceptible infants would have qualified for immunoglobulin prophylaxis if their guidelines had been followed. Mass screening of all exposed infants using the varicella zoster enzyme linked immunosorbent assay (ELISA) test was the only reliable means of determining the immune status. Of the four risk factors evaluated for the prediction of antibody status: gestational age, postnatal age, birthweight and episodes of blood transfusion, only postnatal age was found to independently predict the immune status of our patients. Because varicella zoster susceptible staff members are difficult to identify on the basis of history, we suggest that prospective screening of staff in high-risk units be undertaken and vaccination with live varicella vaccine be offered to susceptibles.

Antibodies, Viral↗

PubMed1996

Investigation of the epidemiology of hospital isolates of Acinetobacter anitratus by two molecular methods.

Two hundred and two isolates of Acinetobacter anitratus from 126 patients in 36 wards belonging to 11 specialties of a university teaching hospital were compared by ribotyping and restriction enzyme digest analysis (REA) of total DNA. Forty-six groups were defined by both techniques and there was 96 center dot 5% agreement between the methods for the designation of isolates into groups. Only two groups were endemic and circulating in the whole hospital while others were less common. Burns and intensive therapy units had the highest number of isolates and these were mainly of the two endemic groups while renal dialysis and neonatal units had isolates belonging to the less common groups. Of the 32 patients with multiple isolates, 17 were infected or colonized at different sites by two and up to four groups of A. anitratus. Both ribotyping and REA of total DNA are discriminatory methods for typing A. anitratus, however, the latter is a simpler and more rapid method and it can be used in a routine clinical laboratory.

Acinetobacter↗

PubMed1996

In-vitro susceptibility of isolates of methicillin-resistant Staphylococcus aureus 1988-1993.

MICs for 423 strains of methicillin-resistant Staphylococcus aureus (MRSA) isolated in Hong Kong during 1988-1993 were performed for 15 antimicrobial agents: erythromycin, chloramphenicol, tetracycline, minocycline, gentamicin, netilmicin, trimethoprim, rifampicin, fusidic acid, ciprofloxacin, vancomycin, teicoplanin, sparfloxacin, clinafloxacin and RP 59500 (quinupristin/dalfopristin). Susceptibility to antibiotics generally remained stable throughout the study period, with the exception of the quinolones. Resistance to ciprofloxacin (breakpoint 4 mg/L) increased from a low of 9% in 1988 to a high of 82% in 1993. For sparfloxacin the corresponding figures were 9% and 78%, respectively. Six (1%) clinafloxacin-resistant strains were found. MIC50s and MIC90s of clinafloxacin increased from < or = 0.06 mg/L and 0.25 mg/L in 1988 to 1.0 mg/L and 2.0 mg/L, respectively, in 1993. All 423 strains were phage typed (typability 70%) and a diversity of phage types which changed during the observation period, with 13 dominating types, was observed. Ciprofloxacin resistance occurred in 12 of the dominating types, in 46 non-typable strains, and also in 23 strains of different, sporadically occurring types, indicating that the emergence of quinolone resistance was not due to dissemination of a single or few MRSA clones. The usefulness of quinolones in the treatment of MRSA infections is likely to be seriously constrained by the emergence of resistance. MICs for RP-59500 were < or = 2 mg/L for all isolates, suggesting that this agent merits further evaluation as an anti-MRSA agent. All MRSA remained susceptible to vancomycin and teicoplanin throughout the study period.

Anti-Infective Agents↗

PubMed1996

Rapid high performance liquid chromatographic assay for antifungal agents in human sera.

Serum concentration of seven antifungal agents, amphotericin B, 5-flucytosine, ketoconazole, fluconazole, itraconazole, miconazole and econazole were assayed using a single step sample preparation and an isocratic High Performance Liquid Chromatography (HPLC) procedure based on three mobile phases of similar components. Our method was simple, flexible and rapid, the assays being completed within half an hour. The method showed high reproducibility, good sensitivity with detection limits of 0.078 to 0.625 mg/L except for miconazole and econazole, and high recovery rates of 86-l05%. Out of 24 therapeutic agents tested only aztreonam and trimethoprim were found to interfere with the assay of 5-flucytosine and fluconazole respectively, using this protocol. HPLC assay should be useful in the clinical laboratory for monitoring patients on antifungal therapy.

Amphotericin B↗

PubMed1996

An increase in Helicobacter pylori strains resistant to metronidazole: a five-year study.

BACKGROUND: Metronidazole is one of the most commonly used antimicrobial agents for the treatment of Helicobacter pylori infection. Resistance to metronidazole has been reported worldwide but with a wide range of prevalence. We started using the classical triple therapy (bismuth, tetracycline, and metronidazole) for H. pylori infection in 1991 but recently have experienced a decline in its efficacy in curing the infection. Thus our aim was to investigate in a single center the prevalence of metronidazole-resistant H. pylori over a period of 5 years. MATERIALS AND METHODS: A total of 1,015 different H. pylori strains collected over a period of 5 years were tested for sensitivity against metronidazole, ampicillin, tetracycline, and imipenem. Antibiotic sensitivity was tested by the disk diffusion and agar dilution methods. To elucidate further the possible relationship between these metronidazole-resistant strains, genomic DNA digestion by the Hae III endonuclease and ribotyping were undertaken in a selected group of isolates. RESULTS: In 1991, 29 of 132 (22.0%) tested strains of H. pylori were found to be resistant to metronidazole. Since our initiation at that time of a triple therapy of bismuth, metronidazole, and tetracycline, the prevalence of metronidazole-resistant strains rose rapidly to 73.2% in 1995. All H. pylori isolates were sensitive to ampicillin, tetracycline, and imipenem. A high degree of genomic heterogeneity was found among these isolates. Thus it is unlikely that the resistant strains of H. pylori were originated from a single clone. CONCLUSIONS: This study shows a rapid increase in metronidazole-resistant H. pylori with the use of an anti-Helicobacter regimen that contains metronidazole. We anticipate that the efficacy of metronidazole-containing anti-Helicobacter regimens will decline with the rapid rise in resistant strains of H. pylori.

Adolescent↗

PubMed1996

Self-inflicted bacteraemia and fungaemia in Vietnamese migrants.

From early 1993, we received a number of blood cultures, all from Vietnamese inmates of the Whitehead Detention Centre, the biggest detention camp in Hong Kong, which grew unusual organisms. Upon follow-up, the majority of the patients were found to abscond from the hospital a few days after having been admitted with a clinical picture of septic shock. During the period from March 1993 to late 1994, we noted a total of 25 positive blood cultures from 21 previously healthy Vietnamese migrants with this syndrome. The mean age was 27.8 years and 20 were males. The organisms isolated from the blood cultures were of low pathogenicity such as Saccharomyces cerevisiae, Trichosporon spp., Baciflus spp. and Micrococcus spp. Fourteen of the patients complained of abdominal pain and 3 others had apical pneumothoraces. Eighteen had shock requiring resuscitation. Multiple puncture or needle marks were found in 11 patients, mainly involving the lower limbs. One patient admitted inducing illness by self-injection, and it was suspected that all these infections were self-inflicted. The range of hospitalization was 1-13 days (mean 3.05 days). Eighteen of the 21 patients absconded.

Adolescent↗

PubMed1996

Rapid emergence of penicillin-resistant pneumococci in Hong Kong.

The prevalence of penicillin resistance in Streptococcus pneumoniae isolated at the Prince of Wales Hospital, Hong Kong, rose from 6.6% of sputum isolates in the first quarter of 1993 to 55.8% of isolates in the second quarter of 1995. Most of the isolates were also resistant to co-trimoxazole, tetracycline, choramphenicol and erythromycin. Type 19F was the most common capsular type in 1993-1994, comprising 40.0% of typed isolates in this period. Type 23F emerged in 1995 as the predominant type, making up 62.2% of typed isolates in the first 2 quarters of 1995. A high population density and excessive community use of antibiotics are likely to be factors promoting the rapid emergence of multiply-resistant pneumococci in Hong Kong.

Drug Resistance, Microbial↗

PubMed1996

Helicobacter pylori infection increases the risk of peptic ulcers in chronic users of non-steroidal anti-inflammatory drugs.

The objective was to study the gastrointestinal complications in chronic NSAID users with Helicobacter pylori infection. Eighty-two Chinese patients on long-term NSAID or aspirin treatment were studied for the occurrence of H. pylori infection and gastroduodenal mucosal injuries by upper endoscopy. H. pylori infection was confirmed by CLO test, histology and bacteriological cultures. Frequency and severity of symptoms of dyspepsia were also assessed. Thirty-three (40%) patients were diagnosed to have H. pylori infection and 49 (60%) patients were not infected. The two groups were comparable in age, sex, smoking and drinking habit and the use of anti-ulcer drags. Twenty-four out of 33 (72.7%) H. pylori-positive patients and 31 out of 49 (63%) of H. pylori-negative patients were found to have macroscopic lesions by endoscopy. The overall incidence of gastroduodenal lesions in the H. pylori positive patients was not significantly different from the H. pylori-negative patients (p = 0.34). However a higher incidence of duodenal ulcers in the H. pylori-infected group than the H. pylori-negative group (33% vs 6%, p = 0.0001) was found. The difference in severity and frequency of dyspeptic symptoms between the two groups did not reach statistical significance. H. pylori infected chronic NSAID users is associated with a higher rate of duodenal ulcer.

Adult↗

PubMed1996

Antimicrobial susceptibility and extended-spectrum beta-lactamases of Hong Kong isolates of enterobacteriaceae.

High levels of resistance to extended-spectrum cephalosporins have been reported in the Western Pacific area but data on the prevalence of extended-spectrum beta-lactamases (ESBLs) is more scanty. 370 Hong Kong blood culture isolates of Enterobacteriaceae isolated in the years 1990 and 1995 were evaluated for resistance to 15 antibiotics and the presence of ESBLs. 1995 isolates showed increased levels of resistance for beta-lactams, trimethoprim, ciprofloxacin and aminoglycosides. The proportion of E. coli harbouring ESBLs was 1/61 (1.6%) in 1990 and 2/77 (2.6%) in 1995. The prevalence in Klebsiella spp. rose from 1/36 (2.8%) in 1990 to 5/49 (10.2%) in 1995. ESBLs were found most frequently in Enterobacter spp. and were present in 7/29 (24.1%) of 1990 isolates and 5/22 (22.7%) of 1995 isolates. ESBLs may not be detectable in routine susceptibility testing and appropriate screening methods such as double disc screening tests are necessary to accurately determine ESBL prevalence.

Drug Resistance, Microbial↗

PubMed1996

Susceptibilities to 23 antimicrobial agents and beta-lactamase production of blood culture isolates of Acinetobacter sp in Hong Kong.

The susceptibility of 140 Acinetobacter spp. isolated from blood cultures of patients from the Prince of Wales Hospital, Hong Kong, from 1990 to 1994 to 23 antimicrobial agents was studied by an agar dilution method. Resistance to most of the beta-lactams, aminoglycosides and fluoroquinolones tested was high, being 11%-92%. Only amikacin, imipenem and meropenem were reliably active against this organism. Most of the isolates produced cephalosporinases with very high pIs while 33% produced beta-lactamases with pI ranges of 5.2-8.7.

Acinetobacter↗

PubMed1996

A retrospective study of clinical characteristics of acinetobacter bacteremia.

High rates of acinetobacter bacteremia were observed in a large teaching hospital in Hong Kong. A retrospective study of 94 acinetobacter bacteremic episodes in patients in 1993-94 revealed 70 episodes of significant bacteremia. 53% of the patients were over 60 years with a male to female ratio of 1.5:1. Cases were most rare during the fourth quarter. The intensive care unit was the commonest location of acquisition of bacteremia. Most infections were hospital acquired. Intravascular catheters, urinary catheters, antibiotic therapy and respiratory tract manipulations were common risk factors. Lower respiratory tract infections and catheter-related sepsis were predominant foci of bacteremia. One-third of the patients received appropriate antibiotics within 48 hours after bacteremia onset. Mortality attributable to acinetobacter infection was 27%. Prognosis of underlying diseases, location in intensive care unit, lower respiratory tract infection as foci of infection as well as diabetes mellitus were associated with mortality.

Acinetobacter Infections↗

PubMed1995

Antibacterial treatment of gastric ulcers associated with Helicobacter pylori.

BACKGROUND: There is a strong association between infection with Helicobacter pylori and gastric ulcers that are unrelated to the use of nonsteroidal antiinflammatory medications. We studied the efficacy of antibacterial therapy without medication to suppress gastric acid for the treatment of patients with H. pylori infection and gastric ulcers unrelated to the use of nonsteroidal agents. METHODS: Patients with gastric ulcers seen on endoscopy and with H. pylori infection confirmed by smear or culture were randomly assigned to receive either a one-week course of antibacterial agents (120 mg of bismuth subcitrate, 500 mg of tetracycline, and 400 mg of metronidazole, each given orally four times a day) or a four-week course of omeprazole (20 mg orally per day). Follow-up endoscopies were performed after five and nine weeks. The patients and their physicians were aware of the treatment assignments, but the endoscopists were not. RESULTS: A total of 100 patients were randomly assigned to treatment, and 85 completed the trial. At five weeks, H. pylori had been eradicated in 41 of the 45 patients in the antibacterial-treatment group (91.1 percent; 95 percent confidence interval, 82.9 to 99.3) and in 5 of the 40 in the omeprazole group (12.5 percent; 95 percent confidence interval, 2.3 to 22.7; P < 0.001). The gastric ulcers were healed in 38 of the patients treated with antibacterial drugs (84.4 percent; 95 percent confidence interval, 73.9 to 95.0) and in 29 of those treated with omeprazole (72.5 percent; 95 percent confidence interval, 58.6 to 86.4; P = 0.28). At nine weeks, ulcer healing was confirmed in 43 of the patients receiving antibacterial therapy and in 37 of those receiving omeprazole (P = 1.0). The mean (+/- SD) duration of pain during the first week of treatment was 1.9 +/- 2.6 days in the omeprazole group, as compared with 3.6 +/- 3.0 days in the antibacterial-treatment group (P = 0.004). One year after treatment, recurrent gastric ulcers were detected in 1 of 22 patients (4.5 percent) in the antibacterial-treatment group and in 12 of 23 (52.2 percent) in the omeprazole group (P = 0.001). H. pylori was detected in the 1 patient with a recurrent ulcer who had received antibacterial treatment and in 10 of the 12 patients with recurrent ulcers who had received omeprazole. CONCLUSIONS: In patients with H. pylori infection and gastric ulcers unrelated to the use of nonsteroidal antiinflammatory drugs, one week of antibacterial therapy without acid suppression heals the ulcers as well as omeprazole and reduces the rate of their recurrence.

Adult↗

PubMed1995

Aeromonas septicaemia in Hong Kong species distribution and associated disease.

During a 5-year study of 2211 patients with clinically significant positive blood cultures in Hong Kong. Aeromonas spp. were isolated in 40 cases. Among 26 episodes in which a single species was isolated. 17 (65.4%) were identified as Aeromonas hydrophila. 8 (30.8%) as A. sobria and one (3.8%) as A. caviae. There were 14 episodes with a mixture of species. Of these, nine (64.3%) were identified as A. hydrophila, two (14.3%) as A. sobria, and two (14.3%) as A. caviae. One (7.1%) was an infection with both A. sobria and A. hydrophila. These polymicrobial infections were usually combined with the presence of Enterobacteriaceae. Hepatobiliary disease was the underlying problem in 24 cases (60.0%) and malignant neoplasia in 14 (35.0%) cases. Most patients presented with fever and leucocytosis. The mortality rate for A. sobria septicaemia was not significantly different from the average rate for all septicaemias. A total of 30 isolates was available for sensitivity testing with 17 antibiotics. More than 86.0% were resistant to ampicillin, and the addition of the beta-lactamase inhibitor sulbactam did not restore its activity. All strains tested were sensitive to cefotaxime, ceftazidime, aztreonam, imipenem, norfloxacin and ciprofloxacin.

Aeromonas↗

PubMed1995

Intravenous ciprofloxacin as treatment for patients with acute suppurative cholangitis: a randomized, controlled clinical trial.

One hundred consecutive patients with acute suppurative cholangitis were randomized in a prospective, controlled clinical trial to receive either ciprofloxacin (200 mg bd iv) or triple therapy comprising ceftazidime (1 g bd iv), ampicillin (500 mg qds iv) and metronidazole (500 mg tds iv); 46 and 44 patients in the ciprofloxacin and triple therapy groups respectively were suitable for inclusion in the analysis of efficacy. In two-thirds of the patients biliary obstruction was caused by ductal calculi and in one-third by malignant or benign strictures of the biliary tract. Bacteraemia was documented in 38% of patients in the ciprofloxacin group and in 34% of patients in the triple therapy group, while bile cultures were positive in 87% and 92% of patients in the ciprofloxacin and triple therapy groups respectively. Escherichia coli, Klebsiella spp. and Enterococcus spp. were the most common biliary isolates. Eighty-five per cent of evaluable patients in the ciprofloxacin group and 77% of those in the triple therapy group responded to therapy. The mean durations of fever, septicaemic shock and hospitalization were also similar in the two treatment groups. Six (13%) patients in the ciprofloxacin group and seven (16%) in the triple therapy group required urgent endoscopy or surgery for uncontrolled infection. Recurrence of fever after an initial response was documented in one (2%) patient receiving ciprofloxacin and in three (7%) patients receiving triple therapy. The incidences of mortality were 4% in the ciprofloxacin group and 2% in the triple therapy group. The results of this study suggest that ciprofloxacin alone is adequate empirical therapy for patients with cholangitis.

Acute Disease↗