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Biomedical subjects

A F Cheng

Publications and source records attributed to A F Cheng.

At least 73 records · Page 4Linked to original sources
PubMed1998

Successful treatment of disseminated coccidioidomycosis with amphotericin B lipid complex.

Coccidioidomycosis is endemic in regions of the Americas, but this infection may be encountered in travellers who return from an endemic region. A case is reported of a disseminated infection in a Hong Kong Chinese man, who was successfully treated with amphotericin B lipid complex (ABLC) after intolerance and toxicity precluded the use of other antifungal agents. Lipid-based formulations of amphotericin B merit further evaluation in the treatment of coccidioidomycosis and other systemic mycoses.

Adult↗
PubMed1998

Rapid diagnosis of smear-negative pulmonary tuberculosis via fibreoptic bronchoscopy: utility of polymerase chain reaction in bronchial aspirates as an adjunct to transbronchial biopsies.

Fibreoptic bronchoscopy was performed on 190 patients with chest radiographic lesions and negative sputum smears for acid-fast bacilli. Aside from obtaining transbronchial biopsies for histological examination, bronchial aspirate specimens were also tested for Mycobacterium tuberculosis complex DNA by a conventional polymerase chain reaction (PCR) technique. Of 177 transbronchial biopsies performed, a diagnosis was found in 64 cases [43 cases of tuberculosis (TB), 17 cases of lung carcinoma and four cases of other infective/inflammatory diseases] giving a diagnostic yield of 36.2%. PCR was positive in 105 of 108 finally diagnosed cases of TB and 22 of 82 non-TB cases. The sensitivity, specificity, positive predictive value and negative predictive value of PCR when applied to bronchial aspirate specimens for diagnosing smear-negative pulmonary TB were 97.2%, 73.2%, 82.7% and 95.2% respectively. Therefore, detection of M. tuberculosis complex DNA in bronchial aspirates by PCR might have an adjunctive place to transbronchial biopsies in the rapid diagnosis of smear-negative pulmonary tuberculosis.

Adolescent↗
PubMed1998

Rotavirus infection in Hong Kong: epidemiology and estimates of disease burden.

Rotavirus gastroenteritis should soon be a vaccine-preventable disease. In a 10-year survey of rotavirus gastroenteritis conducted at the Prince of Wales Hospital (PWH), 2281 cases were detected of which 2213 (97%) occurred in children < 5 years old. A consistent epidemic occurred each winter during the months of December and January. Of all laboratory-confirmed cases, 78% were community-acquired with a mean hospital stay of 4.7 days. The estimated incidence of rotavirus-attributed hospitalization was 2/1000 children < 5 years old. Over the 10 years, rotavirus was responsible for one death, and contributory to three other deaths. On average each year, 195 children < 5 years old were hospitalized for a total of 917 days in PWH, accounting for an estimated expenditure of HK$2.8 (approximately US$0.4) million on hospitalization costs. The annual financial burden for rotavirus gastroenteritis for the whole of Hong Kong could be in excess of HK$9.6 (approximately US$1.2) million.

Age Factors↗
PubMed1998

One-week use of ranitidine bismuth citrate, amoxycillin and clarithromycin for the treatment of Helicobacter pylori-related duodenal ulcer.

BACKGROUND: Proton pump inhibitors have been widely used in combination with amoxycillin, clarithromycin or metronidazole for the treatment of Helicobacter pylori infection. AIM: To study the effects of 1-week ranitidine bismuth citrate (RBC)-based triple therapy in the treatment of H. pylori-related duodenal ulcers. METHOD: Patients with duodenal ulcers and H. pylori infection were prospectively randomized to receive either RBC with amoxycillin and clarithromycin for 1 week (RAC), or omeprazole with amoxycillin and clarithromycin for 1 week (OAC). No additional ulcer healing drug was used after the 1-week medication. Patients were assessed for H. pylori eradication, ulcer healing and side-effects after receiving the therapies. RESULTS: One hundred consecutive patients were recruited to this study, with 50 patients randomized to each treatment group. In the intention-to-treat analysis, duodenal ulcers were completely healed in 45 (90%) patients in the RAC group and 43 (89.6%) in the OAC group (P = 1.0). H. pylori eradication was confirmed in 47 (94%) in the RAC group and 42 (87.5%) in the OAC group (P = 0.31). There was no significant difference in the severity of side-effects experienced by the two treatment groups. CONCLUSION: One-week RBC-based triple therapy is an effective treatment for H. pylori-related duodenal ulcers. The therapeutic effects are comparable to a 1-week course of proton pump inhibitor-based triple therapy.

Adolescent↗
PubMed1998

Risk factors for Enterobacter septicemia in a neonatal unit: case-control study.

Thirty cases of Enterobacter aerogenes or Enterobacter cloacae septicemia diagnosed over a 32-month period in a tertiary care neonatal unit were enrolled in a case-control study. Each case patient was matched with two controls (patients occupying the cots nearest the case patient when the latter developed septicemia). Of the 32 perinatal characteristics evaluated, 11 were identified by univariate analysis to be significantly associated with the infection. These included parents being residents of the Vietnamese refugee camps, respiratory distress syndrome, necrotizing enterocolitis, umbilical arterial catheterization, umbilical venous catheterization, bladder catheterization, mechanical ventilation, antibiotic treatment, peripheral venous catheterization, nasogastric intubation, and parenteral nutrition. Multivariate analysis, however, showed that preceding bladder catheterization and ongoing parenteral nutrition were the only independent risk factors for enterobacter septicemia. Strict aseptic technique in the preparation of parenteral nutrition fluid and avoidance of bladder catheterization are measures that may reduce the risk of enterobacter sepsis for newborns.

Bacteremia↗
PubMed1998

False-negative biopsy urease test in bleeding ulcers caused by the buffering effects of blood.

OBJECTIVES: A false-negative biopsy urease test (BUT) is common in Helicobacter pylori-associated bleeding peptic ulcers. Although blood in the stomach is thought to interfere with the biopsy urease test, the underlying mechanism remains unknown. This in vitro experiment sought to identify the blood component(s) that interfere with the biopsy urease test, and delineate the mechanism of inhibition. METHODS: The modified Hazell's microtiter test was used to detect the urease activity of H. pylori. A positive result was indicated by a color change of the pH indicator, bromothymol blue, at 630 nm. Human whole blood, sera with and without anti-H. pylori antibody, electrolytes, and enzymes were incubated with H. pylori to identify the blood component(s) causing the inhibition of urease activity. In addition, any interference of the pH color indicator was tested by adding different concentrations of serum albumin to the urease reagent that contained a fixed quantity of ammonia in the absence of H. pylori. RESULTS: The color change of the microtiter urease test was significantly reduced by blood (p < 0.0001), regardless of the presence of anti-H. pylori antibody. Electrolytes and serum enzymes did not interfere with the urease test. The color change of the pH indicator was progressively suppressed by higher concentrations of serum albumin. CONCLUSIONS: Blood adversely affects the performance of the BUT. This is mediated by the buffering effect of serum albumin on the pH indicator, rather than by a direct inhibition on the urease activity.

Biopsy↗
PubMed1998

Antimicrobial resistance in Shigella flexneri and Shigella sonnei in Hong Kong, 1986 to 1995.

Three hundred and thirty-three Shigella isolates obtained in 1986 to 1995 were tested for their susceptibilities to 19 antimicrobial agents. Nalidixic acid resistance had emerged in 59.6% of Shigella flexneri isolates during 1994 to 1995, with all tested resistant isolates having the mutation in gyrA encoding the Ser-83 alteration. Multiresistance (resistance to four or more agents) was more common in S. flexneri than in Shigella sonnei.

Anti-Infective Agents↗
PubMed1998

Evaluation of a selective transport medium for gastric biopsy specimens to be cultured for Helicobacter pylori.

Since the means of culturing Helicobacter pylori may not be available in some laboratories, prolonging the survival of this organism during transportation is a major concern in terms of improving detection rates. A selective transport medium was evaluated for the preservation of H. pylori from 254 gastric biopsy specimens collected from a rural area in China where culturing is not feasible. Gastric biopsy specimens were inoculated in sterile broth consisting of brain heart infusion (BHI) broth, horse serum, and yeast extract supplemented with vancomycin, amphotericin B, and nalidixic acid (VAN). Of the 254 biopsy specimens, 238 were identified by histology to have H. pylori infection. Total rates of recovery of H. pylori from the H. pylori-positive gastric biopsy specimens stored in the BHI-VAN broth ranged from 76 to 46% after storage of specimens for 5 to 9 days. In conclusion, the selective medium is useful for prolonging the survival of H. pylori in gastric biopsy specimens for which immediate culture is not feasible.

Adult↗
PubMed1998

Antimicrobial susceptibilities and molecular epidemiology of Salmonella enterica serotype enteritidis strains isolated in Hong Kong from 1986 to 1996.

The incidence of salmonellosis has been increasing in Hong Kong since 1989. The most common Salmonella enterica serotype isolated in 1994 was S. enteritidis. The antimicrobial susceptibilities and molecular epidemiology of 275 S. enteritidis strains isolated in this locality between 1986 and 1996 were studied. Over 99% of the isolates were susceptible to 17 of the 19 antimicrobial agents tested. One isolate harbored an autotransferring plasmid that confers resistance to tetracycline and trimethoprim-sulfamethoxazole. Another isolate harbored a mobilizable plasmid that confers resistance to ampicillin and cephalothin. This isolate was found to produce a beta-lactamase with a pI of 5.2. A total of 264 isolates (96%) were found to harbor one to five plasmids, and the majority (254) harbored a 60-kb plasmid. Of these isolates, 94% contained identical 60-kb plasmids. Based on plasmid profiles, plasmid and chromosomal fingerprints, ribotypes, and randomly amplified polymorphic DNA (RAPD) patterns, 170 (62%) isolates were allocated to group 1b. About 90% of isolates had identical or similar DNA fingerprints, ribotypes, and RAPD patterns, suggesting that a predominant clone of S. enteritidis was circulating in Hong Kong during the period being studied.

Anti-Bacterial Agents↗
PubMed1998

Study of the relatedness of isolates of Shigella flexneri and Shigella sonnei obtained in 1986 and 1987 and in 1994 and 1995 from Hong Kong.

We used pulsed-field gel electrophoresis (PFGE) to study the genetic relatedness of 235 isolates of Shigella flexneri and Shigella sonnei collected in Hong Kong (97 isolates from 1986 and 1987 and 138 isolates from 1994 and 1995). Altogether, 13 gels were run with bacteriophage lambda ladder DNA (Pharmacia) as an external reference in every sixth lane, standardized reagents and methods, and isolates randomized for species and years. For quantitative illustration of the relationships within a large body of isolates, computer-generated dendrograms were used to determine the number of isolates in pulsotypes at Dice coefficients of similarity of 75% (PT75) and 50% (PT50). For S. flexneri, there was a significant difference in the distribution of isolates collected during the two periods in both PT75 and PT50, with 68% of isolates collected in 1994 and 1995 sharing a coefficient of similarity of >/=68%. For S. sonnei, a significant difference was observed in PT50 only. We also used Upholt's formula for an approximation of the fraction of nucleotide difference between isolates and Molecular Evolutionary Genetics Analysis to determine relative genetic distances. For both species, the relative genetic distances between isolates of the earlier collection period were significantly greater (P < 0.0001), i. e., they were further apart and therefore more diverse than those of the later period. We conclude that it is possible for a typical clinical laboratory to analyze a large amount of PFGE information on Shigella isolates obtained under controlled conditions. Such data analysis should enhance surveillance capabilities and give indications of further work to be done on various aspects of bacterial pathogenicity of the species.

Bacteriophage lambda↗
PubMed1998

Double blind, randomised, placebo controlled study of oral vancomycin in prevention of necrotising enterocolitis in preterm, very low birthweight infants.

AIMS: To evaluate the effectiveness of oral vancomycin in the prophylaxis of necrotising enterocolitis in preterm, very low birthweight infants. METHODS: A prospective, double blind, randomised, placebo controlled study in a tertiary referral centre of a university teaching hospital was conducted on 140 very low birthweight infants consecutively admitted to the neonatal unit. The babies were randomly allocated to receive oral vancomycin (15 mg/kg every 8 hours for 7 days) or an equivalent volume of placebo solution. Prophylaxis was started 24 hours before the start of oral feeds. All suspected cases of necrotising enterocolitis were investigated with a full sepsis screen and serial abdominal radiographs. Necrotising enterocolitis was diagnosed and staged according to modified Bell's criteria. RESULTS: Nine of 71 infants receiving oral vancomycin and 19 of 69 infants receiving the placebo solution developed necrotising enterocolitis (p = 0.035). Infants with necrotising enterocolitis were associated with a significant increase in mortality (p = 0.026) and longer duration of hospital stay (p = 0.002). CONCLUSIONS: Prophylactic oral vancomycin conferred protection against necrotising enterocolitis in preterm, very low birthweight infants and was associated with a 50% reduction in the incidence. However, widespread implementation of this preventive measure is not recommended, as it would only be effective in necrotising enterocolitis caused by Gram positive organisms and could increase the danger of the emergence of vancomycin resistant or dependent organisms. Its use should be restricted to a high prevalence nursery for a short and well defined period in a selected group of high risk patients.

Administration, Oral↗
PubMed1997

Comparison of E-test with agar dilution for determining susceptibility of Streptococcus pneumoniae to penicillin.

Minimum inhibitory concentrations (MICs) of penicillin for Streptococcus pneumoniae were determined by the E-test and the agar dilution method. Ninety Streptococcus pneumoniae strains were tested, of which 16 were resistant, 33 intermediate, and 41 susceptible by agar dilution. By the E-test, 80 (88.9%) strains agreed with these determinations within one log2 dilution step, and no strains disagreed by more than two dilution steps. Sixty-eight of the 70 strains with discrepant MICs read lower in the E-test, resulting in 15 strains being placed in different susceptibility categories when classified by this test. Exact MICs rather than classification groups should be used to determine appropriate antibiotic therapy, since small differences in MICs determined by different methods can lead to a significant degree of misclassification.

Colony Count, Microbial↗
PubMed1997

One-week antibiotics versus maintenance acid suppression therapy for Helicobacter pylori-associated peptic ulcer bleeding.

Bleeding peptic ulcer is the most important cause of upper gastrointestinal bleeding. Our aim was to compare the effect of anti-Helicobacter therapy with maintenance treatment of H2-receptor antagonist in the prevention of relapses of ulcer and bleeding. Patients with bleeding duodenal or gastric ulcers and H. pylori infection were randomized to receive either a one-week course of triple therapy with bismuth subcitrate, metronidazole, and tetracycline plus ranitidine or a six-week course of ranitidine 300 mg/day. After the ulcers healed, the antibiotic-treated patients were not given any medication, whereas the ranitidine-treated patients continued to receive a maintenance dose of 150 mg/day. One hundred twenty-six patients were randomized to receive anti-Helicobacter therapy and 124 patients to receive long-term ranitidine. H. pylori eradication was achieved in 98.2% in those who received triple therapy and 6.1% in those who received ranitidine (P < 0.0001). At the six-week follow-up, ulcer healing was documented in 88.2% in those who received triple therapy and 86.1% in those who received ranitidine (P = 0.639). Recurrent ulcer developed in nine of the ranitidine-treated patients and three of them presented with recurrent upper gastrointestinal bleeding. One patient in the antibiotic group developed recurrent ulcer without rebleeding (P = 0.01). It is concluded that eradication of H. pylori is sufficient for the prevention of recurrent bleeding ulcers.

Adult↗
PubMed1997

Living with methicillin-resistant Staphylococcus aureus: a 7-year experience with endemic MRSA in a university hospital.

A review of our infection control records revealed 3,159 new isolations of methicillin-resistant Staphylococcus aureus (MRSA) from 1988 to 1994. Prior to this period, our approach to MRSA had changed from eradication to containment measures. We found a decline in MRSA rates from 11.4 to 5.2 first isolations per 1,000 deaths and discharges over the study period.

Cross Infection↗
PubMed1997

In-vitro activities of aminoglycoside-aminocyclitols against mycobacteria.

Aminoglycoside-aminocyclitols including streptomycin, kanamycin, capreomycin and amikacin showed considerable activity against Mycobacterium tuberculosis, with MICs well below their Cmax and relatively low MBC/MIC ratios. Kanamycin, capreomycin and amikacin remained highly active against 'resistant' and 'multidrug-resistant' M. tuberculosis isolates except for some 'multidrug-resistant' isolates which showed complete cross-resistance between streptomycin and the selected 2-deoxystreptamines. Gentamicin displayed anti-tuberculous activity but was bacteriostatic only. Non-tuberculosis mycobacteria, in particular Mycobacterium chelonae and Mycobacterium avium-intracellulare, were more resistant than M. tuberculosis. Amikacin was inhibitory against Mycobacterium kanasii, Mycobacterium scrofulaceum and Mycobacterium fortuitum, but was bactericidal against M. scrofulaceum only. Kanamycin was also bactericidal against M. scrofulaceum. Growth of M. fortuitum was inhibited by amikacin and neomycin which was also inhibitory against M. tuberculosis and M. scrofulaceum. Although the application of neomycin has been limited by its high toxicity, this study suggested that this drug might be useful as a topical agent for cutaneous infections by M. fortuitum.

Amikacin↗