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Biomedical subjects

A F Cheng

Publications and source records attributed to A F Cheng.

At least 145 records · Page 8Linked to original sources
PubMed1991

A five-year prospective study of septicaemia in hospitalized children in Hong Kong.

In a 5-year prospective study in a Hong Kong teaching hospital there were 344 clinically significant episodes of paediatric septicaemia. Many of the microbiological and clinical features were similar to those reported in Japanese and Western studies but there were some important differences. Half of the episodes (or 70% if neonatal infections are excluded) were community-acquired. The commonest organisms found were Salmonella spp (15% of all and 27% of community-acquired infections); this was related to the high local incidence of salmonellosis and typhoid fever. Salmonella typhi, which was responsible for one-third of the salmonella septicaemias, was usually seen in school-age children, while non-typhoid salmonellae were common in infants. Methicillin-resistant Staphylococcus aureus, which are now endemic in Hong Kong hospitals, was a common cause of hospital-acquired septicaemia. Pneumococcal septicaemia accounted for 22% of episodes in infants and pre-school children, but Haemophilus influenzae was uncommon (2% of all episodes) and there was no case of meningococcal septicaemia. The rarity of invasive infection with H. influenzae and Neisseria meningitidis in Hong Kong children is unexplained.

Adolescent↗
PubMed1990

Hong Kong strains of methicillin-resistant and methicillin-sensitive Staphylococcus aureus have similar virulence.

While most authorities agree that methicillin-resistant Staphylococcus aureus (MRSA) are as pathogenic as methicillin-sensitive strains (MSSA), some believe that MRSA are relatively avirulent opportunists, and that their importance has been exaggerated. We present evidence that Hong Kong strains of MRSA and MSSA are equally pathogenic: they have similar virulence in animal models; they are isolated in similar proportions from both deep and superficial clinical sites including blood; in patients with hospital-acquired bacteraemias mortality rates are similar when adjusted for clinical factors; and in both animals and patients with systemic MRSA infection, mortality rates are significantly reduced by vancomycin therapy. Efforts to control the spread of MRSA are justified, and in invasive sepsis early treatment with vancomycin may be life-saving.

Animals↗
PubMed1990

Septicaemia in Hong Kong.

In a five-year prospective study of blood culture-positive septicaemia in a Hong Kong teaching hospital there were 2211 clinically-significant episodes, of which 16% occurred in children less than 15 years old. The microbiology and clinical features were broadly similar to those seen in Europe and North America, but with some important differences. Two-thirds of episodes were community-acquired. The most common organism isolated from community-acquired septicaemias was Escherichia coli and the source, most commonly, the urinary tract. However, the biliary tract was the second most common source of community-acquired infection (25%), reflecting the frequency of liver disease in Hong Kong. Three per cent of community-acquired septicaemias were associated with endocarditis; half of these were with viridans streptococci, usually in patients with rheumatic heart disease, and 40% were in drug addicts with methicillin-sensitive Staphylococcus aureus. The commonest organisms causing community-acquired childhood infections were Salmonella spp. (27%) and Streptococcus pneumoniae (22%), whereas pneumococci accounted for only 3% of adult community-acquired micro-organisms. Haemophilus influenzae infections were uncommon and there was no case of meningococcal or gonococcal septicaemia. The commonest cause of hospital-acquired septicaemia was Staph. aureus (24%), of which 46% were methicillin-resistant. The characteristics of septicaemia in Hong Kong are influenced by the patient population structure, endemic disease patterns, local medical practice and socio-economic factors, but the rarity of Str. pneumoniae in adults and of H. influenzae and Neisseria meningitidis in children is unexplained.

Adolescent↗
PubMed1990

Rapid diagnosis of bacterial meningitis by the detection of a fatty acid marker in CSF with gas chromatography-mass spectrometry and selected ion monitoring.

A chemical marker of bacterial meningitis was sought by comparing derivatives of sterile cerebrospinal fluid (CSF) with cultures of organisms in spinal fluid and artificial media. The technique of gas chromatography-mass spectrometry with selected ion monitoring (GC-MS-SIM) was used, optimised for the analysis of fatty acids. Twenty candidate ions were screened, and an ion of mass: charge ratio (m/e) 268 was chosen for detection in clinical specimens. The origin of this marker is unknown, but it is probably the molecular ion of a C16:1 fatty acid. In 135 clinical specimens of CSF examined, the m/e 268 ion was found to be a useful marker for the common organisms that cause bacterial meningitis, giving a sensitivity of 88% and a specificity of 98%. The method was more rapid and more sensitive than conventional microscopy and culture, but CSF containing coagulase-negative staphylococci, Mycobacterium tuberculosis, Cryptococcus neoformans and some other uncommon pathogens gave inconsistent results. Many organisms produced characteristic ion profiles with multiple-ion monitoring, and this method of chemical analysis holds promise for the rapid diagnosis of bacterial infections to genus or species level.

Biomarkers↗
PubMed1989

Repeated prevalence surveys for monitoring effectiveness of hospital infection control.

In a 1400-bedded teaching hospital single-day prevalence surveys of hospital infection were done every six months for 3 years. The prevalence of community-acquired infection remained constant; but, after the introduction of a general infection-control policy, the prevalence of hospital-acquired infection (HAI) fell linearly from 10.5% in the second survey to 5.6% in the last. After the introduction of a specific urinary catheter care policy, the prevalence of hospital-acquired urinary tract infection (HAUTI) fell from 3.2% in the first four surveys to 2.0% in the last three. These differences persisted when the results were adjusted by logistic regression for patient risk factors, which varied between surveys: the declines for HAI and HAUTI were then 9.9% to 6.0% and 2.9% to 2.2% respectively. Infection control policies, therefore, can have substantial impact on the prevalence of HAI, and their effectiveness can readily be measured by repeated prevalence surveys.

Chi-Square Distribution↗
PubMed1989

Special precautions reduce oropharyngeal contamination in bronchoalveolar lavage for bacteriologic studies.

Despite the use of quantitative culture, oropharyngeal contamination of bronchoalveolar lavage (BAL) specimens is still a factor that limits the usefulness of this technique in the diagnosis of lower respiratory tract infection. To investigate whether special precautions could reduce contamination, 20 noninfected patients undergoing diagnostic bronchoscopy were randomized into 2 groups of 10 patients: BAL was performed routinely in group R and with special precautions in group P. These precautions consisted of giving topical lidocaine by inhalation rather than by bolus injection, and passing the bronchoscope used for BAL through a previously inserted endotracheal tube. Quantitative culture of BAL specimens showed that 5 patients in group R (50%), but none of the patients in group P (0%), had at least 1 organism recovered in concentrations greater than or equal to 10(4) colony-forming units CFU/ml (p = 0.016). Fifteen of 39 isolates (38.5%) in group R and none of 18 isolates in group P (0%) were present in concentration greater than or equal to 10(4) CFU/ml (p = 0.001). We conclude that oropharyngeal contamination of BAL specimens can be minimized by adopting special precautions during the procedure and by using quantitative culture with 10(4) CFU/ml as the cut-off point. This may increase the specificity of the technique in the diagnosis of lower respiratory tract infection without reducing its sensitivity.

Bacteriological Techniques↗
PubMed1988

Methicillin-resistant Staphylococcus aureus bacteraemia in Hong Kong.

In the first 22 months of operation at the Prince of Wales Hospital, 26 (46%) of 56 hospital-acquired Staphylococcus aureus bacteraemias were due to methicillin-resistant organisms (MRSA). There were 10 plasmid profiles amongst 24 of the MRSA strains analysed. MRSA bacteraemias were first seen in the hospital 1 year after opening when the isolation rate of MRSA from all sites had risen to about 1% of patient admissions. During the last 3 months of the study period, 17 out of 18 S. aureus bacteraemias were due to methicillin-resistant strains. Patients with MRSA bacteraemia were significantly more likely than those with methicillin-sensitive S. aureus bacteraemia to have had a severe underlying disease, a poor clinical prognosis, prolonged hospitalization, and prior antimicrobial therapy, especially with aminoglycosides. They also had a significantly longer hospital stay after infection, a significantly higher cost of antimicrobial therapy and a higher mortality rate. The lower mortality rate in MRSA patients treated with vancomycin (18%) compared with those treated with other antimicrobials (40%) confirms that, at present, vancomycin is the treatment of choice for invasive MRSA infections.

Cross Infection↗
PubMed1988

Thyroid abscess caused by Eikenella corrodens.

To our knowledge, this is only the fourth case recorded of thyroid abscess due to Eikenella corrodens and the first in which the causative organism has been isolated in pure culture from the site of infection. E. corrodens may be the cause of apparently sterile thyroid abscesses encountered in head and neck surgery and should be considered in their differential aetiology.

Abscess↗
PubMed1988

Eikenella corrodens as a cause of brain abscess.

A case of brain abscess due to Eikenella corrodens in a 67-year-old woman is reported. To our knowledge, this is the first case in which the causative organism has been isolated from the occipital lobe. E. corrodens may be the cause of apparently sterile brain abscesses encountered in neurosurgery and should be considered in the differential etiology of brain abscess.

Aged↗
PubMed1987

Septic arthritis caused by Streptococcus suis serotype 2.

A case of septic arthritis and septicaemia due to Streptococcus suis serotype 2 is reported. To our knowledge, this is the first case in which the causative organism has been isolated from the joint-fluid. Involvement of joints is a feature of S. suis infection in pigs, and may be more common in human beings than previously realised. Infectious arthritis caused by beta-haemolytic streptococci may be due to S. suis and result from contact with pigs or raw pork.

Aged↗
PubMed1987

Comparative evaluation of the Abbott TDX, the Abbott ABA200, and the Syva LAB5000 for assay of serum gentamicin.

Three automated chemical assays for serum gentamicin were compared for accuracy, reproducibility and cost. One method utilized fluorescence polarization (Abbott TDX), and the other two enzyme-multiplied immunoassay (Abbott ABA200, and the Syva Lab5000). All three systems produced a high degree of accuracy and reproducibility with spiked samples when the concentrations of gentamicin were within the range of 3.0-8.0 mg/l. However, with concentrations below 2.0 mg/l or above 8.0 mg/l, only the TDX system gave acceptable coefficients of variation and accurate recoveries. Similarly, excellent correlations were obtained between all three systems for assays of clinical specimens containing 2.0-8.0 mg/l gentamicin, but above and below this range, the correlations were poor except between TDX and Lab5000 within the range of 0.0-2.0 mg/l. The Abbott TDX was thus the most accurate and reproducible of the three systems for the assay of serum gentamicin in the critical concentrations below 2.0 mg/l and above 8.0 mg/l. The cost per assay by the Abbott TDX was US$4.57 compared with US$5.40 for the Abbott ABA200, and US$3.20 for the Syva Lab5000.

Costs and Cost Analysis↗
PubMedDate not supplied

Mucosal pharmacokinetics and pilot study of short course of parenteral imipenem in the eradication of Helicobacter pylori.

Eradication of Helicobacter pylori infection is known to reduce the incidence of duodenal ulcer recurrence. The most commonly used regimen for H. pylori infection is triple antimicrobial therapy for 1-2 weeks. This treatment is associated with frequent side effects and hence unsatisfactory compliance. As in vitro data showed that H. pylori is sensitive to imipenem, the pharmacokinetics of this drug in the gastric milieu, and the clinical efficacy of imipenem with omeprazole in eradicating H. pylori infection were studied. Imipenem/cilastatin levels in serum, gastric secretion and gastric mucosa were assayed in four patients after intravenous injection of a bolus dose of 500 mg. The serum and gastric secretion levels of imipenem achieved were more than 10 times the minimum inhibitory concentration of the drug for H. pylori. Gastric mucosal levels of imipenem vary considerably with time, which probably indicates rapid elimination of the drug into the gastric lumen. In the second part of this study, imipenem/cilastatin was given intravenously for the first 2 days after diagnosis of H. pylori infection in patients with endoscopically confirmed duodenal ulcers. The patients were also treated with 4 weeks of omeprazole. Clearance of H. pylori was initially achieved at the end of 2 days in 20 out of 22 (91%) patients. However, when the biopsies were repeated at 8 weeks, recurrence of H. pylori infection was evident in 19 cases (86.3%) indicating a failure of eradication. It was concluded that imipenem/cilastatin in combination with omeprazole failed to eradicate H. pylori infection.

Biopsy↗
PubMedDate not supplied

Detection of fluoroquinolones in urinary specimens from patients undergoing anti-tuberculous therapy.

A paper strip impregnated with ferric chloride has been developed for visual detection of fluoroquinolones in urine based on a change of colour due to the chelation of the transition metal ion to the beta-oxo acid array in the 4-oxo-1,4-dihydropyridine-3-carboxylic acid moiety of the fluoroquinolone molecule. In urine specimens, the detection limit of the strip was 100 mg/l for pefloxacin, 200 mg/l for ciprofloxacin, fleroxacin, levofloxacin, norfloxacin, ofloxacin and sparfloxacin, and 300 mg/l for trovafloxacin. In 193 urine specimens taken from 138 patients on ofloxacin therapy and 55 controls preliminary evaluation of the strip showed that all the 55 specimens from control patients were negative, while 112 out of the 138 ofloxacin-treated patients were positive. Quantitative analysis by high-performance liquid chromatography of the 26 strip-test-negative specimens taken from patients with ofloxacin treatment indicated that these urinary specimens contained less than 200 mg/l of the antimicrobial, mostly because of poor renal function and in some occasions, non-compliance. This strip method would provide a convenient way of monitoring drug compliance in patients who receive fluoroquinolone therapy for tuberculosis.

Anti-Infective Agents↗
PubMedDate not supplied

In vitro activity of trovafloxacin (CP 99,219), a new fluoroquinolone against hospital isolates.

The susceptibility of 492 Enterobacteriaceae, 227 other gram-negative bacteria, 448 gram-positive bacteria and 108 anaerobic organisms was determined by the agar dilution method against trovafloxacin and other antibiotics. Trovafloxacin was highly active against most of the Enterobacteriaceae including Enterobacter spp. and Citrobacter spp. [minimum inhibitory concentration (MIC)90 <1 mg/l], Acinetobacter spp. and Pseudomonas aeruginosa (MIC90 = 0.25 and 2 mg/l, respectively). The antimicrobial activity was extended to the gram-positive bacteria including streptococci, Streptococcus pneumoniae, coagulase-negative staphylococci and methicillin-sensitive Staphylococcus aureus with MIC90 <1 mg/l. Enterococci and methicillin-resistant S. aureus were inhibited (MIC90 = 2 mg/l; sparfloxacin and ciprofloxacin were 16 and 64 mg/l, respectively). Almost all anaerobic organisms were inhibited by trovafloxacin (MIC90 = 1 mg/l).

Anti-Bacterial Agents↗
PubMedDate not supplied

A 13-year study of antimicrobial susceptibility of common gram-negative bacteria isolated from the bloodstream in a teaching hospital.

The choice of antimicrobial therapy for the treatment of bacteremia is often empirical and based on the knowledge of susceptibility profiles of the most common bacteria. We analyzed blood culture isolates from a teaching hospital for 13 years prospectively. This study examined the susceptibility profiles of 6,616 gram-negative bacteria. Escherichia coli ranked among the commonest bacteria, representing 43.6% (2,890) of all gram-negative isolates. Klebsiella sp. ranked second, 17.7% (1,171) and 16.7% were resistant to ceftazidime in 1997. There was a trend towards an increase in resistance to fluoroquinolones in the common gram-negative bacteria. Imipenem was the most active agent against gram-negative bacteria. The results of the susceptibility of gram-negative bacteria causing bacteremia provide valuable information for implementing the appropriate chemotherapy for bacteremia.

Anti-Infective Agents↗