Biomedical subjects
Publications and source records attributed to G L French.
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.
Tuberculostearic acid, a structural component of Mycobacterium tuberculosis, was identified by gas chromatography/mass spectrometry with selected ion monitoring in cerebrospinal fluid (CSF) from 13 patients with proven and 8 out of 9 patients with suspected tuberculous meningitis; the negative result was in a patient whose symptoms and CSF abnormalities may have been due to systemic lupus erythematosus. Tuberculostearic acid was found in the CSF of only 1 patient out of 87 with non-tuberculous meningitis or non-infectious disorders; the single false-positive result was probably caused by intrathecal treatment with amikacin. Other aminoglycosides and antituberculous drugs did not interfere with the assay. In serial CSF samples from patients with tuberculous meningitis tuberculostearic acid was still present after 8 months of continuous supervised chemotherapy. Detection of tuberculostearic acid in CSF is a rapid, sensitive, and specific test for tuberculous meningitis, and can be used for retrospective diagnosis in patients who have been started on therapy.
A 1-day prevalence survey of hospital infection was performed in June 1985 at a new general teaching hospital in Hong Kong. The 1980 British national survey protocol was used, and the results were analysed by microcomputer. The major part of the survey was carried out by nine people over a period of 3 days and was completed within 6 weeks. The rate of hospital-acquired infection was 8.9% and of community-acquired infection was 16.5%. Antibiotics were mainly used in infected patients. The British protocol is suitable for Hong Kong hospitals, and with microcomputer data analysis such surveys can be completed quickly and accurately even with limited resources.
Melioidosis is endemic in Southeast Asia but reports of prostatic involvement are rare. We describe a patient with Pseudomonas pseudomallei septicemia and a prostatic abscess who presented with signs and symptoms of a urinary tract infection. The organism was cultured from the blood, urine and prostatic pus, and was treated successfully with co-trimoxazole and surgical drainage. Genitourinary infection with Pseudomonas pseudomallei should be considered in patients from endemic areas, and bacteriological investigation is essential for the diagnosis and management.
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.
The bacterial populations of six freshwater streams in populated areas of the Hong Kong New Territories were studied. There is considerable faecal contamination of these streams, with coliform counts as high as 10(5) c.f.u./ml and the contaminating organisms show a high prevalence of antibiotic resistance and multiple resistance. With direct plating of water samples onto antibiotic-containing media, an average of 49% of the gram-negative bacteria were ampicillin-resistant, 3% chloramphenicol-resistant and 1% gentamicin-resistant. At individual sites resistance to these drugs was as high as 98%, 8% and 3% respectively. More than 70% of strains were resistant to two or more antibiotics, 29% to five or more and 2% to eight or more. A total of 98 patterns of antibiotic resistance were detected with no one pattern predominating. Twenty-eight gram-negative bacterial species were identified as stream contaminants. Escherichia coli was the commonest bacterial species isolated and other frequent isolates were Enterobacter sp., Klebsiella sp. and Citrobacter sp., but no enteric pathogens were detected. The greatest prevalence of resistance and multiple resistance was associated with the heaviest contamination by E. coli. Analysis of selected stream isolates revealed multiple plasmid bands arranged in many different patterns, but multiple antibiotic resistances were shown to be commonly mediated by single transferable plasmids. Faecally-contaminated freshwater streams in Hong Kong may be reservoirs of antibiotic resistance plasmids for clinically-important bacteria.
Tuberculostearic acid [(R)-10-methyloctadecanoic acid (TBSA)] is a structural component of mycobacteria, and its detection in appropriate clinical specimens has potential application as a rapid screening method for the presence of Mycobacterium tuberculosis and other mycobacteria. We used the highly sensitive technique of gas chromatography-mass spectrometry (GC-MS) combined with selected ion monitoring (SIM) of m/e 312 and m/e 167 for detecting TBSA in 405 clinical sputum specimens collected in Hong Kong, where tuberculosis is still common. TBSA was detected in 39 M. tuberculosis smear-positive, culture-positive specimens; 63 of 66 smear-negative, culture-positive specimens; and 1 of 300 smear-negative, culture-negative specimens. Thus, for screening of sputa from individuals with suspected pulmonary tuberculosis, the detection of TBSA by GC-MS/SIM is highly specific and more sensitive than conventional microscopy and more rapid but slightly less sensitive than conventional culture methods.
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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.
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Four-hundred and seventy-six isolates of Staphylococcus aureus from patients in Hong Kong were tested for methicillin-resistance by agar dilution and disc diffusion methods, using heavy inocula. With Mueller-Hinton agar incubated at 30 degrees C for 24 h, 216 (MRSA) isolates were resistant to 8 mg/l of methicillin and grew up to the edge of a 10 micrograms methicillin disc, and 260 strains were susceptible to greater than or equal to 4 mg/l methicillin and produced inhibition zones of at least 20 mm diameter. Incubation for 48 h, the addition of sodium chloride, or the use of a 5 micrograms disc had little effect on these results, but a significant number of MRSA strains produced inhibition zones when disc diffusion tests were incubated at 35 degrees C, and many sensitive strains showed scanty growth on salt-containing agar at high methicillin concentrations in agar dilution tests. Iso-Sensitest agar did not appear to support the growth of the minority resistant populations of MRSA unless supplemented with menadione and thiamine, and even with supplemented Iso-Sensitest medium a few presumptively resistant strains appeared methicillin-sensitive in both disc diffusion and agar dilution tests.
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Of 74 paediatric inpatients with acute glomerulonephritis, 58 (78%) had a raised (greater than 1/200) antistreptolysin O titre. Serum C3 concentration was low in 73, but returned to normal within six weeks. Streptococcal infection remains the commonest cause of acute nephritis in children in Hong Kong, possibly due to overcrowded living conditions.
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Laboratory surveillance of clinical isolates for Serratia spp. revealed a sudden increase from babies in the Special Care Baby Unit (SCBU). It was established that breast-milk pumps on the post-natal wards were being disinfected inadequately, resulting in contamination of milk and cross-infection within the SCBU. Thirty babies were colonized and no deaths were attributable to the organism. Rectal carriage by the babies was common and often prolonged. The outbreak was brought under control when the method of disinfection of the pumps was changed from soaking in hypochlorite solution to washing at 80 degrees C.
A simple isocratic HPLC method is described for the rapid analysis of cephalosporins in body fluids. Sample preparation by protein precipitation takes only five minutes; HPLC analysis is completed within two to ten minutes, using one of two simple solvent mixtures eluted on a single C18 reversed phase column. Nine cephalosporins and nine types of body fluid were formally analysed, but the system was also found to be suitable for the assay of benzyl penicillin, ampicillin, cloxacillin, carbenicillin and chloramphenicol. It is likely that this method, with only minor modifications, would be suitable for the analysis of most beta-lactam antibiotics in most clinical specimens. The method is therefore particularly recommended for use in clinical laboratories.