- Volume 29, Issue 3, 1989

We report the relative frequencies of members of the Bacteroides fragilis group in the faeces, in colon lavage fluid obtained pre-operatively, and in colonic tissue specimens obtained at operation from 10 patients with colonic cancer. B. vulgatus was the most and B. fragilis and B. ovatus were the least frequently isolated Bacteroides spp. in the faeces of the 10 subjects. B. uniformis and B. thetaiotaomicron ranked second and third in the faeces. The relative frequencies of all species except B. fragilis were lower in the lavage fluid and in cultures of mucosa. The relative frequency of B. fragilis increased from 4% in faeces to 39% in the final lavage fluid and to 42% in the colonic mucosa culture. Our results suggest that B. fragilis has a more intimate association with the gut mucosa than other members of the B. fragilis group, which might be one explanation for the high incidence of this species in gut-associated intra-abdominal infections.

A new species of Fusobacterium, F. ulcerans, was isolated from 46 tropical ulcers. All the isolates had shown identical soluble cell protein patterns on polyacrylamide gel electrophoresis although there were two morphological types with slightly different biochemical properties. A representative strain of each of the two groups was selected for in-vitro cytotoxicity testing on a range of tissue-culture cell lines. Both strains of F. ulcerans induced a marked cytotoxic effect on Vero and Int-407 cells. This effect may contribute to the pathogenesis of tropical ulcers.

The adherence of Candida albicans to dacron fibre microcolumns was significantly suppressed after interaction with human neutrophils. The adherence-inhibiting properties of neutrophils were shown to reside in their cytoplasmic granules and granular enzymes. Oxygen-derived free radicals produced by the respiratory burst may also be responsible, as shown by experiments in which oxygen radicals were generated by the cell-free hypoxanthine-xanthine oxidase system. Dose-response studies with H2O2 and β-glucoronidase demonstrated that lower concentrations of these agents inhibited adherence without affecting viability of C. albicans. These results suggest that interference with adherence mechanisms may be an effective means of host defence by neutrophils against the colonisation of mucosal surfaces by C. albicans.

Cryptococcus coagglutination (COA) test reagent was prepared locally and showed no cross reactions with different species of bacteria or yeasts or with 75 control sera including 25 that gave positive results for RA factor. We used the COA test to detect cryptococcus antigen in the CSF and we could confirm the diagnosis of 11 out of 115 suspected cases of fungal meningitis; the titre varied from 4 to 128. A four-fold rise in titre confirmed the diagnostic value and a steady fall in titre in three patients on therapy indicated the prognostic value of the test. The earliest confirmation was in a renal transplant patient on the eighth day after onset of symptoms. The COA test was negative with the CSF of 118 patients with chronic meningitis. Cryptococcal colony forming units (cfu) in CSF varied from 100 to > 100 000/ml and correlated well with microscopy and with the COA antigen titre in CSF. Four out of the 11 patients who had cryptococcaemia, had 50 000-100 000 cfu/ml in the CSF. Cryptococcus antigen was detected by COA in the serum of all 11 patients, even in those with only 100 cfu/ml in CSF. In the three post-renal transplant patients, who were being monitored regularly, the diagnosis was made early and all three recovered on antifungal therapy with no relapse to date (1-2 years). All the others, including the two primary CNS infections, succumbed to the disease because they presented late for diagnosis and therapy. The cryptococcus COA test is a simple and specific test that can be used as a rapid test to confirm early diagnosis and permit prompt therapy, which should improve the prognosis in CNS and other forms of systemic cryptococcosis. Moreover, it is reproducible and cost-effective, particularly in countries where the latex and other expensive test reagents are not generally available.

A simple adherence test to detect IgM antibodies in patients with typhoid is described. The test utilises the IgM-“capture” approach, in which the test serum is applied to microtitration plate wells previously coated with anti-human IgM, followed by application of a stained Salmonella typhi antigen suspension which shows adherence in positive cases. By this test, 58 (95%) of 61 sera from confirmed cases of typhoid possessed IgM antibodies to the H or O or both antigens of S. typhi. In patients for whom a diagnosis of typhoid was based only on a significant Widal-test titre, 31 (41%) of 76 sera had IgM antibodies to the H or O or both antigens of S. typhi. Some cross-reactivity of the IgM antibodies was detected, especially with the O antigens of S. paratyphi A and B. A total of 82 sera from non-typhoidal fevers (leptospirosis, typhus, dengue fever) showed no reactivity in this test. In normal sera there was no detectable IgM to the O antigen of S. typhi and only a small number (3.9%) had low levels of IgM to the H antigen. The significance and potential importance of this simple, sensitive, specific and economical test is discussed.

Rickettsia rickettsii and Rickettsia conorii are the causative agents of two common and serious diseases, Rocky Mountain spotted fever and Mediterranean spotted fever, respectively. In patients naturally infected with either of these organisms, antibodies are produced which cross-react with antigens of the other so extensively that diagnostic tests usually cannot identify the causative agents. The results of this study indicate that serodiagnostic tests with antigen from one of these two organisms could be used to detect antibodies in patients with either of the two rickettsial diseases.

Ninety-one biochemical tests were done on each of 50 strains of Campylobacter pylori isolated from the gastric mucosa of patients with gastritis and peptic ulcers in Singapore. The API ZYM system distinguished three biotypes of C. pylori. The organism was found to be biochemically different from C. jejuni and C. coli. We propose a biochemical identification kit that would be of use in identifying and differentiating biotypes of C. pylori, and would distinguish them from C. jejuni and C. coli.

Within a collection of 749 strains of group C streptococci (Streptococcus equisimilis) and 2348 of group G, isolated over a period of 6 years, there were clusters from 63 probable outbreaks of infection. These occurred in burns and maternity units, hospital wards, outpatient clinics, army camps and religious communities. Overall, it was possible to identify T-protein antigens in 88% of the group C strains and in 82% of group G. Serotyping by the identification of T-protein antigens was a useful method for the subdivision of these strains.

The effect of sub-inhibitory concentrations of 16 antibacterials on the bactericidal activity of the 4-quinolones nalidixic acid, ciprofloxacin and ofloxacin against Escherichia coli KL16 in nutrient broth was investigated. Sub-inhibitory concentrations of rifampicin, clindamycin, chloramphenicol, erythromycin or tetracycline antagonised the bactericidal activity of the 4-quinolones. Conversely, all seven aminoglycosides tested enhanced the bactericidal activity of the 4-quinolones whereas the cell wall antagonists, azlocillin, mezlocillin, ceftazidime and vancomycin had no effect on the bactericidal activity of the 4-quinolones.

Gardnerella vaginalis has a very thin cell wall with a characteristic gram-negative staining pattern and an apparent lamellar structure when viewed at an oblique angle by electronmicroscopy. Examination at right angles to the cell-wall plane and by freeze-etching showed absence of an outer membrane or any other lamellar structure. Cell-wall extracts made by methods specific for lipopolysaccharide (LPS) gave negative reactions by silver staining and for endotoxin in the limulus amoebocyte lysate assay. 2-Keto-3-deoxy-D-manno-2-octonoic acid (KDO), heptose and hydroxy fatty acids specific for LPS were not detected in the extracts. G. vaginalis cell walls are unequivocally gram-positive in their ultrastructural characteristics and chemical composition.