Rapid PCR-based detection of Streptococcus pneumoniae DNA in cerebrospinal fluid.
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Biomedical subjects
Publications and source records attributed to A M Kearns.
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The BCG vaccine strain cannot, with confidence, be differentiated from other members of the Mycobacterium tuberculosis complex on phenotypic tests alone. Isolates from clinical sites not associated with vaccination may be confused with M. tuberculosis. A characteristic of BCG strains is the deletion of the genomic region RD1; detection of this forms the basis of a multiplex polymerase chain reaction (PCR) assay to distinguish BCG strains. In this study, 28 M. tuberculosis complex strains were analysed by the PCR assay. A DNA sequence displaying the characteristic deletion was detected in all eleven of the BCG strains tested and was not found in representatives of other members of the complex, including M. bovis. Thus, the assay affords a rapid, simple and effective method for the discrimination of the BCG vaccine strain from other members of the M. tuberculosis complex.
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A rapid in-house polymerase chain reaction (PCR) assay is described for the direct detection of Mycobacterium tuberculosis complex in clinical material. Its performance is compared with two kit based systems. The results of the in-house assay were comparable with the commercial assays, detecting M tuberculosis in 100% of smear positive, culture positive samples. The in-house assay proved to be rapid, easy, and inexpensive to perform, and the inclusion of an internal inhibitor control permitted validation of the PCR results.
Mycoplasma fermentans has attracted much interest both as a cofactor for the progression of AIDS and as a pathogenic agent in non-AIDS related diseases. Previous studies with serological and genetic techniques suggest that M. fermentans represents a homogeneous group of organisms, with no significant differences identified among the strains examined. In this study, 25 cultures of M. fermentans, including isolates from human sources and tissue culture cells, were compared by pyrolysis mass spectrometry (PMS). It was possible to distinguish the 'type' strain PG-18 from an AIDS-associated M. fermentans strain 'incognitus' by this technique. PMS was also able to differentiate laboratory-induced aminoglycoside-resistant variants from their fully susceptible parents. Four AIDS-associated isolates were distinguished from each other, whilst five European cell culture isolates were shown to be closely related, as were six M. fermentans isolates from an outbreak of acute respiratory infection in Canada. PMS has proved useful in distinguishing isolates of M. fermentans, providing epidemiological data. In addition, PMS may help in determining the likely origin of a given isolate, and in the future may be of use in assessing the role of this micro-organism in human disease.
The action of white blood cells (WBC) against Proteus mirabilis was assayed in 22 children following meningitis or septicaemia and compared with that in control groups of: (1) adult volunteers, (2) children undergoing minor surgical procedures for non-infective conditions, and (3) children being investigated for suspected renal disease. WBC bacterial killing tests were normal in all 55 adult volunteers. Abnormal results were obtained in 11 of 22 (50%) children with meningitis or septicaemia, 10 of 21 (47.6%) children undergoing surgery and six of 13 (46%) children with suspected renal disease, thereby indicating that there were no significant differences in phagocytic function among these three groups. Of children aged 1 year or less, 75% had abnormal phagocytic function. The significance of this finding is discussed.
Six strains each of Enterococcus faecium and E. faecalis were investigated with respect to their resistance to heat and sodium hypochlorite. All enterococci survived the temperatures and holding times specified by the Department of Health (DoH) for the disinfection of 'foul and used' or 'infected' linen (65 degrees C for 10 min or 71 degrees C for 3 min). In addition, three strains (one E. faecium and two E. faecalis) could withstand 150 ppm available chlorine for 5 min, the treatment suggested by the DoH for the disinfection of heat labile materials. Further, our results showed that four strains of E. faecium were able to survive the British Standard for heat disinfection of bedpans (80 degrees C for 1 min). The significance of these findings with particular reference to the potential for enterococci to survive and disseminate in the hospital environment is discussed.
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Mycoplasma species are often found colonising the female genital tract. Their ability to become invasive and pathogenic, however, is often ignored, since attempts may not be made to culture these organisms from the bloodstream. We have investigated the ability of three types of blood culture media to support the growth of genital mycoplasmas. The media studied included brain-heart infusion broth, brain-heart infusion broth supplemented with 30% V/V sucrose and fastidious anaerobe broth. Genital mycoplasmas were cultured from the latter medium only. Since this was the sole medium which was liquoid-free, the inhibitory effects of liquoid on Mycoplasma spp. is discussed. This study comprised an investigation of 75 patients in obstetric and gynaecological wards with postpartum or post-operative fever. Genital mycoplasmas were isolated from five (6.7%) patients, four with Ureaplasma urealyticum and one with M. hominis. The value of considering these organisms in the differential diagnosis of fever in 'at risk' patients and of including appropriate media for their isolation is emphasised.
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Samples of middle ear effusions from 102 children with serous and mucoid otitis media were cultured for mycoplasmas and bacteria. No sample yielded mycoplasmas but bacteria were cultured from 48 (47 per cent). Organisms commonly regarded as pathogens were present in 25 samples (Haemophilus influenzae 17, Streptococcus pneumoniae four, other streptococci four). The only sample from which anaerobic bacteria were isolated was from a patient with cholesteatoma.
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After a recent report showing the in vitro susceptibility to mebendazole of a strain of Trichomonas vaginalis that was resistant to metronidazole, we present two cases of metronidazole resistant infection, both of which failed to respond to oral mebendazole.
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A study was carried out of the microbial content of three types of incontinence underpads and a clinical absorbent protection pad. Coagulase-negative staphylococci and Bacillus spp. were isolated from unused samples of all makes of pad examined. Clostridium spp., including C. tetani and C. perfringens, were isolated from a proportion of pads containing re-cycled waste material. We recommend that incontinence underpads are used solely for the purpose for which they were marketed, namely, the containment of excreta.