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M J Alfa

Publications and source records attributed to M J Alfa.

42 records · Page 3Linked to original sources
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Screening pregnant women for group B streptococcal colonization.

The recovery rates of group B streptococcus (GBS) from anorectal swabs (RS) and vaginal swabs (VS) that were enriched were compared to the routine method to determine the optimal procedure. Separate RS and VS were collected from women attending antenatal clinics. RS and VS were placed in 2 ml enrichment and selective broth. Swabs were inoculated onto colistin/nalidixic acid agar (CNA) upon arrival in the laboratory and onto 5% sheep blood agar (SBA) and CNA after 24 h enrichment. The routine method consisted of a VS sent in transport medium and inoculated in the laboratory onto SBA (no enrichment). The overall GBS colonization rate was 24% (64/264). Of the 64 GBS carriers, 77% were colonized in the vagina and 89% were colonized in the anorectum. The anorectum was the only site of colonization in 24% of the women, whereas the vagina was the only site of colonization in 11% of cases. Enrichment increased the detection of GBS from both RS (55 versus 42; P < 0.025) and from VS (49 versus 27; P < 0.001). Of the 64 cases, enriched RS detected 86%, enriched VS detected 77% and the standard VS detected only 41%. Enriched RS and enriched VS collectively detected 99% of cases. SBA was better than CNA for subculture of the enrichment broth because of a higher recovery rate (98-100% versus 80-82%; P < 0.01) and the fact that the hemolysis on SBA made it easier to differentiate GBS from enterococci. The data confirm that optimal screening of pregnant women for GBS should include a combined RS/VS swab placed in enrichment broth that is then subcultured onto SBA after 24 h incubation.

Culture Media↗
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The co-existence of genital Mycoplasma and Neisseria gonorrhoeae isolated from the male urethra.

Ureaplasma urealyticum and Mycoplasma hominis, separately or together, were co-isolated along with 34 of 102 strains of Neisseria gonorrhoeae cultured from urethral swabs from men with urethritis. For approximately half of the N. gonorrhoeae strains, the mycoplasma(s) persisted for at least five passages on agar medium. U. urealyticum was isolated in 31 of the 34 instances. No association between particular serotype(s) of U. urealyticum or auxotypes of N. gonorrhoeae was identified. The auxotypes of the N. gonorrhoeae isolates were not altered by the presence of U. urealyticum. To screen cultures of N. gonorrhoeae for the presence of genital mycoplasmas, we recommend direct microscopy of growth on agar: for M. hominis, after the colony epifluorescence test, and, for U. urealyticum, after the urease spot test.

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PubMedDate not supplied

Effects of Mycoplasma hominis on in-vitro studies of Neisseria gonorrhoeae.

This study examined the effects Mycoplasma hominis might have on Neisseria gonorrhoeae. Two auxotype standard strains of N. gonorrhoeae were found by culture and by light, fluorescence, and electron microscopy to be contaminated with M. hominis. In the presence of M. hominis, these strains of N. gonorrhoeae were typed as prototrophic. Removal of the mycoplasmas by passage of the N. gonorrhoeae on serum-free medium resulted in a second change in growth requirements rather than a reversion to the initial auxotypes. For one of these gonococcal strains, the presence of M. hominis also coincided with a change in colonial morphology and the appearance of a 2.6 X 10(6)-dalton plasmid, changes which persisted after the mycoplasmas had been eliminated from the culture of N. gonorrhoeae. The plasmid was not detected in a pure culture of the M. hominis strain or when it and the N. gonorrhoeae strain were intentionally co-cultivated. While these findings cannot be fully explained, they emphasize the importance of ensuring that all strains of N. gonorrhoeae used for in vitro studies are free of mycoplasmas.

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Characterization of the cytopathic effect of Haemophilus ducreyi.

BACKGROUND AND OBJECTIVES: Haemophilus ducreyi is the etiologic agent of chancroid, which is a genital ulcer disease that increases the risk of acquiring and transmitting HIV. The pathogenesis of H. ducreyi is not well understood. GOAL OF THIS STUDY: The goal of this study was to use a quantitative tetrazolium-based XTT assay to characterize the cytopathic effect of H. ducreyi on human foreskin fibroblasts. STUDY DESIGN: Haemophilus ducreyi strains 35000, R018, A77 and CIP542 were evaluated using the XTT assay. The role of attachment on resultant CPE was assessed using a wash step 2 hours post-infection. Internalization was evaluated by the gentamicin kill assay. Secreted exotoxin was studied using permeable inserts to separate the bacteria from the HFF monolayer. RESULTS: HFF cell damage did not appear to be mediated by a secreted H. ducreyi cytotoxin. Direct contact of viable H. ducreyi with HFF cells was required for cell damage. H. ducreyi strains that attached poorly could be readily removed by a wash step. This reduced their capacity to damage HFF cells significantly. Although some H. ducreyi strains attach to high levels within 4 hours, no HFF cell damage was detected by the XTT assay. However, once HFF cell damage was detected by 24 hours, it was not easily reversible, despite antibiotic treatment that eradicated H. ducreyi. Internalization of H. ducreyi by HFF cells apparently did not occur to a significant degree. CONCLUSION: This study indicates that classic "soluble exotoxins" are not likely the key component in H. ducreyi pathogenesis. Attachment or direct contact with HFF cells are required for H. ducreyi to cause a CPE.

Bacterial Adhesion↗
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Use of an adsorption enzyme immunoassay to evaluate the Haemophilus ducreyi specific and cross-reactive humoral immune response of humans.

Serodiagnosis of chancroid is limited by the cross-reactivity of Haemophilus ducreyi with Haemophilus influenzae and Haemophilus parainfluenzae. This research describes an adsorption enzyme immunoassay (EIA) that assesses the humoral immune response of North Americans and Africans to H. ducreyi. Adsorption effectively removed anti-H. influenzae and anti-H. parainfluenzae antibodies, revealing that North American control sera had no residual anti-H. ducreyi reactivity. However, African control sera still had a residual anti-H. ducreyi response. Assessment of the duration of the humoral immune response in sera from African patients with chancroid showed that the humoral antibodies persisted for up to 8 months after the diagnosis. This may explain the lack of specificity of the adsorption EIA in areas where chancroid is endemic. The detection of the humoral immune response was affected by the strain of H. ducreyi used, with indigent strains being most useful. Using H. ducreyi 35000 for Canadian sera, the sensitivity of the adsorption EIA was 100% and the specificity was 88%. For African sera, H. ducreyi strain R018 was used, and the adsorption EIA had a sensitivity of 81% and a specificity of only 23%. These data reveal that the existing humoral response in a country where chancroid is endemic differs from that in a country where it is not, and that care must be used interpreting unadsorbed humoral immune responses. The adsorption EIA approach may prove useful as an epidemiologic tool for definition of existing (past and present) levels of exposure to H. ducreyi.

Adolescent↗