- Volume 43, Issue 6, 1995

Rotaviruses are the most important cause of severe gastro-enteritis in infants and young children. However, the determinants of protective immunity are poorly understood. Human immunity to rotavirus can be acquired passively or actively. It may be humoral or cell-mediated, protective or non-protective, homotypic or heterotypic and mucosal or systemic, or any combination of these. Mucosal immunity is protective against rotavirus illness, but not against infection, whereas systemic immunity reflects exposure, but probably has little if any role in protection. Both local and cell-mediated immunity are likely to be important in protection. However, there is no agreement as to a reliable surrogate marker of small intestinal protective immunity, and little is known about small intestinal cell-mediated immunity in man, especially infants. Passive mucosal immunity, but not systemic immunity, may contribute to protection in breast-fed infants, and in those at increased risk of serious illness who have been given oral immunoglobulin, either as prophylaxis or therapeutically. Animal and adult studies may have only limited relevance to those who are at greatest risk of serious illness. However, it is probably from such studies that hypotheses about small intestinal cell-mediated immunity in the protection of infants against rotavirus infection and illness will come. The determinants of susceptibility to serious rotavirus infection in man remain unclear, and this continues to hinder vaccine research.

Ethambutol enhanced the effects of chlorhexidine diacetate and cetylpyridinium chloride against Mycobacterium avium, M. bovis BCG, M. fortuitum and M. phlei. The findings show that it is possible to increase the susceptibility of mycobacteria to agents that normally exhibit poor activity against these organisms because of their reduced cellular penetration.

A rapid method for genotyping Acinetobacter baumannii based on PCR-fingerprinting with fluorescent primers was evaluated. Automated laser fluorescence analysis (ALFA) enabled on-line generation of high resolution DNA-fingerprints during poly-acrylamide gel electrophoresis of randomly amplified polymorphic DNA (RAPD) products. The results were in concordance with macro-restriction fragment patterns produced by pulsed-field gel electrophoresis (PFGE) of ApaI digests of chromosomal DNA. RAPD-ALFA was able to identify homologous strains suggestive of horizontal transmission in < 8 h after colonies were obtained on solid media, whereas PFGE analysis took c. 90 h. Speed and digitised data format renders RAPD-ALFA attractive for routine in-house epidemiological screening of isolates from intensive care and other hospital units.

Polymerase chain reaction (PCR) ribotyping detects differences in the intergenic spacer region between the 16S and 23S rRNA genes. This method was applied to Burkholderia cepacia isolates from 16 Welsh cystic fibrosis (CF) patients attending three different clinics. Amplification of the intergenic spacer followed by an additional digestion step with TaqI restriction endonuclease identified seven distinct electrophoretic patterns among the patient isolates. Each of the seven patterns was distinct from that of the so called “epidemic strain” commonly isolated from patients attending clinics elsewhere in the UK. Two environmental isolates from the hospital clinics and four NCTC reference strains gave different patterns. The simplicity of the method lends itself to use in a general microbiological laboratory.

An association between human papillomavirus (HPV) and cervical neoplasia has been widely reported and HPV DNA is commonly detected in cervical carcinoma tissues. However, estimates of the prevalence of HPV infection differs among various detection methods. Seventy cases of cervical carcinoma were screened for HPV 16 infection by Southern blot hybridisation (SBH) and nested polymerase chain reaction (PCR). According to SBH, the prevalences of HPV 16 DNA in stage I (n = 40) and stage II (n = 30) cervical carcinomas were 52.5 and 63.3%, respectively, and the overall prevalence was 57-1 % (40 of 70). By nested PCR, the prevalences of HPV 16 infection in stage I and II cervical carcinomas were 87.5 and 93.3 %, respectively, and the overall prevalence was 90.3%. The prevalence of HPV DNA detected by nested PCR was significantly greater than that detected by SBH. The combined concordance of positive and negative results between SBH and nested PCR was 61.4 %. The discrepancy resulted mainly from 25 cases (35.7%) that were positive by PCR but negative by SBH. A small copy number of HPV DNA in these 25 cases was documented by a semi-quantitative PCR method. The nested PCR was more sensitive than SBH and detected cases with low amounts of HPV DNA. The detection of HPV infection varied between these two prevailing detection methods and this should be kept in mind in assessing various epidemiological data concerning HPV infection.

The “Streptococcus milleri” (SMG) group have been shown to possess factors in vitro that may be involved in pathogenesis. All SMG strains are able to bind fibronectin via a cell-surface protein; the binding ranged from 12 to 198 mol/cell. Strains also bound to platelet-fibrin or fibrin clots and fibrinogen, giving maximum adhesion values of 16.5%, 21.8% and 151 mol/cell respectively. Members of the species S. constellatus produced thrombin-like activity. Lancefield group C SMG aggregated rat platelets, a bacterial cell-surface protein acting as mediator in the reaction. Most of the in-vitro factors did not correlate with each other, an indication that SMG strains possess a wide variety of pathogenic properties that may be involved in the production of abscesses or endocarditis. However, there was a correlation between the binding of large amounts of fibrinogen (> 100 mol/cell) and the ability to aggregate platelets. This suggests that fibrinogen binding may aid in platelet aggregation.

The increased prevalence of oral candidosis associated with HIV infection must be intrinsically related to immunological changes in the host, but might also involve alterations to the infecting strains of yeast. This study aimed to determine if strains of Candida albicans isolated from asymptomatic HIV-infected individuals or AIDS patients possessed altered adherence properties in an in-vitro buccal epithelial cell (BEC) adherence assay. C. albicans isolates from 49 patients with HIV infection or AIDS adhered to BEC in significantly higher numbers than isolates from 49 control subjects (p < 0.01). No significant differences in adherence were detected between strains isolated from HIV-infected or AIDS subjects, or between strains isolated from C. albicans carriers (low salivary C. albicans counts) or subjects with oral candidosis. The presence of whole saliva significantly inhibited the binding of Candida to BEC (p < 0.001), but the significant difference in adherence between the HIV/AIDS and control isolates was maintained. The effect of saliva was independent of salivary Candida antibodies and was abolished by treatment with protease or neuraminidase, suggesting the involvement of salivary mucins. The results of this study suggest that HIV infection is associated with the selection of strains of C. albicans with an increased ability to adhere to oral mucosa.