- Volume 44, Issue 1, 1996

Phosphorylcholine (PC)-containing antigens were sought in 269 bacterial isolates from the mouth and respiratory tract by an enzyme immunoassay method. Only 41 (15%) isolates were PC-positive and of these 29 (70%) were strains of Haemophilus influenzae. Other species that produced positive results included two of five isolates of Gemella haemolysans, two of five isolates of Micrococcus spp., and a single strain each of Bacillus sp., Corynebacterium jeikeium, Lactococcus sp. and H. parainfluenzae. The presence of PC-containing antigens in H. influenzae may be an important source of cross-reaction in antigen detection techniques that detect the C-polysaccharide antigen of Streptococcus pneumoniae in respiratory specimens and would result in false positive results.

Some human bacterial pathogens produce specific immunoglobulin A1 (IgA1) proteases that cleave the heavy chain of human IgA1, generating intact Fab and Fc fragments. Other pathogenic bacterial species express surface proteins which bind to the Fc part of human IgA in a non-immune manner. To analyse whether IgA-binding proteins affect the activity of IgA1 proteases, the ability of seven different IgA1 proteases to hydrolyse IgA1 in the presence of either of two different bacterial IgA-binding proteins was tested. Data obtained in two different types of experiment suggest that IgA1 bound to IgA-binding proteins still functions as a substrate for IgA1 proteases. As Fc fragments produced by cleaving IgA1 with IgA1 proteases still bind to IgA-binding proteins, we conclude that these two types of bacterial protein act independently of each other.

Strains of Klebsiella spp. are often inagglutinable by O-specific antisera because of the copious capsule produced by most isolates. A competitive ELISA method based on the observation that bacterial supernates containing homologous O antigen specifically inhibited the reaction of type-specific antisera with purified LPS coated on ELISA plates was used to examine the O antigen of 82 isolates of different Klebsiella species and subspecies. The O antigens O1/2ab (19 isolates), O2ab (13 isolates), O2ac (11 isolates) and O3 (16 isolates) were found to account for > 70% of the O antigenic types. Overall, 65 (79%) of the strains could be assigned to a specific O serogroup. The method is suitable for examining the role of individual O antigens in systemic klebsiella infections such as nosocomial septicaemia and pneumonia.

Five men received high-dose, uneven, whole-body γ-irradiation by accidental exposure to an unshielded 137Cs source. Analysis of the faeces 9-12 days post-irradiation showed low numbers of anaerobes and high counts of enterobacteria and staphylococci in four of the patients and total viable counts of < 103/g in one. All five were treated with systemic ampicillin and gentamicin and oral nystatin commencing 4-7 days after irradiation. Three of the patients were also treated orally with a suspension of an antibiotic-resistant strain of Bifidobacterium longum for 30 days commencing 10-12 days post-irradiation. At 3 weeks post-irradiation, B. longum had appeared in their faecal flora and total anaerobe counts exceeded those of facultative and obligate aerobes. At 4 weeks and 5-7 weeks post-irradiation, this normalisation of the faecal flora continued. In contrast, in the two patients who received a placebo the faecal flora was dominated by enterobacteria (Klebsiella, Enterobacter and Serratia spp.) showing multiple antibiotic resistance 3 weeks post-irradiation. These potential opportunist pathogens were not isolated from the B. longum-treated group. Only one patient in the control group survived beyond 3 weeks; he continued to show high faecal counts of enterobacteria and staphylococci and low counts of obligate anaerobes. ‘Probiotic’ treatment with this antibiotic-resistant strain of B. longum may be of benefit in the treatment of radiation sickness, aiding normalisation of the faecal flora and inhibiting colonisation and overgrowth with opportunist pathogens.