- Volume 35, Issue 3, 1991

Patients with chronic obstructive pulmonary disease (COPD) often have chronic or recurrent pulmonary infections with non-typable Haemophilus influenzae. A model of these infections exploited agar bead vehicles to protect the inoculum from rapid clearance, and a chronic lung infection of at least 42 days duration was established in rats. This infection induced increases in serum IgG titres to outer-membrane (OM) and lipo-oligosaccharide (LOS) antigens; immunoblotting demonstrated that this humoral response was directed partly against the outer-membrane proteins (OMPs). Lung lavage fluid also contained an increased titre of IgG antibodies to OM and LOS 42 days after infection. Antibodies produced during infection with one strain of H. influenzae cross-reacted with OMPs from another, non-typable H. influenzae strain. Despite their encasement in agar beads, pulmonary H. influenzae remained susceptible to amoxycillin. This model of chronic pulmonary infections due to non-typable H. influenzae appears to resemble the situation in COPD patients and may be useful for experimental therapeutic studies.

The biochemical characteristics of group G streptococci isolated from cats were markedly similar to the characteristics of group G streptococci from man. Both cat and human isolates of group G streptococci were also very similar in biochemical characteristics to group A streptococci so that to identify the source of group G streptococci by biochemical reactions is not a reliable procedure. The group G streptococci found in many cats could be pathogenic to man, since their physiological and biological characteristics are very similar to those of group A streptococci.

The use of probes derived from rRNA sequences to detect restriction fragment length polymorphisms (RFLPs) associated with the ribosomal RNA genes for epidemiological typing (ribotyping) is a powerful and readily applicable tool. Different probes and enzymes for ribotyping were compared for a series of 73 unrelated Legionella pneumophila serogroup 1 strains. The probes compared were cDNAs, transcribed from L. pneumophila or Escherichia coli rRNA subunits, and a cloned L. pneumophila rRNA gene. The cloned rRNA gene probe gave the best discrimination and this probe was further compared with cloned probes comprised of randomly selected (non-rRNA) parts of the L. pneumophila chromosome. In this instance the greatest discrimination was achieved when one of the non-ribosomal RNA gene probes was employed. The overall discrimination of RFLP typing was enhanced by combining the data obtained with both rRNA and non-rRNA probes.

A new DNA probe assay (PACE 2, Gen-probe) was compared with cell culture for the detection of Chlamydia trachomatis in 909 women attending the Royal Women’s Hospital, Melbourne, Victoria. The DNA probe assay had a sensitivity of 86.2%, a specificity of 99.9% and a positive predictive value of 96.2% in a population with 3.2% prevalence, indicating that it may be a suitable alternative to culture for the detection of C. trachomatis in specimens from the genital tract.

To assess the role of enterotoxigenic Escherichia coli (ETEC) in infantile diarrhoea, 482 children with diarrhoea and 103 healthy controls, from three localities of Galicia, northwestern Spain, were investigated between 1985 and 1988. Rotavirus (37.3%) and lmonella spp. (12.8%) were the most common causal agents, followed by ETEC (3.9%), Campylobacter jejuni (2.3%), Shigella spp. (0.9%) and Yersinia enterocolitica (0.5%). ETEC were significantly more frequently isolated from children with diarrhoea who were under 1 month of age (26.5%) than from older diarrhoeic children (2.2%) (p <0.001) or from healthy children who were under 1 month of age (0%) (p < 0.05). Among children who harboured ETEC, five of the nine children under 1 month of age developed diarrhoea in hospital, whereas none of the 10 children over 1 month of age did so. Seventeen ETEC isolates produced heat-stable enterotoxin (STa) only, four produced only heat-labile enterotoxin (LT), and two produced both toxins. Colonisation factor antigens CFA/I and CFA/II were detected in 11 (55.0%) of the 20 ETEC isolates that remained enterotoxigenic after maintenance in the laboratory. Most ETEC isolates belonged to serotypes O153:K-:H45 (nine STa+ CFA/I+ isolates), O27:K-: H7 (three STa+ isolates) or O6:K15:H16 (two LT+ STa+ CFA/II+ isolates). Our results suggest that ETEC constitute an important cause of neonatal diarrhoea in this part of Spain.

Changes in somatic (O) lipopolysaccharide (LPS) antigenic specificities of Campylobacter coli serostrains were observed after continuous laboratory subculture. Two serostrains (C. coli O34 and C. coli O48) lost O specificity and did not react with homologous or any of the available heterologous antisera. The C. coli serostrain for serogroup O5, after subculture, yielded a variant that had acquired a new specificity which was detectable with a heterologous antiserum. In a repeat experiment with the original isolate of the O5 strain, a second variant was obtained which had not only acquired the same new determinant but had, unlike the first variant, lost reactivity with the homologous antiserum. Immunoblot experiments with homologous and heterologous antisera indicated that changes in antigenic specificity were associated with the O side chains of the LPS molecules. Results of restriction endonuclease analysis of chromosomal DNA of the variants and their parents revealed minor differences in restriction patterns which suggested that C. coli is capable of undergoing genomic re-arrangements that lead to changes in LPS specificity and structure.