- Volume 25, Issue 1, 1988

Intravenous injection of eight human strains of Campylobacter fetus ss fetus and Campylobacter jejuni into mice at various stages of pregnancy demonstrated significant strain differences in ability to affect implantation of the fertilised ovum and to cause resorption of the mouse fetus. Implantation was significantly impaired when C. fetus ss fetus was injected intravenously on day 2 of pregnancy, but no effect was observed in mice receiving C. jejuni. On day 6 of pregnancy, before the development of placental circulation, both C. fetus ss fetus and C. jejuni impaired fetal growth; one strain of C. jejuni had a greater effect than others of the same species. In animals inoculated on day 13 of pregnancy, after the development of placental circulation, six of the eight campylobacter strains caused resorption of the mouse embryos. A similar effect on the embryos was observed after injection of heat-killed organisms, and endotoxin-like substances may have been responsible. It is also suggested that factors other than endotoxin-like substances have a deleterious effect on embryonic growth.

A strain of Mycobacterium leprae resistant to rifampicin (RMP) failed to infect normal mice when injected into the foot pads (FP) at a dose of 10 or 100 bacilli/FP, although it could be maintained by serial passage in mice by the use of inocula of 104 bacilli/FP; normal mice can be infected by RMP-sensitive M. leprae at a dose of 10 bacilli/FP. By contrast, nude (athymic) mice could be infected with an inoculum of 10 bacilli/FP of the RMP-resistant strain. It is suggested that the strain concerned possessed reduced virulence for normal mice, and the implications of this for the probability of occurrence of human disease caused by RMP-resistant strains of M. leprae are discussed.

A collection of 198 clinical isolates of strains belonging to the tribe Proteeae was examined for haemolytic activity on blood agar and in Brain Heart Infusion Broth. The strains were of diverse bacteriocin and O-antigenic types and from a wide variety of sources. They included representatives of all species of Morganella, Proteus and Providencia. Approximately half of the M. morgani strains were haemolytic on blood agar. This activity was not associated with any particular bacteriocin type. The haemolysin was also produced during exponential growth in broth and was thermolabile and calcium dependent. All P. mirabilis strains and some P. vulgaris strains were non-haemolytic on blood agar. However, most strains of the Proteus spp., irrespective of their bacteriocin and antigenic type, produced, over a short period during exponential growth in broth, a heat-stable, cell-associated calcium-independent haemolysin. A smaller proportion of P. vulgaris and P. penneri strains produced, in addition, a thermolabile, calcium-dependent haemolysin which was associated with the formation of large haemolytic zones on blood agar. The relationship of these haemolysins to Escherichia coli haemolysin and their possible role in virulence is discussed. Haemolysin production was not found in any of the 74 strains of four species of Providencia.

A collection of 100 strains of Proteeae, in which all species within the tribe were represented, was examined for IgA protease production. The strains were isolated from various clinical specimens from sick and healthy persons in several countries. IgA protease-producing strains were not found amongst species of Providencia and Morganella but were common in Proteus spp. All the strains of P. mirabilis and P. penneri and many of the strains of P. vulgaris examined produced an EDTA-sensitive protease that cleaved the IgA heavy chain outside the hinge region. The proteus enzyme was different in this respect from the EDTA-sensitive, hingecutting proteases of other bacteria. The ability to produce IgA protease was unrelated to the O antigenicity, biotype or bacteriocin type of the strain. IgA protease production may be an important virulence mechanism for Proteus strains.

An experimental Escherichia coli septicaemia-peritonitis model was adapted to immunosuppressed mice. The mice were made neutropenic by a sublethal dose of cyclophosphamide, which resulted in a 100-fold increase in their susceptibility to intraperitoneal injection of E. coli O18: K1. A lethal infection could be prevented by passive immunisation with anti-K1 capsular or anti-O18 LPS antibodies but not with anti-J5 bacterial antibodies. The anti-K1 and anti-O18 antisera were able to increase the LD50 of the E. coli challenge by factors of 50 and 5, respectively. The role of nonspecific, lipopolysaccharide (LPS)-mediated resistance to infection was also investigated in this model, in which only long-living phagocytic cells such as macrophages are believed to be functional. Pretreatment of mice with LPS was shown to prevent growth of the bacterial challenge in the peritoneal cavity and blood and to result in a five-fold increase in the LD50 of the challenge strain. These findings suggest an important role for macrophages as effector cells in defence against E. coli infection.

Highly susceptible inbred male C57BL/6 mice were infected intraperitoneally with 2 × 107 cfu of a virulent Salmonella typhimurium strain. Tissue sections were taken from the spleen 2 and 3 days after infection for examination by electronmicroscopy. Rapid infiltration of polymorphs and macrophages was evident at the site of infection. These inflammatory phagocytes displayed avid destructive action against ingested bacteria. Bacterial multiplication occurred primarily in extracellular locations within sinusoids or in lesions containing disintegrating host cells.

We developed an immunoblotting procedure to characterise the polyspecific immunoglobulin response to the proteins of herpes simplex virus (HSV)-l. We found that 8–20% gradient polyacrylamide gels provided no advantage over fixed 8·5% gels for preparing Western blots for use in immunoblotting. The amount of protein loaded on the gels markedly influenced which proteins were detected by immune serum. The presence of Triton-X-100 0·5% in washes and buffers improved band clarity on immunoblots. In optimal conditions, immune mouse serum reacted with up to 33 HSV-1 lysate proteins. Six bands or regions appeared to be of major immunogenic reactivity, including the (122–130) × 103-mol. wt region, a 75 × 103-mol. wt protein, the gD region of approximately (56–64) × 103-mol. wt and two non-glycosylated bands at mol. wts(103) 42 and 44. Minor proteins, more weakly reactive, were detected at 27 other areas. The relative antibody titres in immune mouse serum to the different major regions showed antibody titre to gD > gB/gC > (42/44) × 103≫P75≫VP154. Most human sera reacted with all of the major and many of the minor immunogenic proteins but individual sera varied markedly in the proteins recognised. We conclude that immunoblotting is valuable for evaluating immunoglobulin responses to major and minor immunogenic proteins of HSV-1.

We studied the immunoglobulin response to individual viral polypeptides in experimental primary and secondary infection with herpes simplex virus (HSV)-1 in mice. After a single footpad inoculation with 105·6 pfu of HSV-1, immunoglobulin to proteins mol. wts (103) 44 and 75 appeared on day 7. Antibodies to gB, gC, gD, 42 × 103- and (48–52) × 103-mol. wt proteins appeared on day 11 and antibody to the major capsid protein, VP154, appeared on day 15 after infection. The secondary immune response was characterised by early production of antibody to gD on day 3 followed by antibodies against the 42 × 103- and 44 × 103-mol. wt proteins on days 4 and 5 respectively. Antibodies to glycoprotein gC and gB were delayed until day 7 of the secondary immune response. In both primary and secondary immune responses the responses against proteins of mol. wts (103) 42 and 44 were particularly intense and of high titre. We conclude that the kinetics of anti-polypeptide antibody appearance is markedly asynchronous; and that the anti-glycoprotein responses occur too late in primary infection to contribute to viral clearance.

Nineteen experimental phages were derived by mitomycin-C induction from methicillin-resistant strains of Staphylococcus aureus collected world-wide. They were assessed for their ability to distinguish isolates of a methicillin-resistant strain of S. aureus epidemic in the London area from other British strains, both sensitive and resistant to methicillin. The experimental phages were most active against strains of phage groups III and I + III. One phage was related to the phages of lytic group I. A typing pattern common to isolates of the epidemic strain was identified and used as an aid in the recognition of this strain. Ten of the phages were retained for further study.