The multiplication of three different isolates of group B streptococci in pregnant mice.

The ability of three streptococcal isolates of different pathogenicity to multiply in the tissues of pregnant mice was investigated following intravenous injection. The highly pathogenic isolate multiplied most rapidly whilst the isolate of low pathogenicity showed the least rapid growth within the observation period of 24 hours. The greatest concentration of streptococci per gram of tissue was found in the placentae of mice injected with the highly pathogenic and moderately pathogenic isolates when compared with the concentration of livers and spleen. Fetal infection did not occur within 24 hours of intravenous injection of the isolates but retarded fetal growth and infection was demonstrable five days after the injection. The isolate of moderate pathogenicity infected a greater proportion of the fetuses than the isolates of low pathogenicity. It is suggested that the outcome of streptococcal infections by the ability of isolates to multiply in host tissues.

The influence of different stages of pregnancy on group B streptococcal infection in mice.

Eight-day pregnant mice were found to be more resistant to the lethal effects of group B streptococci than those which were 17 days pregnant. From studies on the multiplication of the organisms in vivo it is suggested that the apparent enhancement of the infection in the 17-day pregnant animals is due to the lethal effects of the greater number of streptococci found in their tissues.

Campylobacters and impaired fetal development in mice.

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.

Variations in the virulence, for pregnant guinea pigs, of campylobacters isolated from man.

Pregnant guinea pigs were used to compare the virulence of four human isolates of Campylobacter fetus ss. fetus and four of C. jejuni on the basis of their ability to cause abortion and bacteraemia. Of the four strains of C. fetus ss. fetus two produced abortion readily after intramuscular injection. The four C. jejuni isolates were, however, of comparatively low virulence and no differences between them were demonstrated. Some of the isolates differed in their ability to survive in vitro in human and guinea-pig serum. It is suggested that campylobacters vary in their virulence for man and that this may influence the outcome of infections. Guinea pigs may prove useful in studying the pathogenesis of systemic campylobacter infections.

The effect of campylobacter lipopolysaccharide on fetal development in the mouse.

Purified lipopolysaccharide (LPS) obtained from isolates of Campylobacter fetus ss. fetus and Campylobacter jejuni impaired fetal development when administered to mice on day 13 of pregnancy. Strikingly more fetal resorption was produced by C. jejuni LPS than by similar amounts of C. fetus ss. fetus LPS. Three of the four Campylobacter strains examined produced LPS that had no effect on maternal health, but LPS from one C. jejuni strain killed all of the mice to which it was administered.

Escherichia coli and group B streptococcal infections in experimental animals.

Small doses of Escherichia coli endotoxin or of viable E. coli caused only a mild illness in pregnant mice but severely impaired fetal development. After intravenous injection and after experimental renal infection E. coli multiplied in placental tissue, causing resorption of the conceptuses and sometimes fetal infection. It is suggested that in humans coliform bacteraemia sometimes results in abortion and premature delivery because of the placental damage brought about by E. coli and its abortifacient endotoxin. Isolates of group B streptococci from various sites in 175 patients varied markedly in their pathogenicity for mice, and pregnant animals were less susceptible to infection than non-pregnant. In late pregnancy streptococci multiplied rapidly in placental tissue, suggesting that the placenta may be a significant focus of infection at the time of delivery. After antibiotic treatment the majority of mice infected with a highly pathogenic strain died but the majority of those infected with a strain of low pathogenicity survived. Preliminary experiments suggest that guinea-pigs and rabbits may be useful for studying the role of maternally derived antibodies in protecting the neonate against group B streptococci.

Bacterial endotoxin and impaired fetal development.

Small doses of E. coli endotoxin given to pregnant mice on the 13th day of pregnancy caused only a mild maternal illness but induced resorption of approximately half the number of fetuses in each mouse. The remaining live fetuses developed normally and showed no evidence of retarded growth or malformations. The weights of their placentas and maternal spleens increased significantly. Endotoxin given on the 6th day of pregnancy caused a small reduction in fetal weights.

The mode of action of antibody in neutrophil bactericidal activity against highly pathogenic group-B streptococci.

An investigation was undertaken into the post-phagocytic action of specific antibody in initiating neutrophil bactericidal activity against highly pathogenic group-B streptococci that survive within these cells. Specific antibody appears to gain access to the interior of the neutrophil and binds to the intracellular bacteria. Activation of Fc receptors on the neutrophil surface is not sufficient to initiate bactericidal activity, but the antibody may utilise the surface Fc receptors to gain access to the ingested organisms. Fusion of the lysosomes with the phagosomes containing the streptococci occurs normally in the cells, and proceeds in both the presence and absence of specific antibody. The organisms are resistant, however, to the microbicidal agents of lysosomes. A significant role is demonstrated for specific antibody in "masking" protective determinants on the bacterial surface during the destruction of these organisms by neutrophils. The relevance of antibody entry into neutrophils in relation to the treatment of bacterial infection is discussed.

Protection of mice against group B Streptococcus type Ia by IgG components of a rabbit antiserum.

IgG fractions were separated by ion exchange chromatography on DEAE-cellulose from hyperimmune rabbit sera prepared against a group B streptococcus type Ia mouse-virulent strain. 50 microgram IgG in conjunction with ampicillin (200 mg/kg) protected mice more effectively against a lethal challenge than ampicillin (400 mg/kg) alone or ampicillin (200 mg/kg) combined with gentamicin (10 mg/kg), when administered up to 12 h after infection.

Phagocytic and bactericidal activity of human neutrophils against two isolates of Group B streptococci Type Ic of differing pathogenicity.

The phagocytic and bactericidal activities of normal adult human neutrophils against 2 strains of Group B streptococci Type Ic of differing pathogenicity were examined. Both isolates were phagocytosed by the neutrophils in the presence of normal and homologous immune serum. However, the highly pathogenicity streptococci were killed less readily in the presence of immune serum than were the streptococci of low pathogenicity in the presence of immune or normal serum. This difference in killing ability was not due to a defect in phagocytosis by the neutrophils, but to a defect in bactericidal activity. The highly pathogenic streptococci were not killed in the presence of normal serum, but were readily phagocytosed by the neutrophils, in which they accumulated and eventually caused their destruction. The streptococci of low pathogenicity, however, were killed equally as well in the absence of specific antibody as in its presence. It is suggested that an in vitro assessment of neutrophil function against streptococci of differing pathogenicity for mice may provide a useful method by which the pathogenicity of streptococci for man can be compared.

An alternative role for specific antibody in neutrophil bactericidal activity against highly pathogenic group B streptococci.

An investigation was undertaken into the role of antibody and complement in neutrophil phagocytosis and killing of group B streptococci of low and high pathogenicity. Phagocytosis of both types of organism appears to be a nonspecific event requiring only nonspecific antibody or complement. However, neutrophil bactericidal activity is mediated by the pathogenicity of the infecting organism. Neutrophils alone can kill some streptococci of low pathogenicity, but their killing ability is considerably increased in the presence of specific antibody or complement. An active role for the alternative pathway of complement in the killing process was demonstrated for organisms of low pathogenicity. Neutrophils did not kill the highly pathogenic organisms in the absence of antibody and complement, and required specific antibody, but not complement, to kill these bacteria. The alternative complement pathway is not involved in killing of highly pathogenic organisms. Addition of specific antibody to neutrophils containing ingested bacteria stimulated the neutrophils to kill the intracellular bacteria, suggesting an alternative role for specific antibody in the killing process other than as an opsonin. It is suggested that activation of Fc receptors on the neutrophil surface initiates the bactericidal action of the neutrophils.

Electron microscopic evidence of antibody entry into neutrophils after phagocytosis of highly virulent group B streptococci.

An electron microscopic study was undertaken of the entry of specific antibody into neutrophils containing surviving intracellular highly virulent group B streptococci after phagocytosis of the organisms had occurred. Electron micrographs are presented to demonstrate that specific antibody gains access to the ingested bacteria. This antibody binds to the surface of the streptococci, which subsequently permits the neutrophils to kill these organisms.

Treatment of wounds from animals suspected of carrying neurotropic viruses.

The methods used at the Clinical Research Centre, Northwick Park Hospital, to treat wounds potentially infected with neurotropic viruses are outlined. Emphasis is laid on first aid and on surgical attention. Patients should remain under medical supervision for at least four weeks after the injury, the need for specific post-exposure treatment depending on the nature of the exposure.

Escherichia coli infection in mice and impaired fetal development.

Investigations were undertaken, using the mouse as an animal model, to study the effect of Escherichia coli on fetal development. The i.v. injection of 7.5 X 10(6) bacteria, originally obtained from a suspected case of human pyelonephritis, caused only a mild and transient disturbance of maternal health but caused severe fetal wastage. Groups of mice were examined 4, 7 and 11 days after infection and the numbers of organisms were determined in the spleen, liver, kidneys, placentas and resorptions. From the findings obtained, it was concluded that the Esch. coli grew preferentially in the placentas. By the 7th day the placentas showed marked degenerative and necrotic changes and the bacteria could be recovered from the majority of fetuses at this time. Histologically, no significant changes were seen in the spleen, liver and kidneys. As a result of these findings in an animal model, and taking into consideration the observations of other workers, it is suggested that coliform bacteraemia in human pregnancies may also cause infections of the placenta and bring about abortion or premature delivery.

The effect of genital mycoplasmas on human fetal growth.

The relation between maternal genital colonization by mycoplasmas and fetal growth was examined in a study of 195 women. Swabs were taken from the endocervix on three occasions during pregnancy and once post partum. Ureaplasma urealyticum organisms (ureaplasmas) were recovered from 42.7 per cent of Caucasian women and from 34.6 per cent of Asian women at their first antenatal visit. These isolation rates remained similar throughout pregnancy, although there was a decrease in isolation after delivery. Mycoplasma hominis was recovered from 6.5 per cent of Caucasians and from 11.5 per cent of Asians at their first antenatal visit and these rates remained fairly constant during pregnancy and after delivery. Caucasian women colonized by ureaplasmas had a longer mean length of gestation (p less than 0.025) than non-colonized women. Furthermore, the colonized women gave birth to infants who had a statistically significant greater mean birth weight and a greater mean birth weight-for-dates than those of the non-colonized Caucasians. There was no correlation between gestational length, birth weight, or birth weight-for-dates and genital colonization of Asian mothers by ureaplasmas or M. hominis. It is clear the ureaplasmas are not associated with low birth weight in our population.

Protection against endotoxin-induced foetal resorption in mice by desferrioxamine and ebselen.

Endotoxin was administered to mice on their 13th day of pregnancy at doses which caused the resorption of approximately 50% of the implanted foetuses. The iron chelator desferrioxamine was found to significantly inhibit the percentage of resorptions induced by endotoxin in a dose-dependent manner. The highest dose of desferrioxamine (5 mg) given intravenously 30 min prior to, immediately after, and 4 and 24 h after endotoxin inoculation, reduced the percentage of resorptions from 56.9 to 17.9%. Administration of the novel selenium-containing compound ebselen, which is both an antioxidant and an inhibitor of leukotriene synthesis, was also found to significantly protect against endotoxin-induced foetal resorptions, reducing the percentage of resorbed foetuses from 52.9 to 26.0% when given at a dose of 50 mg/kg (s.c.) at the time of endotoxin inoculation and 24 and 48 h following. Both these compounds also significantly reduced the increase in spleen weights observed when the mice were given endotoxin. These results provide evidence that the iron-catalysed production of hydroxyl radicals from other oxygen-derived species and the formation of leukotrienes play an important role in the mechanism by which endotoxin causes foetal resorptions in the mouse.