- Volume 5, Issue 2, 1972

Forty strains described as Mycobacterium abscessus, Myco. borstelense, Myco. chelonei or Myco. runyonii, and isolated in three different continents, have been examined culturally, biochemically and serologically. In common with others we were able to divide the strains into two groups, but these were too similar to one another to merit separate specific status. All the American strains, most of the African strains and only one European strain belonged to one group. Twenty out of 21 European strains and a single African strain constituted the second group. It was concluded that these were two geographical variants of a single species for which the oldest valid name is Mycobacterium chelonei Bergey et al., and it is recommended that this name be adopted.

Groups of mice were immunised against Salmonella typhimurium with heatkilled (HK) and acetone-killed (AK) vaccines or with their ultrasonic or Mickledisintegrated forms and subsequently challenged by the oral or intraperitoneal routes. All six vaccine preparations conferred statistically significant protection against intraperitoneal challenge as measured by reduced mortality, lowered infection rate and prolonged survival. Of the six vaccines, only the Mickledisintegrated HK vaccine significantly reduced the mortality rate of mice challenged by the oral route.

Filtered bacteria-free extracts of homogenates of infected mouse liver conferred active immunity against a massive intraperitoneal challenge, but similar extracts of normal liver or of spleen from normal or infected animals were without effect.

Strains of Proteus mirabilis and P. vulgaris produce metabolites which inhibit their own growth and that of other members of the group, but not that of P. rettgeri, P. morganii, Providence or Escherichia coli. These metabolites are dialysable, volatile and inactivated by ether and by chloroform. They are active in solid media for a long time after excretion. These properties are like those of the negative chemotaxic metabolites that have been held responsible for the swarming of proteus organisms. These metabolites do not influence parallelstreak tests for syntrophism between auxotrophs of P. mirabilis.

Experimental neonatal diarrhoea (E.N.D.) was produced in litters of piglets derived from gilts after oral administration at birth of a washed live suspension of an enteropathogenic strain of Escherichia coli belonging to the O149:K91(B), K88ac(L) group. Different litters varied in their susceptibility to the strain; the mortality attributable to E.N.D. was 38 per cent. (20 of 53 piglets) but two of six litters were almost completely resistant to the enteropathogenic strain. This resistance did not appear to be related to a high level of bacterial agglutinins, somatic (O) antibodies or bactericidal activity in the colostrum.

A formalin-killed vaccine derived from two isolates of the O149:K91(B), K88ac(L) group was administered in two doses without an adjuvant to six gilts during the last 4wk of pregnancy. The mortality attributable to E.N.D. in piglets from vaccinated dams was 20 per cent (11 of 54 piglets) following administration of the challenge dose. Although there was a reduction in the mortality of piglets from vaccinated compared with non-vaccinated dams, the reduction was not significant when the variation between Utters was taken into account. However, the bacteriological observations suggest that an antibacterial factor impaired the ability of the enteropathogenic strain to become established in the intestinal tract of piglets from vaccinated dams. This factor did not appear to be related to a high level of bacterial agglutinins, somatic (O) antibodies or bactericidal activity in colostrum and has yet to be identified in vitro.

The surface growth of several species of clostridia was assessed in terms of the contribution made to the total viable count by spores and vegetative cells respectively. In some cases a large proportion of the surface count was derived from vegetative cells. This conclusion is based on the finding that in many cases the viable count considerably exceeded the maximum estimates for the number of spores in the inocula. Thus vegetative cells may be the significantly viable particles in the surface growth of common pathogenic clostridia. In general, good recovery of the anaerobes tested was obtained with traditional methods.

The possibility that the growth of clinically important anaerobes might be enhanced by the supplementation of 10 per cent, equine blood agar with either (i) sterile iron filings sprinkled on to seeded plates, or (ii) a development of Moore’s cysteine-dithiothreitol system, was explored. There was no evidence that enhancement occurred, except with organisms of the Cl. oedematiens group.

The bacterial flora of aspirates from the stomach, the upper jejunum, the mid-gut, and the terminal ileum of 13 patients with Crohn’s disease was compared with that obtained from similar sites in healthy subjects. The relationship of the bacterial flora to the site of disease and to the absorption of vitamin B12 and fat was examined.

Increased colonisation of the upper gut was seen only in patients with obvious stasis due to upper-gut disease, or when the upper and lower gut were connected by a fistula. In patients with comparatively normal motility, or in whom disease was restricted to the terminal small bowel, the flora was similar to that of healthy subjects. Aerobic diphtheroids were virtually absent from and higher counts of yeasts were present in all areas of the gut of patients with Crohn’s disease.

No consistent relationship could be demonstrated between absorptive defects and the presence of an abnormal bacterial flora. Malabsorption of vitamin B12 usually depended more on loss or disease of the terminal ileum than on increased numbers of bacteria in the small gut. Three patients who showed significant deconjugation of bile salts had steatorrhoea but bacterial overgrowth, including species able to deconjugate bile salts, was not always associated with increased excretion of fat.

Diagnosis of rubella by direct immunofluorescent staining of infected cells from throat swabs was studied in children and adults and compared with virus isolation. Under 12 yr of age both methods are equally sensitive, while in older patients virus isolation is the more sensitive. Since the immunofluorescence technique takes less than 24 hr to perform and virus isolation may take 3 wk or longer, the former method has obvious advantages in the rapid diagnosis of rubella.

The normal responses of rubella-specific IgM and IgG antibodies were studied in eight patients with proven rubella by the indirect immunofluorescent technique. To evaluate the detection of rubella-specific IgM for diagnosis, a “blind” study of sera from 13 other patients with proven rubella was carried out and the method proved to be 100 per cent, reliable. Its sensitivity was compared with virus isolation and with direct immunofluorescent staining of virus antigen in infected cells from throat swabs.

Ligated intestine tests in pigs, piglets, calves and lambs indicated that the enterotoxin produced by a group of atypical pig strains of Escherichia coli was probably identical with that produced by enteropathogenic calf and lamb strains. It resembled the ST rather than the LT form of the enterotoxin produced by typical pig enteropathogenic strains.

The enterotoxin produced by some of the atypical strains and the calf and lamb strains, like that produced by some typical pig strains, was probably controlled by a transmissible plasmid. So was a K antigen common to many of the calf and lamb strains. Infection experiments indicated that this antigen was important in the pathogenesis of E. coli diarrhoea.

The sensitivity of three strains of Mycobacterium leprae to dapsone (DDS) and rifampicin (RMP), administered continuously in the diet, was determined in the mouse footpad system. All three strains were inhibited by 0.0001 per cent. DDS. Sensitivity to RMP varied, the minimum inhibitory dose (MID) being 0.001 per cent, for two strains and 0.0003 per cent, for the third.

During the administration of 0.01 per cent. RMP, the concentrations of RMP in mouse serum, estimated by microbiological assay, was relatively constant at about 6 pg per ml over a 66-day period. The considerations for assuming a linear relationship between dietary dosage and the resultant serum concentration are discussed. It is inferred that a minimum inhibitory dose of RMP for M. leprae of 0.001 per cent, is equivalent to a minimum inhibitory concentration for the organism of 0.3 μg per ml.

The bactericidal action of DDS and of RMP on M. leprae was assessed by means of the kinetic technique of Shepard. The DDS treatment used apparently had no significant bactericidal effect. The bactericidal action of RMP was found to be relatively high, confirming the previous finding of Rees et al. in patients with lepromatous leprosy. Complete killing of M. leprae was obtained after 30 days’ treatment with 0.01 per cent. RMP in the diet (equivalent to a serum concentration of about 5 μg per ml). The relationship between the concentration of RMP in the serum of mice and its bactericidal action on M. leprae appears to be very similar to the corresponding relationship found in patients treated with the drug.

The morphological and biochemical characters of 27 aeromonas strains of human origin are reported (24 from faeces, two from blood and one from bile). Twenty-one strains were identified as Aeromonas hydrophila, biotype 1, four as Aeromonas punctata subspecies caviae, one as Aeromonas hydrophila, biotype 2 and one as Aeromonas punctata.

On examining the oxidase reactions of 767 strains of staphylococci and micrococci, it was found that positive reactions were confined to Baird-Parker’s Micrococcus group. All yellow-pigmented Micrococcus subgroup 7 strains were oxidase positive, and this provides a rapid distinction between these and strains of Staphylococcus aureus.

A case of infection with Isospora belli is described in a patient recently returned to England from West Africa. It is thought to have been responsible for a diarrhoeal illness and is believed to be the first such case reported in this country since 1916, other than a known laboratory-acquired infection.