The aerosol survivals in air and nitrogen of radiation sensitive and resistant mutants of Escherichia coli B have been determined with logarithmic and resting phase bacteria. No consistent correlation was found between radiation sensitivity and aerosol sensitivity in the strains tested. Hence, the phenotypes Fil Her Exr, which determine sensitivity to radiation, do not influence aerosol survival, i.e. these known mechanisms which repair radiation-induced damage do not operate in aerosol stressed E. coli. In all cases the survival in air was less than that in nitrogen particularly so for E. coli Bs-1. The effect is explained in terms of a toxic action of oxygen. Comparison of survival of log and resting phase bacteria show that log phase cells are less aerosol stable than are resting phase cells. The ability to synthesize DNA in bacteria collected from the aerosol was less than in control unstressed bacteria, and this effect was independent of the presence of oxygen. Reduced ability to synthesize DNA could have been caused by reduced metabolic activity. It is shown that two different death mechanisms occur simultaneously in aerosols at low relative humidity. One mechanism is oxygen dependent and the other oxygen independent. The former was not through a decrease in metabolic activity, whereas the latter could be.

The germicidal efficiencies of hot water (140–150° F.) under pressure (method 1), hot water + 2% (w/v) detergent solution (method 2) and hot water + detergent + 200 p.p.m. solution of available chlorine (method 3) were compared at six sites in a bacon factory. Results indicated that sites 1 and 2 (tiled walls) were satisfactorily cleaned by each method. It was therefore considered more economical to clean such surfaces routinely by method 1. However, this method was much less efficient (31 % survival of micro-organisms) on site 3 (wooden surface) than methods 2 (7% survival) and 3 (1% survival). Likewise the remaining sites (debarring machine, black scraper and table) were least efficiently cleaned by method 1. The most satisfactory results were obtained when these surfaces were treated by method 3.

Pig carcasses were shown to be contaminated by an improperly cleaned black scraper. Repeated cleaning and sterilizing (method 3) of this equipment reduced the contamination on carcasses from about 70 % to less than 10 %.

The action of trypsin and pronase on the haemagglutinins and neuraminidases of eight strains of influenza virus has been examined.

The haemagglutinins of all the strains were highly susceptible to digestion by pronase but there were great variations in resistance to trypsin.

The neuraminidases of the eight strains were of three types. The neuraminidases of the A1 strains and the DSP strain of virus A were highly susceptible to destruction by both enzymes. The neuraminidases of the PR 8 and Swine strains showed partial resistance especially to trypsin, while the A 2 strains and the lee strains of virus B possessed neuraminidases that were completely resistant to both trypsin and pronase.

Proteolytic enzymes released free neuraminidases from the A 2 and lee viruses the morphology of which was different from that of neuraminidases released by detergent treatment.

Desiccates of Salmonella ndolo dried in sodium glutamate have been exposed to 100° C. in air or in vacuo; in the presence of wet or dry P2O5; and with desiccant maintained at either 25° or 100° C. Of the eight treatments thus compared, rapid killing occurred where the desiccate was heated in vacuo and in the presence of dry P2O5 maintained at 100° C. There was little difference among the death-rates of the other seven treatments. Sublimation of the P2O6 with resultant attack on the desiccate would appear to be responsible for the rapid killing in the treatment where it was observed.

The survival of salmonellas on the finger-tips is considered with reference to the ease with which they can be transferred to food by handling.

Escherichia coli and several Salmonella serotypes were shown to survive on the finger-tips for various periods of time, for example, S. anatum could be recovered 3 hr. after artificially contaminating them with between 500 and 2000 organisms. S. anatum could also be recovered from the finger-tips after contaminating them with more than 6000 organisms followed by a 15 sec. hand-wash 10 min. later. Similarly, the survivors from minimal inocula of less than 100 S. anatum/finger-tip were, after 10 min., still capable of infecting samples of corned beef and ham. E. coli was isolated from the finger-tips of 13 of 110 butchers soon after they had left the meat line at a meat products factory, but was not detected on the finger-tips of 100 volunteers at the Central Public Health Laboratory.

The implications of the present findings to the spread of salmonellas from raw to cooked foods, and the relevance of this to outbreaks of Salmonella infection in the general population and in hospitals, are discussed.

Thirty-three adults were vaccinated subcutaneously with Wistar RA. 27/3 (live attenuated) rubella vaccine at the Wellcome Research Laboratories, Beckenham. All subjects with pre-vaccination haemagglutinating-inhibiting antibody titres of 1/20 or less and three of seven subjects with pre-vaccination titres of 1/40 showed at least fourfold rises of titre. Reactions encountered were mild and of short duration.

A total of 1537 strains of Salmonella typhimurium belonging to seven prevalent phage types were examined on solid media for their ability to ferment rhamnose, xylose and inositol, for colicine production and for nutritional requirements. Most of the strains in each phage type were almost completely homogeneous, especially in their sugar fermentation reactions. However, strains of phage type 1a/2 were not homogeneous, but could be assigned to one of four subgroups on the basis of ability to ferment inositol, inhibition of growth by meso-tartrate and auxotrophy for nicotinic acid. The subdivision proved to have epidemiological value. The inhibition of growth by meso-tartrate was observed on a denned medium containing citrate as the energy source. Inhibition did not occur if glucose, casein hydrolysate or aspartic acid were added to the medium.

A single dose of inactivated louping-ill oil-adjuvant vaccine elicited a serologically detectable immune response in sheep lasting for at least 1 year. These sheep when exposed to a natural focus of louping-ill virus were completely protected from clinical disease and 1 year after vaccination were able to pass on a substantial maternal immunity to their lambs.

Twenty-nine per cent of unvaccinated sheep, exposed at the same time, died from clinical louping-ill; half of the survivors showed positive sero-conversion and became immune, while the other half remained susceptible. The incidence of fatal encephalomyelitis in sheep which were known to have circulated virus exceeded 50% in 2 out of 3 trials conducted simultaneously in different locations in Scotland in 1969.

Nine gnotobiotic piglets, when 8–9 days old, were exposed to an aerosol of strain TR 32 of Mycoplasma hyorhinis and killed at intervals from 14 to 37 days after infection. The aerosol of M. hyorhinis caused bronchopneumonia in 1 pig, pleurisy alone in 2 pigs, pleuropneumonia in 2 pigs and no lung changes in 4 pigs. M. hyorhinis was re-isolated from the lungs of all infected pigs, irrespective of the presence or absence of lesions, though it was only isolated from the serosa and joints when lesions were present. Four control pigs exposed to aerosols of mycoplasma medium had no lesions.

In terms of the rate of positive diagnoses the indirect fluorescent antibody (FA) test was rather more effective than iodine for demonstrating trachoma (TRIC) inclusions in conjunctival scrapings, but the degree of advantage was not statistically significant. In duplicate scrapings stained at random by one or the other method, FA staining yielded the higher inclusion count significantly more often than did iodine. Some inclusions that failed to stain with FA were found on subsequent staining with Giemsa. A method is described for improving the post-FA Giemsa staining of conjunctival smears stored at subzero temperatures. Given adequate facilities, the FA stain is preferable to iodine for demonstrating TRIC inclusions in the conjunctiva; but the iodine method, properly used, holds advantages for field use.

Clinical salmonellosis in cattle is infrequently recorded in Botswana, the majority of salmonella isolations being made from apparently healthy animals. A salmonella carrier rate of 6·7% was found in testing faeces samples from 89 apparently healthy cattle. A total of 35 salmonella serotypes were isolated from specimens of bovine origin. Salmonella dublin was isolated infrequently, possibly in part because of prophylactic vaccination.

For isolating trachoma (TRIC) agent from conjunctival scrapings, both streptomycin and neomycin were effective in preventing bacterial contamination, but at high concentrations neomycin was rather more inhibitory to TRIC agent. Prolonging storage of scrapings with neomycin at 4° from 30 min. to 24 hr. reduced the bacterial contamination rate, but also diminished the chance of isolating TRIC agent at the 1st passage. Two freshly isolated TRIC agents differed in their susceptibility to neomycin and streptomycin. Kanamycin and framycetin appeared to be less suitable than streptomycin for use in isolation of TRIC agent. In isolation studies, the possibility of inhibiting TRIC agent by high concentrations of antibotics, including streptomycin, should be borne in mind.

A subclinical infection of Salmonella typhimurium in a broiler flock was investigated and attempts were made to eradicate the infection by treatment with furazolidone. One-quarter of the chickens were still infected after they had been through the processing plant. Washing in heavily chlorinated water reduced the number of contaminated carcasses. Infected chickens were also found in four other companion flocks on the same farm.

Trachoma vaccines are usually assayed by testing their ability to protect monkeys or baboons against subsequent challenge of the conjunctiva with a pathogenic strain of trachoma/inclusion conjunctivitis (TRIC) agent. In such experiments the course of infection in vaccinated baboons was compared in terms of arbitrary scores assigned to a range of clinical signs, and of counts of TRIC inclusions in conjunctival scrapings. Analysis of many such scores indicated that after a large challenge dose of strain MRC-4s, the scores for signs of inflammation reached their maximum earlier than the follicle score; the inflammation score was closely related to the number of inclusions, whereas the follicle score was not. With this system, the optimum periods for eliciting differences between vaccinated and control measures varied according to the sign used; it was later for follicles than for inflammation or inclusions. For assessing the influence of vaccination, the mean of the inflammation scores read weekly for the first 3 weeks after challenge and the mean inclusion score over the same period were equally satisfactory, and either was rather better than the mean of three follicle scores taken over the period 3–6 weeks.

For assessing the influence of vaccines or therapeutic agents on experimental trachoma it is important to determine which signs discriminate best between treated and control animals, and the optimum times for measuring them.