Mycoplasma pulmonis was isolated from the pneumonic lung of a rat. Two groups of mycoplasma-free rats were inoculated, one with a culture of the M. pulmonis strain winch had been cloned four times (group A) and the other with a lung homogenate of the rat from which the strain had been isolated (group B). A third group (C) consisted of uninoculated control animals. Each group was kept in strict isolation and allowed to breed so that the progeny was naturally exposed to any pathogens present in the inoculated animals. After different periods of exposure, rats were autopsied, respiratory tracts and inner ears were cultured for mycoplasmas and bacteria, and sera were tested for complement-fixing antibodies to murine mycoplasmas.

In group-A rats, M. pulmonis was consistently isolated from the inner ears or lungs from 50 to 715 days after exposure. Complement-fixing antibody to M. pulmonis was detected 20 days after inoculation, but in the naturally exposed progeny antibody took longer than 50 days to develop. Antibodies to the other known mycoplasmas of murino origin, M. arthritidis and M. neurolylicum, were never found. Purulent otitis interna was consistently found from day 55 onwards, while lung lesions were first observed at 85 days and persisted to 715 days. Pulmonary lesions developed more slowly in inoculated parents than in exposed progeny. Similar results were found in group-B rats, which were examined up to 441 days after inoculation. Uninoculated group-C rats were examined up to 768 days of ago, but M. pulmonis was not recovered; of tho 54 animals whose serum was tested all wore negativo to tho three species of mycoplasmas, except one which had a titre of 16 with M. pulmonis. Pneumonia, bronchiectasis or lymphoroticular hyperplasia wore not seen in any of these control rats. Bacterial respiratory pathogens were not isolated from rats in any of the groups, nor was antibody to Sendai virus detected.

Tho results suggest that M. pulmonis alono can cause pneumonia and bronchiee-tasis in rats since mechanical carry-over of another pathogen with the initial cloned inoculum is very unlikely and there was no evidence for the participation of any other rat pathogen. The respiratory disease induced by the cloned culture was comparable with that induced by the lung homogenate, and with the well-known syndrome of chronic respiratory disease and bronchiectasis in the rat.

The frequency of herds affected with 13 different diseases is shown to bear a simple relationship to the frequency of affected animals. The relationship seems to be useful for predicting proportions of affected herds.

A comparison was made of beef cooked in conventional and moist air (Rapidaire) ovens. In both large (ca. 4·5 kg.) and small (ca. 2·7 kg.) joints, spores of Clostridium welchii survived after cooking but vegetative cells, Escherichia coli, and Staphylococcus aureus, did not, regardless of the type of oven used

Cooling at room temperature after cooking permitted growth of Cl. welchii. Although some multiplication also occurred in the centre of large roasts cooled under refrigeration, the viable counts were considered too low to constitute a potential health risk

The inoculation of large doses of unadapted influenza virus intranasally into mice results in the production of severe lung lesions. This toxic effect is a result of the entry of virus particles into the lung cells followed by uncoating of the virus ribonucleic acid.

The toxic property of the virus is destroyed by procedures which destroy or niodify the nucleic acid such as exposure to monochromatic UV light of wavelength 2537 Å, or treatment with hydroxylamine or Bayer A139. Reagents acting on amino groups are particularly effective as they react with the nucleic acid and probably also interfere with penetration of virus into the cell.

Toxicity is also destroyed by mercurials which probably prevent uncoating of the nucleic acid by union with disulphide bonds, and by oxidizing agents such as iodine, permanganate, osmic acid and hydrogen peroxide under conditions which suggest possible action on some constituent of the virus containing methionine

The toxic effect produced by the inoculation of large doses of unadapted virus intranasally in miceis associated with the occurrence of an incomplete growth cycle in which there is full production of RNP antigen but no production of haemagglutinin or infective virus.

An investigation to test the efficiency of chemical closets in treating excreta from typhoid carriers is described. The use of these closets kept a stream, which had in the past frequently contained Salmonella typhi, typhoid free for 24 months. Selenite broth as made in this laboratory, containing a final concentration of 0·8% sodium hydrogen selenite when inoculated with the water sample, was significantly better than commercial selenite brilliant green enrichment broth for the recovery of S. typhi.

Samples of Fermi, Semple, modified Semple, Duck embryo and tissue culture rabies vaccine were inoculated by different routes and in different doses into rabbits, mice and hamsters. The vaccines induced neither detectable interferon nor immediate protection against lethal challenge with CVS rabies virus.

Under similar conditions, high but transient levels of interferon were induced in control animals of the same species with the polynucleotide complex Poly I.C. Hamsters but not mice were protected by Poly I.C.-induced interferon.

No autointerference by vaccine with challenge virus was established. Vaccineinduced protection in mice was directly related to immune response.

Using animal inoculation, three out of six Lebanese and three out of nine Argentinian and two out of two Pakistan separate commercial consignments of bone meal imported during 1970 were found to be infected with anthrax.

Osmotic injury in frozen-thawed T4 phage was caused by the sudden and large fall in the electrolyte concentration of the unfrozen aqueous phase during rapid thawing of frozen samples. In accordance with the classical interpretation of osmotic shock it was found that DNA was quantitatively liberated from T4 phage inactivated by the osmotic injury of rapid thawing.

The degree of inactivation of osmotically shocked T4 phage was temperature dependent, being much increased by lowering the temperature, but was independant of the pH of the suspending medium. The T4Bo osmotic shock-resistant phago was refractory to the osmotic injury of rapid thawing.

Peptides of rabbit globin produced by tryptic digestion, were found to be highly protective against inactivation of freeze-thawed T4 phage. In concentrations of about 10−3 M the peptides protected the phage against inactivation by both concentrated NaBr in the unfrozen aqueous phase and the eutectic phase change.

Fractionation of the poptides by G25 Sephadex showed that peptide concentration rather than peptide size was the more important factor in determining the degree of protection of the phage by electrolyte effects. In contrast, protection against eutectic injury was strongly dependent on peptide size.

Possible mechanisms of action of the protective peptides are discussed.

The indirect immunofluorescent technique has been used to study the specific immunoglobulin responses in twelve adult cases of acute uncomplicated rubella. IgG, IgA and IgM antibodies increased virtually simultaneously. IgG antibody persisted throughout the period of study but showed a slight tendency to fall in titre after 7 months. IgM antibody was detected in nine cases. In these patients it was present in high titre 5–15 days after the rash but was not detected after 20 days. IgA antibody was detected in all cases. It was present in high titre 5–20 days after the rash but was no longer detectable after 29 days except in one patient who had a very low titre at 78 days. The presence of specific IgA and IgM indicates recent rubella in uncomplicated cases, and if the immunofluorescent method is used both types of antibody should be sought.

The development of immunity in mice to Bordetella pertussis induced by intracerebral, intravenous or intraperitoneal vaccination was analysed in terms of the viable bacteria in the brain after intracerebral challenge, the serum antibodies, and protection against the sublethal infection of the lung that follows intranasal inoculation.

A vaccine introduced intracerebrally was five to ten times more effective than that given intraperitoneally or intravenously, as measured for each route by the amount of vaccine required to protect half the mice against an intracerebral challenge 14 days later (ImD50). Intracorebral vaccination induced higher antibody titres than vaccination by the other two routes. The survival of infected mice given 1–3 ImD50 doses of vaccine intracerebrally 14 days before, followed a pattern similar to that after intraperitoneal or intravenous vaccination with up to 10 ImD50 of vaccine: the numbers of organisms increased for 3 days and then declined. Injection of about four ImD50 of vaccine intracerebrally produced a local immunity, resulting in an immediate kill of challenge organisms given 14 days later. Such an effect following intraperitoneal vaccination was achieved only against challenges with an avirulent strain. It is suggested that better stimulation of circulating antibody and local immunity in the brain together account for the better protection induced by intracerebral vaccine.

Immunity to an intracerebral infection appears therefore to have at least three components, each specific for pertussis. The first, like that induced by intraperitoneal and intravenous vaccination, reaches a maximum in 2 or 3 weeks and is probably an expression of a general response by the animal operating not earlier than 3 days after infection. The second is a local immunity, appearing after the same interval. The third is a short-lived local immunity which has been described by previous workers; it immediately follows the injection intracorebrally of ten times less vaccine than that needed to protect against a challenge 14 days later and lasts only 2–3 days. The second and third types result in immediate sterilization of the infection.

Mice recovering from sublethal brain infection with avirulent organisms were immune to a second infection with a virulent organism, but this was achieved not by the ability to kill the re-infecting organisms immediately on injection into the brain, but only after the 3–4 days lag such as follows intraperitoneal vaccination.

In three years, Corynebacterium diphtheriae was isolated from 1238 people, consisting of 820 North American Indians or Metis, 318 people of Caucasian origin, 97 Eskimos and 3 Asiatic Indians. Diphtheria infection of the throat, nose, ears and skin was common in the North American Indian and Metis people, but rarely caused severe symptoms. The infection occurred less often in white people but was more serious; of 27 cases of toxic respiratory diphtheria, 25 were white people. The public health significance of the endemic infection of the North American Indian and Metis people is discussed.

Six milking cows were inoculated with bovine and human T-mycoplasmas and control materials into the udder via the teat canal. Control materials produced only a slight transient cell response in the milk. Bovine T-mycoplasmas produced clinical mastitis in nine out of ten quarters inoculated. Seven developed clinical mastitis together with visible changes in the milk, excretion of T-mycoplasmas and greatly increased cell counts in the milk. In three of these quarters, in two different cows, milk secretion ceased completely. Two quarters in a different cow showed visible milk changes, excretion of T-mycoplasmas and increased cell counts. Two quarters were inoculated with human T-mycoplasmas and neither produced any signs of mastitis.

Infection of the udder with T-mycoplasmas did not stimulate high-titre serum antibody levels as measured by the metabolic inhibition test, but whey samples gave high titres in two of the cows that were able to control and resolve the infection.

Surveys for respiratory virus antibodies in the Jamaican population have shown that adenovirus, respiratory syncytial virus and parainfluenza types 1 and 3 virus antibodies are acquired early in life. The incidence of haemagglutination-inhibiting antibodies to parainfluonza viruses increases rapidly with age and almost all adults possess parainfluenza type 3 antibody, usually in high titre. Parainfluenza type 1 antibodies are only slightly less common. Complement-fixing antibodies to the adenovirus group were also observed to increase in incidence with age.

Complement-fixing antibody to respiratory syncytial virus was less common in Jamaican sera than antibody to the other respiratory viruses described here. The highest titres were observed in the youngest age-group.

Forty-nine subjects were vaccinated with either live attenuated, detergent split, or oil adjuvant A2/Hong Kong influenza vaccines, or a saline influenza B vaccine as control. Respiratory symptoms occurred more frequently in subjects who received the live vaccine but in total there was little difference between the symptoms in the four groups. Antibody titres hi nasal washings and serum were measured by haemagglutination inhibition, neuraminidase inhibition and virus neutralization tests. The oil adjuvant vaccine stimulated larger antibody responses than the other procedures. Six weeks after vaccination the volunteers were challenged with partially attenuated live A2/Hong Kong influenza virus administered intranasally. The live attenuated and oil adjuvant vaccines provided the best protection against challenge.

An isolation policy in a hospital for skin diseases is reported. Patients carrying penicillin- and tetracycline-resistant organisms were to be isolated in single rooms, though barrier nursing was not practised. The policy failed because the single beds rapidly became blocked with long-stay patients and because even in a single-bed unit patients acquired staphylococci within 3–7 days of admission. Patients with skin diseases often do not feel ‘ill’ and resent isolation.

The air of loose-boxes which had previously held pigs infected with foot-and-mouth disease was sampled for virus after various procedures. Removal of infected pigs led to a 12- to 16-fold reduction in the amount of virus after 5 min. and a 400-fold reduction after 60 min. After heavy spraying (1·2 mm. of water in 5 min.) the amount of virus was reduced 500-fold compared to 30-fold after light spraying (0·20 mm. of water in 5 min.). The partition of infectivity associated with particle size was measured. The partition found after light spraying was similar to that found 5 min. after the pigs had been removed. Heavy spraying brought about a reduction in the infectivity associated with the large particles (> 6 μm.) but had no effect on particles less than 3 μm. A similar partition was found 60 min. after the pigs had been removed. The findings are discussed in relation to the spread of foot-and-mouth disease by the airborne route.

Human skin scales which have been shed naturally bear a flora of micro-organisms which is unknown until tested. To replace these scales in a study of the micro-environment of both the human body and of models a method has been devised of making synthetic scales which behave both physically and aerodynamically in a similar way to the natural material. The synthetic materials carry no natural flora and it is possible to include in them test markers of several kinds to assist in identification after dispersion.

A comparison was made of four methods of thawing frozen chickens and an average thaw time for each method was determined.

Fully and partially thawed chickens, inoculated with salmonellas, Clostridium welchii and Slaphylococcus aureus were cooked in a spit-roasting oven at different temperatures for different lengths of time. The chickens were examined freshly cooked and after storage under various conditions.

Spit roasting fully thawed chickens until the outer skin was golden brown was sufficient heat-treatment to kill salmonellas and Staph. aureus but Cl. welchii could survive. Salmonellas could also survive if the chickens were not fully thawed before cooking.

Incorrect storage after cooking was shown to encourage the growth of pathogens.

The incidence of intestinal pathogens in frozen dressed chickens and environmental hazards in spit-roasting establishments were also studied. Of raw chickens examined 35% contained salmonellas (9 serotypes), 63% contained Cl. welchii and 63% Staph. aureus.

During the winter of 1967–8 Sonne dysentery affected neighbouring North London primary schools. This was not simply due to cross-infection between the two schools, for two different, unusual strains of Sh. sonnei were distinguished. One was a novel kanamycin-resistant colicine type 7 strain, and as far as we know this was the first school outbreak due to such a strain to be documented. The other strain was kanamycin-sensitive and of colicine type 0 with a rare specific requirement for aspartic acid. There was some evidence to suggest that the kanamycin-resistant strain was more infective for adults and possibly more pathogenic than the kanamycin-sensitive.

Studies on the transfer of drug resistance and of colicinogeny revealed that the factor determining colicine type 7 was carried on a transmissible plasmid, a new observation. Various drug resistances were also transmissible experimentally, and some were spontaneously unstable. Non-transferable ampicillin-resistance in the colicine type 7 strain and aspartic acid dependence in the colicine type 0 strain enabled all but one of the isolates to be classified into two distinct lines. No common ancestor was found and it was concluded that although occurring together they must have arisen from separate sources.