The susceptibility of the tissue culture system to small amounts of residual live virus was not influenced by the inactivated antigen present. The depth of inoculum over the cell sheet did not affect results. Negative cultures frequently gave positive first (but not second or later) sub-cultures.

Baby hamster kidney cells were always more sensitive than cattle tongues to infection with any of the strains used.

Confidence in the safety test depends on the number of vaccination doses used; the tissue culture test can be made much more reliable than the cattle test because it is not limited to the 15 ml. of inoculum that restricts the cattle test.

The relationship between the serological findings for brucellosis and the epidemiological factors has been studied in veterinary surgeons in Northern Ireland. The anti-human globulin (Coombs) test and the complement-fixation test for brucella were used in two groups of veterinary surgeons, those self-employed and those employed by the Ministry of Agriculture.

Significant serological differences were found to exist between the two groups. Those in private practice showed changes related to age, cattle skin rash, reactions to S. 19 vaccine accidents and symptoms suggestive of brucellosis in the past or the last year. But those working for the Ministry only showed titre changes related to the length of their private practice experience before joining the Ministry. In neither group was there a relationship between serological findings and the type of milk drunk or any particular group of symptoms suggestive of brucellosis.

The findings indicate that high titres to brucella by the Coombs and complement-fixation test can occur in people repeatedly exposed to infection at work. Titres which would be of diagnostic importance in the rest of the population may be of little diagnostic significance even when they are as high as 160 Coombs and 128 complement fixation.

A survey was carried out on the occurrence of Vibrio parahaemolyticus on fish and shellfish, as sold in The Netherlands.

The optimal mode of detection of this bacterium appeared to be: (i) enrichment of swabs taken from the surface and the gills in freshly prepared meat broth with 5% NaCl; (ii) streaking onto Teepol bromothymol blue agar (BTB) and taurocholate bromothymol blue sucrose agar (TCBS); (iii) confirmation of suspect colonies by testing for mode of growth in butts/slants of a Kligler type glucose sucrose iron thiosulphate agar, formation of indole in 2% NaCl 2% trypticase water, anaerobic utilization of starch in the presence of 5% NaCl and oxidase reaction according to Kovacs (1956).

A total of 407 samples, stemming from 17 types of fish and shellfish, taken at three fish shops, was examined by this technique. Only one specimen, i.e. a haddock, was found to contain V. parahaemolyticus. This contamination rate of approximately 0·3% correlates well with data found earlier for fish landed in Northern Germany.

Vaccines were prepared from a single pool of high-titred vaccinia virus and inactivated by six methods, namely heat, formalin, hydroxylamine, β-propiolactone, ultraviolet irradiation, and visible light and methylene blue. Large doses of the vaccines were required to protect mice against intracerebral challenge. Differences in protection were not attributable to the method of their inactivation. The vaccines also induced similar degrees of skin immunity in rabbits which showed no severe dermal reactions when challenged with either homologous killed vaccine or live virus. The virus-neutralizing, haemagglutinin-inhibiting and complement fixing antibody responses to the vaccines differed; heat-inactivation preserved these antigens least well and β-propiolactone apparently the best. In both rabbits and mice there was little association between the different antibody responses to each vaccine or between the degrees of antibody response and the protection they induced. The relation of these findings to pox-virus immunity and the use of inactivated smallpox vaccine in man is discussed.

The direct complement fixation test was performed to follow the antibody response in chickens infected with avian infectious bronchitis virus. Concentrated allantoic fluid (4 units) was used as an antigen and allowed to react with serially diluted antiserum in the presence of two complete units of guinea-pig complement for 3 hr. at 4°C. and ½ hr. at 37°C. before the addition of sensitized cells. Serum was unheated and used either fresh or within one month of storage at −30°C. Individual birds showed a rise and fall of complement-fixing antibody both after primary and secondary inoculations. The complement-fixing antibody was detected as early as the seventh day after primary inoculation. The highest complement fixation titre (1/32 to 1/64) was recorded from 14 to 21 days after inoculation with a subsequent gradual decline.

The results of the direct complement fixation tests have been correlated with the serum neutralization test. The neutralizing antibodies usually appeared by the 14th day but were not detected at a significant titre until the 21st day after primary inoculation. Serum neutralizing antibodies were still present at high titres even after 7 weeks of infection but the complement-fixing antibodies had disappeared by that time.

There is no official scheme for testing disinfectants and detergent/disinfectants for use in the retail food trade and few recommended procedures have been given for the cleaning of equipment with these agents. Therefore, field trials were carried out in a large self-service store. Comparisons were made of the various cleaning efficiencies, as determined by bacterial plate counts, of detergent and disinfectant solutions and machine cleaning oils applied with either clean cloths or disposable paper towels to items of equipment. The most satisfactory results were always obtained when anionic detergent (0·75 % w/v) and hypochlorite (200 p.p.m. available chlorine) solutions were applied in a ‘two-step’ procedure.

Tests were made to compare the calcium alginate swab-rinse and the agar sausage (Agaroid) techniques for the enumeration of bacteria on stainless steel, plastic, formica and wooden surfaces before and after a cleaning process. Although recovery rates were always greater by the swab-rinse technique, the agar sausage technique was considered to be a useful routine control method for surface sampling.

Trials were made in volunteers in 1967 and 1968 of various virus vaccines against influenza virus B. Sera and serially collected nasal washings before and after immunization were tested respectively for haemagglutination-inhibiting and tissue culture virus-neutralizing antibodies to the same strain of influenza B/Eng/65 virus as that used in the vaccines. Infection, as determined by recovery of virus and serological changes following intranasal instillation of attenuated live virus, was accompanied by the subsequent appearance of neutralizing antibodies in nasal secretion. Inactivated vaccine subcutaneously did not evoke nasal antibody formation in 1967 but did so in 1968.

In 1968 intranasal challenge of the volunteers with the attenuated virus 1 month after immunization demonstrated a correlation of susceptibility or resistance to infection with nasal and serum antibodies. Resistance appeared to depend either on a high level of serum antibodies or nasal antibodies, or both.

Air containing olefin vapour was treated with known amounts of ozone simulating natural concentrations. The bactericidal effect of the mixture was tested using microthreads sprayed with washed cultures of Escherichia coli var. communis or Micrococcus albus, aerosol strain. With 20 different olefins a wide range of activity was found, those in which the double bond formed part of a ring being the most bactericidal; petrol vapour was about as active as the average open-chain olefin. The two organisms behaved similarly at the experimental relative humidity of 80%. The estimated amount of bactericidal substance present was only about one hundredth of that required to give the same kill with a ‘conventional’ air disinfectant; a simple physical explanation is proposed for this enhanced effect.

An analysis of the 1967–8 foot-and-mouth disease epidemic with reference to the initial spread, the origin of outbreaks more than 60 km. from the main epidemic area, the series of outbreaks near Worcester, a specific case history and the daily rate of spread of the epidemic, strongly suggests that the weather played a major part in the spread of disease. The two main factors involved in this type of spread are wind and precipitation. It is noted that after the epidemic had been checked, following anticyclonic weather, the association between the weather and the spread of disease was less apparent.

A mixture of sucrose, glycerol and bovine serum albumin produces a stable coating in a Petri dish which remains adhesive for up to an hour when exposed in a slit sampler. Virus aerosols can be collected on this surface followed the direct addition of cell cultures to demonstrate the presence of viable virus. The technique is applicable to the Andersen sampler. A modified version of this sampler has been produced with the same particle collection efficiency as the standard Andersen sampler. The plaque counts obtained the adhesive surface sampling technique are believed to give an indication of the number of particles collected bearing viable virus.

Thirty-five consecutive infants admitted into hospital in Newcastle upon Tyne with acute respiratory disease had cough/nasal swabs and nasopharyngeal secretions taken. Both types of specimens were examined the fluorescent antibody technique for respiratory syncytial virus; isolation techniques were also used. Twenty-eight specimens of nasopharyngeal secretion were positive, as were 26 of the corresponding cough/nasal swab preparations. Respiratory syncytial virus was isolated from all but one.

Sixteen consecutive children who were only suitable for examination cough/nasal swab preparations were also investigated isolation and fluorescent antibody techniques for respiratory syncytial virus. Respiratory syncytial virus was isolated from eight, seven of whom were positive the fluorescent antibody technique. The use of cough/nasal swab preparations stained the fluorescent antibody technique, although not as efficient as nasopharyngeal secretions, may have a place in the rapid diagnosis of respiratory virus infection in older children and children in general practice. The importance of rapid diagnosis for respiratory virus infection in relationship to antiviral therapy was also discussed.

The use of a gamma radiation process for the elimination of Salmonella from frozen meat is considered with particular reference to the treatment of boned-out horsemeat and kangaroo meat imported into the UK and intended for use as pet meat.

Examination of dose/survival curves produced for several serotypes of Salmonella in frozen meat shows that a radiation dose of 0·6 Mrad. will reduce a population by at least a factor of 105. The influence on the radiation resistance of salmonellas of such factors as preirradiation growth in the meat and temperature during irradiation have been examined and considered. It is also demonstrated with both preinoculated and naturally contaminated meat that postirradiation storage in the frozen state does not lead to the revival of irradiated salmonellas.

The properties of Salmonella survivors deliberately produced in meat using conditions of irradiation designed to simulate a commercial process are studied after six recycling treatments through the process. There were no important changes in characteristics normally used for identification of Salmonella but radiation resistance was lowered. Survivors grown in situ in meat after irradiation showed an abnormally long lag phase, and removal of competitive microflora in meat by the radiation treatment can influence the growth of salmonellas.

In previous work in this laboratory, Mycoplasma suipneumoniae was recovered in liquid medium from 13 % of individual cases and 18 % of outbreaks of enzootic pneumonia in pigs. In the work now described, however, these recovery rates, when judged by the same criteria, were 45 and 75 %, respectively. As there was evidence to suggest that this second series of pneumonic cases was less suitable for cultural examination than the first series, some of the other factors that might have improved the recovery rate were investigated.

Some improvement was probably achieved by inoculating the liquid medium with three or four different dilutions of pneumonic tissue, each dilution always being in duplicate, and by incubating the inoculated tubes for over 3 weeks before discarding them.

A second advantage could have derived from the fact that all batches of liquid medium were tested for their ability to support the growth of M. suipneumoniae before being used to culture field material.

The effect of varying one constituent at a time was observed in controlled experiments: different batches of pig sera had a marked, variable effect on the growth of both M. suipneumoniae and Mycoplasma hyorhinis; medium made with purchased Hartley's broth was found to be superior to medium incorporating broth made in this laboratory, more so for the growth of M. suipneumoniae than M. hyorhinis; the incorporation of yeast extract made in this laboratory gave a marginal advantage for the growth of M. hyorhinis; and both mycoplasmas grew equally well in medium containing or lacking thallium acetate.

Some batches of medium were, by chance, markedly selective for the growth of M. suipneumoniae compared with M. hyorhinis. As the full reasons for this were not known, attempts were made to develop selective media in a more direct way. One such medium contained 5% pig serum and 15% horse serum, and a second was of similar composition, except that the pig serum used inhibited preferentially the growth of M. hyorhinis compared with M. suipneumoniae. Both media markedly favoured the growth of M. suipneumoniae when tested separately with cultures of M. suipneumoniae and M. hyorhinis. The second medium yielded M. suipneumoniae when inoculated with a 10-1 dilution of a culture of M. suipneumoniae and a 10-2 dilution of a culture of M. hyorhinis, whereas a standard batch, of liquid medium, similarly inoculated with M. suipneumoniae did not yield this mycoplasma until the M. hyorhinis culture included in the inoculum was diluted to 10-6.

Both selective media, when tested on a small number of field cases, gave improved isolations of M. suipneumoniae compared with the routine batches of liquid medium used initially.

Considerable difficulty was experienced in producing a sufficiently high level of antibodies to M. hyorhinis in pig sera and to M. suipneumoniae in rabbit sera. This exacerbated the problem of isolating and identifying M. suipneumoniae from field cases of enzootic pneumonia by this cultural method.

Fourteen cases of enzootic pneumonia, nearly all of which had presented diagnostic difficulties using the metabolic-inhibition test, were re-examined using specific pig antisera in the passive haemagglutination test (PHA). All proved positive for Mycoplasma suipneumoniae, indicating that the test, used in this manner, might be particularly valuable for routine diagnosis.

The PHA test was also used to demonstrate antibody to M. suipneumoniae in pneumonic tissue and the associated bronchial lymph nodes.

To allay our concern that cross-reactions might interfere with this and other serological tests—the complement-fixation test (CF) and precipitation in agar-gel—the specificity of our reagents and the antigenic relationships of Mycoplasma hyorhinis, Mycoplasma granularum, mycoplasmaB3, Mycoplasma hyopneumoniae and three strains of M. suipneumoniae (including cloned and uncloned isolates of the J strain) were studied in various ways. Antibodies to medium constituents occurred in rabbit antiserum but did not present a problem with pig antisera. These antibodies were successfully absorbed from the rabbit antisera but it was not possible to remove medium constituents from the antigens used to produce antisera in rabbits by repeated washing.

By all these tests, the main species of mycoplasmas studied seemed to be anti-genically distinct. No major antigenic differences between the three strains of M. suipneumoniae were revealed by the PHA test and the CF test; a slight difference in the precipitation lines of one of these strains (MG) in agar-gel might have indicated an antigenic variation or been a measure of some other factor.

Haemophilus influenzae type b was isolated from 4·5% of outpatient children living in various parts of Kampala city and its surroundings. In contrast, this serotype was carried by up to 53 % (average 29 %) of 14 to 18 children living as a group in an orphanage. This finding indicates that the high carriage rate for this serotype demonstrated by Turk (1963) in a group of orphanage infants in Jamaica was not an isolated finding, and that it may be expected where large groups of children live together.

H. influenzae type b did not appear to be a readily transmitted organism even in that group of children with a high carriage rate. This suggests that in ordinary open communities the transmission of this serotype from one household to another may be an extremely rare event.