The onset, duration and magnitude of antibody responses to a poxvirus infection were examined. Mice were inoculated intravenously with the WR strain of vaccinia virus and developed pocks on their tails. The number of pocks was related to the size of the inoculum. Virus was detectable in the spleen and infected mice were subsequently immune to intravenous and intra-nasal challenge. Sera of infected animals neutralized both cell-free and cell-associated virus. Antibody against cell-free virus appeared first; maximum titres were reached sooner but were lower than those of antibody neutralizing cell-associated virus. Titres remained high for at least 100 days after infection.

The appearance of specific hypersensitivity to virus antigens was examined in mice infected intravenously with vaccinia virus. Both immediate hypersensitivity, transferable by serum, and delayed-type hypersensitivity, transferable only by cells, were apparent 8 days after infection and demonstrable for at least a further 130 days. Production of macrophage migration inhibitory factor by lymphocytes from infected mice was measured directly in terms of inhibition of migration by antigen or indirectly by determining the effect of soluble factors elaborated by the stimulated lymphocytes. The irregular results may have been the resultants of antigen-mediated macrophage stimulation, toxicity and induction of migration inhibitory factor. Transformation of spleen cells – presumably lymphocytes – from infected mice could be induced in vitro by virus antigens for at least 139 days after infection. Virus/lymphocyte interaction appears to be a particularly fruitful area for further study.

In a study on a Caucasian population in Western Australia the prevalence of antibodies to Epstein–Barr virus (EBV) was 41% in the 9- to 10-year age group, 80% in the 16 to 19-year age group and 92% in young adults. The age-specific annual seroconversion rates indicated two peaks of primary EBV infection in the population studied – one under 5 years of age and the other at adolescence. The geometric mean titre rose with age, from 23 at 5–6 years to 53 at 36–40 years.

It was shown that in 73 families studied there was evidence of probable spread of EBV infection among siblings, particularly between those of the same sex.

Serological study of patients with infectious mononucleosis indicated that 100% of those examined had antibody to EBV and the geometric mean titre was elevated to 210. Rising titres and seroconversion was demonstrated in these patients together with successful establishment of EBV-carrying cell lines from the peripheral blood in two-thirds of the cases.

Winter thermal sensations of secondary and primary school-children in Queensland are related to air temperature. Neutrality is estimated by regression analysis of over 6000 assessments and a lower comfort limit is suggested to include 80% of the children. Cold discomfort is seen as the main problem, and comparison is made to an earlier study in England.

A new test, the water agar test, is described that gives a qualitative index of the presence of bacteria that indicate contamination of the cream, poor storage conditions or both of these factors. The method is simple and requires little equipment. The bacteria grow in a film of diluted cream adsorbed on the surface of a non-nutrient base. After incubation at 30 ± 0.5° C. for 18–20 hr., a proteolytic and mucoid colony count is obtained which has the same percentage coefficient of variance as a standard plate count.

An examination of the effect of storage at different temperatures on the types of bacteria present in cream showed that of all the tests done initially, only the water agar test could predict subsequent bacterial growth with any consistency. The multiplication of presumptive coliform organisms occurred even at 3.5° C. Irrespective of the colony count, the methylene blue reduction time was not shorter than 7½ hr. unless the bacteria were in the logarithmic phase of growth when sampled.

A survey was made of the bacterial flora of 188 retail samples of double cream of 15 different brands. The age of the samples varied from freshly separated cream to cream that had been kept in the shop for a day longer than that recommended for sale. The water agar test was compared with the colony count, the presumptive coliform test, a confirmatory coliform count in violet red-bile agar, a lipolytic colony count, a staphylococcal count and the methylene blue reduction test.

The use of a fluid-enrichment technique increased by 10–16% the recovery rate of Brucella abortus from milks of herds positive to a milk ring test. Three solid media for direct cultural techniques were also tested on the same milks. Combinations of these techniques produced a recovery rate of ca. 88% from MRT-positive-herd milks using a mixture of the centrifuged deposit and cream layer as the inoculum as against a recovery rate of ca. 75% using the MRT cream layer as inoculum. B. abortus biotypes 1–5 and 9 were isolated and growth of all the biotypes was supported by all media used.

Abattoir drain swabs, bovine faeces and a few other veterinary samples were examined for the presence of Salmonella dublin. Three selective agar media and four enrichment broths were investigated. The two most efficient plating media were deoxycholate citrate agar and brilliant green MacConkey agar. Wilson and Blair's bismuth sulphite agar (de Loureiro's modification) was least successful. Selenite F broth, whether incubated at 37 or 43° C., was better than the other enrichment broths used which contained a triphenyl methane dye as one of the selective ingredients.

Inocula of polluted water naturally infected with salmonellas effectively distinguished six brands of selenite and six brands of tetrathionate enrichment media into satisfactory and unsatisfactory categories. Minimal inocula of pure cultures differentiated the tetrathionates, but not the selenites. Inocula of naturally infected chicken giblets suggested that there was a difference between two comparable brands of tetrathionate, but this was not statistically significant. The difference was, however, clearly demonstrated by minimal inocula of pure cultures.

Intensive investigation of two inferior tetrathionates revealed inhomogeneity in the distribution of brilliant green in one bottle of one brand. The importance of the salmonella serotype and even the colonial variant used for the pure culture inoculum was also demonstrated.

Ten mycoplasmas were isolated from 130 nasopharyngeal swabs from thoroughbred horses with acute respiratory disease and three from 198 apparently normal horses. Two mycoplasmas were isolated from 21 tracheal swabs taken at necropsy. These mycoplasmas, together with six isolated from the equine respiratory tract by other workers, were subjected to biochemical and serological tests. Other properties examined in certain representative strains were appearance under the electron microscope, ability to adsorb or agglutinate the erythrocytes of various animal species and the electrophoretic pattern of the cell proteins.

On the basis of these tests, mycoplasmas from the equine respiratory tract were divided into seven species. Three species belonged to the genus Acholeplasma, members of which do not require sterol for growth, and were identified as A. laidlawii, A. oculi (formerly A. oculusi) originally isolated from the eyes of goats, and a recently named species A. equifoetale, previously isolated from aborted equine fetuses.

Of the four sterol-dependent Mycoplasma species, one was identified as M. pulmonis, a common rodent pathogen. Another cross-reacted serologically with M. felis and should probably be classified as that species. The other two species probably represent new species peculiar to the horse. One of these, represented by the strains N3 and N11, ferments glucose and is serologically distinct from 19 recognized species of glucose-utilizing mycoplasmas and from two species which do not metabolize either glucose or arginine. The other species, represented by four strains, hydrolyses arginine and, because it is serologically distinct from all the named arginine-hydrolysing Mycoplasma species, the name M. equirhinis sp.nov. is proposed for it.

Of the seven species, only M. pulmonis and the glucose-utilizing species represented by N3 and N11 were found exclusively in horses with acute respiratory disease. A. oculi was isolated from an apparently normal horse. The other four species were found in normal horses as well as those with respiratory disease, although three out of the four strains of M. equirhinis were from sick horses.

The influence of the Open Air Factor (OAF) and daylight on the survival of foot-and-mouth disease (FMD) virus held as captured aerosols on spider micro-threads has been investigated. Virus inactivation due to OAF was slight. Similarly, the effect of daylight on the survival of virus was not marked. The results are discussed in relation to the airborne spread of FMD virus in nature.

The virulence of field strains of myxoma virus is increasing in the Mallee region of Victoria where the resistance of the rabbit to myxomatosis is high. This suggests that the climax association will be a moderately severe disease.

An attempt was made to correlate serological relationships determined by the pili, the flagella and the O-somatic antigens of Pseudomonas aeruginosa, and to make a preliminary assessment of use of the pilus antigen as an epidemiological marker. A method is described for the preparation of antiserum specific for the ‘normal’ PSA pili of P. aeruginosa. A high titre of pilus antibodies was obtained by immunizing rabbits with mutants whose pili had lost their ability to retract into the cell. The ‘normal’ form of the organism, with retractile pili, was poorly agglutinated by high-titre anti-pilus serum, but suspensions of it that had been treated with osmium tetroxide showed greatly increased agglutinability. Antibody labelling for electron microscopy was used to determine the serological relations of pili and of flagella for P. aeruginosa strains belonging to different serological groups as defined by O-somatic antigens. The distribution of pilar and flagellar antigens among strains was not correlated with the O-somatic serotype. A strain of P. aeruginosa carrying a drug-resistance plasmid had fewer ‘normal’ PSA pili than the background strain.

Pseudomonas aeruginosa normally possesses thin polar pili (fimbriae) which constitute one of the classes of heat-labile antigens of the organism. A previous study of the flagellar antigens (Pitt & Bradley, 1975), which are also heat-labile, was an essential preliminary to the development of a useful typing system based on heat-labile antigens. The present work extends this to the pilus antigens. The principle object is to define serological differences determined by pili, flagella, and heat-stable O-somatic antigens. In order to make this comparison, it has been necessary to develop a method for preparing specific antisera against pili, free from flagellar and O-somatic antibodies.

Many studies have been made of P. aeruginosa pili; two basic types of pili have so far been established: (1) the ‘normal’ polar pili mentioned above (Bradley, 1966), to be called PSA pili for convenience and (2) the non-polar pili determined by the intergeneric P-group drug-resistance plasmid RP1, called RP1 pili (Bradley, 1974a; C. H. To & C. C. Brinton, in preparation). Non-polar pili have also been found in association with the P. aeruginosa-specific drug-resistance plasmid R130 (L. E. Bryan, University of Alberta, Canada, personal communication), but they are still under study and little is known about them. Since the present work is principally aimed at evaluating the usefulness of pilus antigens as serological markers, emphasis has been placed on PSA pili, though obviously the presence of R-factor-determined pili cannot be ignored.

There are two ways of observing the serological relationships of bacterial appendages such as pili: either qualitatively by the direct observation of adsorbed antibodies in the electron microscope (Lawn, 1967), or quantitatively by conventional agglutination tests. In this work we have used the first method to define different serological types of pilus, and the second to study in detail the reactions of antibodies specific to the pilus.

Although the injection into rabbits of formolized suspensions of P. aeruginosa results in the formation of flagellar antibody in high titre, the antibody response to the pili is poor (Pitt & Bradley, 1975). The pilus is in the form of a long thin filament consisting of polymerized pilus protein or pilin. It has been demonstrated (Bradley, 1972a) that under certain influences, such as chemical action or bacteriophage adsorption (see below), the filaments withdraw into the cell, the pilin probably being depolymerized by a mechanism at the base. Certain P. aeruginosa mutants that lack the ability to retract their pili (Bradley, 1972a, 1974b) have many more filaments than do normal strains. We now show that these mutants are valuable in producing high-titre antiserum. Other mutants without pili have been isolated (Bradley, 1972b), and absorption of sera with these organisms removes antibodies to other components of the cell.

Certain bacteriophages use P. aeruginosa pili as receptors (Bradley, 1966, 1973a, b, 1974a; Bradley & Pitt, 1974). One aspect of the present work has been to determine whether the phage-sensitivity pattern varies with pili of different serological types.

Incidents of non-specific illness associated with the consumption of oysters have highlighted the lack of published information on the bacteriology of shellfish suitable for consumption. Investigations showed that the majority of molluscan shellfish entering English markets conform to the accepted standard of less than 5 Escherichia coli/ml. tissue. The numbers of E. coli were related to the sanitary quality of the growing area but no relation could be established between numbers of E. coli and coliforms, faecal streptococci or Clostridium welchii. The numbers of non-specific bacteria varied considerably but shellfish from sources associated with non-specific illness yielded relatively high counts at 37° C. The results showed that there was no justification for a standard based on total plate counts, which often exceeded 106/g. Such a standard would have to be coupled with spoilage or the incidence of non-specific illness. The relation between the numbers of non-specific bacteria growing at 20 and 37° C. appears to be a useful measure for assessing the likelihood that raw shellfish are a public health risk.

The efficacy of difenacoum as a new anticoagulant rodenticide was evaluated by blood coagulation studies and laboratory feeding tests using warfarin-resistant and non-resistant common rats (Rattus norvegicus), ship rats (R. rattus) and house mice (Mus musculus). Prothrombin assays indicated that the compound had as marked an activity with warfarin-resistant common rats as coumatetralyl had with non-resistant animals. Feeding tests confirmed that 0.005% would be a near-optimal concentration for field use, although there was some evidence of unpalatability.

Results with ship rats and house mice were less favourable. Trials with enclosed colonies of warfarin-resistant mice confirmed the laboratory finding that although difenacoum was more effective than all other currently used anticoagulants, it was unlikely to give complete control.

It is concluded that difenacoum is a valuable new rodenticide, especially for controlling warfarin-resistant common rats.

The anticoagulant difenacoum was tested at two concentrations, 0·005 and 0·01%, in bait against warfarin-resistant rat infestations in farm buildings. Twelve out of the 14 treatments in which the lower concentration of the anticoagulant was used resulted in complete control. One of the remaining two treatments was probably also completely successful, but in the other a few rats, that were not eating the poisoned baits, were still active after 30 days of baiting. All six treatments done using the stronger concentration of poison were completely effective.

Since it took as long to control infestations with 0·01% as with 0·005% difenacoum in treatments carried out under similar conditions, the lower concentration is recommended for use against warfarin-resistant rats.