Particle concentration in patient rooms at various ventilation rates and with differing methods of air supply has been investigated experimentally in a specially built test room. The size of the test room corresponded to an ordinary bedroom for two patients. Air was supplied isothermally to this test room, either through induction units or through a perforated ceiling, and the number of air changes per hour varied from 1 to 16. When the air was supplied by means of induction units, tests with different airflow patterns in the room were also carried out. The principle of the measurements was to estimate the decrease in particle concentration at certain points when the initial concentration was uniform all over the room and no generation took place during the measuring period. Talc powder was used as test dust, and the particle concentration was measured at up to six points in the room with a particle counter.

Intranasal vaccines of inactivated or living attentuated A2/Hong Kong influenza viruses were compared for clinical acceptability, serological effects and protective efficiency against natural epidemic influenza in a large industrial and clerical population.

Recent studies have established that the occurrence of common cold epidemics amongst men in Antarctica shows a pattern similar to that seen in other isolated communities such as Tristan da Cunha (Cameron & Moore, 1968; Shibli, Gooch, Lewis & Tyrrell, 1971). Colds occur during relief periods when ships and aircraft call, and disappear during the months of winter isolation, but no statistical analysis of the incidence of such colds is available.

Six of 12 men wintering at an isolated Antarctic base sequentially developed symptoms and signs of a common cold after 17 weeks of complete isolation. Examination of specimens taken from the men in relation to the outbreak has not revealed a causative agent.

Regular examination of rectal swabs revealed the presence of very low numbers of trimethoprim resistant Escherichia coli in the faeces of 10 batches of calves successively reared in the same shed and none of these strains transferred trimethoprim resistance to E. coli K12. All the calves had received oral doses of 30 mg/kg day of trimethoprim-sulphadiazine for 5 consecutive days. From two subsequent batches of calves reared in the same shed, however, several isolations were made of E. coli with transmissible R factors determining trimethoprim and streptomycin resistance. Shortly before these strains were detected, isolations of E. coli with similar properties had been made from other calves, in a different shed, which had been fed much higher doses of trimethoprim-sulphadiazine. Serological evidence indicated that all the E. coli isolated carrying this R factor belonged to the same strain, which had apparently spread from the second shed to the first. No evidence of ‘in vivo’ transfer of the R factor to other enteric bacteria was obtained.

A dipthericin typing scheme has been constructed using 441 strains of Corynebacterium diptheriae isolated in eastern Australia from 1962 to 1971. Ten types have been distinguished using seven strains of C. diphtheriae and two strains of C. belfanti as indicators of the diphthericins produced by the newly isolated strains. Strains grouped into types L2, L3 and L3a were found only in Melbourne and types L1 and L4 were predominant in Sydney. Type L5 strains were isolated intermittently throughout the period of study and were found in all eastern states. Numerical analysis of the characteristics of the strains suggests that associations exist between, on the one hand, diphthericin type and, on the other hand, bacteriophage type, serotype and biochemical activity.

Strains of Corynebacterium diphtheriae isolated from a small outbreak in the restricted environment of a Mental Hospital were examined. All belonged to one serotype, but there was marked variation in diphthericin type, in sensitivity to bacteriophages and in the minor antigens possessed. One strain was non-virulent and laboratory-produced variants of this non-virulent strain showed changes in some of the characteristics used in the identification and typing of the organism, such as diphthericin type, sensitivity to bacteriophages and diphthericins, virulence, starch fermentation and, to a lesser extent, in antigenic structure. The epidemiological and experimental findings are consistent with the hypothesis that the strains isolated, both in the hospital and in the laboratory, were derivatives of a single parent and the mechanism of some of the variations could be related to changes in some structural component such as the cell membrane or the cell wall.

The findings of a survey on the ecology of an alphavirus over the years 1964–9 are reviewed. Evidence is presented to show that wild birds constitute a vertebrate reservoir of the virus and that mosquitoes, primarily Culiseta tonnoiri and Culex pervigilans, which are both endemic New Zealand species, are responsible for summer transmission.

Serological evidence of infection was obtained in all years and evidence is presented to indicate that the virus is enzootic rather than being reintroduced each spring. The number of birds with antibody increased before mosquitoes became active in the spring and possible explanations of this are discussed.

The mean temperature in the hottest month in the study area is substantially below that in other areas with enzootic mosquito-borne viruses and experimental studies showed that Whataroa virus was able to replicate more rapidly in mosquitoes at low temperatures than any arboviruses previously studied.

The main natural focus of infection appeared to be in a modified habitat and the introduced song thrush (Turdus philomelos) to be the main vertebrate reservoir host.

Two outbreaks of human infection with Yersinia enterocolitica in Shizuoka, Japan are described. This is the first report of community outbreaks of infection with this organism in Japan, and possibly in the world. All the strains isolated in each outbreak belonged to 0 antigen group 3, biotype 4, of the species. Despite much effort, the source and mode of spread of the infection were not established.

The cell membrane of Mycoplasma gallisepticum was isolated by lysing the cells with digitonin. Chemical and density-gradient analyses and electron microscopy showed the isolated membranes to be relatively free of cytoplasmic contaminants. The density of the membranes exceeded that of other mycoplasma membranes, indicating a higher protein content. Small vesicular extensions seen in the sectioned membranes were interpreted as empty blebs.

The isolated membranes, but not the cytoplasmic fraction, elicited in chickens the production of growth-inhibiting, agglutinating and haemagglutination-inhibition antibodies to M. gallisepticum in titres resembling those obtained by injection of whole cells. The peak of the serological response varied with the serological test employed. The rapid slide-agglutination test became positive as early as 3 days after the first injection of only 50 μg. of membrane protein. The haemagglutination-inhibition antibody titre reached its peak at about 10 days after the first injection, while that of the growth-inhibiting antibodies was reached only at about 25 days. The addition of adjuvant to the membrane antigen did not improve the production of the growth-inhibiting antibodies in chickens, but it produced some improvement in rabbits. Our results support the thesis that the chief immunogens of M. gallisepticum reside in the cell membrane of this organism.

Two mincing machines were cleaned by different methods, i.e. (a) a detergent/ sterilizer method and (b) scrubbing parts in boiling (98·8° C.) water. Initial results indicated that, on reassembly, post-treatment contamination took place. Efforts to clean each machine as consisting of two distinct parts, (a) the casing and (b) removable parts, were more satisfactory. Four other mincers which could be completely dis-assembled were satisfactorily cleaned, but only in terms of percentage organisms surviving and not in terms of actual numbers surviving.

Sub-lethal exposure of Aspergillus fumigatus spore suspensions to formalin resulted in prolongation by 1–22 days of the period of less than one day normally needed by spores to produce visible growth in Sabouraud's liquid medium at 37° C.; the degree of delay depended on the concentration of formalin and the duration of exposure, and was due to an increase in the germination-time of spores. The formalin concentration could be adjusted so as to affect the germination-time of almost all spores in a suspension without reducing viability. The effect on germination was not abolished by thorough washing or treatment with sodium sulphite. The spores of four different strains of A. fumigatus and of cultures aged 3 to 14 days reacted similarly to formalin treatment. Although of greatly reduced virulence for mice, affected viable spores were still capable of producing infection and death following intravenous inoculation, provided they were not eliminated by the host before germination occurred.

Skin reactions have been produced in normal subjects by the injection of highly purified influenza A and B viruses. The reactions reached a maximum at 24–48 hr. and the histological pattern was compatible with a delayed hypersensitivity reaction. There was no close relation between skin test results and circulating antibodies. Twenty-seven subjects were challenged intranasally with attenuated influenza A (H3N2): 5 of 14 skin-test-negative subjects were infected, but none of 13 skin-test-positive subjects.

Airborne bacteria surveys in nuclear submarines show that the total microbial load was maintained at satisfactorily low levels during prolonged patrols despite factors which were expected to increase this form of pollution.

The isolation rates of Staphylococcus aureus and Neisseria meningitidis from nasal and nasopharyngeal swabs respectively, together with the serum antibody titres to Mycoplasma pneumoniae, before and after patrols suggested that the transmission of these organisms between individuals was not much increased by patrol conditions. The finding of higher numbers of airborne gram-negative rods and bodily contamination by enterobacteria is frequently reported in submersibles but does not appear to cause major outbreaks of illness in nuclear submarine crews.

Of 173 epidemiologically unrelated strains of Escherichia coli isolated from the pericardial sac of chickens that had died from infection with these organisms in England in 1972, approximately 1 year after the introduction of legislation forbidding the routine use of feeds containing ‘therapeutic’ antibiotics, 83·8% were resistant to sulphonamides, 31·2 % to tetracyclines, 20·8% to furazolidone, 18·5% to streptomycin, 2·9% to spectinomycin and 1·2% to ampicillin; none of the strains were resistant to chloramphenicol, neomycin, polymixin, trimethoprim or nalidixic acid. The sulphonamide resistance and possibly some of the resistance to other agents might have been the consequence of sulphonamides being exempted from the legislation. Much of the resistance, with the exception of that to furazolidone, was of the transferable type. Many strains possessed transfer factors in the absence of any known transferable characteristic. Colicine production was twice as common in the pathogenic strains as in a collection of strains isolated from the faeces of healthy chickens; about half of it was transferable.

By means of serology, antibiotic resistance and other markers, it was found that several different kinds of E. coli were usually incriminated in any one outbreak of E. coli infection in broiler chickens. Sometimes the same kinds of E. coli were found in outbreaks in consecutive crops of chickens on the same farm. New kinds, too, appeared to be brought in by replacement chickens.

Lactose tryptone ricinoleate broth (0·3% lactose, 2% Oxoid tryptone, 0·1% Na ricinoleate; pH 7·1) was found to be as good as the currently recommended combination of lactose ricinoleate broth and tryptone water for the detection of Escherichia coli in the positive tubes of presumptive coliform counts.

The dispersal of Staphylococcus aureus from burned patients, the relation between nasal carriage by the staff and exposure to airborne Staph. aureus, and the transfer of Staph. aureus-carrying particles within the ward have been studied. The dispersal of Staph. aureus from burned patients was correlated to the size of the burn wound. The median values varied from 21 c.f.u./m.2/hr. for patients with small burns to 453 c.f.u./m.2/hr. for extensively burned patients. The size of the dispersed particles appeared to be smaller than that usually found in hospital wards. Carriage of nasal strains by the staff was correlated to the air counts; the number of patient sources did not seem to be of great importance. The transfer of Staph. aureus within the ward was at least 6 to 20 times that which would have been expected if transfer was due to air movement only.

The contamination of gowns and uniforms worn in a burns unit and the transfer of patient's staphylococci by means of nurses' uniforms was investigated. The median values of staphylococci found on gowns and jackets worn during a routine nursing procedure were 3·0 × 104 and 1·4 × 103 respectively. From the results of model nursing experiments it appeared as if the fraction of staphylococci transferred from a patient's room to the air in a receiving room was 4 to 10 times less when protective gowns were worn than when no gowns were worn. The corresponding transfer directly to the model ‘patient’ was 100 times less. The protection afforded by a gown seemed mainly to be due to protection against contamination of the uniform worn underneath when nursing a burned patient. The discrepancy between the transfer of an airborne particle tracer and Staph. aurats-carrying particles earlier found in the ward could be explained by the dispersal of Staph. aureus from nurses' clothing.

Forty-five samples of unsliced, cooked, ready-to-eat meats on sale in retail premises and supermarkets were examined. Thirty-six (80%) had Escherichia coli I and 21 (47%) had coagulase positive staphylococci in numbers ranging from 1 to > 1000/100 cm.2. Twenty-one samples contained Clostridium spp. in numbers from 1 to > 100/100cm.2. Of the 45 samples tested, 11 (factory-produced) and 7 (home-produced) were examined after cooking but before being offered for sale. Cooked hams were contaminated after handling in a factory, as were samples of canned corned beef after sale and exposure for 24 hr. Some sources of contamination were: (a) raw beef, (b) factory and shop surfaces and equipment, and (c) workers' hands. Curing brines used in retail shops and supermarkets to produce corned beef were a potent source of contamination. The effect of holding cooked meats at ambient temperature on their spoilage (22° C) and food-poisoning (37° C) microflora was demonstrated.

In the villages of Fiji, apart from Viti Levu, rubella is a disease occurring solely in widely spaced epidemics. Some villages may not be infected for over 20 years and will then contain substantial numbers of susceptible women of child-bearing age.

Evidence is produced that haemagglutination-inhibiting (H.I.) antibody to rubella is very long lasting in Fijians. The infectivity of the virus is discussed and it is suggested that, on the average, 50% of susceptibles are infected in a Fijian village during a rubella epidemic, but there are large variations.