Dilution had an adverse effect on the infectivity of 24 h cultures of a strain of Fusobacterium necrophorum, which became apparent at or near the minimum lethal dose. Thus in mice inoculated subcutaneously the mortality produced by 0·01 ml of undiluted culture was almost invariably greater than that produced by 0·1 ml of a 1 in 10 dilution. The explanation appeared to lie in the increased physical separation of bacterial cells that was the inevitable consequence of dilution.

The bacterial status of beef carcasses at a commercial abattoir was monitored before and after slaughterline automation. Bacterial counts did not differ significantly overall (P>0·05) between the original manual line and the automated line for either morning or afternoon slaughter. On the manual line counts in the morning were lower than those from carcasses slaughtered in the afternoon, but on the automated line there was no difference between morning and afternoon counts. Due to highly significant line × sample site interaction for both morning and afternoon counts, overall differences among sample sites were not found by analysis of variance. However, principal components analysis revealed a significant shift in bacterial contamination among some sites due to slaughterline changes. The incidence of Enterobacteriaceae increased marginally following automation.

Quantitative bacterial counts, concentrations of bile acids and bacterial enzyme profiles were measured in faecal samples from three tribal groups with distinctive dietary patterns in a rural area of northern Nigeria. Samples were obtained from Maguzawa (with a predominantly cereal diet), Hausa (cereal with regular meat consumption) and Fulani (cereal with frequent consumption of cows' milk). Numbers of bacteroides, clostridia and concentrations of bile acids were lower in the Maguzawa than the other dietary groups but these differences were not statistically significant. Bacterial enzyme profiles in each group were similar. The results are discussed with respect to possible influences of diet on the human intestinal microflora.

DNA restriction endonuclease analysis was used for intra-specific typing of Mycobacterium bovis isolates from 83 brush-tailed possums (Trichosurus vulpecula) obtained between 1982 and 1984 from the three major regions in New Zealand with endemic bovine tuberculosis. All the isolates were found to be genetically very similar. Differentiation of the isolates into 33 restriction types was achieved by using high-resolution electrophoresis and the combined results from separate digestions with the restriction enzymes Bst EII, Pvu II and Bcl I. The typing system was entirely reproducible. Isolates of the same type were usually found in adjacent localities and were always limited to one of the three major regions. In some cases, isolates of the same type were found in both 1982 and 1984. The phenotypic significance of the small genetic differences identified between different isolates is unknown. The typing system will be useful for monitoring the transmission of M. bovis to other species and the future spread of different M. bovis types through possum populations.

Young adult mice were inoculated intravenously with strains JB or Peter C of Mycoplasma pulmonis. A few were inoculated intranasally with strain JB. This strain but not Peter C was isolated for 50 days or more from the urines of more than half of the mice. Those of strains TO, C3H and CBA, but not CFLP, were susceptible. Recovery of mycoplasmas was intermittent and sometimes the numbers isolated varied within individual mice and between mice of a particular strain, ranging from 5 × 101 to <5 × 107 colour-changing units/ml. Fifty serial passes of M. pulmonis, strain JB, in mycoplasmal medium resulted in attenuation, the organisms after inoculation of TO mice not being recovered from the urine and excretion not being stimulated by treating the mice with progesterone. At autopsy, the organisms of early passage were usually but not invariably isolated from the kidneys of mice that had been urinary excretors. About half of the latter had no renal histopathological changes. The others had usually minimal renal perivascular lymphocytic infiltrates but occasionally more widespread inflammatory changes. The findings may have relevance to the spread of mycoplasmal infection within mouse colonies and suggest that an association between such infection and nephritis in other species, including man, should be sought more closely.

An outbreak of staphylococcal food poisoning in Europe caused by contaminated lasagne was detected and monitored by both national and international surveillance systems. The common source was a pasta-producing factory in Italy and high levels of Staphylococcus aureus were detected in packets of dried lasagne distributed in Luxembourg, the UK, France and Italy. Forty-seven cases were reported in the UK. Outbreaks of staphylococcal food poisoning attributed to mishandling during the food processing stage are uncommon and pasta as the food vehicle is rare. Prompt recognition of the outbreak and rapid identification of the food vehicle enabled most of the consignment to be withdrawn from the market.

Methicillin-resistant Staphylococcus aureus (MRSA)strains present an increasing clinical problem. Analysis of 2679 strains submitted to a reference laboratory in the first quarter of 1983 and 3050 strains submitted in summer 1984 showed 479 and 593 multi-resistant strains. The proportion of methicillin-resistant strains classified as epidemic rose from 5·9 to 10·2%. Other methicillin-resistant strains continued to occur but other methicillin-sensitive multi-resistant strains appeared to fall. A strain with defined characters could be recognized in the Thames regions.

A total of 6593 serum samples from birds, received for diagnostic testing or surveys between 1974 and 1983, were titrated by direct complement fixation (CF) test against Chlamydia psittaciantigen. The percentage of positive reactions found was variable for domestic poultry, ranging from 1·5 in chickens to 22·2 in geese, and was highest in pigeons Columba livia (47·3) and collared doves Streptopelia decaocto (51·4). A moderate incidence was found for game birds (29·0), wild ducks (23·3) and imported birds of the order Psittaciformes (15·9). The highest titres were found in pigeons, collared doves and psittacines, confirming that infection is both frequent and active in these birds in Britain. Results of isolation of chlamydia from similar sources will be reported subsequently.

Natural water sources used as drinking-water supplies by rural settlements in Sierra Leone were examined monthly over a one-year period to detect any seasonal variations in bacterial quality. The 37 °C colony count, levels of selected faecal indicator bacteria and the incidence of Salmonella spp. were monitored. A seasonality was demonstrated for all the variables, counts generally increasing with the progression of the dry season, culminating in peaks at the transition from dry to wet season. Some complications with respect to the interpretation of counts of faecal indicator bacteria from raw tropical waters are noted.

The cellular fatty acid composition of 41 strains of suspected Campylobacter jejuni, 23 from human cases of gastroenteritis and 18 from animals, was examined by gas-liquid chromatography. Three of the 23 human isolates and 2 of 18 animal isolates did not contain 19:0 cyclopropane fatty acid and were identified as C. laridis. The remaining 36 strains had cellular fatty acid profiles consistent with C. jejuni but could be divided into three groups on the ratio of the concentration of 18:1 and 19:0 eycloproprane. Most human isolates (85%) were in groups II or III whereas most animal isolates (56%) were in group I. It is proposed that gas-liquid chromatographic analysis of cellular fatty acids is a relatively easy method for epidemiological typing of C. jejuni isolates.

In developing countries tuberculous meningitis is a difficult infection to differentiate from other central nervous system (CNS) infections. This paper presents the history, physical findings, laboratory data, and clinical course of 100 patients who were admitted to a special ward and had CSF cultures positive for Mycobacterium tuberculosis. Fifty-four patients were comatose when admitted and 76 had meningeal signs. Mean admission CSF values were WBC 531, glucose 23 mg/dl, and protein 166 mg/dl. Only two CSF AFB smears were positive. Sixty-one percent of the chest X-rays taken were consistent with pulmonary tuberculous and 39% were normal. Twenty-four patients died within the first week after admission, before the clinical diagnosis was made and anti-tuberculous therapy could be started. Fifty-three of 76 patients given antituberculous therapy died. Neurologic sequelae developed in 48% of the survivors. The high mortality and morbidity rates in this patient-group were due to the severity of illness on admission and the predominance of children (54%).

A total of 1531 diagnostic submissions from birds were examined by culture for the presence of Chlamydia psittaci between June 1976 and December 1984 by growth in NCTC 929 clone L mouse fibroblast cells, pretreated with an inhibitor of cell division, followed by direct immunofluorescence microscopy. Of these, 196 were found positive. The continued importance of psittacine birds as potential sources of infection was shown by the high number of positives (139) obtained from birds of that order. The percentage of submissions found positive was highest in parakeets (30·1) and was fairly high in psittacines as a group (16·6), but the latter figure was exceeded by the group ofcollared doves (Streptopelia decaocto) and wood pigeons (Columba palumbus) (25·0). Domestic poultry generally gave low rates, turkeys being the highest.

Both the numbers of submissions and their rates of positives increased between 1980 and 1984.

Comparing the isolation rates from the various organs sampled, the intestines gave the highest rate (20·4 per cent positive), closely followed by the other internal sites. The superficial swabbed sites (eye, nasal cavity, cloaca) gave lower rates.

Duplicate specimens were taken with cotton-wool swabs from the upper tarsal conjunctiva of 63 patients living in Gambian villages in which trachoma is endemic and from 34 infants with ophthalmia neonatorum (ON) attending an outpatient clinic in The Gambia. The detection of Chlamydia trachomatis by direct immunofluorescence (IF) using a conjugated monoclonal antibody to its principal outer membrane protein was compared with isolation in cycloheximide-treated McCoy cells. For trachoma, the sensitivity and specificity of the immunofluorescent technique were 62% and 100% respectively if ten elementary bodies (EBs) was taken as the minimum requirement for positivity by IF. If all cases with one or more EB were considered positive, the sensitivity was 81% and the specificity 85%. For ON the sensitivity and specificity were 100% and 95% respectively, regardless of which criterion was used. In view of its simplicity and easy applicability to field conditions it seems likely that direct IF using monoclonal antibodies may be a useful technique for the detection of C. trachomatis in the conjunctival epithelium of patients with trachoma.

The eradication of smallpox was achieved by surveillance and containment vaccination after the failure of mass immunization campaigns. The reasons for this failure are considered in this paper. Comparison of population densities in the Indian subcontinent and Africa show that in highly populated areas even an 80% vaccine coverage will still leave a density of susceptibles high enough to maintain the disease, a finding with important implications for other vaccine campaigns.

Two hundred and fifty clinical strains of Candida albicans and six isolates from a cross-infection outbreak were studied for their ability to assimilate 19 carbohydrates in the API-20C system (API Laboratory Products Ltd., Basingstoke, UK). The assimilation profiles were stable on repeat testing; at intervals in the 72 h duration of the test; and when incubated at different temperatures.

Although not a complete system of biotyping, the API-20C system shows high typability, and fair reproducibility and discrimination, having a limited role in indicating which isolates should be typed by more elaborate methods.

Water samples from home filters in nine residential areas of a Nigerian university community were studied. The membrane filter technique was used to determine the total coliform and faecal coliform counts/100 ml of water. Most of the 100 samples studied were grossly contaminated with total coliform counts/100 ml ranging from 0–442, faecal coliform counts/100 ml, 0–216 and the total aerobic plate count per millilitre ranged from 3·0 × 103 to 1·9 × 109 c.f.u. The source (dams) of water, fitness of filter candles, frequency of cleaning candles and pH of water did not significantly (P > 0·05; X2) affect the microbial quality of either filtered boiled or unboiled tap water.

Escherichia coli type I was isolated from 17·9% of the faccal coliforms tested but from only 2·3% of total coliforms. Enterobacter aerogenes was most predominant (38·5%) amongst faecal coliforms isolated while Enterobacter cloacae was the most frequent (37·2%) of the total coliform isolates.

The gross contamination of filltered water from all households sampled calls fpr am englightenment of residents on the proper use of home water filters.

The anticoagulant rodenticide flocoumafen was tested against warfarin-resistant Norway rats (Rattus norvegicus Berk.) infesting farm buildings. Complete control was obtained in 10–21 days (mean 14·2 days) in six treatments in which baits poisoned with 0·005% flocoumafen were maintained, in surplus, until rats ceased to feed from them. A further six treatments, in which the application of poisoned bait was restricted to periodic placements of 50 g, were also completely successful in 15–30 days (mean 21·0 days). Less poisoned bait was used in the restricted flocoumafen treatments than in the unrestricted treatments but the time taken to control the rat infestations was significantly longer.

An outbreak of cryptosporidiosis in a circumscribed semi-rural population is described; some cases were infected concurrently with campylobacter. The results of a detailed case-control study and environmental surveillance are discussed.

The sera of healthy blood donors from the Wellington area of New Zealand, collected between 1976 and 1980, were analysed by the complement fixation test for antibody to Mycoplasma pneumoniae. A high prevalence of antibody to this organism was demonstrated and the occurrence of an M. pneumoniae epidemic in New Zealand within the survey period was shown to be reflected i the immune status of this healthy adult population. This would suggest that during an epidemic many people within the Wellington community may have M. pneumoniae infections involving littl overt illness.

A two-year prospective survey of patients with diarrhoea at a children's hospital detected 65 cases of cryptosporidiosis; 56 were index cases representing 1·4% of patients examined. There was a marked seasonal variation with fewer index cases in July–September (0·4–0·6%) than February–April (3·5%). All four adult cases were contacts of infected children and 21 (32%) of the patients were 12 months old or younger. Cryptosporidium was the fourth commonest diagnosed cause of gastroenteritis, the second most common non-viral cause, was responsible for 7·2% of all cases, and 14·7% of non-viral cases where a cause was identified. As such it should be sought routinely in cases of gastroenteritis in children.