Some recent advances in the subject of bacterial variation and cytology are:

(1) The white race of Bact. coli-mutabile contains lactase, inhibited by some cause unknown (Deere et al. 1939). Deere (1939) suggests that the cells of the white race may be impermeable to lactose while the lactase system is intracellular.

(2) Variation from non-lactose-fermenter to lactose fermenter in Bact. coli-mutabile takes place on lactose only (Stewart, 1942).

(3) The nucleus of Myxococcus xanthus consists of definite chromatin masses. A process resembling karyokinesis and autogamic conjugation precedes spore formation (Beebe, 1941).

(4) The nucleus of vegetative bacterial cells consists of a pair of dumbbell-shaped chromatinic bodies, which split longitudinally before cell division. The dumbbell bodies are comparable to the chromosomes of animals and plants (Robinow, 1942).

(5) Careful plating provides unquestionably pure lines in the coliform group (Stewart, 1942).

The development of the bacterial flora of neonates with congenital abnormalities of the gastro-intestinal tract was studied in 31 infants during the first 10 days of life. Specimens were collected from the umbilicus, mouth and gastro-intestinal tract on the pre-operative day, at operation and on post-operative days 1, 2, 3, 5, 7 and 10. Bacteria were isolated semi-quantitatively on a variety of plain and selective media and identified by conventional methods.

Staphylococcus albus was the predominant species isolated from the umbilicus; it was recovered from 24 of the 31 babies. The viridans group of streptococci and Streptococcus salivarius were the commonest species isolated from the mouth; there were no differences between the babies with different abnormalities and treatment with antibiotics had no effect on the bacterial flora. Ten babies were colonized by each species on the pre-operative day, and 25 and 19 respectively by the tenth post-operative day. Anaerobic gram-positive cocci were the predominant oral anaerobes. Bacteria were not isolated from the rectal swabs of babies with tracheo-oesophageal fistula (TOF) or small bowel atresia on the pre-operative days. Post-operatively the predominant faecal isolates from babies with TOF were Str. faecalis, Escherichia coli and Clostridium perfringens. About 80% of the babies with small bowel atresia were colonized by Str. faecalis and Bacteroides vulgatus, 60% each by E. coli, Klebsiella aerogenes and Str. faecium. The five babies with necrotizing enterocolitis were colonized by Str. faecalis, E. coli, Cl. perfringens and Cl. difficile; Bacteroides spp. were not recovered from any of them. The commonest facultative species recovered from babies with large bowel obstruction were Str. faecalis and E. coli. B. vulgatus, Cl. perfringens and Bifidobacterium spp. were the commonest anaerobes and anaerobes outnumbered aerobes. No significant isolates were recovered from the wound swabs and none of the babies developed post-surgical sepsis.

1. The present inquiry was designed to provide information on the relative frequency of infection in non-pulmonary tuberculosis with the human and bovine type of tubercle bacillus throughout the whole of England. A total of 149 pathologists at 120 collecting centres and 32 bacteriologists at 27 typing centres took part in the scheme. Two questionnaires relating to each patient were used, one to be filled in by the laboratory workers and one by the Tuberculosis Officer or other responsible official.

1. Tubercle bacilli were isolated and typed from 112 patients in Wales. of these strains, 19 or 17·0 % belonged to the bovine and 93 or 83 % to the human type (Table 16).

The theory of assigning an upper limit to the estimate of the degree of contamination of a medium is briefly explained. Tables to save computational labour are presented and their use elucidated by examples.

Contact tracing of persons with meningococcal disease who have travelled on aeroplanes or other multi-passenger transport is not consistent between countries. We searched the literature for clusters of meningococcal disease linked by transient contact on the same plane, train, bus or boat. We found reports of two clusters in children on the same school bus and one in passengers on the same plane. Cases within each of these three clusters were due to strains that were genetically indistinguishable. In the aeroplane cluster the only link between the two cases was through a single travel episode. The onset of illness (2 and 5 days after the flight) is consistent with infection from an unidentified carrier around the time of air travel. In contrast to the established risk of transmission from a case of tuberculosis, it is likely that the risk from a case of meningococcal disease to someone who is not identified as a close contact is exceedingly low. This should be considered in making international recommendations for passenger contact tracing after a case of meningococcal disease on a plane or other multi-passenger transport.

Rubella vaccination histories were taken from 333 young women working in the head office of a retail organization: 29% said they had had vaccine and 47% said they had not. The remainder did not know. Forty-six per cent of those ≤ 25 years old (who should have been offered vaccine at school), and 6% of those > 25 years old, said they had been vaccinated. When screened for immunity to rubella by radial haemolysis (RH) 3% had a low level of antibody (< 15 i.u./ml) and 11% had no antibody. After immunization with Cendevax the specific rubella IgM response was measured by an IgM antibody capture radioimmunassay (MACRIA). It was only detectable in the group without RH antibody, and was present in 26/31 of them. The Ig M response to Cendevax was strongest in specimens taken 20–39 days after immunization, but in 10 out of 11 cases tested was still present at around 71 days. The specific Ig M responses to Cendevax were very similar to those in women given Almevax in an earlier study, when measured in parallel tests.

Taking both vaccines together, specific Ig M was present in 35 out of 36 vaccinees without pre-existing antibody tested between 40 and 77 days post-immunization. Detection of specific IgM by MACRIA would therefore be an effective means of determining susceptibility retrospectively in rubella vaccinees found to be pregnant.

A total of 475 Salmonella strains belonging to 5 serovars, isolated from a pig farm which had been heavily contaminated with Salmonella for the past 2 years were tested for antibiotic susceptibility and detection of R plasmids. Thirty-three Escherichia coli isolates from the same farm were also examined in a similar way.

Out of 475 strains 348 (73·2%) were resistant to one or more antibiotics such as tetracycline (Tc), streptomycin (Sm), sulfadimethoxine (Su), chloramphenicol (Cm) and kanamycin (Km), and 247 (85·2%) out of 290 strains belonging to 3 serovars examined harboured conjugative R plasmids. There was no change in the pattern of drug resistance during this survey nor any variation in the pattern of resistance of R plasmids, whatever the serovar. The antibiogram pattern Tc Sm Su, mainly S. typhimurium, was common among Salmonella strains. Among the transferred resistance patterns, the thermosensitive R plasmids conferring the Te marker detected in this study were Fi-, and belonged to incompatibility group H1, whereas the R plasmids conferring Sm Su resistances which coexisted in the same host were Fi+, and compatible with the reference R plasmids tested. The la plasmid conferring Cm resistance alone was isolated from S. anatum and the FII plasmid conferring Sm Km resistances was also isolated from S. typhimurium. In contrast, the 33 E. coli strains examined were resistant to three or five antibiotics and most of the resistance markers were located on conjugative R plasmids. la plasmids conferring Cm resistance alone or FIT plasmids conferring Cm or Km markers were common in the E. coli strains. H1 and H2 plasmids conferring multiple resistance markers were also found in them. The genetic properties of R plasmids derived from Salmonella or E. coil strains are compared, and the potential spread of R plasmids between strains of Salmonella andE. coli is discussed.

Plasmids present in multiply-resistant salmonella strains including Salmonella typhimurium, S. johannesburg, S. wandsworth, S. derby, S. newport, S. london and S. choleraesuis causing diarrhoea in patients in Queen Mary Hospital in Hong Kong from 1973–82 were studied. In multiply-resistant S. typhimurium, plasmids belonging to groups F1me, H1, or H2 and plasmids encoding trimethoprim-resistance which were compatible with standard plasmids of testable incompatibility groups were detected. In S. johannesburg, both the ASTCKSu- and ASCKSu- resistant strains which were predominant in two consecutive periods of an outbreak were found to harbour the same plasmid which belonged to the incompatibility group F1me. S. wandsworth strains isolated from a hospital outbreak in 1980 harboured an identical R-plasmid belonging to group N. A few strains of the other salmonellae showing resistance to multiple antibiotics were found to harbour R-plasmids belonging to groups H1, H2 and F1me. The only salmonella of the enteric fever group resistant to ampicillin, chloramphenicol and trimethoprim was an S. paratyphi B strain. The resistances were encoded on a plasmid of an unknown incompatibility group. The occurrence and distribution of plasmids in these salmonellae isolated within the 10-year period are discussed.

The following experiments constitute an attempt to follow out in detail the stages by which immunity is established, in the course of a generalised bacterial infection (Pseudotuberculosis of rabbits). Two aspects of immunity are considered, firstly the presence, in the circulating fluids, of specific antibacterial substances, and secondly the power of rapidly producing such substances in answer to the specific stimulus. That is to say, attention is directed, not only to the quantity of specific antibodies present on any day of the disease, but also to the response which the animal can make to various doses of bacterial vaccine. For the immune animal is both more vigorous and more sensitive than the normal, in its reaction to a renewed dose of poison (Wassermann and Citron, 1905). Naturally the facts established with regard to one disease only, cannot be predicated at once of other diseases, in other animals. Still it is hoped that the systematic study of one disease may give some help in coordinating the large but somewhat disjointed mass of clinical observation which is already available.

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.

A retrospective space–time permutation model with non-Euclidean distance criteria was applied within a high-complexity hospital setting to quantitatively explore cluster patterns of 273 patients infected with or colonized by carbapenemase-producing Klebsiella pneumoniae during 4 years. Results were compared to standard nosocomial active-surveillance methods. Two clusters were identified in the period, suggesting that space–time strategies for cluster quantification within confined environments may be useful.

1. A new colicine type (type 15) of Shigella sonnei is described.

2. The epidemiological circumstances associated with its appearance in Edinburgh and Glasgow are summarized.

3. Our indices of reliability as an epidemiological marker are fulfilled by this new type.

The prevalence of anti-retroviral therapy (ART) use over time and the incidence of AIDS in a cohort of HIV-seroconverting injecting drug users (IDUs) were assessed by means of a hospital-based study of IDUs with a well documented date of HIV infection. Use of ART and clinical endpoints were assessed by hospital records. Three calendar periods (before 1992, 1992–6 and 1997–2000) were defined as corresponding to modalities of ART available. Prevalence of ART usage in each calendar period, changes in medication and, hazard of AIDS in patients reaching the same duration of HIV infection at different calendar periods were analysed. In total, 132 IDUs with a median age of 23 years at seroconversion were followed up for 6.8 years (median) (range 0.2–15.7). At the end of the study, 58 patients (44%) had developed AIDS. Before the introduction of highly active anti-retroviral therapy (HAART) 12% of patients were on ART. Starting in 1997, an increasing proportion were receiving HAART with a prevalence of 39.5% by January 2000. Taking 1992–6 as the reference category the relative hazard of AIDS during 1997–2000 was 0.42 (95% CI, 0.1–1.1) (P = 0.09). A 40% penetration of HAART in a cohort of IDUs with known dates of seroconversion resulted in a 58% reduction of the hazard of AIDS.

Sera from healthy Greeks, Liberians and East Africans were tested for dye test and direct agglutinating toxoplasma antibodies. At a titre of 1/16 or more 137/228 Greeks, 84/133 Liberians, 2/13 Bondei infants, 3/7 Bondei adults, 3/9 Masai infants and 20/43 Baganda adults gave a dye test positive result. This confirms the wide-spread occurrence of this infection.

A bacteriological study was carried out on the first Leisure Centre swimming pools in the United Kingdom to be disinfected with ozone/chlorine. Results suggested that a free chlorine concentration of approximately 0·8 mg/l was necessary to maintain the pools in a bacteriologically satisfactory condition. This amount of free chlorine was similar to that required when the pool was disinfected with chlorine alone. However, the associated amount of combined chlorine was much lower when disinfection was by ozone/chlorine and this gave more acceptable bathing conditions. Implications for the management of pools disinfected by this method are discussed.

Bank voles (Clethrionomys glareolus) serve as the reservoir for Puumala (PUU) virus, the aetiologic agent of nephropathia epidemica. The animals are believed to be persistently infected and the occurrence of serum antibodies is usually taken as an evidence of active infection. We found serum antibodies to PUU virus in 42 of 299 wild bank voles captured in a PUU virus endemic area. PUU virus RNA was demonstrated in lung specimens of 11 of these 42 animals and in 2 of them antigen was also found. Thus in the lungs of 31 of 42 seropositive animals neither PUU virus RNA nor antigen was detected. In 2 of 257 seronegative animals, lung specimens showed presence of PUU virus antigen and RNA. Isolation of PUU virus from lung tissue was successful in all 4 antigen-positive bank voles but in none of 16 tested antigen-negative animals. In conclusion, only a minority of bank voles with serum antibodies to PUU virus showed evidence of current infection.

A hygienic programme, which has been developed and maintained during several years at a large Swedish university hospital, is presented in detail. The composition and working methods of the Infection Control Committee are described and some economic calculations given. The possible connexion between the hygienic measures and a marked decrease of the incidence of infections is discussed. This decrease did not occur until a satisfactory method for the routine hand disinfection had been introduced, using a commercial antibacterial cleaner containing 3% hexachlorophene.

Comparison of bacterial counts of poultry carcass skin by the cotton swab and alginate swab methods showed no differences between the two sampling methods in total counts and Enterobacteriaceae counts. Also no differences were found in Salmonella isolations.

Dengue fever (DF) has been a growing public-health concern in China since its emergence in Guangdong Province in 1978. Of all the regions that have experienced dengue outbreaks in mainland China, the city of Guangzhou is the most affected. This study aims to investigate the potential risk factors for dengue virus (DENV) transmission in Guangzhou, China, from 2006 to 2014. The impact of risk factors on DENV transmission was qualified by the q-values calculated using a novel spatial-temporal method, the GeoDetector model. Both climatic and socioeconomic factors were considered. The impacts on DF incidence of each single factor and the interaction of two factors were analysed. The results show that the number of days with rainfall of the month before last has the highest determinant power, with a q-value of 0.898 (P < 0.01); the q-values of the other factors related to temperature and precipitation were around 0.38–0.50. Integrating a Pearson correlation analysis, nonlinear associations were found between the DF incidence in Guangzhou and the climatic factors considered. The coupled impact of the different variables considered was enhanced compared with their individual effects. In addition, an increased number of tourists in the city were associated with a high incidence of DF. This study demonstrates that the number of rain days in a month has great influence on the DF incidence of the month after next; the temperature and precipitation have nonlinear impacts on the DF incidence in Guangzhou; both the domestic and overseas tourists coming to the city increase the risk of DENV transmission. These findings are useful in the risk assessment of DENV transmission, to predict DF outbreaks and to implement preventive DF reduction strategies.