Arginine has been shown to be essential for the replication of several orthopoxviruses in mouse sarcoma 180 cells and in chick embryo fibroblast cultures. Both host systems are characterized by their inabilities to utilize citrulline for the biosynthesis of arginine due to deficiencies in the requisite cellular enzymes and cell multiplication is absolutely dependent on the availability of exogenous arginine. Virus replication in such cells maintained with citrulline results from the induction of virus-specific enzymes. Significant virus yields in the absence of exogenous arginine or citrulline can arise from the replenishment of intracellular amino acid pools by increased utilization of arginyl residues in cellular proteins. The extent of the phenotypic expression of these characters in infected cells permitted significant discrimination between the viruses examined. Distinctions could be drawn between rabbitpox, ectromelia, cowpox, buffalopox and vaccinia strains. However, cowpox could not be distinguished from other viruses isolated from diseased animals in European zoos.

Hepatitis B core antigen (HBcAg) synthesised in Escherichia coli by recombinant DNA techniques was compared with HBcAg prepared from infected livrer tissue. The two antigens were used in radioimmunoassays (RIA) to detect antibody to HBcAg (anti-HBc) in sera from patients attending a clinic for sexually transmitted diseases. Out of 2151 sera tested, 260 were anti-HBc positive with both HBcAg preparations but seven were positive with the liver-derived antigen alone. Reasons for these discrepant results are discussed. The slight loss of sensitivity of the anti-HBc RIA using E. coli HBcAg was not considered significant when compared with the potential advantages of a synthetic antigen.

The presence of other hepatitis B markers in the 267 anti-HBc positive sera was determined: 25 contained HBsAg, 220 anti-HBs and, of the 22 that were HBsAg/anti-HBs negative, 12 contained anti-HBe. In the 10 remaining sera, anti-HBc was the only hepatitis B marker that could be found.

The co-transfer of plasmid-borne genes governing resistance to gentamicin, tetracycline, erythromycin and chloramphenicol has been demonstrated on human and mouse skin. Two different gentamicin resistance plasmids have been studied in detail; both appear to have the ability to mobilize in vivo otherwise non-transferable resistance plasmids from coagulase-negative to coagulase-positive staphylococci. This emphasises the role of the skin in maintaining a pool of resistance genes available to pathogenic staphylococci.

The course of experimental infection in groups of 6-month-old castrated lambs with field isolates of Mycoplasma agalactiae from France was followed culturally and serologically for 7 months. Infection with an ovine field isolate following inoculation by different routes and contact exposure was compared with that caused similarly by a caprine field isolate. The prolonged infections produced were symptomless apart from limited arthritis in one animal inoculated with the isolate from sheep and increased lachrymation in another associated with the goat isolate. The ovine isolate was more virulent in that ante- and post-mortem recoveries of the organism were more consistent and the serological responses more pronounced. Serological responses varied between animals and between strain infections, and the results of the film inhibition test were more consistent than those of the complement fixation test. The limitations of both these tests for detecting carrier infections are discussed.

An epidemic caused by Serratia marcescens that involved 26 infants admitted to the Neonatal Intensive Care Unit (NICU) and 82 infants admitted to the Nursery of the 2nd Medical School of Naples is reported. Two different biotypes of S. marcescens with two completely different epidemiological patterns were identified. The prevalent biotype (A8b trigonelline –) was isolated in the delivery room, in the operating room, in the Nursery and in the NICU from items, healthy infant excreters and affected infants; the second biotype (A3a) was isolated only in the NICU from staff, two healthy infant excreters and two affected infants. Colonization of the throat and the gastrointestinal tract was frequent. Infected and colonized infants were the most important reservoir for serratia in the Nursery and in the NICU particularly for the type strain A3a. A mucus aspiration apparatus contaminated in the delivery room and the contamination of several instruments and items probably had a major role in the initiation and maintenance of the spread of the A8b strain. Mass contamination of the nursery has been related to overcrowding and a lack of the control measures; the transfer of high-risk colonized infants caused spread in the NICU.

In the NICU the attack rate was 26%; 69% of infants became ill; the case fatality ratio was 19%. Epidemiological investigation of the infants at risk showed some factors predisposing to infection with serratia. The hygienic measures failed to control the spread of serratia and it was necessary to refuse new admissions to pregnant women in order to decontaminate and re-organize the wards.

Since 1973 epidemiological surveillance of laboratory-confirmed hepatitis B virus infection has been undertaken in Scotland. During the ten-year period, 1973–82, 2893 persons with laboratory evidence of infection were reported and the number increased by almost threefold between the beginning and the end of this time. Males accounted for 66 % of the patients and intravenous drug abuse was the most commonly encountered risk factor. The low risk to laboratory staff is confirmed, but among National Health Service hospital staff nurses accounted for 54% of those reported.

In vivo methods were used to study the F38-type mycoplasma in parallel with related mycoplasmas.

Three of five strains of ‘bovine serogroup 7’ with an unknown history of subculture produced mycoplasmaemia in mice inoculated intraperitoneally. A strain of ‘bovine serogroup L’ also produced mycoplasmaemia, but no evidence of similar ability could be found for single strains of Mycoplasma capricolum, M. equigenitalium and M. primatum, or for two strains of the F38-type mycoplasma.

In cross-immunization tests a bovine serogroup 7 strain (NCTC 10133) and a strain (‘Blenheim’) of the SC (small colony) type of M. mycoides subsp. mycoides were used for the purpose of challenge. Cross-protection was described as ‘complete’ or ‘partial’, depending on whether it was as great as, or less than, that produced by homologous vaccine. Although strain NCTC 10133 protected strongly, possibly completely, against Blenheim, and Blenheim gave partial protection against NCTC 10133, challenge with NCTC 10133 and Blenheim gave strikingly different results. Thus (1) F38-type strains, M equigenitalium and M. primatum all gave partial cross-protection against NCTC 10133 but not against Blenheim, (2) NCTC 10133, unlike Blenheim, was seldom susceptible to partial cross-protection by LC (large colony) strains of M. mycoides subsp. mycoides, and (3) three SC strains – which would have protected completely against Blenheim – protected only partially against NCTC 10133. NCTC 10133 and Blenheim were similar, however, in that M. capricolum and M. mycoides subsp. capri failed to cross-protect against them both.

A Salmonella agona strain has caused a hospital outbreak of gastroenteritis in a pediatric unit in Rio de Janeiro. It bears two plasmids, a small (6·5 MDa molecular weight) plasmid coding for type B colicin production and a larger one (36 MDa molecular weight) determining resistance to ampicillin, gentamicin, kanamycin and trimethoprim-sulphamethoxazole. The R-plasmid, but not the Col-plasmid, is self-transferable to a Escherichia coli recipient strain. Curing for the R-plasmid was achieved by treatment with 0·05 % SDS followed by incubation at 44°C. It has not been possible to cure the S. agona strain for its Col-plasmid.

The survival and growth of toxigenic Vibrio cholerae 01 in water under various conditions of salinity, pH, temperature and cation composition and concentration were studied in an extensive series of laboratory experiments. Inter- and intra-strain variation in stress response (of 01 and non-01 strains) and the ability of V. cholerae to adapt to stressful environments were also studied. Toxigenic V. cholerae 01 were able to survive for at least 70 days at 25 °C in solutions of sea salt. The optimal salt concentration was 2·0% though all solutions in the range 0·25–3·0% gave good support. Substrains with enhanced capacity to persist at sub-optimal salinity (0·1%) were demonstrated. A great degree of inter-strain variation in stress response at low salinity (0·05%) was found among 59 strains, and this variation was unrelated to serogroup (01 or non-01), source (clinical or environmental) or country of origin (Tanzania or Bangladesh). At optimal salinity, inter-strain variation was less and 18 out of 20 strains remained viable at high concentrations for at least 40 months at 25 °C. V. cholerae 01 could not survive beyond 45 days at 4 °C and optimal salinity, either with or without nutrients. The optimal pH range for survival at 25 °C was 7·0–8·5 at optimal salinity, and 7·5–9·0 at low salinity. V. cholerae 01 require Na+ for survival in the absence of nutrients, and for enhanced growth in their presence. The presence of Ca2+ or Mg2+, in addition to Na+, further enhanced survival. These, and other results reported in this paper, suggest that toxigenic V. cholerae 01 are able to survive for extended periods in warm water containing no nutrients but having a salinity of 0·25–3·0% and a pH of around 8·0. With added nutrients and under the same conditions, rapid growth is possible. The implications of these findings for the identification of putative aquatic reservoirs of V. cholerae 01, and for the epidemiology of cholera, are considerable.

The RNA genome of rotaviruses consists of 11 segments in four size-classes which can be separated by polyacrylamide gel electrophoresis, although 11 separate bands are not shown by all strains. We propose a cryptogram (Rotacode) based on the relative distance of migration of adjacent bands in each size-class for coding the typical pattern of each strain of virus. This provides a shorthand for recording details of each strain and for grouping electrophoretically similar strains.

Rotacode was found to be reliable and reproducible, with identical codes being obtained for the same samples in repeated experiments under code and by various observers. Rotacode was also used to analyse 189 strains obtained over a three-year period and differentiated 13 electrophoretypes. This confirms the considerable electrophoretic variability of wild strains.

An inactivated vaccine against respiratory syncytial virus (RSV) was compared with two live vaccines. The inactivated (GC) vaccine consisted of glutaraldehyde-fixed bovine nasal mucosa cells persistently infected with RSV and emulsified with oil adjuvant. The live vaccines were a modified virus (MV) derived from a bovine strain of RSV and a temperature-sensitive mutant (ts-1) derived from a human strain. The GC vaccine was inoculated subcutaneously into 12 calves and the live vaccines intramuscularly into eight calves each. Nine unvaccinated calves acted as controls. The vaccines were administered in two doses 3 weeks apart and all calves were challenged intranasally with 2 × 107 p.f.u. of bovine RSV 3 weeks after the second dose.

At the time of challenge calves given GC, MV and ts-1 vaccines had mean serum neutralizing antibody titres of 25, 19 and 2 respectively; mean titres of IgG1 antibody by radioimmunoassay were log10 4·5, 1·3 and 2·6 respectively and mean zone areas by single radial haemolysis (SRH) were 107, 27 and 36 mm2 respectively.

Eleven of 12 calves given GC vaccine were completely protected against challenge but all control animals and those given the two live vaccines were infected. The mean peak titre of virus in nasal swabs of control calves was 3.0 log10 p.f.u./ml and the mean duration of virus shedding was 6·8 days. Both these parameters were significantly reduced in animals given MV and ts-1 vaccines: mean peak titres were 2·1 and 2·4 log10 p.f.u./ml and mean duration of shedding was 3·4 and 3·3 days respectively.

Thus, protection correlated better with RSV antibody detected by radio-immunoassay and SRH than with neutralizing antibody. These results are discussed in relation to the possible mechanism by which protection was mediated.

Erythema infectiosum (EI) or fifth disease is a mild, acute exanthematous disease, occurring mainly among children, for which a causative virus has long been sought. In May 1983 an outbreak of exanthematous illness was reported in a primary school in North London. Children attending the school were investigated by questionnaire and 162 (43·9%) reported an illness with the features of EI. In each of 36 cases investigated virologically the illness was associated with parvovirus infection. Moreoever, pre-existing antibody to parvovirus was correlated with protection from EI in 16 of 17 close family contacts of cases. We propose therefore that EI is the common manifestation of infection with the human parvovirus.

In a series of 519 intravenous cannulae with valved injection side-ports the incidence of cannula-related local inflammation was 25·2% and bacteraemia 0·2%. Severe local inflammation was associated with a longer mean duration of cannulation, 59·4 v. 81·4 h (P = <0·05). There was no significant association between the presence of local inflammation and microbial colonization of either the intravascular segment of the cannula, the adjacent skin, or the side-port. The data suggest that colonization of the cannulae was usually secondary to prior skin colonization. Side-port colonization did not, predispose to cannula colonization. Organisms colonizing the side-port were biologically different and were possibly derived from the skin of medical attendants. In the final 157 patients, randomized to receive either isopropyl alcohol or 0·5% chlorhexidine in 70% spirit skin preparation, there was no difference in the incidence of either local inflammation or microbial colonization.

Observations on the circulation of influenza viruses in Northern Greece during the winters of 1972/3 to 1982/3 are presented.

Influenza A viruses were detected every winter with the exception of those of 1973/4 and 1981/2, when neither type A nor type B was isolated. The strains of type A isolated during the study period were similar to those circulating world-wide over the same time scale.

Influenza B viruses were isolated only during the winters of 1972/3 and 1979/80; influenza A viruses were also circulating in the community at those times. The B strains detected were similar to those recorded world-wide during the period of study.

One hundred and eighteen herpes simplex virus isolates were typed in a diagnostic virology laboratory using their standard procedure by pock size on the chorioallantoic membranes (CAMs) of fertile hen's eggs. Forty-three were typed as type 1 and 75 as type 2. The isolates were then sent to a research laboratory in which they were typed blind, with or without subsequent passage in tissue culture, by neutralization with type-specific antisera. Discrepant results were found with only two isolates. The isolates were then typed by the more time-consuming but unambiguous method of restriction endonuclease analysis of their DNAs. Typing by this method confirmed the typing by neutralization and established that typing by pock size on CAMs was correct in about 98% of cases.

Operating in ultraclean air and the prophylactic use of antibiotics have been found to reduce the incidence of joint sepsis confirmed at re-operation, after total hip or knee-joint replacement. The reduction was about 2-fold when operations were done in ultraclean air, 4·5-fold when body-exhaust suits also were worn, and about 3- to 4-fold when antibiotics had been given prophylactically. The effects of ultraclean air and antibiotics were additive. Wound sepsis recognized during post-operative hospital stay was, however, reduced by these measures only when it had been classed as major wound sepsis. This was reported after 2·3% of operations done without antibiotic cover in conventionally ventilated operating rooms.

Joint sepsis was much more frequent after wound infection and especially after major wound sepsis, although most cases of joint sepsis were not preceded by recognized wound sepsis. This was particularly noticeable after major wound sepsis associated with Staphylococcus aureus; after 37 such infections the same species was subsequently found in the septic joint of 11 patients. The sources of wound colonization with Staph. aureus, when this was not followed by joint sepsis, appeared to differ widely from those where joint sepsis occurred later. Operating-room sources could bo found for most of the latter and the risk of infection appeared to be similar with respect to any carrier in the operating room whether a member of the operating team or tho patient. For wound colonization that was not followed by joint sepsis, operating-room sources could only be inferred for fewer than half and of these more than one half appeared to be related to strains carried by the patient at the time of operation.

During tho follow-up period, which averaged about 2¼ years with a maximum of four years, there were, in addition to the 86 instances of deep joint sepsis confirmed at re-operation, 85 instances in which sepsis in the joint was suspected during this period but was not confirmed, because re-operation on the joint was not done. The incidence of suspected joint sepsis was, like that of confirmed joint sepsis, less after operations done in ultraclean air: 1/2·5, or with prophylactic antibiotics, 1/2·3

Although re-operation was more frequent on tho knee-joint than on the hip, and pain after the initial operation was more frequent after knee operations, there was no evidence that this was the result of any increased risk of infection.

There was some indication of an increased risk of joint sepsis and of major wound sepsis, after operations on patients with rheumatoid arthritis compared with other diagnoses. The increase could have been as much as twofold but, because of the small numbers involved, the statistical limitations of the study render these differences only marginally significant.

When wound washout samples had been obtained from the surgical wound after the insertion of the prosthesis the risk of subsequent joint sepsis was found to be considerably greater for those patients from whose wounds larger numbers of bateria were isolated than from those of other patients at the same hospital.

The Kermack & McKendrick theory of epidemics has been applied to data on deaths from influenza and influenzal pneumonia in Greater London in the years 1950–78. As a whole the theory gives a good description of the data, and the estimated values of the parameters can be plausibly related to the natural history of the disease. However, the possibility exists that the agreement is merely empirical, and field studies would be required to confirm its validity.

Hepatitis A is an acute inflammation of the liver caused by a virus (HAV) whose morphology and physical characteristics resemble members of the enterovirus group. The disease, which is characterized by fever, malaise, anorexia, nausea, abdominal discomfort and jaundice has an average incubation period of 28–30 days and is spread from person to person by the faecal-oral route. Common-vehicle outbreaks have been reported following contamination of food or water and epidemics may occur in closed communities (institutions, day-care centres) or in the general community when there is a breakdown of environmental sanitation. Many infections, especially in children, are subclinical; the case fatility rate for patients requiring hospitalization is low and long-term sequelae are unknown.

Milk samples from 251 nursing mothers were screened for enterotoxigenic staphylococci. The incidence of staphylococci in milk samples was 71·3%. Two hundred and sixteen strains were isolated from 179 mothers. Eighty-six (39·8%) of the 216 strains were found to be toxigenic. Enterotoxin type A (SEA) predominated, with 41 strains (19·0%) elaborating it. Twenty-one strains (9·7%) produced enterotoxin B (SEB) while only eight (3·7%) produced enterotoxin C (SEC). Ten strains (4·6 %) produced all three types. Enterotoxigenic strains usually produced coagulase, thermonuclease and alpha haemolysin.

In this series breast-feeding alone was more common than combined breast and bottle feeding, especially among mothers less than 30 years old. The incidence of reported infantile diarrhoea decreased with increasing age of the mother. Of 16 babies with diarrhoea, 10 (62·5%) had mothers whose milk yielded staphylococci. Six of these were toxigenic. Although no direct relationship between enterotoxigenic staphylococci in the milk of nursing mothers and infantile diarrhoea could be demonstrated, these findings reveal a potential health risk to these infants.

Swabs of rectal faeces were obtained daily for 28 days from 90 calves reared in five batches during the summer of 1983. The calves were purchased unweaned in markets and fed a milk-substitute diet. Salmonella typhimurium phage type DT204c was isolated from calves in four batches and Salmonella newport from one. When the data from the 90 calves were considered together the incidence of salmonellas, excretion rose to peak between 5 and 7 days after purchase before declining to low levels during the fourth week. Salmonella was isolated from 55 (61%) calves; 30 were positive on up to four occasions while 21 and 4 animals respectively were positive between 5 and 11 and 15 and 20 times. In the majority of animals infection was probably subclinical since treatment with antibacterial drugs and excretion of S. typhimurium coincided in four calves only.