Bacteriophage typing of enteric pathogens and staphylococci and its use in epidemiology

Efficacy of one or two doses of Ty21a Salmonella typhi vaccine in enteric-coated capsules in a controlled field trial. Chilean Typhoid Committee

Typhoid fever remains an important public health problem in many areas of the world and an effective, non-reactogenic vaccine would be useful to control this disease. An attenuated Salmonella typhi strain (Ty21a), which has shown promise in previous trials, was evaluated in a controlled field trial in Santiago, Chile. In this trial, 82,543 schoolchildren were randomly assigned to receive one or two doses of Ty21a vaccine in enteric-coated capsules or placebo. The enteric-coated vaccine formulation was well tolerated and practical for mass oral immunization. In the first two years of surveillance, 213 cases of bacteriologically-confirmed typhoid fever were found in schoolchildren participating in the trial; annual rates in the placebo group were 139 and 227 per 100,000. Vaccine efficacy in the first two years after vaccination was 59% for two doses and 29% for one dose; no efficacy was found 3-5 years after vaccination. These results indicate that it will be necessary to identify a vaccine formulation and schedule for Ty21a S. typhi that is practical and provides high level protection for greater than 2 years.

Numerical index of the discriminatory ability of biotyping for strains of Salmonella typhimurium and Salmonella paratyphi B

An index of discrimination was used to assess the discriminatory power of biotyping for salmonellas of selected serotypes. Three collections of phage-typed strains of Salmonella typhimurium and Salmonella paratyphi B, previously tested for biotype, were examined. The results established that the discrimination index was high when full biotyping alone was used for differentiation of strains from international series. When biotyping was combined with phage typing, the discrimination achieved was greater than for either method used alone. These findings confirm that biotyping affords excellent discrimination of strains of S. typhimurium and S. paratyphi B and indicate that the results obtained from biotyping can be interpreted with confidence.

Efficient selection of tests for bacteriological typing schemes

To simplify the selection of tests for bacteriological typing methods, such as bacteriophage, bacteriocin, and biotyping, a computerised method was assessed. This uses a numerical index of discrimination (D) to facilitate the selection of an efficient typing set. The computer programs take the most discriminatory test as the initial test in the partial typing set, and then select the next test by combining each of the remaining candidates with the partial set and choosing the test which maximises D. This cycle is repeated until the remaining candidates do not increase the discriminatory power of the typing set. Options are provided for the investigator to pre-select certain tests for inclusion or exclusion from the typing set. It is concluded that the numerical index D is a simple means of test selection, but it must be emphasised that it is important to combine its use with data on the incidence of reaction in each test, on reproducibility, and on the similarity among tests.

R-plasmids in Salmonella isolates from sporadic cases of gastroenteritis

Five-hundred and twenty seven strains of Salmonella isolated from different patients admitted to hospitals in Rome from 1982 to 1985 were screened for their resistance to antimicrobial drugs. Sixty-one strains (11.6%) were found to be resistant to two or more antibiotics; the most frequent resistances were to sulfathiazole, streptomycin, tetracycline, chloramphenicol and ampicillin. Of the thirty-eight strains showing resistance to three or more antibiotics, 17 were able to transfer their resistance to E. coli K 12. The isolates were heterogeneous in plasmid population: only few strains harbored a sole plasmid, most harbored many plasmids ranging between 20 and 120 megadaltons in weight. Most strains were found to carry a conjugative plasmid of incompatibility group Inc H of 100-120 megadaltons and Inc I alpha of 60-70 megadaltons.

A phage-typing scheme for Salmonella enteritidis

For many years phage typing has proved invaluable in epidemiological studies on Salmonella typhi, S. paratyphi A and B, S. typhimurium and a few other serotypes. A phage-typing scheme for S. enteritidis is described. This scheme to date differentiates 27 types using 10 typing phages.

Salmonella serotypes and incidence of multiply-resistant Salmonellae isolated from diarrhoeal patients in Hong Kong from 1973-82

Salmonella was the most frequent bacterial pathogen isolated from patients with acute diarrhoea in Hong Kong. In Queen Mary Hospital, the major hospital on Hong Kong Island, 94.7% of salmonellae isolated from faecal specimens from patients during the period 1973-82 belonged to the gastroenteric group, while 5.3% belonged to the enteric fever group. Amongst the gastroenteric group, 68 salmonella serotypes were identified, with Salmonella derby, S. typhimurium and S. anatum being the predominant ones. Three outbreaks caused by S. johannesburg, S. worthington and S. wandsworth were detected. Of S. typhimurium, 61.6% were resistant to multiple antibiotics and belonged to four major phage types: 193, 22, 138 and U288. The majority (96.8%) of S. johannesburg strains which caused a widespread epidemic were multiply-resistant. Multiple antibiotic resistance was rarely observed in most other gastroenteric salmonellae. S. typhi was the commonest of the enteric fever group isolated from the blood of patients. Nineteen phage types were identified; E1 being the commonest (18.5%) while 21% were nontypable. Many of these isolated were resistant to streptomycin or sulphadiazine, but none were resistant to ampicillin, chloramphenicol or trimethoprim.

Attempts to establish phage typing as an epidemiological marker for Salmonella enteritidis

The notable increase in the number of Salmonella enteritidis strains seen in Spain in recent years (from 27.10% in 1980 to 66.36% in 1985) makes it necessary to find an additional epidemiological marker for this serotype. Phage typing was considered because of its discriminatory capacity toward other Salmonella serotypes. Wild and lysogenic bacteriophages were sought for a set of autochthonous bacteriophages. Our set consisted of 6 bacteriophages, 5 wild and 1 lysogenic. When tested on 1,500 selected strains, they produced 9 different phage types. The most abundant phage types were A (74.66%) and B (19.73%). The percentage of non-typable strains was low: only 1.4% from a total of 1,500 strains failed to produce lysis with our set. This reflects the high typability of the bacteriophage set proposed.

A new scheme for phage typing Salmonella bareilly and characterization of typing phages

A new phage typing scheme using wild bacteriophages isolated from sewage for phage typing Salmonella bareilly is described. Six hundred and thirty-seven strains of Salm. bareilly could be separated into 11 different phage types using five wild phages. Overall typability was 94.5%. These phages belonged to two different morphotypes. A1 and B1, and showed varying host range.

Morphology of staphylococcus bacteriophage P 1

The group D staphylococcal phage P 1 was examined in the electron microscope after preparation by a variety of procedures. The virion was found to have an icosahedral capsid attached to a long contractile tail structure, the viral tail could be seen in partially contracted configurations. Morphological variants in the length of the sheath and needle were frequently found.

An international point source outbreak of typhoid fever: a European collaborative investigation

A point source outbreak of Salmonella typhi, degraded Vi-strain 22, affecting 32 British visitors to Kos, Greece, in 1983 was attributed by a case-control study to the consumption of a salad at one hotel. This represents the first major outbreak of typhoid fever in which a salad has been identified as the vehicle. The source of the infection was probably a carrier in the hotel staff. The investigation demonstrates the importance of national surveillance, international cooperation, and epidemiological methods in the investigation and control of major outbreaks of infection.

Development of a bacteriophage typing system for Campylobacter jejuni and Campylobacter coli

A bacteriophage typing system for Campylobacter jejuni and Campylobacter coli was developed with phages isolated from poultry feces. Data for phage selection were generated from a set of isolates of C. jejuni and C. coli from humans in Illinois. Selection of 14 phages from the 47 phages available was assisted by determination of the Sneath-Jaccard similarity coefficients and subsequent unweighted pair-group arithmetic averaging cluster analysis. The typing set was reproducible and stable in the 255 isolates from Illinois. Of these isolates, 94.5% were typable, with 46% represented by the four most common phage patterns. In a set of 51 isolates from humans outside of Illinois, 88.1% of the C. jejuni isolates were typable. Phage typing for C. jejuni and C. coli has excellent epidemiologic potential and should serve as a useful adjunct or alternative to serotyping systems in current use.

Lactose-fermenting, multiple drug-resistant Salmonella typhi strains isolated from a patient with postoperative typhoid fever

Two lactose-fermenting Salmonella typhi strains were isolated from bile and blood specimens of a typhoid fever patient who underwent a cholecystectomy due to cholelithiasis. One lactose-fermenting S. typhi strain was also isolated from a pus specimen which was obtained at the tip of the T-shaped tube withdrawn from the operative wound of the common bile duct of the patient. These three lactose-fermenting isolates: GIFU 11924 from bile, GIFU 11926 from pus, and GIFU 11927 from blood, were phenotypically identical to the type strain (GIFU 11801 = ATCC 19430 = NCTC 8385) of S. typhi, except that the three strains fermented lactose and failed to blacken the butt of Kligler iron agar or triple sugar iron agar medium. All three lactose-fermenting strains were resistant to chloramphenicol, ampicillin, sulfomethoxazole, trimethoprim, gentamicin, cephaloridine, and four other antimicrobial agents. The type strain was uniformly susceptible to these 10 drugs. The strain GIFU 11925, a lactose-negative dissociant from strain GIFU 11926, was also susceptible to these drugs, with the sole exception of chloramphenicol (minimal inhibitory concentration, 100 micrograms/ml).

Phage types of Salmonella typhi isolated in Malaysia over the 10-year period 1970-1979

The pattern of phage types of 2553 strains of Salmonella typhi isolated over the 10-year period 1970-9 was studied. During the period 29 different phage types were encountered, not including the categories of 'untypable strains', 'degraded Vi-strains' and Vi negative strains. For the period as a whole, the commonest phage types encountered were A (20.9%), E1 (14.8%), D1 (10.3%), degraded Vi positive strains (10.3%), untypable Vi strains (7.3%), C4 (7.1%), D2 (4.4%), E2 (3.9%) and type 25 (2.6%). There were phage types which appeared in the early years of the period and then disappeared (types B2, D9 and D1-N). Others only made their appearance in recent years (K1 and 53). Notable differences were also seen in the predilection of some phage types for certain geographical areas.

Bacteriophage types of Salmonella typhi in the United States from 1974 through 1981

From 1974 through 1981, 4,089 isolates of Salmonella typhi were phage typed at the Centers for Disease Control and nine regional laboratories in the United States. The most prevalent types were degraded Vi (27%), E1 (20.6%), A (9.8%), C1 (5.7%), untypable Vi (3.5%), W form (3.5%), D1 (3.4%), B3 (3.4%), and F1 (2.4%). There were less than 2% of each of the remaining types. The distribution of phage types for this time period was similar to that seen in the periods 1966-1969 and 1970-1973, except that phage type B3 was one of the 10 most prevalent types in 1974-1981 but was not seen in 1966-1973. Phage typing is presently the most valuable laboratory tool for differentiation of strains of S. typhi in epidemiological studies.

Staphylococcus aureus isolated from poultry in Australia. I. Phage typing and cultural characteristics

The phage typing and cultural characteristics of 574 strains of S. aureus of poultry origin in Australia were examined. With the avian phage set of Shimizu (1979) it was possible to type 74.2% of strains. A number of significant variations in the phage typing patterns of Australian strains compared to those reported from Japan and Europe were observed. A lower proportion of Australian strains were of avian phage group I and a higher proportion of group III. A high proportion of strains were of mixed lytic groups. No locally isolated phages were able to increase significantly the percentage of typeable strains, although four local phages appeared to be of greater value for phage typing poultry strains of S. aureus than some other phages of the avian phage set. The international (human) phage set was of limited value in typing Australian strains of poultry origin although four strains were identified which were indistinguishable from strains of human origin. Using cultural characteristics of the strains in conjunction with phage typing, the Australian strains of S. aureus were assigned to one of three major groups and nine subgroups. A list of typing phages considered to be valuable for use on Australian poultry strains of S. aureus is given.

New bacteriophage typing system for Yersinia enterocolitica, Yersinia kristensenii, Yersinia frederiksenii, and Yersinia intermedia: correlation with serotyping, biotyping, and antibiotic susceptibility

Yersinia enterocolitica is listed as a single species in Bergey's Manual of Determinative Bacteriology, but has recently been split into "true" Y. enterocolitica, Y. kristensenii, Y. intermedia, and Y. frederiksenii. From 48 bacteriophages isolated from raw sewage, 24 were chosen as being the most useful for differentiating strains within the four Yersinia species. The composite set of 24 phages typed 92% of 236 Y. enterocolitica strains, 100% of 16 Y. kristensenii strains, 97% of 29 Y. frederiksenii strains, and 90% of 20 Y. intermedia strains. The most common phage type in any of the groups contained 22% of the strains tested, but most of the phage types contained greater than 5% of the strains. The new typing schema was tested in three outbreaks of Y. enterocolitica, and the results agreed well with serotyping and epidemiological findings. In the same outbreaks, biotyping (API 20E profiles; Analytab Products, Plainview, N.Y.) and antibiograms were less reliable markers and probably should be used only in conjunction with serotyping or phage typing or both. Caution should be used in identifying cultures of Y. frederiksenii and Y. intermedia with the API 20E system, since the tests at 37 degrees C for L-rhamnose and melibiose fermentation are often delayed past 24 h, which is the cut-off point for the final reading in the API system. There were distinct differences in the susceptibilities of Y. enterocolitica and Y. kristensenii to ampicillin, carbenicillin, and cephalothin, which adds further support for classifying the latter as a separate species.

The role of lysogeny in the modification of phage typing patterns of Staphylococcus aureus isolated from dairy cows

Strains of Staphylococcus aureus were isolated at a single sampling from cows in a dairy herd. When typed by phage most showed a complex pattern of lysis with group III and IV phages. Cross-spotting of strains showed great lytic activity and ten phages were isolated. The parent strains were lysogenized with these phages and the effect on the phage typing pattern of 202 daughter strains from 25 parent cultures was studied. Phage action was often blocked completely, with up to four being blocked on the one strain. Those most frequently blocked were phage 101, 117, 367 and 42D.

The use of a new phage set for typing poultry strains of Staphylococcus aureus obtained from seven countries

1. Eighty per cent of poultry strains of Staphylococcus aureus tested from French, Belgian, English, West German, Japanese and Argentinian sources were typable using a set of typing phages isolated in this laboratory. Strains from Bulgaria, however, with few exceptions were not typable with this phage set. 2. Strains isolated from lesions generally resembled those from apparently healthy poultry. 3. The existence of two distinct Staph. aureus biotypes on poultry was confirmed by isolates from six of the countries; one of these biotypes closely resembled Staph. aureus variety gallinae as described by Witte et al. (1977).

Salmonellosis in Indonesia: phage type distribution of Salmonella typhi

The distribution of phage types was studied among 577 strains of Salmonella typhi from Indonesia. Chemotype, colicinogeny, and tetrathionate reductase activity were also studied for most of these strains. The current phage type formula for Java was determined to be: A, D2, D6, E1a, E2, M1, and 46, but two other large groups of strains were also found, I + IV and degraded Vi+ strains. Significant differences in S. typhi strain distributions were noted between two localities on Java with respect to phage type and tetrathionate reductase activity. Comparisons were made with past phage typing studies in Jakarta as well as with more recent studies in other parts of south-east Asia. Phage types A, D1, D2, and E1 persisted at a rather steady level in Jakarta for 28 years. Evidence was found for epidemiological links to European and Asian areas. Antibiotic resistance among these Indonesian S. typhi strains was rare.

The problems, diagnosis and treatment of infection by Staphylococcus aureus

Present-day problems of infection by Staphylococcus aureus are described against a brief historical account of the evolution of the multiple antibiotic resistant 'hospital staph'. which caused such immense problems of hospital cross-infection in the 1950's and 1960's. These problems have lessened considerably since that time, but staphylococcal infection still remains as a cause of morbidity and mortality. Diagnosis and treatment are not always straight-forward. Apart from applying general supportive measures, and appropriate surgical intervention when necessary, the attending doctor is faced with making a choice from a multiplicity of antibiotic agents. A brief account of the main antibiotic agents currently available is given with comments on some of the disadvantages and complications attendant on their use. The potential dangers of staphylococcal sepsis and the need for rapid diagnosis and prompt vigorous treatment are stressed.

Correlation of phaga type, biotype and source in strains of Salmonella typhimurium

A series of 2092 cultures of Salmonella typhimurium isolated from human, animal and other sources in 57 countries were differentiated into 204 phage types and 19 primary and 147 full biotypes. Different biotypes belonged to the same phage type and different phage types to the same biotype, so the combination of typing methods differentiated strains more finely than either method alone: 574 different ;phage type/biotypes' were distinguished in 1937 cultures belonging to the 204 recognized phage types.The combination of biotyping with phage-typing was valuable in studying the phylogeny and spread of epidemic strains by distinguishing clones of different biotype within the same phage type and by confirming the relationship between cultures isolated from widely dispersed clones and that between cultures isolated before and after a clone had undergone variation in phage type, biotype, colicin type or antibiotic-sensitivity pattern.A widespread outbreak of infection with S. typhimurium phage type 141 in Scotland comprised independent dissemination of three clones of different biotypes, 1f, 9f and 31bd. During its epidemic spread in cattle in Britain between 1962 and 1969, another strain underwent variations in phage type (type 44 to type 29), biotype (type 26a to types 26d, 26bd, 26dgi, 26dz and 26i) and antibiotic sensitivity. A group of 275 non-fimbriate, non-inositol-fermenting and non-rhamnose fermenting (FIRN) strains, particularly associated with avian infections and thought to be clonal in origin, contained 27 phage types and 22 full biotypes in the primary biotypes 29-32.

Clonal distribution of resistance plasmid-carrying Salmonella typhimurium, mainly in the Middle East

Strains of Salmonella typhimurium of predominantly Middle Eastern origin, but distributed from England to India, were found to carry at least three types of resistance plasmid. The most important was initially identified as an F(I) plasmid by compatibility tests, but differs from the F factor on the one hand and the F(I) factors R162 and ColV on the other. The three groups of F(I) plasmids can be distinguished by their compatibility reactions with the MP10 plasmid of S. typhimurium (Smith, Humphreys, Grindley, Grindley & Anderson, 1973) and group H(1) factors: the F factor is unilaterally incompatible with group H(1) (Smith, Grindley, Humphreys & Anderson, 1973; Anderson, 1975b); the F(I) factors are compatible with MP10 and group H(1); and F(I)me factors are incompatible with MP10 but compatible with H(1). The majority of S. typhimurium cultures belonged to phage type 208; most of those that did not, belonged to types related to 208. Only a minority of their F(I)me plasmids were autotransferring. The remainder were mobilizable by F-like plasmids, and by group H(1) and H(2) factors, but not by the fi(-) I(1) factor Delta, or by plasmids of the I(2), B, P, W, N and com 7 groups. The compatibility reactions of the autotransferring F(I)me plasmids were identical with those of the non-transferring members of the group, and both were large, single-copy plasmids.The S. typhimurium strains of this series carried A or AK, and SSu resistance determinants: small, probably multicopy, non-transferring plasmids similar to those originally described in phage type 29 of S. typhimurium (Anderson & Lewis, 1965b).These S. typhimurium cultures probably represent a clone of wide geographical distribution. The accurate epidemiological study of such clonal outbreaks requires, in addition to phage typing, precise identification of the plasmids harboured by the epidemic strains, and may have to be carried to the molecular level.F(I)me plasmids were identified in other drug-resistant salmonellas, notably in a strain of S. wien which caused large outbreaks of mainly paediatric infection in Algeria, and also spread to Britain. An F(I)me plasmid was found in S. typhi phage type 44 from Algeria, in which the phage-restricting properties of the plasmid are responsible for the specificity of the type.

Salmonella serotypes, Salmonella typhi phage types, and anti-microbial resistance at the University Hospital of the West Indies, Jamaica

Bacteriologically proved cases of salmonellosis presenting at the University Hospital have increased nearly threefold since 1957. The most striking change has been a considerable increase in the incidence of Salmonella heidelberg and Salmonella derby in the last 5 years, probably resulting from hospital acquired infection. About 80 cases of typhoid fever are reported each year in Jamaica. There has been little change in the prevalence of different phage types of Salmonella typhi since 1961. Paratyphoid fever is rare. Standardized antimicrobial disk-sensitivity testing was performed on selected surviving salmonella strains since 1964. S. typhi has remained fully sensitive to all the agents tested except streptomycin. Other salmonellas, however have shown a significant increase in antimicrobial resistance since 1970. Most of this increase was due to multiple resistance in S. heidelberg and S. derby, and the survival and dissemination of these strains in the hospital environment may be related to antibiotic usage.

Salmonellosis in Indonesia: phage type distribution of Salmonella paratyphi A

The distribution of phage types among 221 human strains of Salmonella paratyphi A in Indonesia was studied. Approximately 50% were phage type 5, a rare type elsewhere in the world. Most other isolates were the cosmopolitan phage type 1. The ratio of phage type 1-5 was compared for two cities on Java, Jakarta and Yogyakarta. The ratios were significantly different, phage type 5 predominating in Jakarta. The ratio of phage types among 10 S. paratyphi A strains isolated from Jakarta river water was similar to that found in Jakarta patients.

Bacteriophage typing of Shigella sonnei

A bacteriophage-typing schema was developed for differentiating strains of Shigella sonnei. Sixty-seven bacteriophages were obtained from other collections, and 36 bacteriophages were isolated from sewage. From these 103 bacteriophages, a provisional set of 12 was chosen by computer analysis as being the most sensitive in differentiating strains of S. sonnei isolated in the United States. The provisional schema was used to type 265 strains from different geographical areas. It divided them into 87 different lysis patterns, and all 265 strains were typable. Smooth and rough colonial variants of the same strain had different lysis patterns, so the technique was standardized to type rough colonies only. Reproducibility was difficult to obtain until all conditions were carefully standardized. Changes in results were noted even on different lot numbers of Trypticase soy agar, which was defined as the standard medium. So that the medium would not be a variable, 100 pounds (ca 453.5 kg) of the same lot number was purchased. Bacteriophage typing was very useful in differentiating strains, and work should continue on establishing a standarized schema.

Automation of Salmonella typhi phage typing

Two steps in the procedure for bacteriophage typing of Salmonella typhi have been automated. The culture inoculum was applied by flooding the surface of phage agar in a 150x20 mm petri dish and removing the excess liquid with a safety pipettor. This step replaced the older method of manually preparing up to 100 individual areas for inoculation. The number of bacteria per unit area was the same with both methods, so the automated method involved no change in the technique. The second automated step involved use of a bacteriophage applicator which simultaneously dispensed 59 uniform drops of bacteriophages onto the inoculated plate. The automated procedure has reduced personnel time by about 90% with no less in sensitivity or accuracy.

Person-to-person spread of Salmonella typhimurium after a hospital common-source outbreak

In September, 1973, diarrhoea caused by Salmonella typhimurium developed in 32 people in a Maine hospital. Both epidemiological and microbiological evidence indicated that raw egg beaten in milk ("egg-nog") was responsible for the infection. However, 6 patients and 8 employees had not had egg-nog, and their illness developed after the source of infection had been recognised and removed. Most of these people had had direct contact with an infected patient, and presumably acquired the infection by person-to-person spread. It is concluded that person-to-person spread of S. typhimurium can occur in hospitals and can be a hazard to patients and staff.

Bacteriophage typing of Proteus mirabilis, Proteus vulgaris, and Proteus morganii

A bacteriphage typing scheme for differentiating Proteus isolated from clinical specimens was developed. Twenty-one distinct patterns of lysis were seen when 15 bacteriophages isolated on 8 Proteus mirabilis, 1 P. vulgaris, and 1 P. morganii were used to type 162 of 189 (85.7%) P. mirabilis and P. vulgaris isolates. Seven phages isolated on 3 P. morganii were used to type 13 of 19 (68.4%) P. morganii isolates. Overall, 84.1% of the 208 isolates were lysed by at least 1 phage at routine test dilution (RTD) or 1,000 x RTD. Fifty isolates, retyped several weeks after the initial testing, showed no changes in lytic patterns. The phages retained their titers after storage at 4 C for several months. A computer analysis of the data showed that there was no relationship between the source of the isolate and bacteriophage type. This bacteriophage typing system may provide epidemiological information on strains involved in human infections.

Preliminary report: a system for typing Salmonella thompson

A system is described for the phage typing of Salmonella thompson. The system is based upon a number of bacteriophages that were isolated from sewage.

Enterotoxigenicity of Staphylococcus aureus cultures isolated from acute cases of bovine mastitis

To determine whether staphylococci causing bovine mastitis are potential causes of human intoxications, 142 cultures identified as etiological agents of acute cases and 18 cultures causing chronic cases of staphylococcal mastitis were obtained from investigators in the United States and Canada, examined microscopically, and tested for carbohydrate utilization, terminal pH, catalase, coagulase, egg yolk hydrolysis, gelatin hydrolysis, cytochrome oxidase, urease production, nitrate reduction, micrococcal nuclease, phage type, and enterotoxin production. Three cultures were not confirmed as Staphylococcus aureus. Of the 157 S. aureus cultures, 23 produced staphylococcal enterotoxins. Although a direct relationship between staphylococcal mastitis and outbreaks of staphylococcal food poisoning was not proved, results indicated that staphylococcal infections of the bovine mammary gland represent a significant reservoir of enterotoxigenic strains of S. aureus.

Bacteriophage typing of Salmonellae. II. New bacteriophage typing scheme

A phage-typing technique for salmonellae is described. One battery of phages was used to type three serotypes of Salmonella, namely, S. typhimurium, S.typhimurium var. copenhagen, and S. heidelberg. In all, 443 S. heidelberg cultures were typed into 22 phage types, 185 S. typhimurium cultures into 35 phage type, and 92 S. typhimurium var. copenhagen cultures into 26 phage types. The stability of the phage types was established by retyping 168 cultures belonging to all three serotypes. The epidemiological significance of the phage types demonstrated was evaluated by comparing phage types obtained from the University of Minnesota and those from the National Animal Disease Laboratory. Further investigation of the S. heidelberg phage types has shown that the cultures represented repeated isolates from the same birds or from a group of birds in the same flock.

Immunofluorescent identification of Salmonella typhi during a typhoid outbreak

Immunofluorescence and conventional bacteriological methods were compared for their ability to detect Salmonella typhi in 134 fecal specimens from 105 individuals associated with an outbreak of typhoid fever. Smears prepared from untreated fecal material (direct method) and after a preliminary incubation in selenite F broth (delayed method) were tested with an anti-Vi serum conjugated with fluorescein isothiocyanate. The delayed method was more sensitive than the direct method in detecting S. typhi. The delayed method was positive in 40 of 41 patients positive by culture methods, but gave positive or questionable reactions in 11 presumably uninfected individuals. The fluorescent-antibody test employing a Vi conjugate is a satisfactory screening procedure for detecting S. typhi, but all positives must be confirmed bacteriologically.

Bacteria in a hospital nursery: laboratory and clinical studies

Two hundred and twenty-two infants and fifty-one staff were examined for carriage ofStaphylococcus pyogenesand Gram-negative bacilli, and the presence of these bacteria in the ward environment was also investigated. Staphylococci were phage-typed and tested for sensitivity to antibiotics. Assessment of clinical infection caused by these bacteria was made.

Infant carriage ofStaphylococcus pyogeneswas maximal on the sixth day, 73·1 % of umbilical swabs yielding significant growth. Carriage of Gram-negative bacilli was maximal on the fifth day, 31·7% of umbilical swabs being positive. Where special nursing was enforced, i.e. premature baby unit, isolation of Gram-negative bacilli was very infrequent.

The low nasal carriage of staphylococci seen in infants and nursing staff is attributed to traces of penicillinase-resistant penicillins in the ward air.

Staphylococcus pyogeneswas recovered from 23 % of ward surfaces, and constituted 0·7% of the air-borne flora. In contrast, Gram-negative bacilli were recovered from 4·7 % of surfaces, and composed only 0·15% of the air-borne flora.

Phage group I constituted 73·0, 44·9 and 41·2% of strains from infants, staff and ward environment respectively.

Antibiograms were grouped into three categories, A, B and C. Category A (sensitive to chloramphenicol, erythromycin and methicillin but penicillin-resistant) composed 79·0% of infants' strains, being found mostly in group I, but was rare among staff strains.

Of 54 specimens taken from 40 infants showing evidence of infection,Staphylococcus pyogeneswas isolated from 16, of which 14 were category A. Gram-negative bacilli were isolated 7 times. Only 21 infants required antibiotic therapy (9·3%) and none were infected with Gram-negative bacilli—this contrasts with the frequency of these bacilli in nursery infection today.

Ward air is considered to be the maindepotofStaphylococcus pyogenes. Infant ‘dispersers’ are probably the principalsourceof the air-borne staphylococci. Infants and staff abstract from the air those staphylococci which become their colonizing strains. No transfer is thought to occur from the staff to the infants. Transmission of Gram-negative bacilli is similar in that the infants are the principal source and the air the maindepotof these bacteria. Nasal colonization by Gram-negative bacilli is low, this is possibly due to poor colonizing properties. Infant umbilical carriage almost certainly results from endogenous faecal spread.

We are grateful to Dr J. C. Gould, Director, Central Microbiological Laboratories, Edinburgh, for his continued interest and advice, and to Mr J. C. Ferguson and Mrs M. M. Winton for skilled technical assistance. This study would not have been completed without the co-operation of Sisters McCartney and Struthers and their nursing staff.

A prospective study of staphylococcal infection and its prevention among infants and mothers after childbirth in hospital and at home

Staphylococcal colonization and infection were studied prospectively in infants, mothers and households after childbirth at home and in hospital. Infants were treated prophylactically with frequent applications of ‘Ster-zac’ hexachlorophane dusting powder. Some were treated in addition with ‘Naseptin’ nasal disinfectant cream.

The incidence of staphylococcal sepsis in infants was much less than before the adoption of hexachlorophane prophylaxis. The sepsis rate was further reduced when ‘Naseptin’ was used in addition to hexachlorophane. Of the two prophylactic agents, hexachlorophane was the more convenient and probably the more effective. ‘Naseptin’ was difficult to employ correctly and unsuitable for routine use.

The treatment of infants with disinfectants reduced nasal carriage markedly in infants and to a smaller extent in mothers. Both agents contributed to the reductions which persisted for some weeks after treatment ceased.

Breast abscesses were almost entirely confined to mothers of infants who became nasal carriers by the second week of life.

Staphylococcal colonization of infant's skin was greater when they wore impervious garments, probably because skin moisture increased.

PHAGE TYPES OF XANTHOMONAS PHASEOLI ISOLATED FROM BEANS

Eight phage types of Xanthomonas phaseoli (E. F. Sm.) Dows. were identified by an experimental phage-typing system using four virulent phages and 310 isolates of this organism. The existence of phage subtypes was also demonstrated by the use of high-titer phage preparations. The phage subtypes could be located geographically. Correlation between strain virulence and phage subtype was demonstrated. Polyvirulent phage Pg 176 for X. phaseoli var. fuscans used in the typing system was partially characterized. The incidence and distribution of phages for strains of X. phaseoli and X. phaseoli var. fuscans in soil samples from southwestern Ontario from 1962 to 1965 were determined. The low ecological significance of soil-borne phage was demonstrated. Seventeen phages for X. phaseoli were isolated from 13 soil samples with the aid of enrichment, none without.

Media and methods for phage-typing mycobacteria

Media widely used for primary isolation, for drug-sensitivity tests and for type differentiation of mycobacteria have been tested for use in phage studies on the tubercle bacilli. Modifications of each of these media provided some improvement in phage activity on some strains of mycobacteria but not on others. During these studies it was observed that certain substances augmented phage activity, while other substances were found to have the opposite effect. On the basis of these results, a new medium has been formulated. This medium can be used without agar as a liquid medium for growth of the mycobacteria or with agar as a solid medium for isolated plaques and routine test dilution (RTD) spots. An outline of a pilot phage-typing test on three species of Mycobacterium is included.

The bacteriology of tropical pyomyositis in Uganda

1. The bacteriology of the pus from 79 cases of tropical pyomyositis has been studied. In 74 cases Staphylococcus aureus was isolated in pure culture.

2. Phage typing showed that 60% of the pyomyositis strains belonged to phage Group II as compared with 22% for miscellaneous hospital infections and 21% for nasal carrier strains.

3. A high proportion of the Group II strains from pyomyositis were found to be penicillin resistant and it is thought that this is unlikely to be due to the use of penicillin therapeutically but is probably a natural characteristic of the strains.

4. Other suggested aetiological factors in pyomyositis such as leptospirosis and syphilis have been investigated but no association has been found.

5. The phage types of staphylococci found in Uganda have been compared with those reported from England and Australia and found not to be strikingly different.