Escherichia coli is the commonest cause of bacteraemia in England, with an incidence of 50.7 cases per 100 000 population in 2011. We undertook a large national study to estimate and identify risk factors for 30-day all-cause mortality in E. coli bacteraemia patients. Records for patients with E. coli bacteraemia reported to the English national mandatory surveillance system between 1 July 2011 and 30 June 2012 were linked to death registrations to determine 30-day all-cause mortality. A multivariable regression model was used to identify factors associated with 30-day all-cause mortality. There were 5220 deaths in 28 616 E. coli bacteraemia patients, a mortality rate of 18.2% (95% CI 17.8-18.7%). Three-quarters of deaths occurred within 14 days of specimen collection. Factors independently associated with increased mortality were: age < 1 year or > 44 years; an underlying respiratory or unknown infection focus; ciprofloxacin non-susceptibility; hospital-onset infection or not being admitted; and bacteraemia occurring in the winter. Female gender and a urogenital focus were associated with a reduction in mortality. This is the first national study of mortality among E. coli bacteraemia patients in England. Interventions to reduce mortality need to be multifaceted and include both primary and secondary healthcare providers. Greater awareness of the risk factors for and symptoms of E. coli bacteraemia may prompt earlier diagnosis and treatment. Changes in antimicrobial resistance patterns need to be monitored for their potential impact on infection and mortality.
Examination of' 729 isolates of' Proteus rettgeri showed that 674 reacted positively in tests for phenvlalanine deamination, indole production, growth on citrate, and acid production from meso-inositol, and negativelv for L-ornithine decarboxvlation and acid production from lactose, maltose, D-xvlose, and L-arabinose. Only 51 isolates diff'ered in one, and four diff'ered in two of these ten reactions, which were taken as the core characteristics of' the species. On the basis of' additional tests (acid production from salicin, L-rhamnose, D-mannitol, adonitol, and D-arabitol), the 729 isolates could be separated into f'ive groups. Groups 1, 2, 3, and 4 could be f'urther separated on the basis of' the reaction with meso-erythritol, and group 5 could be subdivided on the basis of' reaction with D-mannitol. Two metabolically distinct kinds of' P. rettgeri were recognized. Isolates of the f'irst kind (groups 1, 2, 3, and 4) each utilized both adonitol and D-arabitol and most utilized meso-ervthritol. Isolates of' the other kind (group 5) were negative with the three polyhydric alcohols but resembled, in their reactions, some strains of' Prouidencia stuartil. These may be intermediates between P. rettgeri that catabolize these substrates and the Providencia. One of the gram-negative species of bacteria that has increased in importance as an infectious agent is Proteus rettgeri. Its importance in
The somatic (O-) antigens of the type strains of the providencia antigenic scheme were examined for their biochemical reactions and their O-specificities. The scheme of 62 O-antigens was reconstituted from 52 original type strains and 10 strains substituted for originals that either were biochemically atypical of the genus or showed inappropriate serological reactions. Thirty-six type strains showed no significant relations with other type strains, and antisera could be used for typing without absorption. Among 26 type strains, significant reciprocal relations were demonstrated, and each cross-reacting antigen was examined for specificity and for its distribution among the type strains. Antisera to these strains required absorption with cell suspensions of other type strains for production of specificity in O-typing. Each typing antiserum, at low dilution, was shown to agglutinate homologous, but not heterologous, cell suspensions of type strains, and this result demonstrated the required specificity for typing on the basis of the O-antigens.
A serotyping system for Proteus rettgeri on the basis of 72 O antigens has been developed in a study of 324 strains obtained from widely distributed sources. In the investigation of the interrelations among the 72 O-type strains by cross-titration of each of the 72 anti-O sera with antigen of each of the O-type strains, both reciprocal and nonreciprocal (unilateral) reactions were observed. The presence of the Kunin common enterobacterial antigen (CA) was noted in each strain of P. rettgeri examined, and the unilateral reactions of two antisera were shown to be due to antibody present against CA. This indicated that CA was in the immunogenic state in two strains of this species. A second common antigen resembling CA in some respects but differing in specificity and in its agglutinability was shown to be the cause of unilateral reactions in a third antiserum. In other cases, unilateral reactive antibodies appeared to be directed against antigens that remained undefined. Each reciprocal reaction was investigated to determine the nature of the interrelations between interacting strains, and the definition of these led to the development of procedures for the production of absorbed anti-O sera with greater specificity. The serotyping scheme has increased the number of strains that may be typed through their O antigens, and its application in epidemiological investigations of infections due to P. rettgeri is indicated.
Both urease-positive and urease-negative Proteeae isolated from cross-infected patients in the same hospitals and, in three cases, from the same patients were examined for their biochemical reactions and somatic (O-) antigens. All isolates gave the same reactions in 17 biochemical tests and possessed O-antigens characteristic of Providenic O-type strains 4 or 17. Study of the isolates indicated that endemic strains are capable of undergoing variation in urease activity. In the current classification urease-positive and urease-negative strains are classified as Proteus rettgeri and Providencia stuartii, respectively. The observed variation in urease activity of nosocomial isolates of Proteeae suggests that taxonomy should be modified so that all such strains would be accommodated in a single group.
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