O-serotyping Providencia alcalifaciens.

The O-serotyping scheme for Providencia was tested on Providencia alcalifaciens isolates collected mostly from two hospitals. The specificites of the somatic (O) antigens of P. alcalifaciens were found to be different from those of Providencia stuartii, and separation of the Providencia typing scheme to allow separate typing of each species led to more efficient typing. All but 4 of 86 isolates were typable. Eighteen serotypes occurred among 53 typable isolates obtained from a pediatric hospital, and 11 occurred among 19 isolates from a general hospital. Thirty-two percent of the isolates from the pediatric hospital belonged to serotype O3, the most frequently isolated and most widely distributed type. The use of the serotyping scheme for P. alcalifaciens is advocated for further studies to examine strains of the species for enteropathogenic types.

O serotyping of Providencia stuartii isolates collected from twelve hospitals.

A collection of 829 isolates of Providencia stuartii, mostly from urological specimens of patients in 12 hospitals, were O serotyped. Hospitals varied in serotype distribution, but most isolates (97%) fell into one or another of 14 O types of P. stuartii. One type (O63) was found in 10 hospitals, and six types (O4, O17, O25, O52, O55, O56) were found in 5 or more hospitals. These seven types were more common than others and included 753 (91%) of the isolates. Only four isolates agglutinated in Providencia alcalifaciens antisera and, for increased efficiency in serotyping, it is recommended that separate schemes be employed for P. stuartii and P. alcalifaciens. Strains endemic in different hospitals may differ in serotype and give rise to nosocomial infections that are clinically recognizable when infections occur in obvious clusters. Nosocomial infections occurring in low frequency among patients not located close to each other in the hospital may be detected with the aid of serotyping.

Cross-protection of mice provided by active and passive immunization against experimental infections with virulent Proteus rettgeri and Providencia bacteria.

Immunization with Providencia and Proteus rettgeri Formalin-treated bacterial suspensions produced high levels of protection in mice against homologous and heterologous challenge. Mice were also cross-protected, but less effectively, by passive administration of rabbit type-specific antisera. The protective activity appeared to be due to an antigen common to strains of different O-serotypes. It was not detectable in agglutination reactions, and preliminary results indicate that it is thermostable, not being inactivated in its antibody binding capacity at 121 degrees C for 1 h.

Nosocomial urinary tract infections caused by two O-serotypes of Providencia stuartii in one hospital.

Providencia stuartii nosocomial urinary tract infections occurring in the same hospital over an 18-month period of retrospective study were shown, by serotyping and biotyping, to have been caused by two endemic strains. Two episodes, involving 38 patients in one ward and 11 patients in another, were caused by a mannitol-positive strain of serotype O55. Transmission of the strain through the movements of one patient appeared to have been the basis for the introduction of the agent from one ward to the other. In another episode, involving two patients in a third ward, the infections were caused by a mannitol-negative strain of serotype O49. The study demonstrated the usefulness of serotyping and biotyping in epidemiological studies of infections caused by P. stuartii.

Variation in urease activity of endemic hospital strains of Proteus rettgeri and Providencia stuartii.

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.

Reconstitution of the somatic (O-) antigenic scheme for Providencia and preparation of O-typing antisera.

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.