Determination of Differences in Virulence of Strains of Salmonella Typhosa

Abstract

In experimental immunology, it frequently is of interest to obtain quantitative estimates of the virulence of strains of microorganisms as evidenced by their ability to produce fatal infections in experimental animals. It is recognized that, in the broader sense, virulence is not a specific intrinsic attribute of an organism but is the result of a combination of a number of factors pertaining to the organism, the affected host, and the conditions (known or unknown) under which the pathological state is established. Nonetheless, when suitable laboratory animals are employed, and when the combination of experimental conditions is propitious, it can be demonstrated with some consistency that even closely related strains of organisms differ in their capability of producing experimental infections. For the purpose of this presentation, such differences in capability can be considered as differences in virulence of the organisms regardless of the true nature of the experimental infective process.Quantitative estimates of virulence have been employed by various workers in studying the relationship of this property to antigenic constitution, bacterial dissociation, and various epidemiological phenomena. Furthermore, it popularly is considered that the immunogenic activity of a strain of bacteria is directly related to its virulence. As a consequence, such tests are employed extensively as a control technique in routine production of bacterial vaccines and in searching for immunogenically superior strains.Mice have been widely accepted as the laboratory animals of choice for determining the virulence of strains of Salmonella typhosa and the testing procedures employed have been of two main types. The first, based on the intraperitoneal injection of graded doses of the organisms suspended in physiological saline, is utilized almost exclusively by British workers. The second, incorporating the use of hog gastric mucin as a suspending medium, has been employed by most American workers since the original reports of the technique by Nungester et al.(1) and of its application to typhoid by Rake (2). A third method, which was reported by Norton and Dingle (3) to show promise, is based on the intracerebral injection of the organisms without the aid of an adjuvant. This latter method has been used successfully in determining the virulence of strains of Hemophilus pertussis by Kendrick and her coworkers (4, 5) and as an experimental infective technique with Shigella dysenteriae by Dubos et al.

A common pathway for O‐linked protein‐glycosylation and synthesis of capsule in Acinetobacter baumannii

“…A. baumannii strains were grown for 18 h at 37°C in Luria broth with appropriate antibiotics and adjusted to the appropriate concentration in physiologic saline. Inoculums were prepared by mixing the bacterial suspensions 1:1 (v : v) with a 10% solution (w/v) of porcine mucin (Sigma, St Louis, MO) which increases the infectivity of A. baumannii , allowing for a lower concentration of bacteria to be used (Batson et al ., ; McConnell and Pachon, ; McConnell et al ., ). Mice were injected intraperitoneally with 0.2 ml of the bacterial/mucin inoculums.…”

Acinetobacter baumannii: human infections, factors contributing to pathogenesis and animal models

“…In these models, the cultured bacteria are mixed with porcine mucin, typically to a final concentration of 5% mucin, before instillation of the inoculum into the lungs (Rodríguez-Hernández et al, 2000Montero et al, 2002Montero et al, , 2004Pachó n-Ibañez et al, 2006Beceiro et al, 2009;Chiang et al, 2009;Pichardo et al, 2010). Its use thus allows for the number of bacteria in the inoculum to be reduced dramatically, in some cases by as much as 1000-fold for some bacterial species (Batson et al, 1950). Its use thus allows for the number of bacteria in the inoculum to be reduced dramatically, in some cases by as much as 1000-fold for some bacterial species (Batson et al, 1950).…”

“…Mucin has long been known to increase the virulence of numerous bacterial species in mouse models (Olitzki, 1948). Its use thus allows for the number of bacteria in the inoculum to be reduced dramatically, in some cases by as much as 1000-fold for some bacterial species (Batson et al, 1950). Although the presence of mucin during the establishment of infection has no role in human infection, the use of lower amounts bacteria in the inoculum followed by bacterial growth and the development of pneumonia may more accurately mimic human disease than the rapid instillation of large quantities of bacteria into the lung.…”

Vaccination with Outer Membrane Complexes Elicits Rapid Protective Immunity to Multidrug-Resistant Acinetobacter baumannii

“…A mouse sepsis model was used in order to characterize the efficacy of the OMC vaccine and of antibody treatment. In this model, mice are infected via intraperitoneal injection of a bacterial suspension containing 5% porcine mucin, which has previously been shown to increase the infectivity of A. baumannii and other bacteria in different experimental models (2,28). A. baumannii strains were grown for 18 h at 37°C in Mueller-Hinton broth and then adjusted to the appropriate concentration in physiologic saline.…”