Fifty years of dysentery research at the Pécs University.

Károly Rauss was appointed as head of the Department of Public Health of the Elisabeth University of Pécs in 1946, Professor Rauss's carrier had started working with Professor Hugó Preisz in Budapest. During his residency years he was already appointed to the Department of Bacteriology chaired by Lovrekovics at the National Institute of Public Health. In this institution--as in all organizations affiliated with the Rockefeller Institute--the state of art diagnostic work together with research focusing on problems derived from everyday medical and public health practice was considered as to be of primary importance.

Biofilms produced by Pseudomonas aeruginosa and by Staphylococcus aureus on model medical devices.

Polyethylene, teflon, tygon, polypropylene, silicon rubber, and rubber tubes or rings contaminated with Pseudomonas aeruginosa or Staphylococcus aureus were implanted subcutaneously into mice. After 5 days the colony forming units developing on, and attaching to them were determined. The highest numbers of bacteria were observed on rubber and silicon rubber, polyethylene was next in order, while significantly lower values were obtained on teflon and on tygon and polypropylene.

A model for testing drug susceptibility of Pseudomonas aeruginosa and Staphylococcus aureus grown in biofilms on medical devices.

UV-sterilized polyethylene rings infected with Pseudomonas aeruginosa or with Staphylococcus aureus were implanted into artificial wounds of mice. During 5 days incubation biofilm was formed on the plastic surfaces. To determine the Minimal Bactericidal Dose on sessile bacteria, rings with biofilm were removed and incubated in Luria broth containing serial dilutions of different antibiotics.

Effectiveness of antibiotics on the autochthonous Escherichia coli of mice in the intestinal biofilm versus its planktonic phase.

The effectiveness of antibiotics was tested on the autochthonous Escherichia coli in biofilm mode of growth in large bowel pieces as well as on the predominant faecal E. coli isolated from the same SPF mice in planktonic phase of growth. Aminoglycoside antibiotics, chloramphenicol, oxytetracycline, erythromycin and lincomycin-clindamycin treatment had a very limited effect in the intestinal biofilm.

[Effect of antibiotics on autochtonous intestinal E. coli population in SPF mice and on planktonic phase isolates].

Representatives of different groups of antibiotics were tested on the autochtonous Escherichia coli of mice being in biofilm mode of growth, as well as on their isolates in planktonic phase. Aminoglycoside antibiotics, chloramphenicol, oxytetracycline, erythromycin, lincomycin-clindamycin, and polymyxins showed a very reduced effectivity on Escherichia coli embedded in the biofilm matrix. On the other hand, beta-lactam antibiotics were equally effective both for sessile and planktonic bacteria.

Shigella-type pathomechanism in the "mouse model".

A strain of Escherichia coli K-12 carrying the 140-Megadalton virulence plasmid of the enteroinvasive E. coli--J53(pSPl)--showed high virulence in the "mouse model", in chick embryos, but not in the Serény test. It expresses the outer membrane proteins thermoregulatedly, encoded also by the virulence plasmid.

Resistance of Escherichia coli to some antibiotics and biocides in the intestinal biofilm of mice.

An artificial monoflora of Escherichia coli in mice, as well as their autochtonous E. coli, exhibited enhanced resistance to streptomycin, chloramphenicol, sodium hypochlorite and silver nitrate. The level of resistance of the monoflora, which was 10-32 times higher than the in vitro determined Minimal Bactericidal Dose (MBCD), reached its maximum on the 7th-9th day after implantation.

Binding of enteric bacteria to hog gastric mucin.

The binding features of enteric bacteria were studied using a model mucin of hog gastric origin. The time requirement of binding is short, it is temperature-independent, but dose-dependent. The binding effectiveness of Escherichia coli, Shigella sonnei and Shigella flexneri, as well as Salmonella minnesota had a narrow range: 1.

[Bacterial biofilms and medical practice].

A suboptimal environment with limited supply of nutrients leads to marked changes in the microbial features. Similar conditions exist also on some tissue surfaces of the human body and on biomedical devices implanted. The basic feature of this environmental adaptation is the adherence of microbes to some surfaces and production of abundant exopolysaccharides.

Biofilm model experiments in vitro with Escherichia coli and Shigella strains.

Escherichia coli and Shigella were cultured together in a glucose-free minimal medium completed only by hog gastric mucin. In mixed cultures inoculated simultaneously one member of the pair more or less overgrew the other. This organism remained predominant when superinfected with its strain pair after 1, 3, 5 or 7 days incubation.

Epidemiology of the enteroinvasive Escherichia coli. Observations in Hungary.

The Hungarian experiences on the epidemiology of enteroinvasive Escherichia coli (EIEC) concerning the dominant serogroup 0124 are summarized. One of the basic differences between Shigella and EIEC infections may be attributed to the higher environmental resistance of EIEC, therefore first of all water-borne outbreaks may be frequent. The other essential difference is in te age incidence: the infection rate of infants is low, the rise of incidence rate begins at the 3rd year and its peak is in the school-children age.

Feeding by mucin and intestinal growth of some enteric bacterial pathogens.

Enteroinvasive Escherichia coli, Salmonella typhi-murium, Shigella sonnei, Shigella flexneri, as well as E. coli K-12 show dose dependent growth in minimal medium completed with purified hog gastric "Granular Mucin". This ability is based on alpha-galactosidase production: defective, melibiose (and galactose) non-fermenting K-12 mutant were unable to utilize mucin.

Protective value of the plasmid-coded outer membrane protein of enteroinvasive Escherichia coli.

O-antigenically not related enteroinvasive Escherichia coli strains and rabbit sera prepared with them were used to study the role of plasmid-coded outer membrane proteins in protective immunity. Active immunization experiments were performed using a mouse model based on a long-lasting symptomless carriership after elimination of the bowel flora by streptomycin. Preliminary histological studies showed adhesion, penetration, intraepithelial multiplication, and epithelial desquamation after infection.

Urinary tract infectivity or R strains of Escherichia coli carrying various virulence factors.

The virulence factors of Escherichia coli supposed to act in urinary tract infections were studied on R strains in a suckling mouse model. The production of alpha-(diffusible-) haemolysin or the possession of antigen K1 enhanced the virulence significantly, while the type 1 (common) fimbriae failed to do so. An isogenic motile and non-motile pair of E.

Immunological approach to the pathogenetical role of Escherichia coli adhesive factor "119" in a suckling mouse urinary tract model.

In the course of urinary tract infections, suckling mice with maternal anti-pilus ("119") immunity showed a massive protection against a 119+ strain of Escherichia coli. Animals could be protected against urinary tract infection by giving pilus antibody or pilus vaccine shortly after the infection. Results showed the importance of adhesive pili in initiating the urinary tract infection by E.

Suckling mouse model of urinary tract infections caused by Escherichia coli.

The role in the vesico-renal pathogenicity of Escherichia coli of mannose resistant fimbriae provisionally designated "119" has been studied in a suckling mouse model. Two to 3 days old mice were infected by route of the urinary bladder and the occurrence and character of the developing infection were investigated. (i) The fimbriated strain caused infection and inflammation of the bladder in almost 100%.

Estimation of Vibrio cholerae and Escherichia coli heat-labile enterotoxin by enzyme-linked immunosorbent assay (ELISA).

By Enzyme-Linked Immunosorbent Assay (ELISA) purified cholera and Escherichia coli enterotoxins can be detected as sensitively as by CHO cells. There is a linear relationship between toxin concentrations and extinction values. In plates sensitized with toxins, antitoxins can be titrated with high sensitivity.

Enterotoxins of enteric bacteria--a review.

A review of the enterotoxins of enteric bacteria was compiled, taking into account recent developments of the field as well as results of the author's own research work. After characterization of enterotoxins of different origin, their pathogenic role is described, with special attention to the genetic background of these agents. The possible use of enterotoxins for active immunization purposes is also discussed.

An altered heart-labile enterotoxin (LT') produced by Escherichia coli serogroup O55 strain.

An Escherichia coli serogroup O55 strain produced heat-labile enterotoxin only, which exerted unusual effects on cell cultures; it caused elongation of CHO and HeLa cells but no changes in Y-1 cells. Injection of this substance, designated LT', into mouse foot pad and rabbit skin caused a well-expressed necrotic effect beside the LT-like activity. LT' showed no cytotoxic effect and failed to produce mouse lung oedema.

Antitoxic immunity against the so-called lung toxin produced by Escherichia coli.

Cross neutralization test with antisera to crude haemolysins produced by some Escherichia coli strains indicated that there were no antigenic differences among the haemolysins tested. These crude preparates showed definite cytotoxicity which could also be cross neutralized by "antihaemolysin" sera. Neutralization experiments were performed in mouse lung test with homologous and heterologous anti-haemolysin sera, and with O and OK sera to the wild type strain and its toxic R mutant.

Shigella dysenteriae 1-like cytotoxic enterotoxins produced by Salmonella strains.

A Salmonella enteritidis strain produced a cytotoxin in addition to heat-labile (LT) and heat-stable (ST) enterotoxins. Two strains of serotypes Salmonella kapemba and Salmonella thompson were LT and ST negative, but exhibited a cytotoxic effect. After Sephadex G-100 fractionation of the crude S.