Influence of Salmonella enterica serovar enteritidis infection on the development of the cecum microbiota in newly hatched chicks.

Terminal restriction fragment length polymorphism and quantitative PCR showed that the cecal microbiota of chicks up to the age of 21 days was dominated by representatives of the orders Enterobacteriales, Clostridiales, and Lactobacillales. Salmonella enterica serovar Enteritidis infection caused the greatest changes in the gut microbiota when 1-day-old chicks were infected, compared with the infection of 4- and 16-day-old chicks.

Distribution of integrons and SGI1 among antibiotic-resistant Salmonella enterica isolates of animal origin.

In Salmonella enterica, resistance to antibiotics can be caused by the presence of SGI1, transposons or conjugative plasmids. In this study we were interested in the relative contribution of these genetic elements to the antibiotic resistance of S. enterica isolates collected within a single year in the Czech Republic from animal sources. Altogether 123 antibiotic-resistant isolates belonging to 16 different S. enterica serovars were classified into 3 groups according to the presence of SGI1 and the presence of integrons. The first group consisted of 62 strains in which neither SGI1 nor class 1 integron was detected. A high diversity among serovars and resistance phenotypes was found in this group. The second group consisted of 56 strains positive for both the SGI1 and class 1 integron, out of which 55 belonged to serovar Typhimurium and one to a nonmotile serovar [4,12] which harboured the SGI1-B variant. The third group comprised five strains which were positive for class 1 integron but negative for the SGI1. Sequencing of the integrons in these isolates identified integron with sat1 and aadA1 gene cassettes in S. Sandiego and S. Pullorum, dfrA1 and aadA1 gene cassettes in S. Typhimurium integron, and aadA21 gene cassette in S. Braenderub and S. Zanzibar.

Septicaemia caused by phenotypic variants of group A streptococci.

Clinical isolates (115) of Streptococcus pyogenes responsible for septicaemia were investigated to determine whether invasiveness may be correlated with a large variety of strains, or concerns only particular phenotypes. Irrespective of their clinical origin, the strains studied displayed seven of the ten biotypes described within this species. As already observed in a series of strains isolated from pharyngitis, a restricted association between M-types and biotypes was demonstrated; each M-type corresponded to a sole biotype. However, the proportion of biotypes 3, 5 and 7 was higher in the septicaemia series than in the pharyngitis series, with a larger variety of M-types and with more non-typable strains. Despite these differences, the restricted associations between these characters were concordant in both series. These results demonstrate that streptococcal septicaemias appear to be caused by a wide variety of strains, suggesting that multiple factors may be involved in the invasiveness of the bloodstream during streptococcal infections.

Vaccination of chickens with Salmonella Pathogenicity Island (SPI) 1 and SPI2 defective mutants of Salmonella enterica serovar Enteritidis.

In this study we were interested in the vaccine potential of two attenuated mutants of Salmonella enterica serovar Enteritidis for poultry. The first mutant was attenuated by the removal of the whole Salmonella Pathogenicity Island 1 (SPI1) and the second mutant was devoid of the whole SPI2. These 2 mutants were used for oral vaccination of 2 chicken lines; Lohmann Brown and ISA Brown. Chickens were vaccinated orally on day 1 of life, revaccinated on day 21 and challenged on day 42. The challenge was performed either orally or intravenously. Despite a slightly different response between the two chicken lines, both the mutants gave protection to poultry against S. Enteritidis challenge as documented by findings such as the bacterial counts in tissues, spleen weight, antibody production and cytokine response (namely IL-17 and IL-22). When the 2 mutants were compared, vaccination with the SPI1 mutant proved to be more effective in the protection of poultry against S. Enteritidis challenge than the vaccination with the SPI2 mutant. On the other hand, vaccination with the SPI2 mutant stimulated a slightly higher antibody production and such a mutant might therefore be a better choice if Salmonella is used as a vector for the delivery of heterologous antigens with a desired stimulation of the humoral part of the immune system.

Salmonella enterica serovar Typhimurium and Enteritidis infection of pigs and cytokine signalling in palatine tonsils.

Pigs are considered as one of the major sources of zoonotic strains of Salmonella enterica for humans. Out of many S. enterica serovars, S. Typhimurium dominates in pigs, however, in several countries in Central Europe, S. Enteritidis is also quite frequent in pig herds. In this study we therefore compared the colonisation of pigs with S. Typhimurium and S. Enteritidis. We found that 3 weeks after infection S. Enteritidis 147 colonised the intestinal tract in higher quantities but was shed in faeces in lower quantities than S. Typhimurium 17C10. In a second experiment we found out that S. Enteritidis 147 and its SPI-1 and SPI-4 mutants increased proinflammatory cytokine (IL-1ß and IL-8) signalling in the ileum 5 days post infection. On the other hand, independent of SPI-1 or SPI-4, S. Enteritidis 147 suppressed expression of IL-18, MCP1, TLR2, CD86, IL-7, IL-10 and IL-15 in the palatine tonsils. The suppression of cytokine signalling may facilitate the initial colonisation of the palatine tonsils by Salmonella. Moreover, immune suppression may also influence pig resistance to opportunistic pathogens and Salmonella infection in pigs thus may become an issue not only in terms of pork contamination but also in terms of affecting the immunological status of pig herds.

Deletion of sodCI and spvBC in Salmonella enterica serovar Enteritidis reduced its virulence to the natural virulence of serovars Agona, Hadar and Infantis for mice but not for chickens early after infection.

Salmonella enterica serovars Typhimurium, Enteritidis, Dublin, Choleraesuis or Gallinarum can colonise liver and spleen in particular hosts while infections with serovars Infantis, Agona, Hadar, etc. are usually limited to gastrointestinal tract. Reasons for this behavior are unknown, although it has been shown that sodCI and spv genes exhibit a strict distribution between more and less virulent serovars and they influence Salmonella virulence. However to what extent the presence or absence of these genes is associated with the increased virulence of serovars which possess them has never been addressed experimentally. In this study we therefore first confirmed the exclusive association of spvB and sodCI genes with the former group of serovars. In the next step we removed these two genes from S. Enteritidis genome and compared the virulence of such a mutant with the virulence of S. Infantis, S. Agona and S. Hadar for chickens and highly sensitive Balb/C mice. Single strain infection showed that the deletion of these two genes from S. Enteritidis resulted in the reduction of its virulence for mice but not for chickens. Mixed infection further confirmed these observations and indicated that in mice but not in chickens the virulence of sodCI and spv mutant was reduced to the natural virulence of serovars Infantis, Agona and Hadar. Although sodCI and spv genes do not influence S. Enteritidis virulence for chickens directly, they may be of an indirect effect through the increased persistence of S. Enteritidis in mice and increased probability of the reintroduction of S. Enteritidis into poultry flocks.

Comparative analysis of Salmonella enterica serovar Enteritidis mutants with a vaccine potential.

If any new live Salmonella vaccine is introduced in the future, it is quite probable that detailed characterisation of its attenuation will be required. In this study we therefore compared 34 isogenic mutants of S. Enteritidis in aroA, aroD, galE, ssrA, sseA, phoP, rpoS, ompR, htrA, clpP, lon, rfaL, rfaG, rfaC, hfq, sodCI, hilA, sipA, avrA, sopB, sopA, sopE, sifA, shdA, fliC, fur, relA, spoT, rel-spoT, misL, rmbA, STM4258, STM4259 and spvBC genes for their resistance to stresses likely to be expected in the host and for their virulence and immunogenicity in Balb/C mice. We found that the cold and bile resistances essentially did not correlate with the resistances to other stress factors. Resistance to acid pH, heat, polymyxin and serum correlated with each other and also with the attenuation. When the residual virulence and immunogenicity were both considered, mutants in htrA, ompR, aroA, aroD and lon performed the best in mice. Furthermore, when a detailed comparison of polymyxin and serum sensitive mutants was performed, the serum sensitive mutants were more immunogenic.

Quantitative character of fibrinogen uptake by M+ and M- variants of Streptococcus pyogenes.

Fibrinogen was labelled with 125Iodine by mild chemical oxidation and its binding to Streptococcus pyogenes was subjected to quantitative analysis, inhibition and desorption studies. Fibrinogen was bound both by virulent and avirulent (M protein-positive and M protein-negative) matched strains of several serotypes. In all pairs of strains fibrinogen uptake was much higher by the M-positive variants. The ratio of bound fibrinogen to total fibrinogen was highly dependent both on the concentration of fibrinogen and the concentration of cocci. Equilibrium binding studies showed that the binding was a multifactorial process. Probably not only receptor fibrinogen interactions but also interactions between bound and unbound fibrinogen molecules took place. The uptake of fibrinogen was highly depressed in avirulent strains and practically uninfluenced in virulent strains by the presence of albumin or immunoglobulin. The bond between fibrinogen and streptococci is therefore different in virulent and avirulent variants. The fibrinogen receptors on the cell surface are specific.

Prospective study of pharyngitis: clinical diagnosis and microbiological profile.

A prospective study of pharyngitis was carried out in the general population of twenty-two thousand in a small country town, over a period of ten weeks in the fall of 1984. It has been confirmed that, as in the past clinical diagnosis "streptococcal" and "nonstreptococcal" pharyngitis without microbiological examination is still highly inaccurate. From the clinical and microbiological parameters, the incidence in the period of follow-up was calculated as 7.2 and 12.0 cases per 100 population per year for streptococcal and nonstreptococcal pharyngitis, respectively. These data document the health importance of this disease which is frequently underestimated. The M (by M or OF antigens) typability accounted for 62% of group A strains isolated, the prevailing types being M 1 and M 12. Comparison of M and OF typability of field strains immediately after isolation and three weeks later proved the superiority of an early typing. The accurate identification of prevailing types is essential for the prospect of streptococcal vaccine. In streptococcal pharyngitis cases treated with penicillin, the increase of antistreptolysin O and antideoxyribonuclease B titres was recorded in very few instances during a three week period after the onset of the disease. The examination of patients with nonstreptococcal pharyngitis aimed at detecting the role of some viruses or of M. pneumoniae proved that the etiology by these agents was practically nil in the cases concerned at this particular period of time. This finding suggests focusing interest on a possible role of other pathogens. The morbidity rates of pharyngitis, and the clinical as well as the microbiological data resulting from the study make it urgent to pay further attention to this infection and to attempt to elucidate the missing points in the etiology and diagnosis of this disease which belongs to the bacterial infections most frequently seen in man in economically developed countries.

Evolution of antibiotic resistance in Salmonella enterica serovar typhimurium strains isolated in the Czech Republic between 1984 and 2002.

In a collection of 66 Salmonella enterica serovar Typhimurium strains isolated between 1984 and 2002 in the Czech Republic, genes coding for antibiotic resistance were determined by using specific PCRs. We found that the pentadrug-resistant ACSSuT clone first appeared in the Czech Republic in 1990. A new variant of the aadA gene designated aadA21 is described, the 5' end of which was identical to aadA2 and the 3' end of which was identical to aadA1.

The concurrent associations of group A streptococcal serotypes in children with acute rheumatic fever or pharyngitis-associated glomerulonephritis and their families in Kuwait.

A group of 146 children with acute rheumatic fever and 256 members from their families, and a group of 125 children with post-streptococcal glomerulonephritis and 199 family members, together with a group of 145 children with non-complicated group A streptococcal pharyngitis were examined over a period of three years. The purpose of the study was to explore the concurrent association and distribution of group A streptococcal serotypes among the three groups. Strains isolated from the children with non-complicated group A streptococcal pharyngitis represented the prevalent strains of group streptococci in the childhood community during the period of study. Rheumatic fever was encountered in a non epidemic situation. As expected, the recovery of group A streptococci was low. The strains however belonged mainly to two patterns, namely type M1 and M non-typable strains. Nephritis was pharyngitis-associated and occured also sporadically throughout the year. Types M12 and 49 accounted for the majority of the isolates. Type M12 accounted for 34.4% of the group A isolates from family members of children with nephritis and was totally absent in family members of children with rheumatic fever (p less than 0.001). The T pattern 8/25/Imp. 19 accounted for 40% of the group A isolates from family members of rheumatic patients compared to 3.3% from family members of nephritis patients (p less than 0.005). Data from this study show that the group A streptococcal serotypes, concurrently isolated from children with acute rheumatic fever and their families are disparately different from those of children with pharyngitis-associated glomerulonephritis and their families in the same population. These findings support the concept of "nephritogenicity" and "rheumatogenicity" and indicated the important role of the biological characteristics of the streptococcal serotypes in the aetiology of acute rheumatic fever and acute poststreptococcal glomerulonephritis.