Salmonella Paratyphi B; Public Health and Parental Choice: When to Treat Asymptomatic Carriers of Infection?

BACKGROUND: Salmonella Paratyphi B (Paratyphoid B) is a rare infection and a notifiable disease in England. Disease is typically mild, and chronic carriage in children has been described in endemic countries. Almost all cases in England are imported, with very few cases of community transmission reported. METHODS: The aim of this work was to describe an unusual cluster of Paratyphoid B cases transmitted within England, examining clinical, epidemiologic and microbiologic data. Detailed phylogenetic analysis is presented to corroborate public health epidemiologic links between cases. RESULTS: One child had recently returned from an endemic area and had mild gastrointestinal symptoms. One year later, 2 other children with no travel history developed invasive disease requiring hospitalization. Epidemiologic links confirmed person-to-person spread between these three cases. All isolates of S. Paratyphi B (n = 93) received by the Gastrointestinal Bacteria Reference Unit between 2014 and 2019 were typed using whole genome sequencing. Three cases of Paratyphoid B were identified in the same geographical location over a 2-year period. S. Paratyphi B strains isolated from the stool and blood of the three cases were closely linked (0-5 single-nucleotide polymorphisms) using whole genome sequencing. CONCLUSIONS: This case series highlights the potential public health risks of paratyphoid B and the range of pediatric complications associated with this illness, especially in younger children. Although rare, chronic carriage of Paratyphoid B can lead to transmission in nonendemic areas and should be considered in all children presenting with signs of enteric fever even where there is no history of foreign travel.

[Molecular biological and phenotypical characterization of human isolates of Salmonella enterica serovar Paratyphi B dT+ or Salmonella java]. / Molekulárno-biologická a fenotypová charakterizácia humánnych izolátov Salmonella enterica serovar Paratyphi B dT+, alebo Salmonella java.

OBJECTIVE: Salmonella Paratyphi B dT+ (or Salmonella Java) is an emerging public health problem. The study objective was to characterize phenotypically and genotypically 13 human isolates from sporadic cases of infection. MATERIAL AND METHODS: Phenotypic characteristics of 13 human isolates were determined by phage typing, disk diffusion method for testing antimicrobial susceptibility to 11 antibiotics and screening for selected virulence markers, i.e bacterial adherence to xylene, motility and biofilm formation. Genotypic characteristics of the study isolates were determined by PCR with primers for the detection of class 1 integrons, plasmid profile analysis and PFGE for the study of genetic diversity. RESULTS: The study isolates were classified into different phage types, with 3aI or 3aI variant being the most common (61.5%). All study isolates were resistant to streptomycin and sulfisoxazole, two of them were multiresistant (to streptomycin, sulfisoxazole, ampicillin and nalidixic acid). The study isolates showed low hydrophobicity, except for one isolate (2/08), and 5 isolates exhibited motility of > or = 50 mm. High biofilm formation was detected in 5 isolates. Class 1 integrons were not detected in any isolate and plasmid profile analysis revealed the presence of a 90-kb plasmid in 8 isolates. XbaI PFGE analysis differentiated the isolates into 6 pulsotypes (X1, X2, X2a, X3, X4,X5). CONCLUSION: Although the study set of S. Paratyphi B dT+ (S. Java) was small, the increasing emergence of this serovar in the human population in Slovakia is noteworthy. The results of gene analysis in PFGE suggest clonal diversity as well as a clonal link between strains of the predominant phage type. In view of possible increase in antimicrobial resistance and the spread of certain clones, continuous surveillance of strains of S. Paratyphi B dT+ is needed.

[Changes in culture and biochemical characteristics of Salmonella paratyphi B after incubation in seawater]. / Modification des caractères culturaux et biochimiques du Salmonella paratyphi B après incubation dans l'eau de mer.

After incubation in seawater Salmonella paratyphi B cells rapidly became unable to grow on bacteriological media. Previous adaptation to high osmolarity conditions greatly slowed down this process. Strains isolated from seawater microcosms after varying incubation periods were qualitatively different and showed changes in some of their growth (colony shape and size) and biochemical properties (acidification of some sugars, gelatinase activity, acetoin production, nitrate reduction). Because of these modifications, the bacteria showed atypical profiles and could not be identified as members of the Salmonella genus. The alteration of the phenotype, although reversible, could explain some of the false-negative results obtained upon isolation and identification of these bacteria in seawater samples.

[Survival of Salmonella paratyphi B and Pseudomonas aeruginosa in seawater after incubation or washing in the presence of osmolytes]. / Survie du Salmonella paratyphi B et du Pseudomonas aeruginosa dans l'eau de mer après incubation ou lavage en présence d'osmolytes.

The authors have compared the survival in seawater of Salmonella paratyphi B and Pseudomonas aeruginosa cells grown at low or high osmolarity, in the presence of organic osmolytes: glycine betaine, choline, proline, and glutamate. The four substrates enhanced the survival potential of S. paratyphi B while only glycine betaine protected P. aeruginosa. In addition only S. paratyphi B cells were more resistant after a preliminary growth at high osmolarity. Both bacteria were sensitive to osmotic down-shock, sensitization of S. paratyphi B being inversely proportional (p greater than or equal to 0.01) to the osmolarity of the medium used to wash cells. The transit in wastewater, at low osmolarity, can therefore modify the behavior of these pathogens in the marine environment.

Genetics of sensitivity of Salmonella species to colicin M and bacteriophages T5, T1, and ES18.

Nearly all of 62 strains of Salmonella paratyphi B were sensitive to colicin M and phage T5 but resistant to phages T1 and ES18 and to colicin B. All tested S. typhimurium strains were resistant to colicin M and phage T5, and many were sensitive to phage ES18. A rough S. typhimurium LT2 strain given the tonA region of Escherichia coli or S. paratyphi B became sensitive to colicin M and phage T5. We infer that the tonA allele of S. paratyphi B, like that of E. coli, determines an outer membrane protein that adsorbs T5 and colicin M but not phage ES18, whereas the S. typhimurium allele determines a protein able to adsorb only ES18. The partial T1 sensitivity of a rough LT2 strain with a tonA allele from E. coli or S. paratyphi B and also the tonB(+) phentotype of an E. coli B trp-tonB Delta mutant carrying an F' trp of LT2 origin showed that S. typhimurium LT2 has a tonB allele like that of E. coli with respect to determination of sensitivity to colicins and phage T1. Rough S. paratyphi B, although T5 sensitive, remained resistant to T1 even when given F' tonB(+) of E. coli origin. Classes of Salmonella mutants selected as resistant to colicin M included: T5-resistant mutants, probably tonA(-); mutants unchanged except for M resistance, perhaps tolerant; and Exb(+) mutants, producing a colicin inhibitor (presumably enterochelin). Some Exb(+) mutants were resistant to a bacteriocin inactive on E. coli but active on all tested S. paratyphi B and S. typhimurium strains (and on nearly all other tested Salmonella). A survey showed sensitivity to colicin M in several other species of Salmonella.