Haemolytic-uraemic syndrome caused by vero toxin-producing Escherichia coli serotype Rough: K-: H49

Taxonomy Meets Public Health: The Case of Shiga Toxin-Producing Escherichia coli

To help assess the clinical and public health risks associated with different Shiga toxin-producing Escherichia coli (STEC) strains, an empirical classification scheme was used to classify STEC into five “seropathotypes” (seropathotype A [high risk] to seropathotypes D and E [minimal risk]). This definition is of considerable value in cases of human infection but is also problematic because not all STEC infections are fully characterized and coupled to reliable clinical information. Outbreaks with emerging hybrid strains continuously challenge our understanding of virulence potential and may result in incorrect classification of specific pathotypes; an example is the hybrid strain that caused the 2011 outbreak in Germany, STEC/EAggEC O104:H4, which may deserve an alternative seropathotype designation. The integration of mobile virulence factors in the stepwise and parallel evolution of pathogenic lineages of STEC collides with the requirements of a good taxonomy, which separates elements of each group into subgroups that are mutually exclusive, unambiguous, and, together, include all possibilities. The concept of (sero)-pathotypes is therefore challenged, and the need to identify factors of STEC that absolutely predict the potential to cause human disease is obvious. Because the definition of hemolytic-uremic syndrome (HUS) is distinct, a basic and primary definition of HUS-associated E. coli (HUSEC) for first-line public health action is proposed: stx2 in a background of an eae- or aggR -positive E. coli followed by a second-line subtyping of stx genes that refines the definition of HUSEC to include only stx2a and stx2d . All other STEC strains are considered “low-risk” STEC.

Genetic analysis for the lack of expression of the O157 antigen in an O Rough:H7 Escherichia coli strain

The O-antigen (rfb) operon and related genes of MA6, an O rough:H7 Shiga-toxigenic Escherichia coli strain, were examined to determine the cause of the lack of O157 expression. A 1,310-bp insertion, homologous to IS629, was observed within its gne gene. trans complementation with a functional gne gene from O157:H7 restored O157 antigen expression in MA6.

Clinical Escherichia coli strains carrying stx genes: stx variants and stx-positive virulence profiles

Altogether, 173 Shiga toxin-producing Escherichia coli (STEC) serotype O157 (n = 111) and non-O157 (n = 62) isolates from 170 subjects were screened by PCR-restriction fragment length polymorphism for eight different stx genes. The results were compiled according to serotypes, phage types of O157, production of Stx toxin and enterohemolysin, and the presence of eae. The stx genes occurred in 11 combinations; the most common were stx(2) with stx(2c) (42%), stx(2) alone (21%), and stx(1) alone (16%). Of the O157 strains, 64% carried stx(2) with stx(2c) versus 2% of the non-O157 strains (P < 0.001). In the non-O157 strains, the prevailing gene was stx(1) (99% versus 1% in O157 strains; P < 0.001). In addition, one strain (O Rough:H4:stx(2c)) which has not previously been described as associated with hemolytic-uremic syndrome (HUS) was found. Ten stx-positive virulence profiles were responsible for 71% of all STEC infections. Of these profiles, five accounted for 71% of the 21 strains isolated from 20 patients with HUS or thrombotic thrombocytopenic purpura (TTP). The strains having the virulence profile that caused mainly HUS or TTP or bloody diarrhea produced Stx with titers of >/=1:128 (90%) more commonly than did other strains (51%; P < 0.001). These strains were also more commonly enterohemolytic (98% versus 68% for other strains; P < 0.001) and possessed the eae gene (100%) more commonly than did other strains (74%; P < 0.001). A particular virulence profile, O157:H7:PT2:stx(2):stx(2c):eae:Ehly, was significantly more frequently associated with HUS and bloody diarrhea than were other profiles (P = 0.02) and also caused the deaths of two children. In this study, the risk factors for severe symptoms were an age of <5 years and infection by the strain of O157:H7:PT2 mentioned above.

Clinical isolates of non-O157 Shiga toxin-producing Escherichia coli: serotypes, virulence characteristics, and molecular profiles of strains of the same serotype

All human Shiga toxin-producing Escherichia coli (STEC) non-O157 strains (n = 56) isolated in Finland from 1990 to August 2000 were characterized for the O:H serotype, stx(1) and stx(2) genes, production of enterohemolysin, and sensitivity to 12 antimicrobial agents. Strains of the same serotype were genotyped by pulsed-field gel electrophoresis (PFGE) after XbaI restriction of total DNA. The 56 non-O157 isolates belonged to 29 serotypes. Two of the serotypes (O102:H7 and OX181:H49) have not previously been described as being associated with STEC infections in humans or isolated from animals. Thirty-four strains (61%) within seven serotypes (O103:H2 [14 isolates], O26:H11 [6 isolates], O145:H28 [4 isolates], O145:HNM [3 isolates], O15:HNM [3 isolates], OX174:H21 [2 isolates], and O Rough:HNM [2 isolates]) were represented by more than one isolate. Of these strains, O103:H2 isolates were divided into seven, O26:H11 isolates were divided into four, and the rest within a serotype were divided into two genotypes in PFGE. In PCR, 31 (55%) of the 56 strains were positive for the stx(2) gene only and 24 strains (43%) were positive for stx(1) only. One strain (O43:H2) carried both stx(1) and stx(2). Forty-two strains (75%) produced enterohemolysin, and 39 strains (70%) possessed the eae gene. Of the latter 39 strains, 36 (92%) were enterohemolytic, whereas only 6 (35%) of the 17 isolates lacking the eae gene were enterohemolytic (P < 0.001). The majority of the strains (44 strains, 79%) were sensitive to all 12 antimicrobials tested. Of the 56 strains, 20 (36%) were associated with small family outbreaks in nine families and 14 (25%) were associated with recent travel abroad.

EPEC, EAEC and STEC in stool specimens: prevalence and molecular epidemiology of isolates

Stool specimens of Finns (n = 695) with (n = 603) and without (n = 92) diarrhea were studied for enteropathogenic (EPEC), enteroaggregative (EAEC) and Shiga toxin-producing (STEC) Escherichia coli by PCR. The specific isolates were subsequently investigated for their O:H serotypes and were genotyped by pulsed-field gel electrophoresis (PFGE). A subset (n = 506) of the diarrheal and all non-diarrheal specimens were also searched for conventional enteric bacterial pathogens by standard methods. Diarrheagenic E. coli were found in 5.5% and other enteric pathogens in 6.7% of the patients with and in 2.2% and 1.1% of the subjects without diarrhea, respectively. Campylobacter (3.8%), EPEC (3.2%) and Salmonella (2.0%) were the most common findings, and were detected in diarrheal patients only. STEC were associated with bloody diarrhea (8/9 isolates), whereas EAEC were equally common (1%) in diarrheal and non-diarrheal subjects. Great genomial heterogeneity was seen among diarrheagenic E. coli, and only one EPEC isolate belonged to the "classic" EPEC serogroup (O55).

Cytomegalovirus meningoencephalitis with paroxysmal course in immunocompetent adults: a new nosographical entity. Clinical, diagnostic and therapeutic correlations, and pathogenetic hypothesis

An immunocompetent adult developed cytomegalovirus (CMV) meningoencephalitis with paroxysmal neurologic symptoms of a self-limited nature and with a favourable outcome. Consistent with known cases in the clinical literature, two clinical forms of CMV meningoencephalitis will be identified: a monophasic form and a paroxysmal form. The clinical, diagnostic and therapeutic aspects of the two types will be analysed, and a pathogenetic hypothesis for the paroxysmal type will be proposed.