Evaluation of the Anti-Shigellosis Activity of Dietary Isothiocyanates in Galleria mellonella Larvae

Cruciferous vegetables, widely present in daily diets, are a rich source of organosulfur compounds with proven health benefits, especially chemopreventive or antioxidative effects. Isothiocyanate derivatives (ITCs) exhibit a broad spectrum of biological and pharmacological activity and recently, their antibacterial properties have been of particular importance. Here, we have focused on the anti-shigellosis activity of sulforaphane (SFN) and phenethyl ITC (PEITC). The genus Shigella causes gastroenteritis in humans, which constitutes a threat to public health. Production of a potent Stx toxin by S. dysenteriae type 1 results not only in more severe symptoms but also in serious sequela, including the hemolytic uremic syndrome. Here, we present evidence that two aliphatic and aromatic ITCs derivatives, SFN and PEITC, have an effective antibacterial potency against S. dysenteriae, also negatively regulating the stx gene expression. The molecular mechanism of this effect involves induction of the global stress-induced stringent response. ITCs also inhibit bacterial virulence against the Vero and HeLa cells. We present evidence for the therapeutic effect of sulforaphane and phenethyl ITC against a S. dysenteriae infection in the Galleria mellonella larvae model. Thus, our results indicate that isothiocyanates can be effectively used to combat dangerous bacterial infections.

[Microcalorimetric investigation on the interaction of six alkaloids from rhizoma coptidis]

How to identify active constituents of traditional Chinese medicines (TCMs) and study their interactions are key problems in the development of TCMs. The inhibitory effect of six alkaloids from Rhizoma Coptidis (RC) on Shigella dysenteriae (S. dysenteria) growth had been investigated by microcalorimetry in this study. Main active constituents of RC were confirmed by comparing their contributions to the bacteriostatic effect, and the interactions among active constituents were further researched. According to the result, in 0.8 mg-mL-1 extract of RC, the contributions of six active alkaloids including berberine, coptisine, epiberberine, palmatine and the combination of jatrorrhizine and columbamine were 52.83%, 36.31%, 2.49%, 4.27% and 3.21%, respectively. Therefore, berberine and coptisine were the main active constituents of RC that inhibited the growth of S. dysenteria. The study of interactions among the six alkaloids indicated that, 1 there were some contstituents antagonizing the inhibitory effect of RC, 2 there was a synergy effect between berberine and coptisine, 3 there were additive effects between other four alkaloids and the main active constituents. These results may provide some useful references for the establishment of the quality standard for RC and the development of multi-component TCMs.

[Effects of lamivudine on growth of intestinal characteristic bacteria by microcalorimetry in vitro]

The study is aimed to investigate the effect of lamivudine on growth and metabolism of three intestinal characteristic bacteria (namely, Bifidobacterium adolescentis, Escherichia coli and Shigella dysenteriae). The growth condition of the three bacteria was quantitatively evaluated by microcalorimetry with four characteristic parameters of the thermal power-time curves, including the growth rate constant (k), thermal power (p), time to peak (t) and calorific value (Q). The results showed that the IC50 value of lamivudine on B. adolescentis was 200 microg x mL(-1), and the IC50 values of lamivudine on S. dysenteriae and E. coli were higher than 3 000 microg x mL(-1) and 6 000 microg x mL(1), respectively. Therefore, lamivudine made different inhibitory effects on the three bacteria, in which the B. adolescentis was most susceptible to lamivudine. This work showed that taking lamivudine chronically is likely to affect the balance of good flora in the intestinal tract, and might increase endotoxin release, leading to inflammation and disease progression in hepatopathy.

Monitoring of growth and physiological activities of biofilm during succession on polystyrene from activated sludge under aerobic and anaerobic conditions

The present research work monitored the successive biofilm development and its catabolic role in the degradation of polystyrene (PS). PS material was artificially colonized with biofilm by incubating it with activated sludge under aerobic and anaerobic conditions. Biofilm formation was monitored by gravimetric weight analysis, spectrophotometric absorbance technique, heterotrophic plate count, and scanning electron microscopy under aerobic and anaerobic conditions. The wet weight (1.59 and 1.17 g) and dry weight (0.41 and 0.08 g) of a biofilm showed a significant constant increase under aerobic and anaerobic conditions, respectively, from first till 9 weeks of incubation. Plate count of the selected bacteria (Escherichia coli, Salmonella typhimurium, Shigella dysenteriae, Pseudomonas aeruginosa) considerably declined (90-99 %) in the biofilm after seventh and fifth weeks of incubation under aerobic and anaerobic conditions, respectively, indicating a positive shift from pathogenic to beneficial microbial community. While most probable number index of fecal coliforms and E. coli in the sludge showed more reduction (98 and 99 %) under aerobic as compare to anaerobic conditions (86 and 91 %) after 9 weeks of biofilm formation on PS cubes. Correspondingly, the decreasing levels of chemical oxygen demand and biochemical oxygen demand (up to 73 %) showed signs of sludge digestion. Scanning electron microscope coupled with energy dispersive X-ray spectroscope revealed nature of PS media containing high carbon content. However, biofilm development proved to be involved in the biochemical transformation of the PS medium as indicated by Fourier transform infrared spectroscopy.

Acanthamoeba castellanii an environmental host for Shigella dysenteriae and Shigella sonnei

The interaction between Shigella dysenteriae or Shigella sonnei and Acanthamoeba castellanii was studied by viable counts, gentamicin assay and electron microscopy. The result showed that Shigella dysenteriae or Shigella sonnei grew and survived in the presence of amoebae for more than 3 weeks. Gentamicin assay showed that the Shigella were viable inside the Acanthamoeba castellanii which was confirmed by electron microscopy that showed the Shigella localized in the cytoplasm of the Acanthamoeba castellanii. In conclusion, the relationship between Shigella dysenteriae and Shigella sonnei with Acanthamoeba castellanii is symbiotic, and accordingly free-living amoebae may serve as a transmission reservoir for Shigella in water.

Protective role of lactobacilli in Shigella dysenteriae 1–induced diarrhea in rats

OBJECTIVE

Studies on lactic acid bacteria exemplify their use against various enteropathogens in vitro. Nevertheless, in vivo effects of Lactobacillus during Shigella infection have not been evaluated. The present study evaluated the effect of Lactobacillus rhamnosus and Lactobacillus acidophilus on neutrophil infiltration and lipid peroxidation during Shigella dysenteriae 1-induced diarrhea in rats.

METHODS

The rats were divided into eight groups (n = 6 in each group). Induced rats received single oral dose of S. dysenteriae (12 x 10(8) colony-forming units [cfu]/mL). Treated rats received L. rhamnosus (1 x 10(7) cfu/mL) or L. acidophilus (1 x 10(7) cfu/mL) orally for 4 d, alone or in combination, followed by Shigella administration. At the end of the experimental period, animals were sacrificed and the assay of the activity of alkaline phosphatase, myeloperoxidase, and antioxidants and the estimation of lipid peroxides were performed. Activity staining of superoxide dismutase and catalase was done in addition to gelatin zymography for matrix metalloproteinase (MMP; MMP-2 and MMP-9) activity. A portion of the intestinal tissue was fixed in 10% formalin for histologic studies.

RESULTS

Administration of S. dysenteriae 1 alone resulted in increased levels of myeloperoxidase, lipid peroxidation, alkaline phosphatase, and the expression of MMP-2 and MMP-9 with concomitant decrease in the antioxidant levels. Pretreatment with the combination of L. rhamnosus (1 x 10(7) cfu/mL) and L. acidophilus (1 x 10(7) cfu/mL) significantly attenuated these changes when compared with the diseased group. Histologic observations were in correlation with biochemical parameters.

CONCLUSION

Lactobacillus rhamnosus plus L. acidophilus offered better protection when compared with individual treatment with these strains during Shigella infection.

Construction, detection and microarray analysis on Shigella dysenteriae A1 IroN, ShuA single, double mutants

In this study, we constructed single mutants MTS-1, MTS-2 of IroN and ShuA gene and double mutant MTS of them in Shigella dysenteriae A1 strain 51197 by insert and absence. The functional detection of every mutant was performed at the level of culture medium and cell experiment. The gene expression profiles of the mutants and the wild-type strains under iron-enriched and iron-limited conditions were analyzed by the SD51197 whole genomic microarray. The results showed that all the mutants grew obviously less well than the wild-type strains in L broth appending iron chelator DIP. The addition of iron to the cultures can stimulate the growth of mutants back to wild-type levels. In either the experiments on the ability of intracellular multiplication or the cell-to-cell spread in HeLa and U937 cell lines, mutants showed no obvious change in virulence compared with the parental strain SD51197. However when DIP was added to the cultured HeLa cells, the ability of intracellular multiplication of MTS-1, MTS-2, MTS has reduced about 23.4%, 25.2%, 43.6% respectively. The analysis of expression profiles under the iron-limited condition showed that the mutants were more sensitive for the changes of iron deficiency than the wild-type strains, many genes have been altered. Up-regulated genes mainly involved genes of transcription, coenzyme metabolism, amino acid transport and metabolism, and unknown functional genes, while down-regulated genes mainly involved genes of energy and carbohydrate metabolism and unknown function genes; the expression levels of known iron-transport associated genes generally showed up-regulated. The results demonstrated that iron-transport associated genes IroN, ShuA were likely to have some effects on the virulence and growth of S. dysenteriae.

ACTIVITIES OF AQUEOUS EXTRACTS OF MALLOTUS OPPOSITIFOLIUM ON SHIGELLA DYSENTERIAE A1-INDUCED DIARRHOEA IN RATS

1. Mallotus oppositifolium is reported to possess medicinal properties and is traditionally used in Cameroon for the treatment of diarrhoea. In the present study, we have evaluated the acute toxicity, in vitro antibacterial and in vivo antidiarrhoeal effects of an aqueous extract of these plant leaves. 2. Shigella dysenteriae A(1) (Sd1)-induced diarrhoeal rats were obtained by oral administration of increasing densities of the Sd1 strain isolated from bloody diarrhoea occurring in East Cameroon. When diarrhoea appeared, rats were treated for 5 consecutive days with 120, 240 or 360 mg/kg extract or norfloxacin (5.7 mg/kg). The weight and frequencies of faeces, as well as the number of Sd1, were assessed during the treatment period and the death rate was recorded. 3. The M. oppositifolium extract was not toxic. In vitro, the minimal inhibitory and minimal bactericidal concentrations of the extracts were 1,172 and 9,375 microg/mL, respectively. In vivo, 12 x 10(8) Sd1 provoked diarrhoea within 24 h, which was characterized by soft or liquid stools, that were moulded, smooth and mucus or blood coated. Diarrhoea went along with an increase in faeces weight and frequency (P < 0.001 by the 3rd day), as well as an increase in the bacterial population to a maximum on the 2nd day after infection (P < 0.05). The death rate was 67% by day 6. 4. Whereas norfloxacin significantly (P < 0.01) reduced Sd1 growth, M. oppositifolium extracts (240 and 360 mg/kg) restored bacterial growth to its initial density and no deaths were recorded. There was a significant (P < 0.05) reduction in stools weight and frequency with 240 mg/kg extract. 5. The results suggest that M. oppositifolium leaves could be a therapeutic alternative for bacterial aetiological diarrhoea in Central Africa, where multidrug supply and access to modern health centres are public health problems.

Batch process solar disinfection is an efficient means of disinfecting drinking water contaminated with Shigella dysenteriae type I

AIMS

The mortality and morbidity rate caused by Shigella dysenteriae type I infection is increasing in the developing world each year. In this paper, the possibility of using batch process solar disinfection (SODIS) as an effective means of disinfecting drinking water contaminated with Sh. dysenteriae type I is investigated.

METHODS

Phosphate-buffered saline contaminated with Sh. dysenteriae type I was exposed to simulated solar conditions and the inactivation kinetics of this organism was compared with that of Sh. flexneri, Vibrio cholerae and Salmonella typhimurium.

SIGNIFICANCE

Recovery of injured Sh. dysenteriae type I may be improved by plating on medium supplemented with catalase or pyruvate. Sh. dysenteriae type I is very sensitive to batch process SODIS and is easily inactivated even during overcast conditions. Batch process SODIS is an appropriate intervention for use in developing countries during Sh. dysenteriae type I epidemics.

GASP phenotype: presence in enterobacteria and independence of sigmaS in its acquisition

The appearance of growth advantage in stationary phase or GASP was originally detected in Escherichia coli. The presence of this phenotype in other enterobacteria such as Enterobacter cloacae, Salmonella typhimurium, Providencia stuartii and Shigella dysenteriae is described in this work. E. cloacae GASP strains presented lower levels of RpoS than the parental strain, although no mutation in the gene or its promoter was detected. This work offers evidence of GASP rpoS-independent pathways as GASP was also acquired in knock-out rpoS E. cloacae and E. coli strains.

Survival of Shigella dysenteriae type 1 on fomites

Studies have shown that various objects, such as utensils, toys, and clothes, can serve as vehicles for transmission of Shigella spp. Shigellae can become viable but non-culturable (VBNC) when exposed to various environmental conditions as shown in earlier studies. The present study was carried out to detect VBNC Shigella dysenteriae type 1 on various fomites by direct viable counting, polymerase chain reaction (PCR), and fluorescent antibody methods. S. dysenteriae type 1 was inoculated onto cloth, wood, plastic, aluminum, and glass objects. Results showed that 1.5-4.0 hours after inoculation, S. dysenteriae type 1 became non-culturable, and after five days, non-culturable but viable S. dysenteriae type 1 could be detected by both PCR and fluorescent antibody techniques. Fomites can be considered an important potential route of transmission of VBNC S. dysenteriae type 1 and a significant factor in the epidemiology of shigellosis.

TonB is required for intracellular growth and virulence of Shigella dysenteriae

To assess the importance of TonB-dependent iron transport systems to growth of Shigella in vivo, a tonB mutant of Shigella dysenteriae was isolated and tested in cultured cells. The tonB mutant invaded epithelial cells, but did not form plaques in confluent monolayers of Henle cells, indicating an inability of this mutant to spread from cell to cell. The rate of intracellular multiplication of the tonB mutant was reduced significantly compared to that of the wild type. The loss of virulence in the tonB mutant was not due to loss of either Shu or Ent, the TonB-dependent systems which allow for transport of heme and ferrienterobactin, respectively. A shuA mutant lacking the outer membrane receptor for heme, an entB mutant defective in enterobactin synthesis, and a shuA entB double mutant each were able to invade cultured cells, multiply intracellularly, and form wild-type plaques. The ability of S. dysenteriae to access iron during intracellular growth was assessed by flow cytometric analysis of an iron- and Fur-regulated shuA-gfp reporter construct. Low levels of green fluorescent protein expression in the intracellular environment were observed in all strains, indicating that iron is available to intracellular bacteria, even in the absence of TonB-dependent iron transport. The failure of the tonB mutant to grow well in an iron-replete intracellular environment suggests that TonB plays a role in addition to heme- and siderophore-mediated iron acquisition in vivo, and this function is required for the intracellular growth and intercellular spread of S. dysenteriae.

Spontaneous tandem amplification and deletion of the shiga toxin operon in Shigella dysenteriae 1

Only one species of Shigella, Shigella dysenteriae 1, has been demonstrated to produce Shiga toxin (Stx). Stx is closely related to the toxins produced by Shiga toxin-producing Escherichia coli (STEC). In STEC, these toxins are often encoded on lambdoid bacteriophages and are major virulence factors for these organisms. Although the bacteriophage-encoded stx genes of STEC are highly mobile, the stx genes in S. dysenteriae 1 have been believed to be chromosomally encoded and not transmissible. We have located the toxin genes of S. dysenteriae 1 to a region homologous to minute 30 of the E. coli chromosome, within a 22.4 kbp putative composite transposon bracketed by IS600 insertion sequences. This region is present in all the S. dysenteriae 1 strains examined. Tandem amplification occurs via the flanking insertion sequences, leading to increased toxin production. The global regulatory gene, fnr, is located within the stx region, allowing deletions of the toxin genes to be created by anaerobic growth on chlorate-containing medium. Deletions occur by recombination between the flanking IS600 elements. Lambdoid bacteriophage genes are found both upstream and within the region, and we demonstrate the lysogeny of Shigella species with STEC bacteriophages. These observations suggest that S. dysenteriae 1 originally carried a Stx-encoding lambdoid prophage, which became defective due to loss of bacteriophage sequences after IS element insertions and rearrangements. These insertion sequences have subsequently allowed the amplification and deletion of the stx region.

Shigella infection as observed in the experimentally inoculated domestic pig, Sus scrofa domestica

The domestic pig, Sus scrofa domestica, was investigated as a potential animal model for shigellosis. We examined the effects of pig age, pig breed and antibiotic pretreatment upon Shigella infection. Shigella dysenteriae, and Shigella flexneri (both virulent and avirulent strains) were utilized. Our results indicated that young (4-week-old), conventionally re ared, domestic pigs were routinely, but briefly, colonized (average=3.5+/-2.5 days) following oral or gavage administration ofS. flexneri, as determined by direct rectal cultures. The duration of S. dysenteriae colonization was significantly shorter. Inoculation of younger (2 days) or older (9 weeks) pigs with S. flexneri had no significant effect on infection duration. Similarly, infection of 4-week-old pigs with virulent and avirulent strains of S. flexneri had no effect upon the duration of infection, nor did the use of a swine-passaged S. flexneri isolate. Marked clinical, histopathological (gross and microscopic) and immunoIhistopathological signs of disease were absent in all infections. However, in instances where microscopic histopathological evidence was used to correctly identify infected pigs, tonsillar lesions were the consistently noted criteria. The tonsils are believed to be an important portal of entry for Salmonella choleraesuis, another member of the Enterobacteriaceae and a prevalent pig pathogen. Taken altogether, our results indicate that the domestic pig is unsuitable as a model for shigellosis.

Inhibition of prokaryotic translation by the Shiga toxin enzymatic subunit

Shiga toxin, produced by Shigella dysenteriae serotype 1, is a member of the large family of ribosome-inactivating proteins (RIPs) which are primarily produced by plants. All RIPs are rRNA N-glycosidases which inactivate ribosomes through the removal of a specific adenine residue from the well-conserved aminoacyl-tRNA-accepting loop of rRNA. As a type II RIP, STX is believed to have little effect on prokaryotic ribosomes. However, we have demonstrated that over-expression of the STX enzymatic (A1) polypeptide which lacks a signal sequence caused a reduced rate of growth of its Escherichia coli host. Over-expression of the same StxA1 polypeptide with a catalytic site substitution had no effect on the growth of E. coli. In addition, purified StxA1 was an inhibitor of prokaryotic protein synthesis as assessed using an in vitro transcription and translation assay. The specific activity of StxA1 was significantly higher than ricin, which is another type II RIP, with both eukaryotic and prokaryotic translation systems.

Effect of growth condition on in-vitro susceptibility of Shigella dysenteriae type 1 killing by murine peritoneal macrophages

The intracellular fate of Shigella dysenteriae type 1 strains grown in casamino acid-yeast extract (CYE) broth and nutrient broth (NB) was studied in casein-elicited mouse peritoneal macrophages. Virulent strains 14731 and W30864 cultured in NB and opsonised with normal mouse serum were susceptible to killing by peritoneal macrophages (66 SEM 1.7% killing by 2 h). In contrast, both strains grown in CYE broth and opsonised with normal mouse serum showed resistance to killing by peritoneal macrophages (76 SEM 1.4% survival by 2 h). Electronmicroscopy demonstrated that the bacteria escaped from the phagosome compartment by lysing the phagocytic vacuole and remained within the cytoplasm. Lipopolysaccharide (LPS) stimulated peritoneal macrophages to kill the opsonised strains 14731 and W30864 grown in CYE broth (85.4 SEM 1.6% killing by 2 h). Recombinant murine gamma interferon (rIFN-gamma) also stimulated macrophages to kill CYE-grown bacteria (52.1 SEM 1.3% killing by 2 h). However, an avirulent rough mutant strain W30864-22 grown in either NB or CYE broth showed marked susceptibility to killing by peritoneal macrophages, which was similar to that of NB-grown strain 14731 or W30864. The results of the present study suggest that in-vitro growth conditions may modulate the susceptibility of S. dysenteriae type 1 to killing by phagocytes.

Starvation- and stationary-phase-induced acid tolerance in Escherichia coli O157:H7

Stationary phase and the starvation of log-phase cells increased the acid tolerance of Escherichia coli O157:H7 strains. Although the degree of acid tolerance varied, the survival of most O157:H7 strains exceeded that of other, related, pathogens in a synthetic gastric fluid.

Methionine uptake and cytopathogenicity of viable but nonculturable Shigella dysenteriae type 1

A pathogenic strain of Shigella dysenteriae type 1 was selected for study to elucidate the physiology and potential pathogenicity of organisms in the viable but nonculturable (VBNC) state in the environment. Studies in our laboratory have shown that S. dysenteriae type 1 survives in laboratory microcosms in the VBNC state for long periods of time, i.e., more than 6 months. VBNC cells of S. dysenteriae type 1 were found to retain cytopathogenicity for cultured HeLa cells. To determine whether VBNC S. dysenteriae type 1 expressed protein after loss of culturability, 35S-labelled methionine was added to suspensions of VBNC cells. Total cellular proteins were extracted and examined by autoradiography. Results indicate that VBNC S. dysenteriae type 1 is capable of both active uptake of methionine and incorporation of methionine into protein. Amino acid uptake and protein synthesis substantiate the viability of cells of S. dysenteriae type 1 in the VBNC state, i.e., although the cells are unable to be cultured on laboratory media by standard bacteriological methods, the cells remain metabolically active. Furthermore, VBNC cells of S. dysenteriae type 1 may pose a potential public health hazard that has not yet been recognized.

Environmental signals induce major changes in virulence of Shigella spp

Growth conditions play a major role in expression of virulence by Shigella spp. both in vitro (adherence and internalization in eukaryotic host cells) and in vivo (keratoconjunctivitis). Optimized expression of virulence required anaerobic growth to log phase in particular media such as brain heart infusion broth. Kinetic studies of guinea pig eye infections showed that as few as 2 x 10(5) S. dysenteriae CG097 or S. flexneri M90T, grown under these optimized conditions, produced keratoconjunctivitis in 15 h. In vitro studies demonstrated that adherence to and invasion of Henle 407 cells, at 37 degrees C, by organisms grown under these optimized conditions, were significantly greater than when organisms were grown aerobically under the same conditions.

Antimicrobial activity of Microgard against food spoilage and pathogenic microorganisms

Microgard, a commercially available fermented milk product containing antimicrobial metabolites, was a potent inhibitor for Gram-negative bacteria such as Pseudomonas, Salmonella, and Yersinia when 1% concentration was incorporated into agar media. Gram-positive Bacillus cereus, Staphylococcus aureus, and Listeria monocytogenes were insensitive to Microgard. Kluyveromyces marxianus, an unidentified black yeast, and Penicillium expansum were partially suppressed, whereas Aspergillus niger and a yogurt spoilage yeast were tolerant to 5% Microgard. Optimum activity of Microgard was at pH 5.3 and below; the concentration that gave complete inhibition depended upon the number of bacteria present as well as the genus tested. Blood agar base reversed the antagonistic activity of Microgard against Pseudomonas putida compared with plate count agar.

Production of vero cytotoxin by Escherichia coli and Shiga toxin by Shigella dysenteriae 1 as related to the growth medium and availability of iron

Six strains of Escherichia coli producing Vero cytotoxin (VTEC) and six strains of Shigella dysenteriae 1 were examined for the production of extra- and intracellular Vero cytotoxin (VT) and Shiga toxin respectively, in relation to the growth medium and availability of iron. VTEC secreted less extracellular VT1 or VT2 when grown in trypticase soy broth (TSB) containing the iron chelator desferal, as compared to bacteria cultured in iron replete TSB. Growth in TSB containing desferal resulted in increased production of intracellular toxin by VT1 producing strains of E. coli; but had little effect on production of intracellular toxin by VT2 producing strains. Both extra- and intracellular levels of Shiga toxin were increased by growth in TSB containing desferal. Combining intra- and extracellular toxin titres, strains of E. coli producing VT1 gave highest titres following growth in TSB where iron was bound to the chelating agent desferal, while strains of S. dysenteriae 1 produced highest levels of toxin when grown in syncaseglucose broth made iron depleted using Chelex-100. Strains of S. dysenteriae 1 did not grow in syncase-glucose broth containing desferal.

Hemagglutinating properties of Shigella dysenteriae type 1 and other Shigella species

Strains of Shigella dysenteriae type 1 cultured in Casamino Acids-yeast extract broth medium in the presence of 1 mM calcium chloride at 37 degrees C for 22 h induced hemagglutination of erythrocytes that was inhibited by N-acetylneuraminic acid, N-acetylneuramin-lactose, and alpha 1-glycoprotein. The hemagglutination was heat labile, and the absence of cell-surface appendages suggested a nonfimbrial adhesin(s). Under the same conditions, strains of Shigella flexneri (types 1a, 1b, 2a, and 2b) showed N-acetylneuraminic acid-resistant hemagglutination of erythrocytes.

Role of Shiga toxin in the pathogenesis of bacillary dysentery, studied by using a Tox- mutant of Shigella dysenteriae 1

A Tox- mutant of Shigella dysenteriae 1, SC501, was genetically engineered by cloning the Shiga toxin operon, inserting a cassette into the A subunit gene, and exchanging this in vitro-mutagenized sequence with the wild-type gene. SC501 produced a low amount of residual cytotoxicity which was not neutralized by a rabbit immune serum directed against Shiga toxin. Invasion of cultured cells demonstrated that Shiga toxin had no effect on the rate of intracellular growth of bacteria or on the rapid killing of invaded host cells. On the other hand, several significant differences were observed in macaque monkeys infected intragastrically with either the wild-type strain or its mutant. The production of Shiga toxin by the invading strain was correlated with the presence of blood within stools, a sharp drop in blood polymorphonuclear cells, and histopathological alterations, such as the destruction of capillary vessels within the connective tissue of the colonic mucosa, severe inflammatory vasculitis of the peritoneal mesothelium, and major efflux of inflammatory cells to the intestinal lumen. It is proposed that Shiga toxin influences the severity of bacillary dysentery by inducing colonic vascular damage, which accounts for bloody stools, intestinal ischemia, and inflation of a polymorphonuclear intestinal compartment during the infectious process.

[Diagnosis of Grigor'ev-Shiga dysentery]

The data on the relative significance and composition of Sh. dysenteriae serovars isolated in some regions of the USSR in 1975-1979 are presented. Special tests revealed that Endo agar was the best medium, while Ploskirev's agar was the worst medium for growing Sh. dysenteriae 1 (the museum strain and the newly isolated strain from Bangladesh). The testing of agar with eosine-methylene blue yielded moderate results in respect of the growth of the museum strain; as to the growth of the strain from Bangladesh, the results were identical to those obtained in testing Ploskirev's agar. The "epidemic" strain from Bangladesh was shown to correspond to the classical characteristics in its fermentative properties: polyvalent dysenteric phage and agglutinating sera produced in the USSR proved to be completely suitable for identification. The present-day clinical course and clinico-laboratory characteristics of dysentery caused by Sh. dysenteriae 1 are described. Practical recommendations on the bacteriological and clinical diagnosis of Grigoryev-Shiga dysentery, brought from an outside infection source, are proposed.

Laboratory transmission of enterobacteriaceae by the oriental cockroach, Blatta orientalis

Methods of maintaining and feeding and of infecting cockroaches with pathogenic organisms were investigated.Cockroaches fed on known concentrations of Escherichia coli O119, Esch. coli O1, Alkalescens Dispar O group 2 and Shigella dysenteriae 1 (Shiga's Bacillus) were maintained in Petri dishes. The effect of various diets on the survival of these organisms within the hind-gut and faeces was observed. With a ;normal' diet of gruel Esch. coli O119 was isolated for up to 20 days, Esch. coli O1 for 17 days and ADO 2 for 15 days. Sh. dysenteriae 1 was isolated only sporadically to the third day.

Analysis of sequential stages in serum bactericidal reactions

Michael, J. Gabriel (House of the Good Samaritan, Children's Hospital Medical Center, Boston, Mass.), and Werner Braun. Analysis of sequential stages in serum bactericidal reaction. J. Bacteriol. 87:1067-1072. 1964.-The bactericidal reaction of "normal" human serum against Escherichia coli was found to be separable into two distinctive stages. The early (first) stage of the reaction lasts for a relatively short period of time, and involves factors that are present in sufficient amounts only in slightly diluted serum. The later (second) stage needs more time and requires factors present in highly diluted serum. The first stage depends on the presence of Ca(++) and Mg(++) and on the activity of all components of complement; the second stage does not require divalent cations and C'1, C'2, and C'4, but requires factors that can be removed by zymosan. Under our conditions, removal of lysozyme did not influence either stage of the reaction. Bacteria exposed to concentrated serum for a short time, during the first stage, are essentially unaffected as far as their potential for subsequent multiplication is concerned; the actual damage to cellular integrity occurs only during the second stage of the reaction. In the absence of cell division, the "sensitization" produced during the first stage can be preserved for prolonged periods, and the bactericidal reaction can be completed later by exposure to antibody-free, highly diluted serum (second stage). Cell multiplication abolishes the sensitizing effects of the first stage.