1. Enterobacteriacea and their diseases
Enteric infections: Escherichia coli, Salmonella spp., Salmonella enterica Typhi/Paratyphi, Shigella spp., Yersinia spp.
Bloodstream infections: Escherichia coli, Klebsiella penumoniae, Enterobacter spp.
Lung infections: Escherichia coli, Klebsiella pneumoniae, Enterobacter spp.
Urinary tract infections: Escherichia coli, Proteus spp., Klebsiella spp., Morganella spp.
Meningitis: Escherichia coli

2. Enterobacteriaceae envelope structures

3. Human infectious diseases caused by Escherichia coli
Enteric Infections
ETEC (enterotoxinogenic)
EPEC (enteropathogenic)
EAEC (enteroadherent)
EIEC (enteroinvasive), very similar to Shigella
STEC (Shiga-toxin), formerly EHEC (enterohemorrhagic)
AIEC (associated with Crohn’s disease)
DAEC (diffusely adherent)
Urinary tract infections
Meningitis in newborns (VLBW) and infants
Ventilator associated pneumonia and bloodstream infections (nosocomial & opportunistic)
T. Escherich

4. Reservoirs and transmission for pathogenic E. coli
General overview of potential reservoirs and modes of transmission for pathogenic E. coli. Pathogenic E. coli strains can be found in various animal reservoirs and can spread between these and other animals. Fecal matter can contaminate food, irrigation water, or recreational/drinking water. Humans can become exposed following the ingestion of contaminated food or water or through direct contact with colonized animals. Secondary transmission can occur between humans, commonly in day care centers or nursing homes. Food can become contaminated through poor cooking practice, where, for example, uncooked meat could come in contact with other food. Additionally, symptomatic or asymptomatic food handlers can contaminate food, particularly when hand hygiene is inadequate. Contamination of recreational or drinking water can occur through exposure of human sewage.

5. Pathogenic E. coli and Shigella and their association with the intestinal tract
Adherence patterns of enteric E. coli. Pathogenic E. coli requires adherence to the host epithelium. Enteropathogenic E. coli (EPEC) (represented in yellow) and LEE-positive Shiga toxin-producing E.coli (STEC) (represented in pink) are extracellular pathogens that attach to the intestinal epithelium and efface microvilli, forming characteristic A/E lesions. Due to the presence of bundle-forming pili, EPEC is capable of forming microcolonies, resulting in a localized adherence (LA) pattern. Enterotoxigenic E. coli (ETEC) (represented in orange) uses colonization factors (CFs) for attachment to host intestinal cells. Enteroaggregative E. coli (EAEC) (represented in green) forms biofilms on the intestinal mucosa, and bacteria adhere to each other as well as to the cell surface to form an aggregative adherence pattern (AA) known as “stacked brick.” Diffusely adherent E. coli (DAEC) (represented in blue) is dispersed over the surfaces of intestinal cells, resulting in a diffuse adherence (DA) pattern. Adherent invasive E. coli (AIEC) (represented in purple) colonizes the intestinal mucosae of patients with Crohn's disease and is capable of invading epithelial cells as well as replicating within macrophages. AIEC uses type I pili to adhere to intestinal cells and long polar fimbriae that contribute to invasion. Enteroinvasive E. coli (EIEC)/Shigella (represented in red) are intracellular pathogens that penetrate the intestinal epithelium through M cells to gain access to the submucosa. EIEC/Shigella escape submucosal macrophages by induction of macrophage cell death followed by basolateral invasion of colonocytes and lateral spread.

6. Enterotoxigenic E. coli
Common cause of watery diarrhea in malnourished infant; major cause of traveler's diarrhea (3-4 days); 79,420 cases in the US
Acquired from feces-contaminated food or water
Organisms reproduce in proximal small intestines, adhere via pili, and release either or both the heat-stable (ST) or heat-labile (LT) enterotoxin
Hypersecretion of fluids and electrolytes watery diarrhea, dehydration; LT is a paralogue of cholera toxin
Diagnosis: Isolation of ETEC from feces
Treatment: oral rehydration for spontaneous recovery; antibiotic therapy is not necessary

7. ETEC, EAEC and DAEC pathogenesis
a ∣ Enterotoxigenic Escherichia coli (ETEC) becomes anchored to enterocytes of the small bowel through colonization factors (CFs) and an adhesin that is found at the tip of the flagella (EtpA). Tighter adherence is mediated through Tia and TibA. Two toxins, heat-labile enterotoxin (LT) and heat-stable enterotoxin (ST), are secreted and cause diarrhoea through cyclic AMP (cAMP)- and cyclic GMP (cGMP)-mediated activation of cystic fibrosis transmembrane conductance regulator (CFTR). b ∣ Enteroagreggative E. coli (EAEC) attaches to enterocytes in both the small and large bowels through aggregative adherence fimbriae (AAF) that stimulate a strong interleukin-8 (IL-8) response, allowing biofilms to form on the surface of cells. Plasmid-encoded toxin (Pet) is a serine protease autotransporter of the Enterobacteriaceae (SPATE) that targets α-fodrin (also known as SPTAN1), which disrupts the actin cytoskeleton and induces exfoliation. c ∣ Diffusely adherent E. coli (DAEC) forms a diffuse attaching pattern on enterocytes of the small bowel, which is mediated through afimbrial (Afa) and fimbrial adhesins, which are collectively known as Afa–Dr fimbriae. Most Afa–Dr fimbriae bind to complement decay-accelerating factor (DAF); a subset of Afa–Dr fimbriae bind to receptors in the carcinoembryonic-antigen-related cell-adhesion molecule (CEACAM) family. The autotransported toxin Sat has been implicated in lesions of tight junctions (TJs) in Afa–Dr-expressing DAEC, as well as in increased permeability. Polymorphonuclear leukocyte (PMN) infiltration increases surface localization of DAF. AMP, antimicrobial peptides; Gsα, stimulatory guanylyl-nucleotide-binding (G) protein α-subunit; MAPK, mitogen-activated protein kinase; PKA, protein kinase A.

8. STEC (EHEC) Shiga-toxin producing E. coli
Epidemiology: US 265,000 illnesses (nationally notifiable), 3,600 hospitalizations (HUS) and 30 deaths; 96,534 STEC O157 and 168,698 STEC non-O157 infections
Symptoms: watery diarrhea, sometimes bloody
Hemolytic uremic syndrome: renal failure, hemolytic anemia, and thrombocytopenia
Diagnosis: culture isolation, STEC detection, PCR (stx detection and classification), O and H antigen characterization
Treatment: oral rehydration; no antibiotic treatment recommended.

9. Enteropathogenic E. coli
Common cause of childhood diarrhea in the developing world
Institutional diarrheal outbreaks
Organisms form small microcolony
aggregates on epithelium
Treatment: symptomatic

10. EPEC & STEC (EHEC): attaching and effacing lesions are produced by type III secretion
Enteropathogenic Escherichia coli (EPEC) and enterohaemorrhagic E. coli (EHEC) are attaching and effacing (A/E) pathogens that efface the microvilli and subvert host cell actin to form pedestals beneath the attachment site. The pedestal formation mechanisms shown for EPEC and EHEC are based on studies of the prototypical strains EPEC E2348/69 and EHEC O157:H7; lineage 2 EPEC strains and non-O157 EHEC strains can use a combination of these mechanisms for pedestal formation61. Effectors secreted by the type III secretion system can affect Cl‐–OH‐ and Na+–H+ exchanger activity, mislocalize aquaporins and inhibit sodium-D-glucose cotransporter 1 (SGLT1). EPEC attaches to the small bowel through the bundle-forming pilus (BFP), forming localized adhesions (LA). Intimate attachment is mediated by the interaction between intimin and the translocated intimin receptor (Tir). Tir is phosphorylated by host tyrosine kinases, and phosphorylated Tir recruits Nck, which activates neural Wiskott–Aldrich syndrome protein (N-WASP) and the actin-related protein 2/3 (ARP2/3) complex to mediate actin rearrangements and pedestal formation. Using the locus of the enterocyte effacement-encoded type III secretion system, a large repertoire of effector proteins is injected into the host cell, subverting host cell pathways. The mechanism of pedestal formation by EHEC is slightly different from that used by EPEC. Tir is not phosphorylated, and pedestal formation is Nck-independent. The actin rearrangements that are necessary for pedestal formation are mediated by Tir cytoskeleton-coupling protein (TccP; also known as EspFU), which is linked to Tir through the host protein insulin receptor tyrosine kinase substrate (IRTKS; also known as BAIAP2L1) and interacts with N-WASP to activate the ARP2/3 complex. In addition to this intimate attachment, EHEC attaches to the large bowel through the E. coli common pilus (ECP) and the haemorrhagic coli pilus (HCP). EHEC injects many of the same effectors as EPEC into the host cell to manipulate host processes. In addition, Shiga toxin (Stx; also known as verocytotoxin) is released following phage-mediated lysis in response to stress, further contributing to disease. Globotriaosylceramides (Gb3s) on Paneth cells in the human intestinal mucosa act as receptors for Stx. CDC42, cell division control protein 42; Cx43, connexin 43 (also known as GJA1); Cif, cycle-inhibiting factor; Map, mitochondrial-associated protein; NHE3, Na+–H+ exchanger 3; NleA, non-LEE-encoded effector A (also known as EspI); SERT, serotonin transporter; TJ, tight junctions.

11. Shiga toxins also designated Vero toxins (for Vero cell toxicity)
a | A cartoon of Shiga holotoxin, consisting of one A subunit (StxA), which is cleaved into fragments A1 and A2, and five B fragments that constitute the homopentameric B subunit (StxB). b | A ribbon diagram of Shiga toxin, highlighting globotriaosylceramide (Gb3)-binding sites on StxB. Gb3 is shown in a ball-and-stick representation. c | An enlargement of StxA at the site of furin cleavage (Arg25-Met252), and showing the disulphide bond (between Cys242 and Cys261) that links the A1 and A2 framents. d | A ribbon diagram of an StxB subunit from the membrane-oriented surface, highlighting the three Gb3-binding sites. Gb3 is shown as a ball-and-stick representation.
Family of AB5 toxins expressed by S. dysenteriae serogroup 1 and by STEC E. coli strains; carried on STX phages
Key factor in the pathogenesis of hemolytic uremic syndrome
B5 subunit binds to Gb3 glycolipid on host cells
A is cleaved by furin to generate A1 and A2, and A1 functions as RNA N-glycosidase to cleave rRNA, blocking ribosomal protein synthesis.

12. Intracellular trafficking of Shiga toxin
An overview of intracellular trafficking of Shiga toxins. Toxin binding to the plasma membrane induces local spontaneous curvature, membrane-mediated clustering and the toxin-driven formation of endocytic invaginations. The toxin then undergoes retrograde sorting in early endosomes, in which retrograde tubules are formed in a clathrin-dependent manner, and Shiga toxins preferentially localize to this tubular environment. Retrograde tubules are processed by scission in a retromer-dependent manner. Shiga toxins bypass the late endocytic pathway and are transferred directly from the early endosome to the trans-Golgi network (TGN) and, from there, on to the endoplasmic reticulum (ER). Finally, Shiga toxins use the ER-associated degradation (ERAD) machinery to facilitate retro-translocation into the host cell cytosol. By contrast, the transferrin receptor protein (TfR) (Y-shaped) becomes enriched in recycling tubules in the early endosome and recycles back to the plasma membrane.

13. Enteroinvasive E. coli Disease occurs mainly in developing countries
Ingestion of feces-contaminated water or food
Organisms invade the intestinal mucosa
Initially watery diarrhea, then bloody and/or mucous diarrhea
Eventually PMNs in stool; resembles bacterial dysentery
Therapy: symptomatic

14. Bacillary dysentery (Shigellosis)
Definition: acute infection of the intestine caused by Shigella dysenteriae (group A), S. flexneri (B), S. boydii (C), or S. sonnei (D)
Transmission: Fecal-oral through person-to-person contact or food, water or fomites; ID 10 bacteria=highly infectious
Epidemiology: world-wide million cases, 600,000 deaths; in the US child care centers are associated with outbreaks in children (typically S. sonnei and S. flexneri); ~14,000 laboratory confirmed cases.
Presentation: After h incubation watery, bloody or mucoid diarrhea, fever, stomach cramps, and nausea for 4-7 days; in young children: vomiting, seizures or postinfectious arthritis. Hemolytic uremic syndrome after infection with S. dysenteriae serogroup 1.
Diagnosis: culture isolation in selenite F broth & MacConkey’s agar.
Treatment: Antimicrobials (fluoroquinolone, ceftriaxone for children), when given early, slightly shorten duration of symptoms and carriage. Oral rehydration therapy.
Prevention: No vaccine available. Hand washing and strict adherence to standard food and water safety precautions.

15. Bacillary dysentery Watery, bloody stool Acute abdomen
Colonic lesions & ulcerations

16. Pathogenesis of Bacillary Dysentery
Entry into colonic epithelial cells & intracellular replication

17. Sereny Test Shigella keratoconjunctivitis in guinea pigs
as a test for invasiveness

18. Human urinary tract infections

19. Pilus assembly of uropathogenic
E. coli

20. Pathogenesis of E. coli urinary tract infections
The different stages of extraintestinal Escherichia coli infections are shown. a ∣ Uropathogenic E. coli (UPEC) attaches to the uroepithelium through type 1 pili, which bind the receptors uroplakin Ia and IIIa; this binding stimulates unknown signalling pathways (indicated by the question mark) that mediate invasion and apoptosis. Binding of type 1 pili to α3β1 integrins also mediates internalization of the bacteria into superficial facet cells to form intracellular bacterial communities (IBCs) or pods. Sublytic concentrations of the pore-forming haemolysin A (HlyA) toxin can inhibit the activation of Akt proteins and leads to host cell apoptosis and exfoliation. Exfoliation of the uroepithelium exposes the underlying transition cells for further UPEC invasion, and the bacteria can reside in these cells as quiescent intracellular reservoirs (QIRs) that may be involved in recurrent infections.

21. Salmonella gastroenteritis first isolated by USDA scientist Daniel Salmon, DVM (1850-1914)
Definition: gastrointestinal infection with Salmonella spp. (there are more that 2,000) causing diarrhea, fever and abdominal cramps hours post infection; higher incidence during summer months
Epidemiology:1.2 million cases in the US per year; ~450 deaths; transmission from animals and animal products to humans
Clinical: diarrhea, nausea, vomiting, abdominal pain and fever; diarrhea ranges from loose stools to profuse watery; not bloody; lasts 4-7 days
Complications: reactive arthritis, bloodstream infection and seeding in many different organ tissues; elderly, infants and immune compromised are at high risk.
Diagnosis: Culture isolation from diarrhea sample; serotyping, reporting with PHRL and CDC
Treatment: oral rehydration; antibiotics (ciprofloxacin, cetriaxone or ampicillin) only for serious illness and high risk patients ; drug resistance occurs in 5%
Prevention: cook it! Wash your hands after handling raw meat, eggs.

22. Prevalence of Salmonella in selected foods sold in the United States, 2001
Food Product
Average (%)
2001 (%)
Chicken Broilers 20 12
Hogs 9 4
Cows 3 2
Steers 1
0.6
Ground Beef 8
Ground Chicken 45
Ground Turkey 50 26

23. Top 20 Salmonella spp. causing Salmonella gastroenteritis in the US

24. World-wide incidence of typhoid fever 22 million cases & 216,500 death in 2012

25. Typhoid fever
Definition: systemic life-threatening infection with Salmonella enterica serovar Typhi; 5,700 cases in the US; human specific pathogen & disease; notifiable in the US.
Transmission: via the fecal-oral route with non-symptomatic long-term carriers as reservoir (Typhoid Mary)
Clinical: febrile illness (≥103F) without specific symptoms , sometimes rose-color spot rash, complicated by intestinal perforation and neurological manifestations (apathy, confusion, psychosis), fatality 20%.
Diagnosis: culture isolation from fecal sample (H2S+ on Bismuth-sulfite agar) sensitive & specific; rapid serologic tests available (Widal test, Tubex TF, and TyphiDot):non-specific and not diagnostic.
Treatment: antibiotics (ciprofloxacin, ceftriaxone or azithromycin) shorten the duration of fever & bacterial shedding and reduce case-fatality rate.
Prevention: 1 x injection with ViPS vaccine (Vi polysaccharide antigen, Sanofi) for ≥2 yoa or live-attenuated oral Ty21a (4x ≥5yoa). Different typhoid conjugate vaccines (TCV) are under commercial development.

26. Typhoid fever disease stages
Infection
Incubation
Active Invasion
Disease
Con-valescence
Late/Focal
Time
Week 1
Week 2
Week 3
Week 4
indefinite
Stool cultures
Positive
Negative
80% positive
50 positive
3% positive in year 1
Blood cultures
Negative (or relapse)
Widal Test
20% positive
50% positive
Widal test=typhoid fever serum antibody agglutinates with S. enterica Typhi

27. Salmonella (Typhi or non-Typhi) invasion of the human gastroinestinal tract
Orally ingested salmonellae survive at the low pH of the stomach and evade the multiple defences of the small intestine in order to gain access to the epithelium. Salmonellae preferentially enter M cells, which transport them to the lymphoid cells (T and B) in the underlying Peyer's patches. Once across the epithelium, Salmonella serotypes that are associated with systemic illness enter intestinal macrophages and disseminate throughout the reticuloendothelial system. By contrast, non-typhoidal Salmonella strains induce an early local inflammatory response, which results in the infiltration of PMNs (polymorphonuclear leukocytes) into the intestinal lumen and diarrhoea.

28. Salmonella uses the SPI-1 type III secretion pathway to invade epithelial cells
On contact with the epithelial cell, salmonellae assemble the Salmonella pathogenicity island 1(SPI1)-encoded type III secretion system (T3SS) and translocate effectors (yellow spheres) into the eukaryotic cytoplasm. Effectors, such as SopE, SopE2 and SopB, then activate host Rho GTPases, which results in the rearrangement of the actin cytoskeleton into membrane ruffles, induction of mitogen-activated protein kinase (MAPK) pathways and destabilization of tight junctions. Changes in the actin cytoskeleton, which are further modulated by the actin-binding proteins SipA and SipC, lead to bacterial uptake. MAPK signalling activates the transcription factors activator protein-1 (AP-1) and nuclear factor-B (NF-B), which turn on production of the pro-inflammatory polymorphonuclear leukocyte (PMN) chemokine interleukin (IL)-8. SipB induces caspase-1 activation in macrophages, with the release of IL-1 and IL-18, so augmenting the inflammatory response. In addition, SopB stimulates Cl- secretion by its inositol phosphatase activity. The destabilization of tight junctions allows the transmigration of PMNs from the basolateral to the apical surface, paracellular fluid leakage and access of bacteria to the basolateral surface. However, the transmigration of PMNs also occurs in the absence of tight-junction disruption and is further promoted by SopA. The actin cytoskeleton is restored and MAPK signalling is turned off by the enzymatic activities of SptP. This also results in the down-modulation of inflammatory responses, to which SspH1 and AvrA also contribute by inhibiting activation of NF-B.

29. Salmonella uses the SPI-2 type III secretion pathway to replicate in the phagosome of host cells (SCV=Salmonella conatining vacuole)
Shortly after internalization by macropinocytosis, salmonellae are enclosed in a spacious phagosome that is formed by membrane ruffles. Later, the phagosome fuses with lysosomes, acidifies and shrinks to become adherent around the bacterium. This is called the Salmonella-containing vacuole (SCV), which contains the endocytic marker lysosomal associated membrane protein 1 (LAMP-1; purple). The Salmonella pathogenicity island 2 (SPI2) T3SS (type III secretion system) is induced within the SCV and translocates effector proteins (yellow spheres) across the phagosomal membrane several hours after phagocytosis. The SPI2 T3SS effectors SifA and PipB2 contribute to Salmonella-induced filament (Sif) formation along microtubules (green) and regulate microtubule-motor (yellow star shape) accumulation on the Sif and the SCV. SseJ is a deacylase that is active on the phagosome membrane. SseF and SseG cause microtubule bundling adjacent to the SCV and direct Golgi-derived vesicle traffic toward the SCV. Actin accumulates around the SCV in a SPI2 T3SS-dependent manner, in which SspH2, SpvB and SseI are thought to have a role.

30. Typhoid toxin
The crystal structure of typhoid toxin depicts its unique architectur: CdtB=cytodistending toxin B, pertussis-like toxin A and B (PltAB). a, Two views of the overall structure of the typhoid holotoxin complex shown as a ribbon cartoon and related by 90° rotation about a vertical axis. CdtB, PltA and PltB are shown in blue, red, and green, respectively. b, Bottom view of the channel formed by the PltB pentamer (in green), depicting the PltA C-terminal α-helix (in red) within it. c, Surface charge distribution of the predicted sugar-binding pockets of different B subunit homologs of the indicated AB5 toxins (SubB for Subtilase and S2 for Pertussis toxins). A highly conserved serine residue critical for sugar binding is indicated within the sugar-binding pocket. The sugars N-glycolylneuraminic acid (within SubB) and N-acetylneuraminic acid (within typhoid and pertussis toxins) are shown. d, Molecular modeling of N-acetylneuraminic acid within the typhoid toxin binding pocket. Critical residues engaged in this interaction are shown. e, Atomic interface between CdtB and PltA. The inset shows a detailed view of a critical disulfide bond between PltA Cys214 and CdtB Cys269.
The genes for typhoid toxin are found in S. enterica Typhi, not in S. enteritica
Typhoid toxin, an A-A-B5 toxin, is only expressed by bacteria inside human cells
CdtB (similar to Campylobacter cytodistending toxin) functions as a DNAse that cleaves nuclear DNA and activates immune signaling
PltA (Pertussis like-toxin A) functions as an ADP-ribosyltransferase
PltB is the typhoid toxin schlepper and binds to host cell glycoproteins

31. Model for the delivery of S
Model for the delivery of S. enterica Typhi CdtB (typhoid toxin) from the Salmonella containing vacuole (paracrine secretion)

32. Cholera a nationally reportable disease
Definition: acute, diarrheal illness caused by intestinal infection with Vibrio cholerae, a human disease without animal models
Transmission by ingestion of contaminated food or water; ID 106 bacteria
Severe Cholera: 5-10% of infected persons infected with V. cholerae O1 or O139 develop severe cholera: diarrhea (profuse rice water stools), vomiting, heart racing, dessication, hypotension, muscle cramps, irritability
Death: Without therapy, severe cholera can advance to acute renal failure, coma, shock and death (25-50%, typically within hours)
Diagnosis: stool sample to culture V. cholerae on TCBS (thiosulfate–citrate–bile salts agar); genome sequence for epidemiology. In the field, Crystal VC® dipstick rapid test can suggest (not diagnose) cholera
Treatment: rapid high-volume rehydration with ORS (oral rehydration solution) for moderate cholera; IV fluids for severe cholera; antibiotics for severe cholera (doxycycline or azithromycin/erythromycin; resistance should be monitored); zinc (10-20 mg) supplementation (reduced time & volume of diarrhea)

33. Fluid, glucose & salt substitution therapy of cholera

34. Countries reporting cholera in 2011-2012
V. cholerae O1 & O139 (toxigenic). In 2012, 18 cases with V. cholerae O1 (El Tor) were reported to CDC: 17 travel related (Haiti 10, Dominican Republic 3, Africa and Asia 4) and 1 laboratory infection
V. cholerae O75 & O141 (toxigenic). In 2012, 4 cases (2 raw clams from New Jersey).

35. Pathogenesis of cholera
After ingestion, V. cholerae colonizes the small intestine and secretes cholera toxin, which has a doughnut-like structure with a central enzymatic toxic-active A (A1+A2) subunit associated with pentameric B subunits (B5). After binding to GM1 ganglioside receptors, mainly localized in lipid rafts on the cell surface, the toxin is endocytosed and travels to the ER via a retrograde pathway which—dependent on cell type—may or may not involve passage through the Golgi. In the ER, the A subunit dissociates from the B subunits and through translocation via the ER degradasome pathway, A1 can reach the cytosol where it can rapidly refold. It binds to and ADP-ribosylates Gs, stimulating the AC complex to produce increased cellular levels of cAMP, leading to activation of PKA, phosphorylation of the major chloride channel, CFTR, and secretion of chloride (Cl−) and water. Cholera toxin-induced chloride (and bicarbonate) secretion is especially pronounced from intestinal crypt cells, whilst in villus cells the increased cAMP levels instead mainly inhibits the normal uptake of NaCl and water.14 Abbreviations: AC, adenylate cyclase; ADPR, ADP ribose; cAMP, cyclic AMP; CTA, cholera toxin A; CTB, cholera toxin B; CTFR, cystic fibrosis transmembrane conductance regulator; ER, endoplasmic reticulum; Gs, GTP- binding protein, Gs; PKA, protein kinase A.

36. Cholera toxin AB type toxin secreted via type II pathway:
A – single subunit
B - five subunits
B pentamer forms a ring structure and binds to gangliosides on human intestinal epithelial cells
A1 subunit ADP-ribosylates GSα protein of adenylate cyclase; A2 links A subunit to B subunit
ctxAB genes encoded on the CTX bacteriophage
5mg causes 1-6L of diarrhea in adult volunteers

37. Lysogenization with CTX bacteriophage generates toxigenic V. cholerae
a | Cholera toxin is encoded by the CTX prophage in toxigenic Vibrio cholerae O1, and a typical CTX genome consists of a core region carrying the cholera toxin genes ctxAB, and psh, cep, pIIICTX, ace, zot—genes responsible for virion morphogenesis. The RS2 region encodes the regulation (rstR), replication (rstA), and integration (rstB) functions of the CTX genome. Direction of transcription is shown by the arrows. b | The integration process involves site-specific recombination, catalyzed by tryosine recombinases XerC and XerD, between the attP site (cataca) of CTXΦ and the attB sequences inside the dif region (tgccgcgccaca) of chromosome 1 of V. cholerae.

38. Phylogenetic relationship of Vibrio cholerae strains
On the basis of the antigenicity of the O antigen component of the outer membrane lipopolysaccharide, more than 200 serogroups (O1–O200) of Vibrio cholerae exist in aquatic environments. Only a subset of O1 and O139 serogroup strains are toxigenic (Tox+) and therefore capable of causing cholera when ingested; such strains are selected for in the host. Other strains are non-toxigenic (Tox−) and are selected against. Different O antigen types are indicated by the colour of the outer membrane and sheathed flagellum (the periplasmic space and the inner membrane are not shown). Capsules are present in a subset of strains. Different strain genotypes are indicated by the colour of the cytoplasm; note that Tox+ O1 and O139 have essentially the same genotype, with the exception of the O antigen genes.

39. Cholera vaccines

40. Modeling the caseload of cholera in rural Bangladesh with or without vaccination
a | Anticipated caseload of cholera during a year following no vaccination and b–d | following vaccination with progressively higher levels of vaccine coverage. Cholera is predicted to be nearly extinguished by a vaccine coverage level of only around 60%.

41. CDC: five basic cholera prevention messages
Drink and use safe water
Wash your hands often with soap and safe water
Use latrines or bury your feces; do not defecate in any body of water
Cook food well (especially seafood), keep it covered, eat if hot, and peel fruits and vegetables
Clean up safely – in the kitchen and in places where the family bathes and washes clothes

42. Carbapenem-resistant enterobacteriaceae (CRE) in healthcare settings
Definition: CRE have high-level resistance to antibiotics, including carbapenems (β-lactam with broad-spectrum antibiotic activity); isolated in all states except ME and ID
 KPC (Klebsiella pneumoniaecarbapenemase), NDM (New Delhi Metallo-β-lactamase) and VIM (Verona Integron-Mediated Metallo-β-lactamase) break down carbapenems
KPC, NDM and VIM occur in enterobacteria (E. coli, K. pneumoniae, Enterobacter) and in P. aeruginosa
CRE infections do not occur in healthy individuals; CRE are hospital associated pathogens who contaminate rooms, equipment (endoscopes) and colonize staff
CRE infections in hospital-patients are associated with high mortality (up to 50%)