Enterobacteriaceae & Campylobacter.docx

Bacteria Proteobacteria Gamma-proteobacteria Enterobacterales **Enterobacteriaceae** - ***Escherichia coli*** - ***Salmonella enterica subsp. Enterica serovar Typhi*** - ***Salmonella enterica subsp. Enterica serovar Typhimurium*** - ***Shigella spp.*** - ***Proteus mirabilis***...

Bacteria Proteobacteria Gamma-proteobacteria Enterobacterales **Enterobacteriaceae** - ***Escherichia coli*** - ***Salmonella enterica subsp. Enterica serovar Typhi*** - ***Salmonella enterica subsp. Enterica serovar Typhimurium*** - ***Shigella spp.*** - ***Proteus mirabilis*** - *Yersinia spp.* - *Y. pseudotuberculosis* -- cause diseases similar to tuberculosis - *Y. enteracalitica* -- diarrheal disease - *Klebsiella peumoniae* - *Enterobacter spp.* - *Serratia spp.* - *Morganella spp.* - *Providencia spp.* ***\ *** ***Escherichia coli*** **Characteristics:** \- Gram-negative bacilli \- Motile; facultative anaerobe \- Catalase +ve: Produces catalase enzyme. \- Lactose fermenter: Produces beta-galactosidase and cleaves lactose into glucose and galactose. \- encapsulated -- some strains are not \- reduce nitrate to nitrite \- Grow on peptone or meat extract media without the addition of sodium chloride or other supplements = Grow on basic, non-enriched media = Growth on NA, peptone water (a water-soluble mixture of peptides and amino acids obtained by digesting proteins), nutrient broth = can differentiate from ***Campylobacter*** **Tests and Cultivation** \- Catalase Test: Adding hydrogen peroxide to a colony; the presence of catalase results in foaming. \- Lactose Fermentation Test: Cultivation on lactose-containing media (e.g., phenol lactose), resulting in acid production and colour change from red to yellow. \- Eosin Methylene Blue (EMB) Agar: Grows into black colonies with a greenish-black metallic sheen. **Virulence factors** - Capsule -- polysialic acid -- K antigens - Fimbriae/pili -- attachment to the host cells - Flagella -- H antigens - Adhesins - O antigens - LPS - Lipid A - Endo - Enterotoxins - Exo - Haemolysins - Exo - Cytotoxic necrotising factor (CNF) - Exo **Serotypes and Diseases** \>150 serotypes All typed by O and H Example: O157:H7 (EHEC) - Associated with hemorrhagic colitis, hemolytic uremic syndrome, and diarrheal outbreaks. **Pathotype Classification** \- Pathotypes: Based on the disease-causing mechanism and virulence factors: 1\. Shiga-like toxin-producing E. coli (STEC) \- Produces Shiga toxin, causes bloody diarrhea, and can lead to hemolytic uremic syndrome (HUS). 2\. Enterotoxigenic E. coli (ETEC) \- Produces heat-labile and heat-stable enterotoxins, causing watery diarrhea. 3\. Enteroinvasive E. coli (EIEC) \- Invades and destroys intestinal epithelial cells, causing bloody diarrhea. 4\. Enteropathogenic E. coli (EPEC) \- Causes disease in children under two years old, leading to watery diarrhea. 5\. Uropathogenic E. coli (UPEC) \- Causes urinary tract infections (UTIs), including cystitis and pyelonephritis. **Pathogenesis of Each Pathotype** **1. Shiga-like Toxin-Producing E. coli (STEC)/EHEC -- Enterohaemorrhagic E.coli** - **Attachment**: STEC attaches to the host\'s intestinal cells using fimbriae. - **Toxin Production**: Produces Shiga-like toxins (Stx1 and Stx2). - **Intestinal Injury**: Toxins cause damage to the intestinal epithelium and blood vessels, resulting in inflammation. - **Bloody Diarrhea**: Inflammation and vessel damage lead to fluid and blood leaking into the intestinal lumen. - **Hemolytic Uremic Syndrome (HUS)**: - **Systemic Toxin Release**: Toxins enter the bloodstream, affecting the kidneys. - **Kidney Damage**: Toxins bind to endothelial cells in the glomeruli, causing apoptosis and gaps in the capillary walls, leading to proteinuria. - **Inflammatory Response**: Cytokines and chemokines are released, activating platelets and causing clot formation. - **Thrombocytopenia**: Decreased platelet count due to clot formation. - **Hemolytic Anemia**: Red blood cells are fragmented (schistocytes) as they pass through obstructed microvessels. - **Ischemic Kidney Damage**: Clots obstruct arterioles, leading to kidney ischemia, reduced filtration, and uremia. **2. Enterotoxigenic E. coli (ETEC)** - **Attachment**: ETEC uses fimbriae to adhere to the intestinal mucosa. - **Toxin Production**: - **Heat-labile Enterotoxin (LT)**: - **Mechanism**: Activates adenylate cyclase, increasing cAMP, leading to chloride and water secretion. - **Heat-stable Enterotoxin (ST)**: - **Mechanism**: Activates guanylate cyclase, increasing cGMP, leading to electrolyte and water secretion. - **Outcome**: Causes watery diarrhea without damaging the intestinal wall. possible fever, and bloating. **3. Enteroinvasive E. coli (EIEC)** - **Attachment and Invasion**: EIEC attaches to and invades intestinal epithelial cells. - **Intracellular Multiplication**: - **Invasion**: Invades and multiplies within epithelial cells, causing cell destruction. - **Inflammatory Response**: Triggers a strong inflammatory response, leading to widespread epithelial damage and bloody diarrhea. **4. Enteropathogenic E. coli (EPEC)** - **Attachment**: EPEC uses bundle-forming pili (BFP) to attach to intestinal epithelial cells. - **Effacement**: - **Mechanism**: Injects effector proteins via a Type III secretion system, causing actin cytoskeleton rearrangement. - **Effect**: Leads to pedestal formation and microvilli effacement. - **Outcome**: Impairs absorption, causing watery diarrhea, primarily in children under two years of age. prolonged diarrhea leading to malnutrition. **5. Uropathogenic E. coli (UPEC)** - **Colonization**: UPEC can colonize the periurethral area and ascend the urinary tract. - **Adhesion and Invasion**: - **Fimbriae**: Uses type 1 fimbriae and P fimbriae to adhere to uroepithelial cells. - **Invasion**: Invades and replicates within bladder cells. - **Toxin Production**: - **Hemolysins**: Produces alpha and beta hemolysins, causing lysis of urinary tract cells. - **Ascending Infection**: - **Cystitis**: Infection of the bladder, causing dysuria and frequent urination. - **Pyelonephritis**: Can ascend to the kidneys, causing flank pain and more severe symptoms. **Diagnosis** \- General Diagnosis: \- Gram Staining: On stool or urine sample. \- Culture: On eosin methylene blue agar. \- HUS Diagnosis: Identifying Shiga toxin in the blood. **Treatment** \- Diarrhea: Hydration and rest. Antibiotics in severe cases (e.g., doxycycline, cotrimoxazole). \- Hemolytic Uremic Syndrome (HUS): Supportive care - Dialysis, corticosteroids, blood transfusions, plasmapheresis. \- UTIs: Antibiotics: Cotrimoxazole, nitrofurantoin, fluoroquinolones (e.g., ciprofloxacin). ***Salmonella enterica*** - Gram -ve bacilli - Motile, facultative anaerobe - Non-spore former - Facultative intracellular pathogens - Encapsulated - Can ferment glucose but not lactose - Oxidase -ve - H~2~S positive - Frequently found in sewage, river, seawater, and certain food; pathogen of animals (poultry, cows, pigs) -- a common source of non-typhoidal Salmonella infections in humans - O, H, Vi antigens -- Vi specific to Salmonella spp. -- capsular polysaccharide (only typhoidal strains) - Virulence factors - Endotoxin - Enterotoxin - Exo - Cytotoxin - Exo ***Salmonella enterica subsp. enterica serovar typhi - typhoidal*** **Pathogenesis** 1\) Ingestion and Targeting: \- Reaches distal ileum of the small intestine \- Targets epithelial layer of the mucosal lining \- Adheres to and is phagocytosed by M cells \- Spit into underlying Peyer\'s patches 2\) Immune Evasion: \- Vi capsular polysaccharide antigen protects against antibody tagging \- Suppresses neutrophil recruitment \- Induces recruitment of monocytes and macrophages \- Can cause hypertrophy, necrosis, and potentially ileal perforation 3\) Survival and Replication: \- Phagocytosed by macrophages, forming a salmonella-containing vacuole \- Type III secretion system injects effector proteins, preventing vacuole-lysosome fusion \- Survives and replicates within the vacuole **- Systemic Spread:** \- Uses macrophages to enter lymphatic vessels and systemic lymphatic circulation \- Reaches reticuloendothelial tissues (liver, spleen, bone marrow, gallbladder) \- Induces macrophage apoptosis, causing bacteremia \- Can lead to sepsis **Transmission** \- Routes: Fecal-oral, poor sanitation, poor hygiene, contaminated water/food, particularly endemic to Asia, Africa, Latin America, and the Caribbean \- Inoculum: Requires about 100,000 microorganisms to cause infection **Symptoms** \- Onset: 1-2 weeks after infection, Duration: 4-6 weeks \- Typical Symptoms: \- High sustained fever \- Abdominal pain \- Constipation followed by diarrhea \- Rose or salmon-coloured spots on chest and abdomen \- Hepatomegaly and splenomegaly \- Dehydration, weakness, headaches, and cloudy mental state in advanced cases **Diagnosis** \- Methods: Blood culture, stool culture, intestinal secretions (vomit or duodenal aspirate), and gallbladder bile culture for carriers **Treatment** \- Symptomatic Management: Fluid and electrolyte replenishment, NSAIDs for pain and fever \- Antibiotics: Broad-spectrum antibiotics like fluoroquinolones or cephalosporins (ceftriaxone) \- Carriers: Combination of antibiotics and gallbladder removal **Prevention** \- Vaccines: Oral live attenuated vaccine and intramuscular vaccine containing VI capsular polysaccharide \- Hygiene: Proper sanitation and hygiene practices ***Salmonella enterica subsp. enterica serovar Typhimurium*** **General Characteristics** \- Serotypes: Over 2,500 serotypes within subspecies enterica \- Common Serotype: Salmonella enteritidis, typhimurium **Pathogenesis** 1\) Ingestion and Targeting: \- Reaches the distal ileum of the small intestine \- Targets epithelial layer of the mucosal lining \- Adheres to and is phagocytosed by M cells \- Spit into underlying Peyer\'s patches 2\) Immune Response: \- Strong pro-inflammatory cytokine response \- Recruitment of immune cells (especially neutrophils) \- Causes enterocolitis (inflammation of the small intestine and colon) \- Can lead to mucosal damage and ulcers 3\) Potential Spread: \- Usually limited to the mucosa and destroyed by local immune cells \- In some cases, can become invasive and cause bacteremia **Transmission** \- Reservoirs: Infected humans and animals (birds, reptiles, mammals, amphibians) \- Routes: Fecal-oral, foodborne (contaminated raw/undercooked animal products, water, fruits, vegetables, peanut butter), direct contact with infected animals **Symptoms** \- Onset: 24-48 hours after infection \- Typical Symptoms: \- Watery diarrhea (sometimes bloody) \- Abdominal cramps \- Nausea and vomiting \- Headache, chills, low-grade fever \- Dehydration **Diagnosis** \- Methods: Stool culture on selective media, additional cultures for invasive infections **Treatment** \- Fluid and electrolyte replenishment, suppressing nausea, alleviating pain \- Antibiotics ***Shigella* spp*.*** **General Information:** \- Species: \- Shigella dysenteriae \- Shigella flexneri \- Shigella boydii \- Shigella sonnei \- All species can cause **shigellosis**, a contagious intestinal infection, which can progress to dysentery. **Anatomy and Physiology:** \- Gram-negative bacilli \- Facultative anaerobe (can survive with or without oxygen). \- Non-motile (lacks flagella). \- Non-spore former \- Non-encapsulated \- Non-lactose fermenter. \- Urease and oxidase -ve. \- H~2~S negative **Virulence factors** - O antigen - Shiga toxin In shigella, but also found in EHEC (causing bloody diarrhea) - Invasiveness -- virulent strains penetrate the mucosa and epithelial cell of the colon. Virulent strains have to get through the mucus layer and through the epithelial barrier of the colon in order to be virulent =\> this is how they cause diseases. **Identification:** \- Culture Medium: Grows on selective media like MacConkey agar. \- Forms white, non-lactose fermenting, non-hydrogen sulfide-producing colonies. \- Microscopy: Stool stains with methylene blue may show polymorphonuclear leukocytes. \- PCR Testing: Direct identification of Shigella DNA. **Pathogenesis:** 1\. Ingestion and Initial Infection: \- Shigella is ingested and multiplies in the small intestine before passing into the colon. \- Targets epithelial cells of the mucosal lining, particularly M-cells. 2\. Invasion and Immune Response: \- M-cells phagocytose Shigella and release it into mucosa-associated lymphoid tissues (MALT). \- Macrophages in MALT gobble up Shigella, but Shigella induces apoptosis in macrophages. \- Release of cytokines (e.g., interleukin-1-beta) triggers intense inflammation, attracting more immune cells, damaging epithelial cells, and causing ulcerations and abscesses. 3\. Spread within the Host: \- Disrupts cellular junctions, allowing Shigella to enter enterocytes. \- Uses type III secretory system to inject proteins into enterocytes, inducing phagocytosis. \- Inside enterocytes, Shigella escapes the phagosome into the cytoplasm, uses actin-based motility to move and spread infection. 4\. Shiga Toxin (specific to Shigella dysenteriae serotype 1): \- An AB toxin (two subunits: A and B). \- B subunit binds to the host cell membrane; toxin engulfed into the phagosome. \- Acidic environment in phagosome breaks disulfide bond, separating subunits. \- A subunit diffuses into the cytoplasm, and cleaves 28S rRNA in ribosomes, halting protein synthesis and causing cell death. \- Can reach the bloodstream and cause hemolytic uremic syndrome (HUS). **Symptoms:** \- Symptoms last about seven days. \- infected person can be a carrier for infection up to 4 weeks after the onset of symptoms. \- Typical Symptoms: \- Severe abdominal and rectal cramping and pain. \- High fever, vomiting, loss of appetite. \- Watery, mucus-like diarrhea, potentially containing **blood** or pus. Bloody diarrhea \- Complications: \- Hemolytic Uremic Syndrome (HUS): Hemolytic anemia, kidney failure, thrombocytopenia. \- Tonic-Clonic Seizures: Particularly in children. \- Sepsis: Mostly in neonates, malnourished children, and people with S. dysenteriae serotype 1 infection. \- Reactive Arthritis: Pain and swelling in knee joints. **Transmission:** \- Fecal-oral transmission. \- Sources: \- Contaminated water or food. \- Flies carrying stool particles. \- Contact with contaminated objects or hands. \- Sexual contact (occasionally). **- Virulence: Extremely virulent; as few as 10 bacteria can cause an infection.** **- Survival: Can survive the acidic environment of the stomach.** **Diagnosis:** \- Fecal Sample: Cultured on selective media like MacConkey agar. \- Stool Stains: Methylene blue may show polymorphonuclear leukocytes. \- PCR Testing: For direct identification of Shigella DNA. **Treatment:** \- General Treatment: Fluid and electrolyte replenishment. \- Antibiotics: Beta-lactams (penicillins and cephalosporins), macrolides, quinolones. ***Proteus mirabilis*** **Overview** \- gram-negative bacillus. \- Widely distributed in soil and water and part of the normal human intestinal flora. \- Causes urinary tract infections (UTIs). **Characteristics** \- Non-spore-forming and highly motile. \- Facultative anaerobic (can survive in both aerobic and anaerobic environments). \- Non-lactose fermenter and oxidase - ve. \- Urease + ve (produces urease enzyme). \- H~2~S +ve **Growth on Agar** \- Blood agar: Exhibits swarming growth, forming thin, filmy layers of concentric circles. \- MacConkey agar: Forms smooth, pale, or colourless colonies; does not swarm. \- Triple Sugar Iron (TSI) test: Produces hydrogen sulphide (H~2~S), which reacts with iron to form a black precipitate. **Virulence Factors** \- Flagella: Confer motility; aids in swarming motility on surfaces, particularly urinary catheters. Swarming motility -- especially in urinary catheters, it can differentiate from short swimmer cells into elongated swarm cells. These swarm cells express many flagella, allowing the bacteria to move and form multicellular rafts. \- Fimbriae: Tiny projections used for **attachment** to uroepithelium cells. \- Hemolysin: Creates tiny holes in cell membranes, causing cell damage. \- ZapA protease: Destroys immunoglobulin A (IgA) and immunoglobulin G (IgG), neutralising the immune system\'s opsonins. *Pseudomonas* also neutralises opsonin. \- Urease: Converts urea in urine to ammonia and carbon dioxide, leading to the formation of **struvite stones**. **Pathogenesis in the Urinary Tract** \- Swarming motility aids in migration along catheter surfaces. \- Ascends from the bladder to the kidneys, causing infections. \- Struvite stones: Formed from phosphate, calcium, magnesium, and ammonium; can lead to staghorn renal calculi or kidney stones. \- Causes urinary stasis, promoting bacterial multiplication and urinary alkalinisation. **Infections Caused** \- Urethritis: Infection of the urethra. \- Cystitis: Infection of the bladder. \- Prostatitis: Infection of the prostate. \- Pyelonephritis: Infection of the kidneys. \- Struvite stones: May lead to xanthogranulomatous pyelonephritis, causing kidney destruction. **Risk Factors** \- Common in elderly hospitalised patients. \- Risk factors include urinary tract procedures (surgery, catheterisation), chronic kidney disease, neurogenic bladder, multiple prior UTIs, prior use of antibiotics, and sexual activity. **Symptoms** \- Urethritis: Dysuria (pain during urination), pyuria (pus in the urine), increased urinary frequency. \- Cystitis: Dysuria, urinary frequency, urgency, suprapubic pain, ammonia-smelling urine. \- Prostatitis: Similar to cystitis; may also include fever, chills, swollen and tender prostate. \- Pyelonephritis: Dysuria, urinary frequency, urgency, flank pain, fever, chills, nausea, vomiting. **Diagnosis** \- Urine culture: Identifies Proteus mirabilis. \- Urinalysis: Shows pyuria WBCs in urine, bacteriuria, and urinary pH above 7. \- Complete blood count (CBC): Shows leucocytosis in pyelonephritis or prostatitis. Or increase in \# of WBCs. \- X-ray: Struvite stones appear radiopaque. **Treatment** \- Cystitis: Trimethoprim-sulfamethoxazole (TMP-SMX), quinolones, or fosfomycin. \- Pyelonephritis: Fluoroquinolones, cephalosporins, or gentamicin. \- Struvite stones: Surgery may be required for removal. Bacteria Proteobacteria Epsilon-proteobacteria Campylobacterales **Campylobacteraceae** - Arcobacter - **Campylobacter** - Sulfurospirillum ***Campylobacter spp.*** - Gram -ve - Slender, curved, Long spiral-shaped rods, maybe coccoid in really old culture (a bit more round) - Motile (single polar unsheathed flagellum at one or both ends) - Non-spore former - Oxidase +ve -- can use oxygen to create ATP - Microaerophilic & capnophilic Different to Enterobacteriaceae - Have to grow them at reduced oxygen and increased CO~2~ - Fastidious - Temperature -- grows at **42°C** -- adapted to chickens with higher body temp. - Unable to use sugars either oxidatively or fermentatively; derive energy from amino acids; Not grow on MAC or NA; Should grow them on chocolate agar. - Virulence factors - Motility Allow them to burrow(dig) down through the mucus layer - Heat-labile enterotoxin = heat sensitive \- **Common Cause**: One of the most common causes of bacterial gastroenteritis worldwide. \- **Common Sources**: Found in foods like poultry and unpasteurised milk. **Medium** Grows on blood agar varieties like Skirrow, butzler, and Campy-BAP. Chocolate agar (fastidious) **Pathogenesis and Virulence Factors:** 1\) Attachment: Uses fimbri-like filaments and cell surface proteins like PEV-1 and CADF to attach to the mucosa of the small intestine and colon. 2\) Invasion: \- Drills into mucosa using its spiral shape and long flagella. \- Releases cytotoxins like cytolethal distending toxins (CDT), causing cell damage and inflammation. **Complications:** \- Toxic Megacolon: Extensive inflammation can lead to colon dilation. Symptoms - Bloating, tachycardia, loss of bowel sounds. \- Bacteremia: Bacteria can enter the bloodstream. \- Guillain-Barré Syndrome: The immune system produces antibodies that attack peripheral nerves, causing paralysis. (starting at the feet and moving upwards) \- Reactive Arthritis: Autoimmune reaction causing joint inflammation. Pain in large joints. **Symptoms:** \- Incubation Period: 1-7 days. \- Initial Symptoms: Fever, muscle pain, malaise, headache. \- Gastrointestinal Symptoms: \- Crampy abdominal pain. \- **Watery diarrhea** initially, which may turn bloody. \- **Bloody diarrhea is more common in children.** **Diagnosis:** Stool Sample Examination: \- Gram-negative, comma-shaped bacteria. \- Presence of white and red blood cells. **Treatment:** \- General Treatment: Hydration and correcting electrolyte imbalances. \- Severe Infection: Antibiotics like erythromycin. **Distinguishing from Enterobacteriaceae** \- Microscopy: Campylobacter is comma-shaped, while Enterobacteriaceae are rod-shaped. \- Motility: Campylobacter is motile (distinguishing it from non-motile Shigella). \- Incubation Conditions: \- Campylobacter grows in low oxygen and warmer temperatures. \- Enterobacteriaceae do not have such specific growth requirements. \- Growth Requirements: \- Campylobacter requires specialised media (e.g., chocolate agar). \- Enterobacteriaceae grow on a wider range of media. \- Oxidase Test: \- Campylobacter is oxidase +ve. \- Enterobacteriaceae are oxidase -ve.