Campylobacter and Helicobacter

Helicobacter

• Briefly describe Helicobacter
  • Previously classified under campylobacter
  • Encompasses and enterohepatic species
    • Gastric
      • Helicobacter pylori
      • Helicobacter heilmanni
    • Enterohepatic
      • Helicobacter hepaticus
  • Helicobater pylori infects humans, primates, and pigs, and is associated with:
    • gastritis
    • peptic ulcers
    • gastric adenocarcinoma, and
    • MALT B-cell lymphomas.
  • Helicobacter cinaedi affects humans and hamsters and causes:
    • gastroenteritis
    • septicemia and
    • proctocolitis.
  • Helicobacter fenneliae affects humans and causes:
    • gastroenteritis
    • septicemia and
    • proctocolitis
• Briefly describe Helicobacter pylori
  • Helicobacter pylori is a GN curved rod.
  • It is spiral shaped, micro-aerophilic, highly motile (cockscrew motility) with lophotrichious flagella (2-6 sheathed unipolar flagellar).
  • It colonizes the stomach in around 50% of the population and is spread via the fecal-oral route. It is the main risk factor for Gastric and duodeal ulcers, Stomach cancer, Gastric MALToma. It produces oxidase, catalase and urease (positive)
  • Helicobacter pylori has the highest incidence of carriage in developing countries (70-90%) of the population and most <10 years of age.
  • Humans are the primary reservoir and colonization is believed to persist for life – Unless the host is specifically treated
  • Transmission is by the fecal-oral route.
  • It is found in 70-100% of patients with gastritis, gastric ulcers or duodenal ulcers.
    • Colonization appears to offer protection from GERD and adenocarcinomas of the lower oesophagus and cardia of the stomach.
  • Helicobacter pylori produces NH3 in more neutral microenvironment.
  • Vacuolating cytotoxin A(VacA) causes apoptosis in eukaryotic cells by producing large cytoplasmic vacules.
  • Cytotoxin-associated gene (cagA) resides in pathogenicity island and encodes a syringe-like structure (Type IV secretion system) that injects CagA protein in host epithelium.
    • CagA activates signal transduction molecules causing morphological and neoplastic changes (actin remodelling, host cell growth and inhibition of apoptosis).
    • CagA-negative strains are significantly less associated with gastric adenocarcinoma.
    • Cag genes also induce IL-8 production causing neutrophil chemoattraction and ROS production.
• List the virulence factors associated with Helicobacter pylori
  • Multiple unipolar flagellae: motility and chemotaxis
  • Urease: neutralizes gastric acid, mucosal injury by ammonia
  • Outer membrane proteins (BabA, BabB, sabA): adhesion to gastric epithelial cells
  • VacA Exotoxin: promotes inflammation and gastric mucosal injury
  • Cytotoxin-associated gee (cagA): codes Type IV secretory system for Cag Proteins
  • Cag(A) proteins: promotes inflammation (Il-8) and carcinogenesis (actin remodelling, host cell growth and inhibition of apoptosis)
  • Protease: modifies gastric mucus reducing ability of acid to diffuse through
  • Mucinase: breaks down gastric mucus allowing the organism to penetrate and adhere to the epithelial cells
• Briefly describe the pathogenesis Gastritis and Gastric Ulcers caused by Helicobacter pylori
  • Initial colonization is facilitated by:
    • Blockage of acid production (by bacterial acid-inhibotory proteins)
    • Neutralization of gastric acid (ammonia produced by urease activity)
  • Passes through gastric mucus
  • Adheres to gastric epithelial cells via multiple surface adhesion proteins (BabA, BabB, sabA)
  • Adhesion proteins aid with immune evasion
  • Localized tissue damage (urease byproducts, mucinase, phospholipases, and activity of VacA)
  • CagA stimulates IL-8 production and subsequent neutrophil chemoattraction
  • Release of proteases and ROS by neutrophils
  • Gastritis (Type B) and Gastric ulcers
• Briefly describe the clinical features of Helicobacter Pylori
  • Gastritis: Inflammation of stomach lining with associated mucosal ijury; infiltration of neutrophils and mononuclear cells into the gastric mucosa
    • Acute gastritis: feeling of fullnes, N, V, and hypochlorhydria +/- recurrent upper abdominal pain, heart burn, anorexia
    • Chronic gastritis (Type B): Confined to the gastric antrum or pangastritis. Approximately 10-15% of chronic gastritis patients progress to PUD. Chronic gastritis also leads to replacement of normal gastric mucosa with fibrosis and proliferation of intestinal-type epithelium
  • Gastric and duodenual ulcers
    • Ulcers occur at sites of intense inflammation commonly at the junction between the corpus and antrum (in gastric ulcert) and proximal duodenum (duodenal ulcers)H.pylori is responsible for 85% of gastric and 95% of duodenal ulcers.
  • Gastric cancer
    • H.pylori increases te patient’s risk for gastric cancer by almost 100-fold. It is influenced by the strain of H.pylori (cagA positive), and the host’s response (Increased IL-1 production)
  • MALT Lymphoma
    • Monoconal population of B cells may deveope and evolve into a MALToma in a small subset of individuals. Not considered a cancer per se.
• Briefly describe the laboratory features of Helicobacter pylori
  • Specimen: Stool, Blood, Biopsy
  • Non-invasive procedures
    • Microscopy: GN comma shaped rods (difficult to visualize + non-pathogenic organisms may be present)
    • Stool Antigen test: positive (95% specificity and sensitivity, easy, inexpensive, active infection, monoclonal is useful before and after treament, polyclonal is done for only a few studies)
    • Blood Antigen test: positive (Is qualititave and quantitative IgG, Widely available, inexpensive, not useful after treatment. Note that IgM disappears rapidly, IgA and IgG can persist for months to years)
    • Urea breath test: positive (Patients drinks urea radio-labelled solution {13C or 14C small radiation tube} then blows into a tube, Detection of CO2 is positive. It is relatively expensive {cost of detection instruments})
    • PCR: expensive, not widely available or standardized
  • Invasive procedures
    • Endoscopy and biopsy: 100% sensitivity and specificity, is considered diagnositc
      • Biopsy in urea solution: alklaline byproduct detected may change wthin miniute-2hours, specificity is 100%
      • Histology (Warthin-starry silver stain): 100% sensitivity and specificity, diagositic
    • Culture: Difficult to isolate in culture and identified by biochemical testing and nonculture techniques
      • Specimen is gastric biopsy. Complex media supplemented with blood, serum, charcoal, starch, or egg yolk in microaerophilic (low O2, High CO2) for up to 2 weeks), temperature range is 30-37 degree.
  • Biochemical tests
    • Oxidase: Positive
    • Catalase: Positive
    • Urease: Positive
• How is Helicobacter pylori infection treated ***treatment is conserved for symptomatic individuals since 2.3 or 50% of population has H.pylori commensals
  • Triple therapy: PPI (osemeprazole) + Clarithromycin + Amoxicillin/Metronidazole. 10-14 days. Compliance is important. OR PPI + metronidazole + tetracycline
  • Quadruple therapy: PPI + Bismuth subsalicylate + Metronidazole + Tetracycline
  • Antibiotic resistant bacteria: associated with clarithromycin resistance +/- metronidazole

Campylobacter

• Briefly describe Campylobacter
  • Campylobacter is derived from the word “kampylos” meaning curved rod.
  • It is a small (0.2-0.5um wide, 0.5-5um long), curved, gram negative rod that is comma or S-shaped or Cigar shaped.
  • It is non-sporing and motile and exhibits rapid motility (darting, in cork-skrew fashion) due to its flagella (1-2)
  • It is microaerophilic (candle extinction jar of CO2) and oxidase positive.
  • The cell wall has LOS instead of LPS endotoxin.
  • The major pathogens are:
    • Campylobacter jejuni (80-90% illnesses, >50 capsular serotypes)
    • Campylobacter festus (Systemic infections – bacteremia, septic thrombophlebitis, arthritis, septic abortion, and meningitis),
    • Campylobacter coli (Gastroenteritis),
    • Campylobacter upsaliensis (incidence unknown, GI infection)
  • Campylobacter shares similarities with Vibrio and Helicobacter (cork-screw motiliy, microaerophilic)
  • Campylobacter is found in the GIT of poultry, cattle, sheep, pigs, birds, dogs, and cats (on illnesses)
  • Transmission to humans is through contaminated food (water and milk), contaminated poultry (>50% infections in developed countries) and fecal-oral (fecal material from infected animals), food handlers (uncommon).
  • It is common in infants and young children with a 2nd peak in 20-40y adults. 1.4-2 million infection are estimated to occur anually in the US (more common than Salmonella and Shigella infections)
  • Incidence is higher in developing countries and it is the most common bacterial cause of diarrhea.
• List the virulence factors associated with Campylobacter jejuni
  • S proteins (proteinaceous, capsule-like, prevents complement-mediated killing and opsonisation – phagocytosis)
  • Heat-labile enterotoxin (Cholera-like enterotoxin that causes diarrhea)
• Briefly describe the pathogenesis of enteritis caused by Campylobacter jejuni
  • Risk of disease influenced by infectious dose
  • Ingestion (Contaminates milk, water, or Fecal-oral)
  • Colonization
  • Infection of Jejunum +/ ileum, colon, rectum
    • Ulcerated mucosal surfaces, edematous, bloody w/crypt abscesses in epithelial glands and inlitration of the lamina propria with neutrophils, mononuclear cells and eosinophils (C.jejuni infection)
  • Involvement of mesenteric nodes and transient bacteremia
• Outline the clinical features of Campylobacter jejuni
  • Acute enteritis: Diarrhea, Fever + Severe abdominal pain. ≥10 bowel movements per day during the pek of the disease. Stool may be bloody. Self—limited. Symptoms may last > a week or longer
  • Bacteremia: (secondary to diarrhea), Risk is associated with pregnancy, HIV, Extremes of age, alcoholism ,post-splenectomy status and other immunosuppressive status
  • Cholecystitis
  • Arthritis
  • Deep abscesses
  • Osteomyelitis
  • Meningitis
  • C.festus: affinity for genital tract and tropism for fetal tissue. Causes perinatal infection, abortion, still birth, and premature labour.
• List the immune-related complication associated with Campylobacter jejuni
  • Guillain-Barre Syndrome: Rare (1 in 1000 infections) Campylobacter jejuni serotype O:19 has antigen cross-reactivity between surface LOS and peripheral nerve gangliosides. Causes an ascending paralysis.
  • Reactive arthritis (Reiter’s syndrome): Joint pain, swelling of the hands, ankles, knees; persisting from 1 week to several months, unrelated to the severity of diarrheal disease, More common in individuals with HLA-B27 phenotype
  • Hemolytic uremic syndrome
  • Toxic megacolon
  • Cholecystitis
  • Meningitis
• Briefly describe the laboratory features of Campylobacter jejuni
  • Specimen: stool
  • **Direct (**phase contrast or darkfield) microscopy: Darting motility like vibrio (on Phase contrast or dark-field microscopy)
  • Culture: ***On campylobacter special media. Microaerophilic (5-7% O2 and 5-10% CO2) and elevated incubation temperatures (42C) on selective agar. Slow growing (incubate 48H or longer) ***differentiate from vibrio by temperature, atmospheric conditions and media used
    • Skirrows media (BA with antibiotics vancomycin, trimethroprim, cephalothin, polymyxin, amphotericin B to inhibit other enteric organisms): Non-hemolytic, spreading, droplet-like colonies
    • Butzlers medium
    • Campy BA
    • Brucella antigen base with sheep blood
  • Gram stain: Gram ngative comma or S-shaped or Cigar shaped bacilli
  • Biochemical tests
    • Oxidase: Positive
    • Catalase: Positive
  • Serotpying
  • Biotyping
  • Phage typing
  • Antibody detection: IgG and IgM for epidemiological surveys
  • Nucleic acid based tests: For Campylobacter jejuni and Campylobacter coli
• How is infection with Campylobacter jejunitreated
  • Self-limiting: rehydration
  • Severe dysentery: erythromycin, azithromyin, ciprofloxavin
  • Severe disease and septicemia: macrolides, tetracyclines, aminoglycosides, CAF, FQs, clindamycin, amoxicillin/clavulanic acid, and imipenem
  • Resistance: Penicillins, cephalosporins, sulfonamides +/- FQs
  • Systemic infections: aminoglycoside, chloramphenicol, imipenem
  • C.coli: TMP-SMX
  • Antimotility drugs: not recommended