Lecture 4: Gram negative bacteria curved rod

Gram - bacilli groups

1.Straight (enteric) - Escherichia and salmonella

2.Curved - Helicobacter and Vibrio

Helicobacter pylori characteristics

Curved (helical) rod shaped, gram -, slow growing, and is acid resistance so it’s able to colonize gastric mucosa and the stomach

H. pylori Transmission

Spread person-to-person by saliva or consuming food or water contaminated with this bacteria (oral-oral or fecal-oral)

H. pylori Conditions

Survives harsh acidic conditions pH=2 (acid resistant) and cell damage

H. pylori Virulence Factors

Acid neutralization (urease)

Motility (flagella)

Adherence factors (colonization of mucus layer) 

Exotoxin production (VacA, CagA)

H. Pylori Diseases

Gastritis, Peptic ulcer, and Stomach cancer

Infections are asymptomatic

H. Pylori Gastritis

irritation and inflammation of the stomach lining

H. Pylori Peptic Ulcer

ulcerative sores in the lining of stomach, SI, &/or esophagus

H. Pylori Stomach cancer

after years of untreated acid irritation/erosion of gastric mucosa (less common than gastritis/ulcers); result of chronic infection

Peptic Ulcer Symptoms

Can be asymptomatic or symptomatic

Symptoms: abdomen pain, bloating, low appetite, dark color stools, and ulcer bleeding

H. Pylori Diagnosis

Using breath (C13-urea test), stool, or blood test.

Examination by endoscopy and/or gastric biopsy

H. Pylori Treatment

Curable with antibiotic therapy at early stages

– Acid blockers (Proton pump inhibitors) aid healing by reducing stomach acid

H. Pylori Prevention

Patients should do therapy (Abx + PPI), good hygiene with washing hands and safe food handling, and lifestyle changes can help recovery

Vibrio Cholerae Characteristics

Highly motile, comma-shaped, Gram - with a single flagellum, non invasive human pathogen

Cholera

Acute diarrheal disease of humans caused by infection of intestinal tract, asymptomatic, and severe fluid and electrolyte loss

Vibrio Cholerae Found

free living or attached to algae, plankton, or shellfish in aquatic environment like coastal waters

Vibrio Cholerae Transmission

By drinking contaminated water and food, linked to lack of water sanitation and access hygiene

Vibrio Cholerae Infects

humans intestines and causes potentially lethal watery diarrhea

Vibrio Cholerae Epidemiology

Endemic infections (47 countries today): Coastal communities are hot spots

Epidemic (pandemic potential) outbreaks (40 countries today): less predictable, can occur inland

Vibrio Cholerae Major virulence factors

Toxin-Coregulated Pilus (TCP)

Cholera Toxin (CT)

Toxin-Coregulated Pilus (TCP)

Critical for colonization of the host gut mucosal layer

Cholera Toxin (CT) – potent AB exotoxin

Binds to receptors on intestinal epithelial cells which causes a build up of ions in intestinal lumen and draws water from cells and tissue via osmosis

rice water stools

the profuse, watery diarrhea, often pale and cloudy with mucus, that is a hallmark symptom of cholera

Fatal dehydration and hypovolemic shock

Caused by severe fluid and electrolyte loss by action of cholera toxin

Cholera diagnosis

Symptoms and fecal culture

Cholera Treatment

Treated with oral rehydration solution, a prepackaged mixture of sugar and salts mixed with water

Cholera Prevention

Proper sewage treatment and safe water management 

Travelers to endemic areas:

• Should only eat or drink items that have been boiled, cooked, or peeled 

• VaxchoraTM (approved in 2016); 3- 6 months protection

H. pylori ulcers summary

Chronic, infects stomach (gastritis), causes stomach pain by weakening mucus layer of stomach, spread person to person via fecal-oral or oral-oral

Cholera summary

Acute, infects small intestine by exotoxin that secretes a lot electrolytes and fluid, causes diarrhea, and spread fecal-oral