GIT Infections: Types and Causes

GIT Infections Classification

• Gastritis affects the stomach
• Enteritis affects the small intestine, most frequent
• Colitis affects the large intestine
• Enterocolitis and Gastroenteritis is when they are often associated

Primary and Secondary Infections

• Primary infections come from infected animal tissues or products like undercooked meat, eggs, and milk, known as zoonoses
• Secondary infections come from food contaminated during processing, resulting in fecal-oral transmission (antroponose)

Alimentary Intoxication

• Alimentary intoxication, also called food poisoning, isn't an infection, but rather intoxication caused by microbial toxins in contaminated food

Common Causative Agents of GIT Infections

• Bacterial agents include Salmonella enterica, Campylobacter jejuni, Yersinia enterocolitica, Shigella sp., Helicobacter pylori, and Escherichia coli
• Viral agents include Rotaviruses, Adenoviruses, Noroviruses, and Astroviruses
• Parasitic agents include Enterobius vermicularis and Giardia intestinalis
• Fungi typically do not cause GIT infections

Salmonella Enterica

• Gram-negative rod, part of the Enterobacterales group
• Out of six subspecies, only Salmonella enterica subsp. enterica causes human infection.
• There are approximately 200 serotypes of this subspecies
• Can shorten names, for example Salmonella Typhimurium
• Use capital letters when indicating a serotype

Diseases Associated with Salmonella Enterica

• Salmonellosis (non-typhoideal) is caused by zoonotic serotypes and is prevalent in Europe
• Typhoid fever is caused by antroponotic serotypes Typhi and Paratyphi, mainly imported to Europe

Salmonella Enterica Details

• A zoonotic disease with animal reservoirs that are serotype-specific (mammals, birds, reptiles)
• Sources of infection: Meat of infected animals, eggs, or products and food or water contaminated by animal feces
• Spread from infected person through temporal human-to-human transmission via the fecal-oral pattern
• Incubation period: 10-36 hours
• Low minimal infectious dose: 10 bacterial cells

Salmonellosis Details

• Salmonellosis is non-typhoideal salmonellosis caused by zoonotic serotypes and is present in Europe
• Typhoid fever is caused by antroponotic serotypes Typhi and Paratyphi and is mostly imported in Europe
• Incubation period: 10-36 hours, typically 10-12 hours
• Symptoms: fever, vomiting, abdominal cramps with profuse, watery, non-bloody diarrhea for 4-7 days
• Complications can include serious dehydration, which may require hospitalization and intravenous fluids
• Has the potential to lead to extraintestinal spread, affecting osteomyelitis, meningitis, endocarditis, soft tissues, and sepsis, and is especially risky for infants and the elderly

Salmonella Enterica Typhi and Paratyphi Serotypes

• Cause typhoid fever
• Are antroponose through human-to-human transmission, with no animals involved
• Enters the lymphatic system, causing a systemic disease
• The endotoxins affect the vascular and nervous systems, leading to fluid imbalance, sepsis, or septic shock
• Symptoms: vomiting, fever, headache, diarrhea, or constipation
• Rare in Europe, with most cases being imports
• Prevention includes a vaccine for travelers and control in areas of occurrence

Diagnosing Salmonellosis

• Specimen: stool or rectal swab
• Selective and differential culture media can be used to inhibit part of the normal microflora (G+ bacteria) and differentiate pathogenic bacteria using MacConkey, Endo, TSI, and XLD media
• Identification of serotype by agglutination with specific antibodies
• S. enterica on Endo agar and XLD agar
• Widal test is used for detection of antibodies in serum by agglutination with dead bacteria and their cellular fractions

Shigella Dysenteriae

• A gram-negative rod in the Enterobacterales group
• Genetically related to Escherichia coli
• Species include: S. dysenteriae, S. sonnei, S, flexneri, S. boydii
• Shiga toxin causes the inhibition of proteosynthesis, leading to cell death
• Damages enterocytes, causing invasion to bloodstream
• Damages endothelium in blood vessels and glomeruli, leading to proteinuria, hematuria, and hemolytic uremic syndrome
• Enterohaemorhagic strains of E. coli have similar toxin (shiga-like toxin)

Shigella Dysenteriae Transmission and Symptoms

• Transmission occurs through the fecal-oral route, it does not come from animals
• Symptoms range from mild abdominal discomfort to severe dysentery with diarrhea, fever, vomiting, and abdominal cramps
• Dysentery is a type of gastroenteritis with blood in the diarrhea
• Possible Complications: dehydration, mucosal ulceration, rectal bleeding, and hemolytic uremic syndrome
• ATB therapy might be problematic in multi-resistant strains
• One of the most frequent bacterial causes of GIT infection globally, but less frequent than salmonellosis in Europe

Diagnosing Shigellosis

• Involves an identical method to salmonellosis
• Differentiated based on H2S production: Salmonella is positive, while Shigella is negative
• Species identification via biochemical tests or mass spectrometry
• Shigella sp. on Endo agar and XLD agar

Escherichia Coli

• Gram-negative rod, part of the Enterobacterales group
• Resident of the normal gut flora in mammals
• Most normal E. coli flora are non-pathogenic in GIT
• Strains may carry virulence factors enabling infection.
• Virulent strains may significantly differ in diseases (incubation period, pathogenesis, symptoms, epidemiology)

Virulent Strains of Escherichia Coli

• Enteropathogenic E. coli (ETEC) causes traveler's diarrhea in developing countries
• Enterohemorrhagic E. coli (EHEC), or Shiga toxin-producing E. coli (STEC), has a shiga-like toxin that can lead to dysentery, hemolytic uremic syndrome, and kidney failure
• Enteropathogenic E. coli (EPEC) is a cause of neonatal and infant diarrhea, also as HAI in neonatal and pediatric units
• Enteroinvasive E.coli (EIEC) causes dysentery

Characteristics of Virulent Escherichia Coli

• Transmission occurs mainly through the fecal-oral route, though some strains are zoonotic with various reservoirs like wild, farm, and pet animals
• Diagnosed via isolation with cultivation, virulent strains cannot be identified by biochemical tests or mass spectrometry
• Identification via antigenic properties using agglutination with specific antibodies
• PCR tests are available for some strains

Vibrio Cholerae

• Gram-negative, curved rod, flagellated
• The disease is acquired through contaminated water, seafood, and the fecal-oral route
• Causes gastroenteritis, releasing Cl- ions and water, leading to profuse diarrhea with liquid loss and vomiting which might not be under control
• Symptom intensity depends on the V. cholerae strain, some are mild, and some are asymptomatic
• Diagnosed through cultivation on selective media
• Occurs globally in local epidemics in crowded places with limited hygiene and/or contaminated water supply
• Seldom present in Czech Republic imports
• Prevented by vaccine when traveling

Yersinia Enterocolitica

• It is a gram-negative rod of the Enterobacterales group
• It is a zoonose contracted from pigs or contaminated pork or water
• It has an incubation period of 3-7 days.
• Symptoms include watery or bloody diarrhea, dissemination into lymphatic nodes, and right lower abdominal pain, similar to appendicitis.
• Can be diagnosed from stool samples cultivated on selective media, and identified through biochemical tests, mass spectrometry, or hemocultures with complicated forms

Campylobacter

• Gram-negative, curved, flagellated
• Campylobacter jejuni is the most common, resides in the GIT of birds, and is often sourced from chicken meat
• Other species include C. coli (pigs) and C. fetus (cattle)
• Often asymptomatic for animals
• In humans, it causes enteritis and enterocolitis
• Transmission is foodborne through insufficiently cooked meat and unpasteurized milk, through the fecal-oral route, and through contaminated water

Campylobacteriosis

• Incubation period: 2-11 days
• Prodromal symptoms include fever, headache, and myalgia
• Symptoms after 12-24 hours include abdominal pain, cramps, diarrhea, and dysentery
• Phase lasts typically more than one week
• Complications can include toxic megacolon and bloodstream infection
• Diagnostics involve cultivation of a stool sample, requires special selective media under microaerophilic atmosphere
• PCR can also be used
• Incidence has increased in Europe in the last two decades and is twice as common as salmonellosis in the Czech Republic

Helicobacter Pylori

• Gram-negative, curved rod
• Is relative to campylobacter and microaerofilic
• Survival by inhibition of HCl production and neutralization of pH
• Humans are often asymptomatic, 30-60% prevalence
• Chronic gastritis, gastric or duodenal ulcers, and Gastric carcinoma can be linked to it
• Classified as category 1 cancerogen

Diagnosing Helicobacter Pylori

• Fecal antigen detection tests can be used
• Blood antibodies can be detected
• Urease breath test may be used
• Samples from gastric biopsy, cultures from tool don't work
• Diagnostic PCR from biopsy or stool

Asymptomatic Helicobacter Pylori

• Therapy is not needed, differences in virulence exist among strains
• Avirulent strains contribute to stomach

Clostridium Difficile

• Gram-positive rod and is anaerobic
• Resident of the normal flora of the colon.
• When intestinal C. difficile increases with toxin and leads to CDAD, or C. difficile-associated disease
• Characterized by diarrhea, abdominal pain, appetite loss, nausea, and fever
• Antibiotics can lead to a disease, iatrogenic
• In severe cases, can result to life-threatening ulceration and necrosis of the intestinal mucosa (pseudomembranous enterocolitis)

Clostridium Difficile Details

• Typical CDAD-inducing antibiotics include clindamycin, fluoroquinolones, and cephalosporins
• Can cause nosocomial infections through transmission
• Diagnostics include anaerobic cultivation and toxin detection, PCR for genes, ELISA and colonoscopy

Alimentary Intoxication

• Caused by ingesting toxins in food (as opposed to infection) due to bacteria or fungi
• Conditions that exacerbate toxins include prolonged storage, increased temperatures, and presence of nutrients
• Bacteria such as Bacillus cereus and Straphylococcus aureus
• Causes nausea, vomiting, diarrhea
• Clostridium botulinum is a neurotoxin that can cause death at high infection
• Causes flaccid paralysis and vision issues and can only be protected against if heated at 60 degrees

Giardia Intestinalis

• Protist, flagellata group
• Has a parasite of duodenum and is non-invasive
• Cysts are present in stool and non-transmissive
• Causes diarrhea
• Often asymptomatic in older people, but causes malabsorption syndrome in kids
• Can be acquired from fecel matter or contaminated water
• Diagnose through microscopy and stool sample

Enterobius Vermicularis

• A helminth, group Nematoda
• Male size is 5mm and Female 12mm
• Parasite of rectum
• The highy contagious worm has a 5-40% prevalence
• Eggs are laid on perianal region

Pinworm Transmission and Prevention

• Sticky eggs laid perianal are responsible for the symptoms of itching at night
• Can be passed by contaminated hands or dust
• Diagnosis can be done by collection of tape from anus
• Personal hygiene is necessary

Common GIT Parasites

• Protozoa GIT Parasites: Giardia and Entamoebic and Endolimax
• Can be identified by a diagnostic coprology
• Helminths, Ascaris lumbricoides, Hymenolepsis can be identified with coprology
• Teania saginata and T. solium can be identified by stool samples
• Enterobius vermicularis mest prevent

Treating Diarrheal Infections

• Rehydration with solutions of salts
• Supplements like zinc
• Fluids in severe cases
• Infants can take rich nutrients
• Antibiotics are not needed
• Anti Parasitics for parasitic infections