[07.09] Agents of Bacterial Gastrointestinal Infections V2.2.pdf

Diarrheal diseases

What is the second leading cause of death in children under 5 years old worldwide?

525,000

How many children are estimated to be affected by diarrheal diseases despite technological developments?

1.7 billion

Approximately how many cases of diarrheal disease occur globally?

Malnutrition

Diarrheal disease is a leading cause of what condition in children under 5 years old?

10-100 organisms

What is the inoculum size required for Shigella dysenteriae to cause infection?

10^5-10^8 organisms

What is the inoculum size required for Vibrio cholerae to cause infection?

Inoculum size

Which pathogenic factor explains why Shigella is more communicable than Vibrio?

Salmonella Typhi

Which bacterium needs to be grown in food to reach a correct inoculum size before it becomes transmissible?

Shigella spp. and E. coli

Which organisms are commonly associated with food-borne or person-to-person outbreaks via fecal matter even if the food is cooked?

Adherence factors

What allows bacteria to attach to the gastrointestinal mucosa?

Enterotoxins, cytotoxins, and neurotoxins

What are the three general types of toxins produced by GI pathogens?

Invasion

What term describes the process of bacteria entering the intestinal tissue?

Normal microbiota

What host factor stops pathogenic microbes from growing in the gut?

Anaerobes

99% of colonic bacteria belong to which category?

pH and volatile fatty acids

Which two factors maintained by anaerobic bacteria aid in resisting pathogen colonization in the colon?

Immature microbiota

Why are infants at a higher risk of gastrointestinal infection?

Proton pump inhibitors and antacids

Which medications can decrease gastric acid pH and resistance to colonic invasion in long-term hospital patients?

Intestinal motility (peristalsis)

What is the natural clearance mechanism for bacteria in the proximal small intestines?

Atropine (Lomotil)

Which antimotility agent can prolong disease, fever, and shedding in Salmonella infections?

Intestinal mucin

What serves as a physical barrier for pathogens in the gut?

Blood group O

Individuals with which blood group are more susceptible to Vibrio, Shigella, and E. coli O157?

Non-inflammatory

Which mechanism of GI infection involves enterotoxins acting in the proximal small bowel?

Watery diarrhea

What is the typical pathology of a non-inflammatory GI infection?

"Rice water" diarrhea

What is the classic clinical description of the stool in Vibrio cholerae infections?

ETEC and EAEC

Which two types of E. coli utilize a non-inflammatory mechanism?

Inflammatory

Which mechanism of GI infection involves invasion or cytotoxins in the colon or distal small bowel?

Dysentery

What is the term for bloody or inflammatory diarrhea?

Shigella and Salmonella

Name two major bacterial agents that cause inflammatory GI infections.

EHEC and EIEC

Which two types of E. coli cause inflammatory pathology?

Penetrating

Which mechanism involves organisms going inside the intestinal wall to the distal small bowel to cause enteric fever?

Salmonella Typhi and Yersinia enterocolitica

Which two bacterial agents are associated with the penetrating mechanism of infection?

Enterics

What is the term for bacteria that live in the gastrointestinal tract?

Enterobacteriaceae

Escherichia, Salmonella, Shigella, and Klebsiella belong to which family of gram-negative rods?

Vibrios and Campylobacter

List two enteric gram-negative rods that are not part of the Enterobacteriaceae family.

O Antigen

Which antigenic structure represents the O side chains of the lipopolysaccharide?

K Antigen

Which antigenic structure refers to the bacterial capsule?

H Antigen

Which antigenic structure refers to the flagella?

Metallic green sheen

What is the characteristic appearance of E. coli on Eosin Methylene Blue (EMB) agar?

Coliform

What term describes bacteria from the Enterobacteriaceae family used as indicators of water contamination?

Fecalith contamination

What does the presence of coliforms in water signify?

Lactose, Indole, and Lysine decarboxylase

List three biochemical tests in which E. coli is positive.

Plasmids

Where are the genes for adherence and toxin production in E. coli typically located?

Enteropathogenic E. coli (EPEC)

Which type of E. coli is commonly seen in infants, nosocomial infections, and childcare outbreaks?

Bundle-forming pilus (BFP)

What pathogenic factor encoded in a plasmid does EPEC use to adhere to small intestine mucosal cells?

Locus of enterocyte effacement (LEE)

What chromosomal factor in EPEC is responsible for enterocyte effacement?

Destruction of microvilli

What is the primary effect of enterocyte effacement caused by EPEC?

Actin pedestal

What is the cup-like structure formed by EPEC upon attaching to the enterocyte membrane?

A/E lesion

What is the abbreviation for the adherence and effacement lesion characteristic of EPEC?

Traveler’s diarrhea

Enterotoxigenic E. coli (ETEC) is most famously associated with which condition?

Colonization Factor Antigen (CFA)

What adherence factor is used by ETEC?

Heat-labile enterotoxin (LT)

Which ETEC toxin activates adenylyl cyclase to increase cAMP?

Heat-stable enterotoxin (ST)

Which ETEC toxin binds to guanylyl cyclase to increase cGMP?

Hypersecretion of water and chloride

What is the physiological result of increased cAMP in ETEC infection?

Antigenic

Why is a person usually immune to re-exposure to ETEC's LT toxin?

Shiga toxin-producing E. coli (STEC)

What is the other name for Enterohemorrhagic E. coli (EHEC)?

STEC O157:H7

What is the most common serotype of EHEC found in epidemics?

Shiga-like Toxin 1 and 2

What are the two main pathogenic factors of EHEC?

Hemolytic uremic syndrome (HUS)

Which severe EHEC complication involves renal failure, microangiopathic hemolytic anemia, and thrombocytopenia?

Antimotility drugs

What class of drugs should be avoided in patients with EHEC to prevent complications like HUS?

Hemorrhagic colitis

What is the severe form of bloody diarrhea caused by EHEC called?

Enteroinvasive E. coli (EIEC)

Which type of E. coli is clinically indistinguishable from Shigellosis?

Non-lactose fermenter and non-motile

What are two biochemical characteristics of EIEC?

Cell-to-cell migration

How does EIEC move from one cell to an adjacent one if it is non-motile?

Enteroaggregative E. coli (EAEC)

Which type of E. coli is associated with chronic diarrhea in HIV patients and growth retardation in children?

Aggregative adherence fimbriae (AAF/AAP)

What specific adherence pattern does EAEC use to form a biofilm?

EAST-1

What is the name of the heat-stable ST-like toxin produced by EAEC?

Shigellosis

What is the name of the disease caused by Shigella spp.?

Non-motile and non-lactose fermenter

List two general characteristics of Shigella spp.

Acid only

Does Shigella produce acid and gas, or acid only from glucose fermentation?

S. dysenteriae, S. flexneri, S. boydii, S. sonnei

What are the four predominant Shigella species?

Mannitol fermentation

How are the four Shigella species differentiated in the laboratory?

Highly communicable

Why is Shigella considered a major public health concern even with low inoculum?

Food, fingers, flies

The transmission of Shigella is often summarized by which three "Fs"?

Tenesmus

What is the term for painful rectal spasms and straining seen in Shigellosis?

ShET-1

Which Shigella enterotoxin is specifically found in S. flexneri and S. boydii?

Shiga toxin (STx1)

Which toxin from S. dysenteriae is identical to the one in EHEC?

Inhibits protein synthesis

How does the Shiga toxin lead to cell death in ribosomes?

Endocytosis

By what process does the Shiga toxin enter the cell?

Blood culture

Which common diagnostic test is usually negative in Shigella despite systemic symptoms?

M cells

Which lymphatic cells in the gut do Shigella and EIEC invade first?

Actin-dependent processes

How does Shigella achieve cell-to-cell transport?

1-4 days

What is the typical incubation period for Shigellosis?

Acidosis

Severe dehydration in children with Shigellosis can lead to what life-threatening state?

S. flexneri

Reiter’s chronic arthritis syndrome is a complication specifically associated with which Shigella species?

Stool mucus flecks or rectal swabs

What is the best specimen to collect for the diagnosis of dysentery?

Certest

What is the rapid immunochromatography test used during epidemics in the Philippines for Shigella?

5-7 days

How long is the typical self-limited course of Shigellosis?

Ciprofloxacin

Which antibiotic is given for severe Shigella infections?

Peritrichous flagella

What structure makes Salmonella spp. motile?

Bismuth sulfate medium

On which medium does Salmonella produce characteristic black colonies?

H2S production

What biochemical property of Salmonella causes the blackening of culture medium?

Salmonella bongori and Salmonella enterica

What are the two species of Salmonella?

Typhoidal and Non-typhoidal (NTS)

What are the two important clinical groups of Salmonella?

Typhi and Paratyphi A, B, C

Which serotypes belong to the typhoidal group?

Person-to-person only

How is typhoidal Salmonella transmitted?

Animals (poultry, pigs, reptiles)

What is the reservoir for non-typhoidal Salmonella?

Typhoid fever

Continuous step-ladder fever is the predominant symptom of which disease?

Hyperplasia of Peyer’s Patches

What is the main pathology seen in the intestines of patients with Typhoid fever?

Gallbladder

Where do chronic carriers of Salmonella harbor the bacteria?

Biofilm on gallstones

What structure allows Salmonella to remain undetected in the gallbladder?