Gram-Negative Bacilli and Gastrointestinal Diseases

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Questions and Answers

What disease is primarily caused by Salmonella typhi?

Neonatal meningitis

Hospital-acquired pneumonia

Enterocolitis

Typhoid fever (correct)

Which of the following is a characteristic of Shigella species?

Highly motile

Animal carriers present

Citrate positive

Non-lactose fermenting (correct)

What is the method of transmission for Salmonella enteritidis?

Fecal-oral route (correct)

Direct contact with skin

Airborne droplets

Vector-borne transmission

Which organism is known to be associated with sepsis and urinary tract infections?

Proteus Species Signup and view all the answers

Which of the following infections is caused by Citrobacter?

Sepsis Signup and view all the answers

What significant characteristic helps in diagnosing Salmonella species?

Non-lactose fermenting Signup and view all the answers

Which factor is a predisposing condition for Salmonella infections?

Use of antacids Signup and view all the answers

Which organism is known for being non-motile?

Shigella dysenteriae Signup and view all the answers

What type of organism is Escherichia coli?

Gram-negative rods Signup and view all the answers

Which of the following diseases is NOT caused by Escherichia coli?

Pneumonia Signup and view all the answers

What is a common predisposing factor for urinary tract infections in women?

Proximity of the anus to the vagina Signup and view all the answers

What is a characteristic of Klebsiella pneumoniae?

Polysaccharide capsule Signup and view all the answers

Which transmission route is associated with neonatal meningitis caused by Escherichia coli?

Vertical transmission during birth Signup and view all the answers

What distinguishes lactose fermenters from non-fermenters in the Enterobacteriaceae family?

Ability to ferment lactose Signup and view all the answers

Which of the following organisms is classified with lactose fermenters?

Klebsiella pneumoniae Signup and view all the answers

What type of bacteria is Serratia marcescens classified as?

Enteric gram-negative rod Signup and view all the answers

Study Notes

Gram-Negative Bacilli: Gastrointestinal Diseases

Gram-negative bacilli cause food poisoning, diarrhea, dysentery, and cholera.
Objectives of the study include causes, diagnosis & prevention of gastrointestinal diseases, specifically focusing on food poisoning, diarrhea, dysentery, and cholera.

Enterobacteriaceae Properties

Gram-negative rods
Ferment glucose with acid production
Reduce nitrates into nitrites
Oxidase negative
Divided into two main groups based on lactose action: Lactose Fermenters (LF) and Lactose Non-Fermenters (LNF).

Lactose Fermenter: Escherichia coli

Diseases: Urinary tract infection (UTI), sepsis, neonatal meningitis, traveler's diarrhea
Habitat: Human colon
Transmission: Colonizes vagina and urethra, ascending UTI, acquired during birth, fecal-oral route in diarrhea.
Diagnosis: Gram-negative rods, ferment lactose, indole-positive.
- Predisposing factors in women include proximity of anus to vagina/urethra, short urethra, urinary tract abnormalities (strictures, valves, stones), and in-dwelling catheters. Colonization of the vagina can lead to neonatal meningitis.

Lactose Fermenter: Klebsiella pneumoniae

Diseases: Pneumonia, UTI, sepsis
Habitat: Human upper respiratory and enteric tracts
Transmission: Inhalation of respiratory droplets, ascending spread of fecal flora to the urinary tract.
Diagnosis: Gram-negative rods, polysaccharide capsule, citrate-positive.
- Predisposing factors to pneumonia are chronic pulmonary diseases, and catheterization predisposes to UTI.

Lactose Fermenter: Enterobacter cloacae & Serratia

Diseases: Hospital-acquired pneumonia, UTI, sepsis
Characteristics: Enteric gram-negative rods similar to K. pneumoniae but motile.
Key Feature: Highly antibiotic resistant

Lactose Fermenter: Citrobacter

Characteristics: Enteric gram-negative rod similar to E. coli, citrate positive.
Habitat: Found in human feces and various clinical specimens.
Relevance: Occasionally causes neonatal meningitis.

Non-Lactose: Salmonella typhi

Disease: Typhoid fever
Habitat: Human colon only
Transmission: Fecal-oral route
Diagnosis: Facultative gram-negative rods, non-lactose-fermenting, produces H2S.
- Predisposing factors include decreased stomach acid due to antacids/gastrectomy, chronic carrier state established in gallbladder, fecal-oral spread to others.

Salmonella enteritidis (Salmonella enterica)

Diseases: Enterocolitis, sepsis with metastatic abscesses
Habitat: Enteric tract of humans and animals (chickens, livestock)
Transmission: Fecal-oral route
Diagnosis: Facultative gram-negative rods, non-lactose-fermenting, produces H2S, motile.

Shigella Species

Diseases: Enterocolitis (dysentery)
Habitat: Human colon only
Transmission: Fecal-oral route
Diagnosis: Facultative gram-negative rods, non-lactose-fermenting, nonmotile.
- Pathogenicity: Invades the ileum and colon mucosa, endotoxin in cell wall causing sepsis (rare). Low infectious dose (1–10 organisms) due to resistance to stomach acid.

Proteus Species

Diseases: UTI, sepsis
Habitat: Human colon and environment (soil, water)
Transmission: Ascending spread of fecal flora to urinary tract
Diagnosis: Facultative gram-negative rods, non-lactose-fermenting, highly motile, produce urease.
- Pathogenesis: Endotoxin causes fever and shock (sepsis). Urease degrades urea to produce ammonia (↑pH), facilitating bladder entry. Predisposing factors include vaginal colonization, urinary catheters, and urinary tract abnormalities.

Yersinia pestis

Disease: Bubonic and pneumonic plague.
Habitat: Wild rodents (e.g., rats)
Transmission: Flea bite
Diagnosis: Small gram-negative rods with bipolar staining. One of the most virulent organisms (very low ID50).

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Description

Explore the role of gram-negative bacilli in gastrointestinal diseases such as food poisoning, diarrhea, dysentery, and cholera. This quiz covers properties of Enterobacteriaceae, particularly Escherichia coli, and their diagnosis and prevention. Test your knowledge about these important pathogens and their implications in human health.