E. coli Infections Quiz

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Questions and Answers

What is a characteristic symptom of EPEC infections?

Severe abdominal cramps

Hemorrhagic diarrhea

High fever and blood in stool

Low-grade fever and vomiting (correct)

Which strain of E. coli is associated with severe diarrhea in children under 1 year old?

EPEC (correct)

DAEC

EAEC

EHEC

What is the main identifying feature of EHEC strains?

Is associated with UTIs

Causes low-grade fever

Produces verotoxin I & II (correct)

Forms a stacked-brick pattern

What is a common method for detecting EHEC?

Latex agglutination test for O157 antigen Signup and view all the answers

DAEC strains are primarily associated with which condition in children?

Chronic diarrhea Signup and view all the answers

Which statement is true regarding EAEC strains?

They adhere to Hep-2 cells in a stacked-brick pattern. Signup and view all the answers

What role does E. coli play in neonatal infections?

It is the most common cause of gram-negative meningitis. Signup and view all the answers

What types of toxins are produced by EHEC strains?

Cytotoxins Signup and view all the answers

What is a characteristic size of Klebsiella spp.?

2.0 – 3.0 x 0.6 µm Signup and view all the answers

What type of agar shows pink/red colonies for Klebsiella spp.?

MAC agar Signup and view all the answers

Which disease is commonly associated with Klebsiella pneumoniae?

Urinary tract infections Signup and view all the answers

What type of colonies do Klebsiella pneumoniae form on blood agar?

Slimy appearance Signup and view all the answers

Which antibiotic is NOT effective against KPC-producing Klebsiella pneumoniae?

Tetracyclines Signup and view all the answers

Which is true about the motility of Klebsiella spp.?

They are non-motile. Signup and view all the answers

What characteristic enables Klebsiella spp. to form moist, mucoid colonies?

Polysaccharide capsule Signup and view all the answers

What is a common transmission vector for Klebsiella pneumoniae?

Direct contact with infected surfaces Signup and view all the answers

What type of colonies do salmonellae produce on selective and differential media like MAC?

Clear, colorless, non-lactose fermenting colonies Signup and view all the answers

What conditions can lead to significant infections by salmonellae in humans?

Contact with contaminated cooking utensils Signup and view all the answers

Which antigenic structures are primarily used for serologic grouping of salmonellae?

Somatic (O) and Flagellar (H) antigens Signup and view all the answers

What is the infective dose necessary to initiate the disease mentioned?

106 bacteria Signup and view all the answers

What are some common symptoms associated with salmonella gastroenteritis?

Nausea, vomiting, fever, and chills Signup and view all the answers

Which type of fever is primarily caused by Salmonella Typhi?

Typhoid fever Signup and view all the answers

In what time frame do symptoms typically appear after exposure to contaminated food causing salmonella gastroenteritis?

8 to 36 hours Signup and view all the answers

How long does it generally take for typhoid fever to develop after infection?

9 to 14 days Signup and view all the answers

Which of the following sources is NOT associated with salmonella transmission?

Fresh fruits and vegetables Signup and view all the answers

Which organ systems are involved in the clinical manifestation of enteric fever?

Liver, spleen, intestines, and mesentery Signup and view all the answers

Which group of individuals is mentioned as having increased risks of complications from salmonella infections?

Patients with sickle cell disease and other hemolytic disorders Signup and view all the answers

Compared to typhoid fever, how are the clinical manifestations of paratyphoid fevers described?

Similar but less severe with lower fatalities Signup and view all the answers

What is the nature of salmonella infections typically described in the text?

Self-limiting with few or no complications Signup and view all the answers

When can urine culture results typically start to show positivity in the diagnosis of enteric fever?

After the second week Signup and view all the answers

What specimen must be taken repeatedly for an effective diagnosis of salmonella infections?

Blood cultures Signup and view all the answers

Which of the following is NOT a Salmonella serotype associated with enteric fever?

Salmonella Typhimurium Signup and view all the answers

Which of the following is a typical first-line agent for treatment?

Ceftazidime Signup and view all the answers

What is a common characteristic of Ertapenem in relation to treatment?

It has intrinsic resistance. Signup and view all the answers

What types of specimens are recommended for the diagnosis of Shigella infections?

Fresh stool, mucus flecks, and rectal swabs Signup and view all the answers

Which therapeutic options are primarily used for drug-resistant infections?

Polymyxins and tigecycline Signup and view all the answers

What is one reason serology is not used for diagnosing Shigella infections?

Healthy individuals commonly have agglutinins against shigella species. Signup and view all the answers

What type of resistance may be encountered with beta-lactams and carbapenems?

Multi-drug resistance (MDR) Signup and view all the answers

Which practice is most important for preventing environmental contamination in healthcare settings?

Regular cleaning and decontamination of patient environments Signup and view all the answers

Which medication is the preferred treatment option for adults with severe Shigellosis?

Ciprofloxacin 750 mg once daily Signup and view all the answers

What is a characteristic of Shigella that affects its recovery from stool samples?

It is susceptible to the acid pH of stool. Signup and view all the answers

What technique is critical for the insertion of central venous catheters (CVC)?

Proper aseptic techniques Signup and view all the answers

Which of the following is NOT a category of therapeutic options for resistant infections?

Beta-lactam antibiotics Signup and view all the answers

What aspect of Shigellosis therapy is emphasized in the provided content?

Treatment typically shortens the illness by 1-2 days. Signup and view all the answers

What is an essential method for ensuring the safety of reusable medical equipment?

Proper decontamination or sterilization Signup and view all the answers

Which of the following agar media are used for culturing specimens suspected of Shigella?

MacConkey and Hektoen enteric agar Signup and view all the answers

What potential outcome may result from treating Shigellosis when it is not severely needed?

Enhanced risk of bacterial resistance. Signup and view all the answers

Which of the following is true about Shigella organisms?

They are fragile and susceptible to various agents. Signup and view all the answers

Study Notes

Gram-Negative Bacteria

Gram-negative bacteria use biochemical pathways to metabolize carbohydrates and generate energy through two main processes: fermentation and aerobic respiration (oxidation).
Fermentation is an anaerobic process, while aerobic respiration is an aerobic process.

Enterobacteriaceae: Non Lactose Fermenters

This group includes bacteria like Salmonella, Shigella, Yersinia, and Proteus.
They are characterized as not fermenting lactose.

Enterobacteriaceae: Lactose Fermenters

Escherichia coli, Klebsiella, Citrobacter, Enterobacter spp., and Serratia belong to this group.
These bacteria ferment lactose.

Other Non Lactose Fermenters

Pseudomonads, Vibrio, and Acinetobacter are examples of non-lactose fermenting bacteria.

Escherichia coli (E. coli)

Commonly found in the colon.
Used as a marker for fecal contamination in water quality.
Mostly motile.
Possesses adhesive fimbriae, sex pili, and O, H, and K antigens.
O antigens share significant cross-reactivity with Shigella species.
Several virulence factors. including lipopolysaccharide (LPS) for example the O side chains, capsule (K), and flagella (H), contribute to its pathogenicity.
Different E. coli subtypes cause various diseases such as gastroenteritis (e.g., ETEC, EIEC, EPEC, EHEC, and Enteroadherent).
E. coli have self-limiting diseases that causes watery diarrhea, abdominal cramps, malaise, nausea potentially without vomiting

Escherichia coli (E. coli) - Virulence Factor

Lipopolysaccharide (LPS)
Capsule (K)
Flagella (H)

Escherichia coli (E. coli) - Culture growth

MacConkey Agar (MAC) is a differential medium.
Bile salts and crystal violet inhibit Gram-positive organisms.
Lactose is a fermentable carbohydrate enabling differentiation.
Lactose fermenters appear as pink colonies, while non-fermenters remain colorless.

Escherichia coli (E. coli) - Uropathogenic E. coli (UPEC)

The most common cause of UTIs in humans.
Strains vary slightly in immunocompetent and immunocompromised patients.
Adherence to the urinary epithelial mucosa is facilitated by various factors (eg, pili).
Other virulence factors such as cytolysins (hemolysins) inhibit phagocytosis.
Aerobactin aids in iron chelation.

Escherichia coli (E. coli) - Gastrointestinal E. coli

Categorized into five groups based on virulence factors, clinical characteristics, epidemiology. Different O and H serotypes are important
ETEC, EIEC, EPEC, EHEC, and Enteroadherent (EAEC/DAEC).

Escherichia coli (E. coli) - ETEC

Common cause of traveler's diarrhea, especially in tropical climates.
Associated with stomach acidity, protective mechanism against infection
Produces a heat-labile toxin (LT) similar to Vibrio cholerae toxin.
Causes hypersecretion of electrolytes and fluids into the intestinal lumen.
Self-limiting disease.

Escherichia coli (E. coli) - EIEC

Rare in developed countries compared to ETEC or EPEC.
Produces dysentery with direct penetration.
Transmission via the fecal-oral route.
Often misidentified.
Symptoms include fever, severe abdominal cramps, malaise, and watery diarrhea.
Nonmotile strains that do not ferment lactose are common.

Escherichia coli (E. coli) - EPEC

Has an adhesive property
Adheres to human epithelial cells and causes low-grade fever, malaise, vomiting, and diarrhea.
Mucus-containing diarrhea without blood.
Commonly observed in children <1 year old.

Escherichia coli (E. coli) - EHEC

Serotype O157:H7.
Linked to hemorrhagic diarrhea, colitis, HUS (hemolytic uremic syndrome).
Produces verotoxin 1 and 2.
Symptoms include watery to bloody diarrhea, abdominal cramps, and low-grade fever.
Toxin detection in stool is essential.

Escherichia coli (E. coli) - Enteroadherent (EAEC/DAEC)

Associated with diarrheal syndromes and UTIs.
DAEC strains may cause cystitis.
EAEC strains cause watery diarrhea.
Identification is based on "stacked-brick" cell growth patterns in cultures.

Escherichia coli (E. coli) - Extraintestinal Infections

Primary cause of septicemia and meningitis in neonates (~40%).
Newborn infection commonly acquired through the birth canal.
Capsular antigen K1 shares similarity with N. meningitidis group B.

Klebsiella spp

Klebsiella pneumoniae is the most common isolated species.
Possesses a large polysaccharide capsule.
Frequently found in the intestinal tracts of humans and animals.
Associated with HAIs (hospital-acquired infections), pneumonia, wound infections, and UTIs.
Gram-negative rods, nonmotile, have a polysaccharide capsule.
Lactose fermenters, facultative anaerobes
Cultures present as moist, mucoid colonies on media like MacConkey agar; on blood agar, they have slimy appearances.

Klebsiella spp. - Diseases

UTIs
Pneumonia
Septicemia

Treatment of Klebsiella and other Gram Negative bacteria

Antibiotic choices vary by the organism and patient condition
Antibiotic treatment may be difficult because the infections are frequently caused by drug resistance strains

Salmonella

Gram-negative, facultative anaerobes that resemble other enteric bacteria.
Colonies on selective/differential media (MAC) are clear and colorless, non-lactose fermenting.
Potential black centers on media with H2S indicators.
Produce significant infections in humans and other animals. Common species are S. Typhi and S. Paratyphi.

Salmonella - Epidemiology

Worldwide variation in incidence.
Presence in a variety of sources.
Various serotypes in animals and humans.

Salmonella - Clinical Infections

Gastroenteritis is prominent.
Enteric fever.

Salmonella - Diagnosis

Specimen collection (e.g., stool).
Culture on selective media.
Blood and urine cultures are done.

Salmonella - Treatment

Complicated infections may require specific antibiotics.

Shigella

Gram-negative, non-motile, non-encapsulated, bacillus
Important strains are S. sonnei, S. flexneri, and S. dysenteriae.
Causes bacillary dysentery.

Shigella - Clinical Infections

Shigellosis is characterized by short-term, self-limiting diarrhea with possible fever.

Shigella - Diagnosis

Specimens include fresh stool, mucus flecks, rectal swabs, and cultures on selective media (e.g., Hektoen enteric agar).

Shigella - Treatment

Antibiotic treatment can shorten the illness.
Reserve the antibiotics for severe cases.

Pseudomonas

Gram-negative, aerobic bacilli (rods).
Includes various species, some produce water-soluble pigments.
P. aeruginosa commonly causes infections in debilitated patients (e.g., cystic fibrosis).

Pseudomonas - P. aeruginosa

Small, gram-negative rod with a single polar flagellum
Aerobic, not fermenting lactose
Oxidase positive
Produces greenish pigment that fluoresces under UV light.

Pseudomonas - Virulence Factors

Flagella: aiding in attachment.
Biofilms: increasing pathogen resistance.
Enzymes which break down host tissues.
LPS (lipopolysaccharide): causing endotoxic shock.
Exoenzymes S, T, U, and Y

Pseudomonas - Clinical Manifestations

Localized and systemic infections.
Endocarditis, pneumonia, meningitis.
Often affecting patients with severe burns or compromised immune systems.

Pseudomonas - Treatment

Broad-spectrum antibiotics are typically used
Drug resistant infections may require more aggressive treatments

Acinetobacter

Gram-negative, coccobacilli / bacilli (rod-shaped)
Primarily non-motile, oxidase negative, catalase positive, aerobic.
Two major groups: saccharolytic and asaccharolytic.
Common in nosocomial infections (hospital acquired infections).

Acinetobacter - Epidemiology

Ubiquitous and frequently present in the environment and the skin, but mostly colonizes the hospital setting during prolonged stays.

Acinetobacter - Virulence Factor

Ability to produce a capsule increasing resistance against chemical disinfectants.
Associated with various infections (e.g., UTI).

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Description

Test your knowledge on various E. coli strains and their associated infections. This quiz covers characteristic symptoms, identification features, and detection methods for the pathogens related to diarrhea in children and neonatal infections. Explore your understanding of E. coli's role in health and disease.