64 Questions
What type of bacteria does Listeria monocytogenes belong to?
Firmicutes
What is a characteristic feature of Listeria monocytogenes?
It exhibits tumbling motility at room temperature
What is the most common source of Listeria monocytogenes infection?
Infected environment and animals
What is the recommended treatment for Listeria monocytogenes infection?
Penicillin and gentamicin
What is the significance of Listeria monocytogenes being psychrotrophic?
It can grow at low temperatures
What is a common food source associated with Listeria monocytogenes outbreaks?
Unpasteurized soft cheeses
What is the outcome of Listeria monocytogenes infection in immunocompetent individuals?
Gastrointestinal upset and flu-like symptoms
What was the outcome of the 2011 Listeria monocytogenes epidemic?
33 deaths and 147 confirmed cases
What was the outcome of the listeria outbreak in 2011?
147 people were hospitalized and 33 died
What was the primary cause of the listeria contamination in the cantaloupes?
Failure to use a chlorine spray feature to kill bacteria
What was the outcome of the Jensens' initial plea to the charges?
They pleaded not guilty to all six counts
What was the maximum sentence the Jensens faced for their conviction?
Up to 6 years in federal prison
What was the consequence of the listeria outbreak for the Jensens' business?
They filed for bankruptcy and suspended farming after lawsuits were filed
What was the reason for the Jensens' lawsuit against the Primus Group?
They claimed the company approved the cleaning operation they used
What was the consequence of the listeria outbreak for one of the victims?
They suffered a miscarriage
What was the charge the Jensens were convicted of?
Introducing adulterated food into interstate commerce
What is the estimated mortality rate of diphtheria even with treatment?
5-10%
What is the characteristic of the lactic acid bacteria?
Non spore forming bacteria
What is the function of the B domain of the diphtheria toxin?
Receptor-binding
Which of the following bacteria is NOT a high GC gram positive bacteria?
Lactobacillus
What is the purpose of the Elek test?
To test for toxigenicity
What is the recommended treatment for diphtheria?
Antitoxin and antibiotic
What is the characteristic of Actinomycetes?
Generate spores at ends of terminal hyphae
What is the role of toxin in the pathology of Diptheria?
It causes destruction of epithelium
What is the mode of action of the diphtheria toxin?
Inhibition of protein synthesis
What is the source of the diphtheria toxin?
Lysogenic phage
What is the characteristic of Corynebacterium diptheriae?
Non-motile, club-shaped rods
What is the purpose of the Gram stain or methylene blue in diagnosing diphtheria?
To identify the bacterium
What is the mode of transmission of Diptheria?
Droplets or contact
What is the characteristic of the pseudomembrane formed in Diptheria?
It is a greyish, thick membrane
What is the approximate lethal dose of the diphtheria toxin for humans?
0.1 μg/kg
What is the effect of the toxin produced by Corynebacterium diptheriae?
It causes destruction of tissues in all parts of the body
Streptomyces is a type of low GC gram-positive bacteria.
False
Clostridium is a type of non-spore forming bacteria.
False
Corynebacterium diptheriae is a type of fungus.
False
Diphtheria is a lower respiratory tract illness.
False
The toxin produced by Corynebacterium diptheriae is absorbed onto the skin and causes destruction of epithelium.
False
The pseudomembrane formed in diphtheria is yellowish in color.
False
Streptomyces produces antibiotics in the roots of plants.
False
The brothers initially pleaded guilty to the charges of introducing adulterated food into interstate commerce.
False
The Jensens faced sentences of up to 10 years in federal prison for their conviction on all six counts.
False
Mycoplasma is a type of high GC gram-positive bacteria.
False
The listeria outbreak led to the hospitalization of 147 people across 30 states.
False
The Jensens filed for bankruptcy in 2010 and suspended farming after lawsuits were filed by people sickened or whose family members died from listeria infections.
False
The Jensens sued a food safety audit firm, the Primus Group, because they did not approve the cleaning operation.
False
The listeria outbreak led to the death of 30 people.
False
The Jensens used a chlorine spray feature to clean their cantaloupes.
False
The Jensens began washing their cantaloupes with devices used to clean potatoes in April 2011.
False
Diphtheria toxin is encoded by a virulent phage.
False
The lethal dose of diphtheria toxin for humans is approximately 1 μg/kg.
False
Antitoxin is used as a vaccine for diphtheria.
False
Diphtheria toxin ADP-ribosylates elongation factor EF1.
False
The Elek test is used to diagnose diphtheria.
True
Listeria monocytogenes is a type of low GC gram-positive bacteria.
True
Diphtheria is treated with antibiotic only.
False
The mortality rate of diphtheria even with treatment is 1-2%.
False
Listeria monocytogenes can cause meningitis and sepsis in immunocompetent individuals.
False
Loeffler's serum media is a selective media for Corynebacterium diptheriae.
False
Listeria monocytogenes is a psychrophilic bacterium.
False
The main reservoir of Listeria monocytogenes infection is infected humans.
False
Penicillin and gentamicin are effective against Listeria monocytogenes.
True
Listeria monocytogenes can cause death in immunocompetent individuals.
True
Listeria monocytogenes is a type of spore-forming bacteria.
False
The 2011 epidemic of Listeria monocytogenes resulted in 33 deaths.
True
Study Notes
Gram-Positive Bacteria
- Firmicutes:
- Low GC gram-positive bacteria
- Examples: Lactic acid bacteria (Streptococcus, Lactobacillus), Staphylococcus, Listeria, Mycoplasma
- Actinobacteria:
- High GC gram-positive bacteria
- Examples: Streptomyces, Corynebacteria, Mycobacteria
Listeria
- Non-spore forming, gram-positive, non-motile rods
- Causes listeriosis
- Important cause of disease in humans and animals
- L. monocytogenes: short, gram-positive, non-spore forming rod; catalase positive, facultative anaerobe; tumbling motility at room temperature but not at 37°C
Listeriosis
- Two types:
- Perinatal:
- Early onset: intrauterine infection, sepsis, and death before birth
- Late onset: infected at birth, meningitis, and sepsis within 2-3 weeks
- Adult:
- Flu-like symptoms and gastro upset in immunocompetent individuals
- Meningo-encephalitis and bacteraemia in immunocompromised individuals
- Perinatal:
- Treatment: penicillin and gentamicin (gentamicin does not enter host cells)
- Source of infection: environment, animals, silage, infected humans
- Normal route of infection: gastrointestinal
- Outbreaks associated with dairy products, packaged meat, and fruit and vegetables
- Prevention: pasteurization of dairy foodstuffs and cooking of food
2011 Epidemic
- 33 deaths and 147 confirmed cases
- Listeria-contaminated cantaloupes killed 33 people
- Two Colorado farmers pleaded guilty to federal criminal charges
Pathogenesis of Listeria
- Infection leads to meningitis and sepsis
Streptomyces
- Abundant soil organisms
- Mycelial
- Generate spores at ends of terminal hyphae
- Strict aerobes
- Nutritionally versatile
- Produce many antibiotics
- Antibiotics produced by Streptomyces include:
- Antibiotic droplets secreted by Streptomyces coelicolor
Corynebacteria
- Diverse group of Gram +, aerobic, non-motile club-shaped rods
- Animal pathogens, plant pathogens, and saprophytes
- Examples: Corynebacterium diptheriae
Corynebacterium Diptheriae
- Pathology of Diptheria:
- Upper respiratory tract illness
- Sore throat, low-grade fever, and adherent membrane of the tonsil(s), pharynx, and/or nose
- Spread by droplets or contact
- Toxigenic strains produce a toxin
- Toxin absorbs onto mucous membrane, causing destruction of epithelium and producing local inflammation
- Necrotic epithelium forms a greyish "pseudomembrane"
- Severe symptoms due to toxin action
- Lesions occur in kidney, heart, and nervous system
- 5-10% mortality even with treatment
- 4000 children die from diphtheria each year
Diphtheria Toxin
- Encoded by lysogenic phage
- A (catalytic) and B (receptor-binding) domains
- ADP-ribosylates elongation factor EF2, preventing protein synthesis
- Lethal dose for humans: 0.1 μg/kg
- Inactivated toxoid used as vaccine
- Antitoxin used for treatment
- Toxin used for Elek test
Diagnosis and Treatment of Diphtheria
- Gram stain or methylene blue show beaded bugs from swab
- Aerobic growth on most media; Loefflers serum media is semi-selective
- Elek test for toxigenicity:
- Antitoxin-soaked filter paper
- Perpendicular streaked samples
- Treatment: antitoxin and antibiotic (e.g., erythromycin)
- Vaccine: Diphtheria toxoid (DPT)
Gram-Positive Bacteria
- Firmicutes:
- Low GC gram-positive bacteria
- Examples: Lactic acid bacteria (Streptococcus, Lactobacillus), Staphylococcus, Listeria, Mycoplasma
- Actinobacteria:
- High GC gram-positive bacteria
- Examples: Streptomyces, Corynebacteria, Mycobacteria
Listeria
- Non-spore forming, gram-positive, non-motile rods
- Causes listeriosis
- Important cause of disease in humans and animals
- L. monocytogenes: short, gram-positive, non-spore forming rod; catalase positive, facultative anaerobe; tumbling motility at room temperature but not at 37°C
Listeriosis
- Two types:
- Perinatal:
- Early onset: intrauterine infection, sepsis, and death before birth
- Late onset: infected at birth, meningitis, and sepsis within 2-3 weeks
- Adult:
- Flu-like symptoms and gastro upset in immunocompetent individuals
- Meningo-encephalitis and bacteraemia in immunocompromised individuals
- Perinatal:
- Treatment: penicillin and gentamicin (gentamicin does not enter host cells)
- Source of infection: environment, animals, silage, infected humans
- Normal route of infection: gastrointestinal
- Outbreaks associated with dairy products, packaged meat, and fruit and vegetables
- Prevention: pasteurization of dairy foodstuffs and cooking of food
2011 Epidemic
- 33 deaths and 147 confirmed cases
- Listeria-contaminated cantaloupes killed 33 people
- Two Colorado farmers pleaded guilty to federal criminal charges
Pathogenesis of Listeria
- Infection leads to meningitis and sepsis
Streptomyces
- Abundant soil organisms
- Mycelial
- Generate spores at ends of terminal hyphae
- Strict aerobes
- Nutritionally versatile
- Produce many antibiotics
- Antibiotics produced by Streptomyces include:
- Antibiotic droplets secreted by Streptomyces coelicolor
Corynebacteria
- Diverse group of Gram +, aerobic, non-motile club-shaped rods
- Animal pathogens, plant pathogens, and saprophytes
- Examples: Corynebacterium diptheriae
Corynebacterium Diptheriae
- Pathology of Diptheria:
- Upper respiratory tract illness
- Sore throat, low-grade fever, and adherent membrane of the tonsil(s), pharynx, and/or nose
- Spread by droplets or contact
- Toxigenic strains produce a toxin
- Toxin absorbs onto mucous membrane, causing destruction of epithelium and producing local inflammation
- Necrotic epithelium forms a greyish "pseudomembrane"
- Severe symptoms due to toxin action
- Lesions occur in kidney, heart, and nervous system
- 5-10% mortality even with treatment
- 4000 children die from diphtheria each year
Diphtheria Toxin
- Encoded by lysogenic phage
- A (catalytic) and B (receptor-binding) domains
- ADP-ribosylates elongation factor EF2, preventing protein synthesis
- Lethal dose for humans: 0.1 μg/kg
- Inactivated toxoid used as vaccine
- Antitoxin used for treatment
- Toxin used for Elek test
Diagnosis and Treatment of Diphtheria
- Gram stain or methylene blue show beaded bugs from swab
- Aerobic growth on most media; Loefflers serum media is semi-selective
- Elek test for toxigenicity:
- Antitoxin-soaked filter paper
- Perpendicular streaked samples
- Treatment: antitoxin and antibiotic (e.g., erythromycin)
- Vaccine: Diphtheria toxoid (DPT)
Test your knowledge of bacteria classification, including Firmicutes, Actinobacteria, and more. Identify the characteristics and examples of different types of bacteria.
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