Unit 2 Diseases

Question 1

Salmonellosis

Answer 1

Gram-negative rods with peritrichous flagella
Characteristics:
Facultative anaerobe
Produce hydrogen sulfide
pH: Opt. = 37 C; Range 4.5 to 9.5
Mesophilic: OGT = 37 C; Max GT < 54 C; survives for extended time in food in freezer or at room temp
Water activity: 0.93 and above
Reservoir: animals (especially chickens, turkeys, pigs, cows, and pet reptiles)
Route of transmission
Eating contaminated food or drinking contaminated water

Question 2

Salmonella enterica Typhi

Answer 2

Reservoir:  humans only
Infected individuals or carriers (2-5% of infected people become carriers)
Infectious dose:  100,000 cells
Route of transmission
Food or water contaminated by infected person or carrier
Water contaminated with sewage which is drunk or used to wash food
Signs and symptoms
Sustained fever as high as 103° to 104° F
Fatigue
Stomach pains
Headache
Anorexia
Rash of flat, rose-colored spots
Hemorrhage in severe cases
May last for 3 to 4 weeks w/o treatment
Death rates range between 12% and 30%.

Question 3

Staphylococcusaureus

Answer 3

Gram-positive cocci
Can grow at water activity as low as 0.83 - tolerant of high salt and sugar concentrations
Biochemical characteristics:
Catalase positive
Facultative anaerobe
Coagulase positive
Reservoirs: humans and animals
Toxic dose: < 1 microgram (achieved with 100,000 cells/g)
Transmission: ingestion of contaminated food
Foods that are at risk
Food made with hand contact which require no additional cooking
Examples: salads, bakery products, sandwiches, milk and dairy products, meat, poultry, and eggs

Question 4

Treponema pallidum (Syphilis)

Answer 4

Gram-negative spirochete
Obligate intracellular parasite
Cannot be cultured on artificial media
Microaerophilic
Mesophilic
Reservoir:  Humans
Mode of Transmission:
Sexual contact
Mother to child during the birth process
Portal of Entry:  Mucous membranes

Question 5

Listeriamonocytogenes

Answer 5

Morphology: Gram + rods with peritrichous flagella
Characteristics:
Facultative anaerobe
Reservoir: moist environments, soil, and decaying plant and fecal material
Mode: consumption of contaminated food.
Sources of contamination: food workers, incoming air, raw materials and surfaces
Problem foods: raw milk or underpasteurized milk, cheeses (especially soft), ice cream; raw vegetables, meat and poultry products; sausages, hot dogs and deli meats; raw and smoke fish and other seafoods

Question 6

Vibrio cholerae

Answer 6

A slightly curved rod with a single polar flagellum
Gram-negative
Halophilic
Facultative anaerobe using aerobic respiration and anaerobic respiration
Reservoir
Brackish waters and estuaries, especially in warmer more tropical climates
Humans
Fish (especially filter-feeders) can act as a secondary source of infection
Modes of Transmission
Ingestion of water or food contaminated with feces
Ingestion of contaminated shellfish

Question 7

Clostridium botulinum

Answer 7

Gram-positive, motile, endospore-forming rod
Obligate anaerobe
Ferments carbohydrates and amino acids

Reservoir:  soil, water, and sewage
Mode of Transmission
Ingestion of toxin in contaminated food
Contamination of a wound by endospores
Ingestion of endospores by infants

Question 8

Bordetella pertussis

Answer 8

Very small nonmotile Gram-negative coccobacillus
Encapsulated
Obligate aerobe
Nutritionally fastidious
Slow growing

Reservoir: Humans
Portal of entry: Respiratory tract
Route of transmission: Respiratory droplet

Question 9

Borrelia burgdorferi (Lyme disease)

Answer 9

Gram-negative spirochete
Microaerophilic
Obligate parasite with limited metabolism
Major: white footed mouse
Minor: deer and birds
Bite from a tick (nymphal stage):
Blacklegged tick (or deer tick,Ixodes scapularis) found in the Northeast, mid-Atlantic or north-central states
Western blacklegged tick (Ixodes pacificus)found on the Pacific Coast
Ixodes ricinusin Europe, Middle East, and parts of Central Asia