WEEK 14: GRAM POSITIVE RODS Flashcards
1
Q
What are the tests used to differentiate Corynebacterium (-) to Listeria(+)?
A
- Motility (22C)
- Bile esculin Hydrolysis
2
Q
- Found as free-living saprophytes
- Water, soil, air
- Resistant to drying
- 80 species, of which 50 are clinically significant
- Members of the usual flora of humans and animals
- Closely related to Mycobacteria and Nocardia
- Clinically significant isolates
- Catalase positive and nonmotile
A
Corynebacterium
3
Q
- Facultatively anaerobic
- Gram-positive, non–spore-
forming rods - Arranged in palisades
- Club-shaped
- Babes-Ernst granules
- Polymerized phosphates
A
Corynebacterium
3
Q
- is the most significant pathogen.
- Causes diphtheria
- Difficult to speciate other species
- Other species may cause infections in immunocompromised hosts.
- Generally thought of as contaminants
A
Corynebacterium diphtheriae
4
Q
- Worldwide distribution
- Rare in places where vaccination programs exist
- Exotoxin is a major virulence factor.
- Diphtheria toxin
- Toxin is produced by certain strains.
- Lysogenized by bacteriophage with toxin gene (tox+)
- Only toxin-producing bacteria can cause diphtheria.
- Toxin production is inversely proportional to iron availability.
- Toxin is antigenic.
- Thus can use immunoglobulin G (IgG) to block toxin effects
A
Toxigenic Corynebacterium diphtheriae
5
Q
What is the major virulence factor of Corynebacterium diphtheriae?
A
Exotoxin
6
Q
- Inhibits protein synthesis
- NAD+ + EF-2 → ADPR-EF-2 + Nicotinamide + H+
- Catalyzes transfer of ADPR to link with EF2 ADPR.EF (inactive)
- Leads to cell/tissue death
A
A: active fragment
7
Q
- Mediates entry of fragment A
- binds to specific cell membrane receptors
A
Fragment B
8
Q
- Respiratory
- Acquired by droplet spray
- Aerosol or hand-to-mouth contact
- Unimmunized individuals are susceptibleb
A
Clinical Infections of Diphtheria
9
Q
- More prevalent in the tropics
- Infections occur at the site of minor abrasions.
- Nonhealing ulcers with a dirty gray membrane
A
Cutaneous form of C. diphtheriae
10
Q
- Used to demonstrate
pleomorphism and
metachromatic granules - Babes-Ernst granules
A
Loeffler’s serum agar
11
Q
- Modified Tinsdale medium
- Selective and differential
- Black colonies with brown
halos around the colonies
A
Cystine-tellurite blood
agar (CTBA)
12
Q
- Common on skin and most frequently recovered species
- Opportunistic infections
- Prosthetic joint infections, sepsis, and endocarditis
- In nosocomial or immunocompromised patients
A
C. amycolatum
13
Q
- Mastitis in cattle
- Contact with animals or unpasteurized milk
A
C. ulcerans
14
Q
- Infections from catheters or prosthetic devices
- Prosthetic valve endocarditis
A
C. jeikeium
15
Q
- Urinary pathogen
- Highly urease positive (within minutes)
A
C. urealyticum
15
Q
- Opportunistic infection
- Often endocarditis
A
C. pseudodiphtheriticum
16
Q
- Contact with sheep
- Dermonecrotic toxin
A
C. pseudotuberculosis
17
Q
- Rare infections
- Normal flora
A
C. striatum
18
Q
Gram-positive non–spore-forming coccobacillary
A
L. monocytogenes
18
Q
Induces phagocytosis
A
Surface protein p60
18
Q
- Cold enrichment
- Grows at 4°C
- Catalase positive
- Rules out Streptococcus
- Negative for hippurate hydrolysis
- Motility
- Motile at 25°C
- “Umbrella” type motility
- Tumbling motility in hanging drop method
A
L. monocytogenes
18
Q
- Likely develop disease from penetration of the intestine
and systemic spread - Septicemia/meningitis in the compromised/elderly
- Also endocarditis
- Mild flulike syndrome in pregnant women could be fatal to fetus
- Premature labor, spontaneous abortion
A
Listeriosis
19
Q
- Gram-positive, nonsporulating forming rods
- Coccobacillus that often appears like cocci
- Widespread in nature
- Primarily infect animals
- Human exposure is limited.
- Generally dairy products because it grows at low temperature
- Processed meats can also contain this bacteria
A
Listeria monocytogenes
19
* Normal oral flora
* Endocarditis
Rothia dentocariosa
19
* Damages phagocytic membrane and prevents killing of the organism
Listeriolysin O
20
* Grows well on sheep blood agar (SBA) and chocolate
agar
* Prefers slightly increased carbon dioxide (CO2)
* Colonies produce a narrow zone of hemolysis.
* Similar to group B Streptococcus
L. monocytogenes
21
Produces a “block” type of hemolysis in contrast to “arrow” shape produced by group B Streptococcus
Christie Atkins Munch-Petersen (CAMP) test (L. monocytogenes)
22
* Gram positive, non–spore-forming, pleomorphic
rods
* Distributed in nature
* Can cause disease in animals (swine, turkey, sheep)
* Infection through occupational exposure
* Erysipeloid
* Heals within 3 to 4 weeks
* Endocarditis
Erysipelothrix rhusiopathiae
23
* CO2 is required.
* Grows on blood or chocolate agar
* Colonies may appear gray or translucent with alpha hemolysis.
* Pleomorphic, gram-positive thin rods that may form long filaments
* Singly, in short chains, or in a V shape
* Catalase negative
* Production of hydrogen sulfide (H2S) on triple sugar iron (TSI)
Erysipelothrix rhusiopathiae
24
* SBA or chocolate agar
* 5% to 7% CO2 at 35°to 37°C
* Human blood bilayer Tween (HBT) agar
* Medium of choice
* Treatment
* Metronidazole
* Clindamycin
Gardnerella vaginalis
24
- Pharyngitis and pruritic scarlatiniform rash with desquamation of the skin of the hands and feet
- Lipase and lecithinase positive
- Exhibits a CAMP inhibition reaction
Arcanobacterium haemolyticum
24
Sepsis and wound infections in those with animal contact
A. pyogenes
24
* Catalase negative
* Narrow zone β-hemolysis
* Black dot on agar surface under the colony
Arcanobacterium
24
* Short, pleomorphic gram-positive rod or coccobacillus
* Often stains gram-variable or gram-negative
* Infections
* Bacterial vaginosis (BV)
* Malodorous discharge
* Vaginal pH of greater than 4.5
* Wet mounts of vaginal fluid
* Observe clue cells
Gardnerella vaginalis
25
Bacteriemia, wound infections, urinary tract infections (UTIs), and septic arthritis
A. bernardiae
25
* Aerobic
* Gram-positive filamentous rods
* Weakly acid-fast and may stain gram-variable
* Sometimes resembling branched hyphae
* Morphologically resemble fungi
* In culture and in types of infections
* Generally found in the environment and mostly affect
immunocompromised individuals
Sulfur granules
Nocardia
26
* Slow growers, may take 3 to 6 days
* Primarily affect immunocompromised
* Rare but high mortality rate (40%)
* Gram-positive branching filaments are seen in direct smears from
sputum or aspirated material.
* May show beading appearance
Nocardia
26
* Confluent bronchopneumonia
* Necrosis with abscesses
* No “sulfur granules”
N. cyriacigeorgica and N. farcinica
27
* Cutaneous infection termed actinomycotic mycetomas
* Trauma to skin
* Major destruction of the tissue and bone
* “Sulfur granules” present
N. brasiliensis
28
* Large, square-ended
gram-positive rods
* Bamboo appearance
* Nonhemolytic on 5%
blood agar; raised,
large, grayish-white,
irregular, fingerlike
edges
* “Medusa head” or
“beaten egg whites”
Bacillus anthracis
28
Nocardia can be identified using?
paraffin bait test
28
* Agent of anthrax, a disease in livestock
* Humans acquire infection by contamination of wound or
ingestion or inhalation of spores.
* Morphology
* Large, spore-forming, gram-positive bacilli
* Spores viable for over 50 years (even restored from fossils)
* Nonhemolytic on SBA
Bacillus anthracis
28
* Found in nature
* Most are saprophytic and are isolated as contaminants
* Gram-positive large rods with “empty” spaces
* Endospores
* Highly resistant to heat, drying, and chemicals
* Catalase positive
Bacillus
29
* Acquired through inhalation of spores
* Mild fever, fatigue, and malaise 2 to 5 days after exposure
* Similar to flu or common cold, lasting 2 to 3 days
* Sudden respiratory distress, disorientation, coma, and
death
* May last less than 24 hours from onset to death
Pulmonary anthrax or "woolsorter's disease”
29
* Polypeptide capsule
* Potent exotoxin
* Edema factor (EF)
* Protective antigen (PA)
* Lethal factor (LF)
Virulence factors of Bacillus anthracis
29
* Acquired by ingestion of contaminated raw meat
* Inoculates into a lesion on the intestinal mucosa
* Abdominal pain, nausea, anorexia, vomiting, and
sometimes bloody diarrhea
* More likely to be fatal but less likely to occur than
cutaneous form
Gastrointestinal anthrax
30
* Enter through cuts causing a localized infection
* Malignant pustule or black eschar
* Painless and non–pus-producing
* Produces a permanent scar
cutaneous anthrax
31
* Acquired by direct injection of the endospores into tissue
* Injection drug use
* Does not form black eschar
* Causes necrotizing fasciitis, organ failure, shock, coma, and meningitis
Injectional anthrax
31
* Caused by distinct enterotoxins
* Diarrheal syndrome
* Associated with meat, poultry, and soups
* Incubation period of 8 to 16 hours
* Fever uncommon
* Resolves within 24 hours
* Emetic form
* Associated with fried rice
* Abdominal cramps and vomiting
* Incubation period of 1 to 5 hours
* Resolves in 9 hours
B. cereus
31
* Infections in the immunosuppressed hosts
* Opportunistic infections of the eye
* Endophthalmitis, panophthalmitis, and keratitis
* Forms abscesses
* Meningitis, septicemia, and osteomyelitis
B. cereus
32
* Boxcar-shaped, gram-negative bacillus
* Produces a double zone of hemolysis on Brucella blood agar or blood agar
Clostridium perfringens
32
Antibiotic-associated diarrhea and pseudomembranous colitis
Clostridium difficile
33
Heavily swarming with terminal spores
C. tetani
33
Heavily swarming with subterminal spores
C. septicum
34
* Enteritis necroticans
* Acute onset of severe abdominal pain and diarrhea, which is often bloody, and may be accompanied by vomiting
* Followed by necrotic inflammation of the small intestines, at times
leading to bowel perforation
* Without treatment it can be fatal
Type C Clostridium perfringens
34
* A through G, but only types A, B, and E are associated with human disease
* Toxin A is now used in medical treatments, including Botox®
Botulinum toxins
35
* Causes flaccid paralysis
* In contrast to tetanus
Clostridium botulinum
35
- Ingestion of enterotoxin causing diarrhea and cramps
- Usually self-resolving
Type A Clostridium perfringens
36
* Home canning
* Home-cured meats
* 2 hours to 8 days later
* Infant botulism
* Ingestion of spores in contaminated honey
* Colonize the colon and produce toxins
Botulism
36
* Also known as gas gangrene
* Contaminated wounds from trauma or surgery
Myonecrosis
36
* Develops from tetanospasmin neurotoxin
* Inhibits neurons by inhibiting neurotransmitters
* Symptoms:
* Begin about 7 days after inoculation
* Muscular rigidity of the jaw, neck, and lumbar region
* Difficulty in swallowing
* Sometimes involves limbs as well
Tetanus
36
most common cause of Myonecrosis
C. perfringens
37
Most common isolate from blood cultures
C. perfringens
37
* Grow, multiply, and produce toxin
* Alpha toxin causes tissue necrosis and deeper invasion
* Causes death of tissue that can require amputation
* Symptoms
* Pain and swelling with obvious tissue necrosis
* Treatment
* Antibiotic and surgical débridement of necrotic tissue
* Hyperbaric oxygen can help destroy anaerobes
Myonecrosis
38
Marker organism for malignancy of GI tract
C. septicum
39
Both isolated from patients with underlying disease
C. tertium
40
* Most common isolate in antibiotic-associated diarrhea
* Can cause pseudomembranous colitis
* Necrosis of colon tissue and bloody diarrhea
C. difficile
41
* Commonly transmitted as a nosocomial infection
* Transferred among patients
* Hands of hospital personnel
Antibiotic-Associated Diarrhea
42
Chronic, granulomatous disease characterized by sinus tracts and fistulae
that erupt to the surface and drain pus that contains “sulfur granules"
Actinomycosis
