Gram Positive Bacilli Flashcards
1
Q
Medically Important Gram-Positive Bacilli
Three general groups
A
Endospore-formers
Non-endospore-formers
Irregular shaped and staining properties
2
Q
Endospore-formers
A
Bacillus, Clostridium
3
Q
Non-endospore-formers - Regular shaped
A
Listeria, Erysipelothrix
4
Q
Non-endospore-formers
Irregular shaped and staining properties
Non-Acid Fast
A
Corynebacterium, Proprionibacterium
5
Q
Non-endospore-formers
Irregular shaped and staining properties
Acid Fast
A
Mycobacterium
6
Q
Non-endospore-formers
Irregular shaped and staining properties
Filamentous, branching cells
A
Actinomyces, Nocardia
7
Q
Found in nature
Most are saprophytic and are isolated as contaminants
Bacillus anthracis as a major pathogen
Others are opportunists
A
Bacillus species
8
Q
Spore-forming Bacilli
A
Genus Bacillus
Genus Clostridium
9
Q
Gram-positive, endospore-forming
Mostly saprobic
Aerobic/ facultative and catalase positive
Often β hemolytic & motile
(except B. anthracis)
Versatile in degrading complex macromolecules
Source of antibiotics
Primary habitat is soil
A
Genus Bacillus
10
Q
Thick walled structures formed by vegetative cells
Resistant to radiation, chemicals, heat, desiccation (dipicolinic acid)
Steam autoclaving necessary for destruction
A
Bacillus Endospores
11
Q
Enzootic in middle east
Transmitted by contact with animal products
Spores remain infectious for years
Usually cutaneous inoculation - slow healing ulcer, bacilli spread to lymphatics and bloodstream
20% mortality if untreated
Respiratory anthrax is usually fatal even if treated
GI anthrax also occurs in some Asian countries
Excellent biological warfare agent
A
Bacillus anthracis
12
Q
Large, block-shaped rods
Central spores that develop under all conditions except in the living body
A
Bacillus anthracis
13
Q
Virulence factors of Bacillus anthracis
A
Polypeptide capsule & exotoxins
14
Q
3 types of anthrax
A
cutaneous
pulmonary
gastrointestinal
15
Q
the organisms gain access through cuts; localized infection
A
Cutaneous anthrax or “malignant pustule”:
16
Q
acquired through inhalation of spores; may result in respiratory distress and death
A
Pulmonary anthrax or “woolsorter’s disease”
17
Q
:acquired by ingestion of contaminated raw meat
A
Gastrointestinal anthrax
18
Q
Gram stain: large, square-ended gram-positive rods; may appear end-to-end giving a “bamboo appearance”
A
Microscopic morphology of Bacillus anthracis
19
Q
Nonhemolytic on 5% blood agar; raised, large, grayish-white, irregular, fingerlike edges described as “Medusa head” or “beaten egg whites”
A
Colonial morphology of Bacillus anthracis
20
Q
Hemolysis on Blood agar plates: Bacillus anthracis
A
B. anthracis - = / non hemolytic
B. cereus - + / hemolytic
21
Q
Motility
A
B. anthracis - = / non motile
B. cereus - + / motile
22
Q
String of pearl
A
B. anthracis - +
B. cerues - =
23
Q
Growth on PEA
A
B. anthracis - =
B. cereus. - +
24
Q
Gelatin hydrolysis
A
B. anthracis - =
B. cereus. - +
25
Susceptibility to penicillin
B. anthracis - suceptible
B. cereus. - resistant
26
Anthrax pathogenesis: antiphagocytic
Poly-D-glutamic acid (protein) capsule
27
Anthrax pathogenesis - exotoxins 3 component
Protective antigen (PA)
Edema factor (EF)
Lethal factor (LF)
28
binds to cells, forms channel that permits EF and LF to enter
Protective antigen (PA)
29
adenyl cyclase causes fluid to accumulate at the site of infection and inhibit immune function
Edema factor (EF)
30
disrupts cell's functions, stimulates TNF-alpha and IL-1-beta, kills infected cells
Lethal factor (LF)
31
Anthrax: Complications and Treatment
Fatality rate of gastrointestinal form is highest although rare
Meningitis may occur in 5% of cases
Antibiotic therapy: penicillin in high doses
Vaccination is available to those with high risk of exposure
32
Control and treatment : Anthrax
Treated with penicillin, tetracycline, or ciprofloxacin
33
Vaccine: Antrax
live spores and toxoid to protect livestock
purified toxoid (avirulent nonencapsulated B. anthracis strain); for high risk occupations and military personnel; toxoid 6X over 1.5 years; annual boosters
34
Common airborne and dustborne; usual methods of disinfection and antisepsis are ineffective
Grows in foods, spores survive cooking and reheating
Ingestion of toxin-containing food causes nausea, vomiting, abdominal cramps and diarrhea; 24 hour duration
No treatment
Increasingly reported in immunosuppressed
Bacillus cereus
35
Associated with meat, poultry, and soups
Incubation period of 8 to16 hours
Fever uncommon
Resolves within 24 hours
Bacillus cereus: Food poisoning - Diarrheal syndrome
36
Associated with fried rice
Abdominal cramps and vomiting
Incubation period of 1 to 5 hours
Resolves in 9 hours
Bacillus cereus: Food poisoning- Emetic form
37
Heat-stable enterotoxin (emetic form)
Heat-labile enterotoxin (diarrheal form)
- Similar to V. cholera – stimulates cAMP watery diarrhea
- Contaminated rice, meat, vegetables
Bacillus cereus: Gastroenteritis
38
Necrotic toxin, hemolysin, phospholipase C
Bacillus cereus: other clinical condition - Ocular infections after trauma
39
Immunocompromised persons and drug abusers
Bacillus cereus: other clinical condition - IV-catheter-related sepsis, endocarditis, meningitis
40
Opportunistic infections of the eye
Meningitis, septicemia, and osteomyelitis
Found as contaminants in drug paraphernalia
Bacillus cereus : Infections in the immunosuppressed hosts
41
Other Bacillus species
Common laboratory contaminant
Bacillus subtilis
42
Gram-positive, spore-forming rods
Anaerobic and catalase negative
120 species
Oval or spherical spores produced only under anaerobic conditions
Synthesize organic acids, alcohols, and exotoxins
Cause wound infections, tissue infections, and food intoxications
Genus Clostridium
43
most frequent clostridia involved in soft tissue and wound infections - myonecrosis or gas gangrene
Clostridium perfringens
44
Where does clostridium in gas gangrene found
Spores found in soil, human skin, intestine, and vagina
45
Predisposing factors of gas gangrene
surgical incisions, compound fractures, diabetic ulcers, septic abortions, puncture wounds, gunshot wounds
46
Virulence factors of Gas gangrene: Clostridium
toxins – alpha toxin – causes RBC rupture, edema and tissue destruction
collagenase
hyaluronidase
DNase
47
Pathology of Gas gangrene: Clostridium
Not highly invasive; requires damaged and dead tissue and anaerobic conditions
Conditions stimulate spore germination, vegetative growth and release of exotoxins, and other virulence factors.
Fermentation of muscle carbohydrates results in the formation of gas and further destruction of tissue.
48
Gas gangrene treatment and prevention
Immediate cleansing of dirty wounds, deep wounds, decubitus ulcers, compound fractures, and infected incisions
Debridement of disease tissue
Large doses of cephalosporin or penicillin
Hyperbaric oxygen therapy
No vaccines available
49
Clostridium difficile-Associated Disease (CDAD)
* Normal resident of colon, in low numbers
*.Causes antibiotic-associated colitis
- relatively non-invasive; treatment with broad-spectrum antibiotics kills the other bacteria, allowing C. difficile to overgrow
* Produces enterotoxins that damage intestines
* Major cause of diarrhea in hospitals
* Increasingly more common in community acquired diarrhea
50
Clostridium difficile-Associated Disease (CDAD)
Treatment and prevention
Mild uncomplicated cases respond to fluid and electrolyte replacement and withdrawal of antimicrobials.
Severe infections treated with oral vancomycin or metronidazole and replacement cultures
Increased precautions to prevent spread
51
Clostridium tetani
Common resident of soil and GI tracts of animals
Causes tetanus or lockjaw, a neuromuscular disease
Most commonly among geriatric patients and IV drug abusers; neonates in developing countries
Tetanus
52
Tetanus pathology
Spores usually enter through accidental puncture wounds, burns, umbilical stumps, frostbite, and crushed body parts.
Anaerobic environment is ideal for vegetative cells to grow and release toxin.
Tetanospasmin
Anaerobic environment is ideal for vegetative cells to grow and release toxin.
53
neurotoxin causes paralysis by binding to motor nerve endings; blocking the release of neurotransmitter for muscular contraction inhibition; muscles contract uncontrollably
Tetanospasmin
54
Tetanus treatment and prevention
Treatment aimed at deterring degree of toxemia and infection and maintaining homeostasis
Antitoxin therapy with human tetanus immune globulin; inactivates circulating toxin but does not counteract that which is already bound
Control infection with penicillin or tetracycline; and muscle relaxants
Vaccine available; booster needed every 10 years
55
rare but severe intoxication usually from home canned food
Clostridium botulinum : clostridial food poisoning
56
mild intestinal illness; second most common form of food poisoning worldwide
Clostridium perfringens: clostridial food poisoning
57
intoxication associated with inadequate food preservation
Botulism
58
spore-forming anaerobe; commonly inhabits soil and water
Clostridium botulinum
59
Botulinum Food Poisoning pathogenesis
Spores are present on food when gathered and processed.
If reliable temperature and pressure are not achieved air will be evacuated but spores will remain.
Anaerobic conditions favor spore germination and vegetative growth.
Potent toxin, botulin, is released.
Toxin is carried to neuromuscular junctions and blocks the release of acetylcholine, necessary for muscle contraction to occur.
Double or blurred vision, difficulty swallowing, neuromuscular symptoms
60
caused by ingested spores that germinate and release toxin; flaccid paralysis
Infant botulism
61
spores enter wound and cause food poisoning symptoms
Wound botulism
62
Infant and Wound Botulism
Treatment and prevention
Determine presence of toxin in food, intestinal contents or feces
Administer antitoxin; cardiac and respiratory support
Infectious botulism treated with penicillin
Practice proper methods of preserving and handling canned foods; addition of preservatives.
63
Clostrium perfringens
Spores contaminate food that has not been cooked thoroughly enough to destroy spores.
Spores germinate and multiply (especially if unrefrigerated).
When consumed, toxin is produced in the intestine; acts on epithelial cells, acute abdominal pain, diarrhea, and nausea
Rapid recovery
Clostridial Gastroenteritis
64
Gram-Positive Regular Non-Spore-Forming Bacilli
Listeria monocytogenes
Erysipelothrix rhusiopathiae
65
Non-spore-forming Gram-positive
Ranging from coccobacilli to long filaments
1-4 flagella
No capsules
Resistant to cold, heat, salt, pH extremes and bile
Virulence attributed to ability to replicate in the cytoplasm of cells after inducing phagocytosis; avoids humoral immune system
Listeria monocytogenes
66
Listeria monocytogenes
Epidemiology and pathology
Primary reservoir is soil and water; animal intestines
Can contaminate foods and grow during refrigeration
Listeriosis - most cases associated with dairy products, poultry, and meat
Often mild or subclinical in normal adults
Immunocompromised patients, fetuses and neonates; affects brain and meninges
20% death rate
67
Listeria monocytogenes
Diagnosis and Control
Culture requires lengthy cold enrichment process.
Rapid diagnostic tests using ELISA available
Ampicillin and trimethoprimsulfamethoxazole
Prevention – pasteurization and cooking
68
Gram-positive bacillus
Common in animals
Transmitted to humans by skin wound
Occupational hazard in butchers, farmers, veterinarians
Self-limited skin lesions with erythema & eruption
May spread to bloodstream
Erisipelothrix rhusopathiae
69
Primary reservoir – tonsils of healthy pigs
Enters through skin abrasion, multiples to produce erysipeloid, dark red lesions
Penicillin or erythromycin
Vaccine for pigs
Erysipelothrix rhusiopathiae
70
Gram-positive, catalase-positive rods
Occur in soil and decaying vegetation
Aerobic Actinomycetes
71
Positive (+) Mycolic acid
Mycobacterium
Corynebacterium
72
Negative (-) mycolic acid
Nocardia
Streptomyces
Rhodococcus
Tropheryma
Others
73
Gram-Positive Irregular Non-Spore-Forming Bacilli
Medically important genera:
Corynebacterium
Proprionibacterium
Mycobacterium
Actinomyces
Nocardia
74
Pleomorphic; stain unevenly
20 genera; Corynebacterium, Mycobacterium, and Nocardia greatest clinical significance
All produce catalase, possess mycolic acids, and a unique peptidoglycan.
Gram-Positive Irregular Non-Spore-Forming Bacilli
75
Gram-positive irregular bacilli
Virulence factors assist in attachment and growth.
diphtherotoxin – exotoxin
Corynbacterium diptheriae
76
part B binds and induces endocytosis; part A arrests protein synthesis
2 part toxin : diphtherotoxin – exotoxin
77
Gram-positive, curved pleomorphic rods
“Chinese Letters”
Aerobic/facultatively anaerobic
Grow readily on Sheep blood agar
Catalase & oxidase positive
Usually non-motile
Commensals on skin
Some species pathogenic
Corynebacterium
78
Corynebacterium
Epidemiology and pathology
Reservoir of healthy carriers; potential for diphtheria is always present
Most cases occur in non-immunized children living in crowded, unsanitary conditions.
Acquired via respiratory droplets from carriers or actively infected individuals
79
- upper respiratory tract inflammation
– sore throat, nausea, vomiting, swollen lymph nodes; pseudomembrane formation can cause asphyxiation
Local infection (2 stages of disease corynebacterium)
80
target organs primarily heart and nerves
Diptherotoxin production and toxemia
( 2 stages of disease corynebacterium)
81
Corynebacterium diagnostic methods
Pseudomembrane and swelling indicative
Stains
Conditions, history
Serological assay
82
Corynebacterium treatment and prevention
Antitoxin
Penicillin or erythromycin
Prevented by toxoid vaccine series and boosters
83
Spreads by droplet
Phospholipase D increases vascular permeability & promotes spread
Phage-coded exotoxin (A&B subunits) acts on respiratory mucous membranes interfering with protein synthesis by inactivating EF-2
Pseudomembrane of fibrin, bacteria, epithelial & phagocytic cells impairs breathing
Toxin spreads to heart, CNS, & adrenals
Selective media (cysteine-tellurite)
Identify in Public Health Labs
Protect by toxoid vaccination – DaPT
Diphtheria (C. diphtheriae)
84
increases vascular permeability & promotes spread ( Diphtheria )
Phospholipase D
85
acts on respiratory mucous membranes interfering with protein synthesis by inactivating EF-2 ( Diphtheria)
Phage-coded exotoxin (A&B subunits)
86
Diphtheria selective media
Cysteine-tellurite
87
Other pathogenic corynebacterium
Opportunistic bloodstream infections in bone marrow transplant recipients
Multiple antibiotic resistance - except vancomycin and tetracycline
Commonly carried on skin of hospitalized persons
C. jeikeium (JK)
88
Occasional cause of UTI & stones (splits urea)
Other pathogenic corynebacterium
C. urealyticum
89
Propionibacterium acnes most common
Gram-positive rods
Aerotolerant or anaerobic
Nontoxigenic
Common resident of sebaceous glands
Causes acne
Genus Proprionibacterium
90
nonmotile filamentous bacteria related to mycobacteria.
Genera Actinomyces & Nocardia
91
May cause chronic infection of skin and soft tissues
Actinomycetes: Filamentous Bacilli
92
responsible for diseases of the oral cavity, thoracic or intestines - actinomycoses
Actinomyces israelii
93
causes pulmonary disease similar to TB.
Nocardia brasiliensis
94
General Characteristics
Aerobic, gram-positive, filamentous rods, sometimes resembling branched hyphae
Weakly acid-fast and may stain gram-variable
Morphologically resemble fungi, both in culture and in types of infections produced
Generally found in the environment and mostly affect immunocompromised individuals
Aerobic Actinomycetes:Nocardia species
95
Aerobic Actinomycetes
Nocardia, Actinomadura, and Streptomyces species
96
Significant Nocardia species
N. asteroides
N. braziliensis
N. caviae
97
Actinomadura species
A. madurae
A. pelletieri
98
Streptomyces species
None
99
Clinical infections
Aerobic Actinomycetes: Nocardia, Actinomadura, and Streptomyces species
Pulmonary form
Mycetomas
100
Laboratory Diagnosis: Nocardia, Actinomadura, and Streptomyces species
MICROSCOPY
Gram-positive branching filaments are seen in direct smears from sputum or aspirated material
May show beading appearance
101
Expectorated sputum with purulence
Gram-positive filamentous bacilli
Suspicious for actinomycetes
Nocardia, Actinomadura, and Streptomyces species
102
Nocardia, Actinomadura, and Streptomyces species
Cultural characteristics
Chalky, matte, dry, crumbly appearance
May be pigmented
103
Nocardia, Actinomadura, and Streptomyces species
Identification
Utilization of carbohydrates
Hydrolysis of casein, tyrosine, and xanthine
104
are not acid-fast
Actinomadura and Streptomyces sp.
105
Sputum smear, partially acid-fast bacilli, consistent
Nocardia sp.
