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What gram stain is Streptococcus pyogenes?
Gr+
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What shape is Streptococcus pyogenes?
Cocci
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Is Streptococcus pyogenes catalase positive or negative?
Negative
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Is Streptococcus pyogenes anaerobe or aerobes?
Facultative anaerobe
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How motile is Streptococcus pyogenes?
Nonmotile
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Can Streptococcus pyogenes do hemolysis?
Yes, beta hemolysis
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True/False: Streptococcus pyogenes is not sensitive to bacitracin
False, Streptococcus pyogenes is bacitracin sensitive, will not grow if there is bacitracin in agar
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True/False: some Streptococcus pyogenes requires carbon dioxide
True, some are capnophilic
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What type of agar is used for Streptococcus pyogenes?
Blood agar
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Is Streptococcus pyogenes fastidious or non-fastidious?
Fastidious
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Streptococcus pyogenes group A could be found where?
- Has a human reservoir
- Normal microbiota of oropharynx
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Streptococcus pyogenes has what kind of capsule?
Hyaluronic
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What kind of infections are caused by Streptococcus pyogenes?
- Necrotizing fasiciitis
- Myositis
- Acute rheumatic fever
- Acute post-streptococcal glomeruloneph
- Etc.
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What are some virulence factors of Streptococcus pyogenes?
- (SMASHED)
- Streptolysins
- M protein
- Against C5a peptidase
- Streptokinase
- Hyaluronidase
- Exotoxin B
- DNases
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What is the function of hyaluronic acid?
It is non immunogenic because we have this too, so our immune system won’t recognize it
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What is ScpC?
A cell envelope proteinase that prevents neutrophil recruitment by clipping IL-8
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What is C5a peptidase?
Blocks phagocyte chemotaxis by inactivating C5a
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What is M protein?
- Adhesins, binds fibronectin, keratinocytes
- Antiphagocytic
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Which hemolysins can Streptococcus pyogenes produce?
Streptolysin S and Streptolysin O
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What is streptolysin S?
- B-hemolysin that causes rapid Cl- into cells that lead to lysis
- Works in aerobic condition
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What is streptolysin O?
B-hemolysin that works only in anaerobic condition, more antigenic than S
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What are some extracellular spreading factors of Streptococcus pyogenes?
- Streptokinase
- Hyaluronidase
- DNases A-D
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What are superantigens?
Pyrogenic exotoxins formed by S.pyogenes
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What is exotoxin B?
A superantigen formed by S.pyogenes that degrades immune proteins
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What gram stain is Clostridium perfringens?
Gr+
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What shape is Clostridium perfringens?
Rods
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Is Clostridium perfringens anaerobic or aerobic?
Aertotolerant to anaerobic
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Do Clostridium perfringens for endospores?
Yes, they are one of the two major clinical bugs that form endospores
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What is characteristic of Clostridium perfringens when it is related to necrotizing infection?
Gas gangrene
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What is characteristic of gas gangrene?
Bronze discoloration
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What is typically associated with gas gangrene?
Deep penetrating wound
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Where are Clostridium perfringens found?
- Soil
- Water
- Normal microbiota of GI tract
- Normal microbiota in female GU tract
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Do Clostridium perfringens have a capsule?
Yes
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Are Clostridium perfringens motile or nonmotile?
Nonmotile
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Do Clostridium perfringens have hemolytic abilities?
Yes, double zone hemolysis from alpha and theta toxins
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How fast do Clostridium perfringens grow?
Very fast in culture
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What are some virulence factors of Clostridium perfringens
- Alpha-toxin = lecithinase
- Theta-toxin
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What are alpha-toxins (lecithinase)?
Phospholipases that disrupt host cell membrane, causing disorganization and responsible for hemolysis and tissue destruction
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What are theta-toxin?
Disrupts cholesterol and lysis of RBC and WBC
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What are some spreading factors of Clostridium perfringens?
- DNase
- Hyaluronidase
- Collagenase
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When do gas gangrene usually occur?
<24 hours after deep, penetrating/traumatic injury
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What is the shape and gram stain of Brucella?
Gr negative Coccobacilli
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Is Brucella aerobic or anaerobic?
Aerobes
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Where do Brucella live in host?
Facultative intracellular – can survive inside macrophages and PMNs
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How fast do Brucella grow?
slow grower
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What kind of agar do Brucella grow in?
Blood agar with carbon dioxide
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What are the source of human Brucella infections?
Pigs, cattle, goats, dogs
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What is the mode of Brucella transmission from animal to human?
- Ingestion of unpasteurized dairy products
- Direct contact
- Inhalation
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How do humans show symptoms of Brucella?
- Granulomatous response
- Undulant fever
- Nonspecific flulike symptoms
- Enlarged lymph nodes, liver, spleen
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How is Brucella diagnosed?
Bone marrow culture is gold standard
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What is the shape and gram stain of Pasteurella multocida?
Gr negative coccobacilli
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What is the common source of human Pasteurella multocida infection?
Infected dogs or cats
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What is the mode of transmission of Pasteurella multocida from animal to human?
Bite, lick, scratch
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Do Pasteurella multocida have capsule?
yes
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Where could Pasteurella multocida be found in its animal source?
Normomicrobiota animal oropharynx
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What are diseases in human that are due to Pasteurella multocida?
- Localized cellulitis and lymphadenitis
- URI
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Systemic infection for immunocompromised patients
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What could happen in Pasteurella multocida infections are left untreated?
Could lead to osteomyelitis and septic arthritis
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What is the shape and gram stain of Bartonella henselae?
Gr negative Rod
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What are other names for Bartonella henselae?
- Cat scratch disease
- Bacillary angiomatosis
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What is the source of human Bartonella henselae infection?
Cats
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What is the mode of transmission of Bartonella henselae from animal to human?
Bite, lick, scratch
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Where do Bartonella henselae live in its host?
Facultative intracellular
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What is a physiological response induced by Bartonella henselae?
Angiogenesis
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How fast do Bartonella henselae grow?
Slow grower
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What diseases are caused by Bartonella henselae?
- Localized, chronic lymphadenopathy in children
- Possible complications including endocarditis, encephalopathy, granulomatous lesion on liver and spleen in immunocompromised patients
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What is a disease caused by Bartonella henselae in HIV patients?
Bacillary angiomatosis
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What are symptoms of bacillary angiomatosis?
- Multiple cutaneous or subQ vascular lesions that bleed profusely when traumatized
- Fever
- Liver lesions
- Osteolytic bone lesion of the long bones
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What is Bartonella quintana mode of transmission?
Body louse
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What is another name for Bartonella quintana?
Trench fever
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True/False: Bartonella henselae is more common cause of bacillary angiomatosis than B.quintana
False
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Which population are Bartonella quintana prevalent in?
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What is necrotizing fasciitis?
- Community acquired deep-seated infection of SubQ tissues
- Progressive destruction of fascia and fat
- May spare skin
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What microbe usually causes necrotizing fasciitis type II?
Group A Streptococcus pyogenes (GAS)
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Describe pathogenesis of necrotizing fasciitis?
- Could occur any part of body, usually begin as cellulitis
- Spreads along fascial planes and causes destruction of those plus fat
- Lead to systemic symptoms
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What are symptoms of necrotizing fasciitis?
- Fevers, hypotension, tachycardia
- Pain out of proportion
- Erythema, skin induration
- Bullae (blue, large blisters)
- Darken, reddish purple color skin within 24-48 hours
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What could happen to patient with necrotizing fasciitis?
- Multiple organ failure
- Death
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How id necrotizing fasciitis diagnosed?
- When symptoms fail to respond to broad spectrum IV abx
- Cutaneous manifestation
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How is necrotizing fasciitis treated?
- immediate surgical debridement
- Abx
- Hemodynamic support
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What is myonecrosis?
Necrotizing infection of the muscle
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What is gas gangrene?
Necrotizing infection of muscle that is caused by Clostridia instead of Streptococcus
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What are symptoms of gas gangrene?
- Sever pain
- Edema, tenderness
- Discoloration
- Crepitus at subQ tissue/muscle
- Systemic findings of toxicity
- Shock
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What could happen to patients with gas gangrene if left untreated within 48 hours?
Multiorgan failure, death
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How is gas gangrene diagnosed?
- Confirm with gram stain, anaerobic cultures
- Double zone hemolysis on blood agar
- Lecithinase activity on egg yolk agar
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What is pyomyositis?
Purulent infection of soft tissue infection that spread to the bone, usually with abscess caused by S.aureus or S.pyogenes
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What is osteomyelitis
Subacute to chronic infection to the bone
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What is the common cause of osteomyelitis?
S.aureus
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What are some symptoms of osteomyelitis?
- Fevers
- Chills
- Malaise
- Localized pain
- Edema
- Erythema
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What are the risk factors for osteomyelitis?
- Diabetes
- Immunocompromised patients
- IV drug users
- Elderly
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What are some types of osteomyelitis?
- Hematogenous (monomicrobial)
- Contiguous (polymicrobial)
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How is osteomyelitis diagnosed?
- Patient unable to bear weight
- Unilateral extremity pain
- Recent trauma or puncture wound
- Chronic draining ulcer
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What are some diagnostic methods for osteomyelitis?
- MRI imaging
- Gold standard – isolation of microbe from bone bx
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How to treat osteomyelitis?
- Abx after bone bx
- Debridement either surgically or non-surgically
- Could consider amputation
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