Wound lecture Cat Neg GPC

Question 1

For B haemolytic strep group A,B, C,F,G how does lancefield grouping work?

Answer 1

detects cell wall polysaccharides and lipoteichoic acids

Question 2

What does group D consist of? What is the haemolysis and which are difficult to ID with maldi tof?

Answer 2

Having variable haemolysis, group D enterococci or streptococci. Maldi tof difficulty with ID of group D strep

Question 3

Which can be alpha haemolytic?

Answer 3

Viridans strep can be alpha or non haemolytic- ID if clinically sig and pneumococci- strep pneumonia is alpha

Question 4

Where does S pyogenes inhabit, how is it transmitted and which isolates are clinically significant?

Answer 4

Skin and mucous mebranes of URT with human as only known reservoir, can carry in throat, transmitted by direct contact/secretions/aerosols.
all isolates clinically sig (even one colony report)

Question 5

Name the virulence factors of S pyogenes (5)

Answer 5

M proteins, haemolysin, Streptococcal pyrogenic exotoxins (SPE), enzyme production, hyaluronic acid capsules (mucoid isolates)

Question 6

What are M proteins encoded by? How does it help in lancefield grouping? How does it help with virulence? How can it cause Acute Rheumatic Fever?

Answer 6

M proteins are surface antigens encoded by the emm gene. terminal sequence is the basis of antigen A test.
Helps with virulence as adherence to epithelial cells mediated with lipoteichoic acid, is acid and heat stabile, R to phagocytosis and intracellular killing- inhibit complement opsonisation (classic and alternate)
Also M proteins promotes binding to PMN so release cytokines which induce vascular leakage (toxic shock)
pepM region of some emm types elicits cross reactive antibody in response with myosin, keratin, laminen

Question 7

Haemolysins of s. pyogenes are?

Answer 7

Haemolysin O - responsible for B haemolysis, toxic to leucocytes and inhibits phago by macrophages and immunogenic- past pharyngeal infection but not skin
Haemolysin S- toxic to variety of cells but not immunogenic

Question 8

Streptococcal pyrogenic exotoxins are? which ones cause scarlet fever and toxic shock and which cause hypotension and shock?

Answer 8

Toxins that activate T cells and cause release of cytokines so that inflam response
A and B cause scarlet fever and toxic shock while A and C cause hypotension and shock

Question 9

how are SPEs encoded?

Answer 9

A and C are encoded by lysogenic bacteriophage, B encoded chromosomally* It is a C5a peptidase that is expressed on the bacterial cell surface

Question 10

how is enzyme production for s pyogenes a virulence factor?

Answer 10

streptokinase hydrolyses barriers at the periphery of a spreading infection.
DNAse - A,B,C,D all immunogenic. anti DNAse B antibodies = past group A infection - can use to monitor disease and treatment, more specific than ASOT (only pharyngeal infections) while there is inc antibodies in past skin and pharygeal infections
hyaluronidase - CT breakdown
C5a peptidase

Question 11

how does hyaluronic acid capsule help virulence

Answer 11

For mucoid isolates, it helps to resist phagocytosis, similar composition to host CT- antigenically invisible
assists cells to adhere to host tissue

Question 12

What infections do strep pyogenes cause?

Answer 12

Most common- pharyngitis/tonsilitis esp in school children - white grey exudate on tonsils. can get scarlet fever (red rash) concurrently, self limiting if no complications
Suppurative (pus producing)- sinusitis, otisis media, bacteremia, abscess of tonsils, pharynx
Non suppurative (sequelae)- acute and chronic rheumatic fever, glomerular nephritis

Question 13

What are the features of post strep pyogenes infection? Rhuematic fever and glomerular nephritis

Answer 13

Rheumatic fever is 1-5wks after pharyngeal infection w sudden onset fever and joint pain - cross rxn of antibodies produced against strep pyo that react with own tissue (heart), can last 3-6months - ASOT can detect infection of throat while inc aDNAseB can happen after both pharyngeal and skin infection.

In glomerular nephritis - post RT infection or skin infection with s pyogenes. onset 10 days w pharyngitis while 3-6wks after skin infection. deposition of abag complex in kidney damages glomeruli- can detect w aDNAseB or ASOT again

Question 14

What is needed to define streptococcal toxic shock syndrome

Answer 14

Isolation of s pyogenes + hypotension + 2 of the below:
renal impairment, coagulopathy, liver disease, respiratory distress syndrome, soft tissue necrosis

or just the isolation of group a strep from a sterile site

Question 15

When do we check for inducible R to clindamycin?

Answer 15

For staph and B haem strep (not enterococci), if D test pos= R to DA

Question 16

What are some precautions to be mindful of in Lancefield grouping?

Answer 16

Some state they are only for B haem strep, reactions can be poorer w D group antigens (d pos org can also cause false pos w s. aureus reagents)
cross rxn w listeria and group B rxn

Question 17

Regarding group C,F,G strep, where is it normal flora, what infections can it cause, what are its features?

Answer 17

They are NF in GIT, vagina, skin and oropharynx. they can cause a variety of infections like strep a and b- septicaemia, cellulitis, pneumonia, pharyngitis, tonsilitis.
group CFG are B haemolytic with a similar colony morph to group A strep. confirm ID w malditof
treat penicillin, ampillicin, erythromicin, cephalosporins
can have antigen overlaps between the groups and group F has distinct caramel smell.
if you see pitted colonies test for CFG rather than A first

Question 18

Where are Bacillus sp found, what does it cause and how can it be treated?

Answer 18

Ubiquitous in nature, NOT NF but can be transcient colonisers of skin, GIT, RT. can be common contam of media.
B anthracis is the main pathogen, B cereus, subtilis S and others can cause food poisoning, conjunctivitis, endocarditis, bacteremia
B anthracis and subtilis S to penicillin, B cereus prod B lactamase (R to AMP, cephalosporins)- treat w erythromycin, chloramphenicol, tetracycline

Question 19

What are the features of Bacillus sp?

Answer 19

GPB large w spores in aerobic conditions that may be seen in gram stain (esp B cereus spores) which resist pasteurisation of milk, can grow at 4-7 degrees, resist gamma irradiation of food.
Aerobes or facultative anaerobes, grow on most media, large dry textured feathered colonies. most aerobes so not really cause of deep wound- maybe contam in media

Question 20

How can we differentiate between B cereus, anthracis and subtilis?

Answer 20

B. anthracis has NO haemolysis and is NON MOTILE as well as lysis by gamma phage positive. Can grow anaerobically and is encapsulated in vivo, LV pos
B cereus has B haemolysis, is motile, not lysed by gamma phage, LV pos, AO2 pos
B subilitis can be gamma or beta haemolytic, motile, not lysed by gamma phage, LV neg and no growth in Ao2

Question 21

Features of clostridium sp- found where

Answer 21

Found in decaying vegetation, soil, GIT of human and animals, can be transient skin flora. spores contam food and survive cooking
large GPB, majority Obligate anaerobes(S to MTZ) - Aero tolerant exceptions
* C. histolyticum
* C. tertium
* C. carnis, cat neg
need enriched media- using BA w CN can inhibit facultative anaerobe GNB
produces powerful exotoxins, enzymes, gas

Question 22

Which clostridium sp can cause- gas gangrene, tetanus, botulism, pseudomembranous colitis?

Answer 22

Gas gangrene caused by c perfingens (80%), septicum, novyi
tetanus by c tetani, botulism by c botulinum, pseudomembranous colitis caused by c difficile and perfingens

Question 23

why do clostridium sp often decolourise?

Answer 23

They deteriorate as they age, no GNB have spores inside like clostridium

Question 24

what diseases do c perfingens cause?

Answer 24

Gas gangrene - inc muscle myonecrosis - pink swollen, gas and smell
anaerobic cellulitis have no muscle involvement
food poisoning - ingesting 10^8 cells, enterotoxins are produced in vivo after cells have sporulation in GIT, symptoms 8-24hrs after food
Necrotising bowel disease
pseudomembranous colitis ( inflam of colon) - less frequent

Question 25

What are the virulence factors of C perfingens?

Answer 25

5 serotypes A-E all produce alpha toxin, capsules, toxins and enzymes (can have 20 simultaneously) (alpha toxin also a necrotising toxin).

Question 26

Clostridium tetani features? causes tetanus (lock jaw). How does the toxin work? When are vaccinations needed?

Answer 26

spores in soil and water, infection after trauma or injury, incubation from few days to weeks, 15-60% fatal.
for toxin, tetanospasmin binds to gangliosides in CNS, affects motor neurone activity = intense reflex responses (inc muscle spasms), lead to spasmic paralysis, convolutions, respiratory spasms so lead to exhaustion and resp failure
Vaccines needed every 10 years

Question 27

How to differentiate c tetani?

Answer 27

Thin long GPB easily decolourised, tennis racquet spores. alpha or b haemolytic.
motile - swarms lacey fine film of growth
fairly non reactive biochemically

Question 28

Previously known as actinomyces congolensis and nocardia dermatonomus
causes dermatophilosis (chronic supparative skin disease) and pustular dermatitis
GPB with branching filaments but not acid fast like nocardia, produce zoospores
cat pos, obligate aerobe, growth on BA as colonies, NG on MAC, NG ON SAB, B haemolytic and motile

Answer 28

Dermatophilus congolensis

Question 29

what does dermatophilus congolensis cause?

Answer 29

equine rain scald when put blacket over horse when still wet

Question 30

What are the characteristics of Burkholderia sp? Which species in endemic in northern aust, which was used as a bioweapons in WW1

Answer 30

GNB ox variable (can be slow pos), motile, NLF on MAC, species can be green or yellow pigments
B, pseudomallei is endemic while B cepacia is a complex both (used to be pseudomonas group) and both found in environment
B mallei used as bioweapons - primarily associated w resp illness in horses, donkeys, mules. human acquire through skin abrasions. Vietnam veterans acquire from soil or environment

Question 31

What infection can b pseudomallei cause

Answer 31

Causes melioidosis which has several forms Skin infection causes abscess formation, skin ulcers so its systemic abscess formation
* Respiratory tract infection-pneumonia-like disease
* Bacteraemia and septic shock

can become latent- symptoms appear days- years later. contracted through abrasion to skin or mucous membrane exposure to soil and water
95% mortality rate without treatment

Question 32

What is the colony characteristics of b pseudomallei?

Answer 32

Wrinkled colonies with inc incubation time with various colours - variety so can be small medium cream on BA at 24hrs, wrinkled after 5 days
Large violet colonies on ashdown media
growth on MAC NLF on mac and good with commercial kits like API20NE (used as well for whole genus, non pigmented Chromobacterium violaceum, pasteruella, aeromonas Pseudomonas, vibrio)

Question 33

How can we treat B psuedomallei?

Answer 33

Resistant to:
- Aminoglycosides (gentamicin CN, tobramycin, amikacin) - Cephalosporins (1GC, 2GC)
- Macrolides, Rifamycins, Colistin
* R to CN, S to AMC a useful laboratory characteristic
ashdowns media has CN to inhibit other gram negs, crystal violet to inhibit gram pos, soil agar and neutral red

Question 34

What are the characteristics of chromobacterium violaceum? What is it about the oxidase result?

Answer 34

seldom associated w human infection tho high fatality rate 60-80, found in tropical and subtropical environment (soil, water)
usually abundant violet pigment (can be non pigmented)
Oxidase pos but impossible to tell because its purple , is indole neg but non pigmented strains may be indole pos, cat pos.
Nitrate Pos, DNAse Pos, ID non-pigmented strains using an ID panel (API etc)

Question 35

Where are pasteurella NF and what are its features?

Answer 35

NF in animal esp URT for many strains, associated w animal bites of human
GNCB, Most species Oxidase Pos, Catalase Pos
Most NG on MAC, Non-motile, Facultative anaerobes

Question 36

What are the 3 subspecies of pasteruella multocida?
what does it cause?

Answer 36

multocida, gallicida, septica. can diff by dulcitol and sorbitol carbohydrates
causes wound infections, cellulitis after scratch or bites, can lead to systemic infection
people exposed to animals can be carriers

Question 37

S pyogenes Types A, C, G, H, I, J, K, L, M are superantigens which do what?

Answer 37

• Stimulate indiscriminate proliferation and activation of host T cells
• Stimulate the release of cytokines
• Enhance the effects of minute amounts of Gram Neg endotoxin by > 100,000-fold

Question 38

how to treat s pyogenes

Answer 38

Treat infections with penicillin (no resistance to date) or erythromycin
* Treat with clindamycin if person is sensitive to P and R to erythromycin