Bacterial Virulence and Skin Infections Flashcards
Define virulence factors
Individual factors that can be tied down to a particular protein that makes it more effective at causing disease
Describe virulence factor adhesin
enables binding of the organism to host tissue
Describe virulence factor impedin
enables the organism to avoid host defence mechanisms
Describe virulence factor aggressin
causes damage to the host directly
Staphylcoccus aureus is a gram ___1__ organism. It is also coagulase ___2______it grows best in ____3___
1) positive
2) positive
3) aerobic conditions but can grow anaerobically (facultatively anaerobic)
Staphylcoccus epidermis is a gram ___1___ organism but coagulase ___2____
1) positive
2) negative
Staph Epidermis is largely ___1____, usually doesn’t cause ____2______ unless in ____3_____
1) self-limiting
2) serious infections
3) hospitals
MRSA is defined by resistance to what?
Flucloxacillin
Describe TSST-1 and super antigens.
TSST-1 is a super antigen that causes toxic shock. Super antigens cause massive release of cytokines & inappropriate immune response. Cytokine storm. Over stimulation of T cells due to non-specific activation of T cells.
Strep pyogenes is a gram __1___ organism that causes ___2____ haemolysis. It is a group _3___ streptococci which can be further divided according to __4_____
1) positive
2) beta
3) A
4) M protein antigens
What organism that can also cause skin problems cause strep sore throat, pharyngitis and scarlet fever?
Strep pyogenes
What two bacteria are usually involved in skin infections?
Staph Aureus and Strep Pyogenes
Describe Impetigo
Highly contagious, relatively superficial as the infection is immediately below the surface, tend to see it in young children.
Describe cellulitis
Deeper skin infection in the dermis that is not associated with necrosis, patient more likely to have fever, feel sick, vomiting, more of an immune response
Describe necrotising fasciitis
Strain penetrates mucous membrane and develop in lesion, rapidly destroys connective. Seems to be linked with streptolysin S (pore forming cytolysis, toxic to PMN, organelles, platelets, important in animal models.
Antibiotic of choice for staph A infection
flucloxacillin
Antibiotic of choice in MRSA?
no flucloxacillin. Use doxycycline, co-trimoxazole, clindamycin and vancomycin.
What does PVL toxin produced by staph a cause?
Necrotising pneumonia
Antibiotic of choice with strep pyogenes?
Sensitive to penicillin but if you are not sure if the infection is staph or strep then you should use flucloxacillin instead as that will cover both organisms.
Name 3 skin commensals unlikely to be the cause of a problem?
Staph epidermis, corynebacterium (diphtheroids) and propionibacterium
Dermatophytes are __1____ that infect ___2__ examples are __3___ which cause a ___4______
1) fungi
2) keratinised tissues (skin, hair, nails)
3) tinea- ring worm
4) ring appearance rash
Describe candida infections
fungal infection that occurs in the skin folds.
Example of an anti fungal?
clotrimazole (if it ends in azole it is an anti-fungal)
Describe scabies and treatment?
Causes an itchy rash, give malathion or benzyl benzoate lotion
How do you treat lice?
Malathion
What causes chicken pox?
Varicella virus
Normal presentation of chicken pox?
Centripetal rash, fever and itch
Who is more likely to get severe chicken pox?
Adults
Complications of chicken pox?
secondary bacterial infection, haemorrhagic rash, scarring, encephalitis or pneumonitis (chicken pox pneumonia- no consolidation)
Describe neonatal VZV?
This can occur secondary to chicken-pox in a mother in late pregnancy. This has a higher mortality so prevention with VZV immune globulin or acyclovir in women exposed late in pregnancy.
How is shingles related to chicken pox?
It occurs due to reactivation of the varicella virus in the sensory nerve roots resulting in dermatomal distribution of the disease
When can shingles cause problems?
When it is associated with motor nerves or ophthalmic division of trigeminal nerve so may need treated with acyclovir
Describe vaccines for chicken pox and shingles
Vaccine for chicken pox exists but is not routinely given in UK. In UK when over 70 offered a high dose vaccine of VZV to reduce chance of shingles.
Describe herpes simplex virus presentation and treatment?
Primary infection may be asymptomatic but can cause extensive ulceration. Can give a aciclovir in severe infections but does not kill the latent virus.
What strains of HPV cause viral warts?
1-4
Viral warts are _______ but can be treated with _______
usually self limiting but can be treated with salicylic acid
What strains of HPV cause cervical cancer?
16 and 18
What strains of HPV causes genital warts?
6 and 11
What does the new HPV vaccine protect against?
Strains 16, 18, 6 and 11
Infection of syphilis is by
How is it investigated
sexual contact which passes on treponema palladium bacteria
Swab and pcr
What happens in primary infection of syphilis
painless ulcers at the site of entry
What happens in secondary phase of symptoms of syphilis
red rash over the body which is prominent on the soles of the feet and palms of the hand. Snail track ulcers on mucous membranes
What happens in tertiary phase of syphilis
CNS and CVS involvement. Gummatous (necrosis that involves non-cancerous growths)
What is syphilis treated with
penicillin injections
What bacteria causes lyme disease? How is it transmitted?
Borrelia burgdorferi transmitted by ticks
Early and late presentation of lyme disease?
Early: erythema migrans (rash that fades in centre)
Late: Heart block, nerve palsies and arthritis
How should lyme disease be treated?
Doxycycline or amoxicillin
Describe virulence factor invasin
Enables an organism to invade a host cell tissue
Describe virulence factor modulin
Induces damage to the host indirectly
What are the different names for tinea affecting different places?
Tinea pedis → Foot, Tinea corporis → Body, Tinea unguium → Nails, Tinea barbae → Beard, Tinea cruris → Groin, Tinea capitis → Scalp, Tinea manuum → Hand
Investigation for fungal infection?
skin scrapings for microscopy and culture and woods light
