Microbiology Flashcards
What are virulence factors?
Factors that contribute to a microbes ability to cause a pathology
What is virulence?
How effective an organism is at causing a pathology
Give examples of virulence factors
Adhesin
Impedin
Aggressin
What does adhesin do?
Enables binding of the organism to host tissue (Adhesive=Adhesin)
What does impedin do?
Enables the organism to avoid host defence mechanisms
What does aggressin do?
Causes damage to the host directly
T/F most of the natural flora of the skin are gram -ve
False
They are mostly gram +ve
Where can gram -ve bacteria be found on the skin?
Underarm
Groin
What can staph aureus cause?
Superficial lesions
Systemic illness
Toxinoses
What are 2 types of toxinoses?
Toxic shock syndrome
Scalded skin syndrome
Is coagulase a virulence factor?
Yes
What does coagulase allow the organism to do?
Coagulate plasma
Are all virulence factors on an organism expressed at the same time?
No
What is TSST-1?
Toxic shock syndrome
What are the symptoms of TSST-1?
High fever Vomiting Diarrhoea Sore throat Muscle pain
What causes TSST-1?
Overstimulation of the immune system
How do toxins get in the blood stream in TSST-1?
Diffuse through the vaginal wall into the blood stream
What are the diagnostic criteria for TSST-1?
Fever
Diffuse macular rash and desquamation
Hypotension
>3 organ systems involved
What do super antigens cause/
Massive release of cytokines and inappropriate immune response
What is PVL?
Panton-valentine-Leukocidin
What does PVL do?
Destroys leukocytes
Who has increased levels of PVL?
Patients with skin disease
List 3 defense mechanisms of intact skin:
Sebum and fatty acids inhibit bacterial growth
Competitive bacterial flora
Dry desiccation of micro-organisms
How is a diagnosis of a skin lesion made?
Swab of lesion if the surface is broken
Pus or tissue if deeper lesion
+/- blood cultures
Is Staphylococcus gram +ve or -ve?
+ve
Is staphylococcus aerobic or anaerobic?
Aerobic but faculatively anaerobic
Is Staph aureus coagulase +ve or -ve?
+ve
What can staph aureus cause?
Boils and carbuncles
Minor skin sepsis
Infected eczema
Impetigo
How can staph aureus infections be treated?
Flucloxacillin
What is the treatment for MRSA?
Doxycycline
Co-trimoxazole
Clinamycin
Vancomycin
What are some toxins that strains of staph aureus can produce?
Enterotoxin
TSST
PVL
Where is coagulase negative staph found?
Epidermis
What is a strain of coag -ve staphylococci that causes UTIs in women?
Saprophyticus
Is streptococcus gram +ve or -ve?
+ve
How are streptococci classified?
Haemolysis on blood agar
Which strep is Alpha haemolytic?
Strep pneumonia
Strep viridans
Which strep is Beta haemolytic?
Group A step
-Step pyogenase
Group B
- Neonatal meningitis
What can strep pyogenase cause?
Infected eczema Impetigo Cellulits Erysipelas Necrotising fasciitis
What is Necrotising fasciitis?
Bacterial infection spreading along fascial planes below skin surface leading to rapid tissue destruction
What causes type 1 NF?
Mixed anaerobes and coliforms
What causes type 2 NF?
Group A strep infection
What is the treatment for NF?
Immediate surgery
What strep causes gamma haemolysis?
Enterococci
What is the pathogenesis of a fungal infection?
Fungus enters abraded or soggy skin
Hyphae spread in stratum corneum
Infects keratinised tissues only
Increased epidermal turnover causing scaling
Inflammatory response provoked
Hair follicles and shafts invaded
Lesions grow outwards and heal in centre giving ring appearance
What is the name for fungal infections in:
- Ringworm
- Scalp
- Beard
- Body
- Hand
- Nails
- Groin
- Foot
Tinea = ringworm Tinea capitis = scalp Tinea barbae = beard Tinea corporis = body Tinea manuum = hand Tinea ungium = nails Tinea cruris = groin Tinea pedis = foot
Which gender is more commonly affected by Fungal infections?
Men
Who does scalp ringworm mainly affect?
Children
How are fungal infection aquired?
Other infected humans
Animals
Soil
How are fungal infections diagnosed?
Clinical appearance
Woods light
Skin scrapings, nail clippings and hair
What is the treatment of fungal infections?
Small areas: -Clotrimazole cream -Topical nail paint Scalp infections -Oral terbinafine -Itraconazole orally
Where do candida infections usually occur?
Skin folds where area is warm and moist
Under breast in females
Groin areas
Nappy areas
How are candida infections diagnosed?
Swab for culture
How are candida infections treated?
Clotrimazole cream
Oral Fluconazole
What organism causes scabies?
Sarcoptes scabiei
What is the incubation period for scabies?
Up to 6 weeks
What are the symptoms of scabies?
Intensely itchy rash affecting finger webs, wrists and genital area
What is the treatment of scabies?
Overnight malathion lotion
Benzyl benzoate
What is the name for Lice in the:
- Head
- Body
- Pubic area?
Head - Pediculus capitis
Body - Pediculus corporis (Vagabond’s disease)
Pubic - Phthirus pubis
What is the treatment for lice?
Malathion
What causes chickenpox and shingles?
Varicella zoster virus
What part of varicella zoster is chickenpox?
Varicella
Who gets chickenpox?
Children
What are the signs and symptoms of chicken pox?
Generalised rash, itch and fever
Macules to papules to vesicles to scabs to recovery
What are the complications of chickenpox?
Secondary bacterial infection Pneumonitis Haemorrhagic Scarring Encephalitis
How does neonatal VSV occur?
Secondary to chickenpox in mother in late pregnancy
Which part of VSV is shingles?
Herpes zoster
How does shingles occur?
Reactivation of VSV
Who gets shingles?
Elderly
Immunocompromised
What is the distribution of shingles?
Dermatomal distribution
What is ramsay-hunt syndrome?
Vesicles and pain in auditory canal and throat
Facial palsy of the 7th nerve
Irritation of Vestibulocochlear nerve causing deafness, vertigo and tinnitus
How many types of Herpes simplex virys are there?
2
What does HSV 1 cause?
Main cause of oral lesions
Causes half of genital lesions
What does HSV type 2 cause?
Rare cause of oral lesions
Causes half of genital lesions
How is HSV treated?
Aciclovir
How is HSV confirmed?
Swab with viral transport medium
Antibody tests
What is eythema multiforme?
Target lesions with erythema
What can tirgger erythema multiforme?
Drug reactions
HSV infections
What does molluscum contagiosum look like?
Fleshy, firm, umbilicated, pearlescent nodules
1 to 2 mm in diameter
