Bacterial and Viral Infections Flashcards
What are commensal bacteria and give some examples of commensals?
Commensal bacteria are bacteria that are found on the skin but not normally causing disease.
Staphylococci
Micrococci
Cornyebacteria
Propionbacteria
Note Staph aureus is considered pathogenic but it can be commensal
What are the two most common causative bacterias in skin disease.
Staph. aureus
Group A Streps (Strep. Pyogenes) this is always considered to be pathogenic. Causes an acute onset and spreads rapidly.
S. aureus and strep. pyogenes cause similar infections and can cause co-infections.
What does the following image show, what is the likely causative organism, how does it present and how would you treat?
Folliculitis: infection of hair follicles.
Characterised by follicular pustules.
S. Aureus
Treat with flucloxacillin or if unresponsive a longer course of tetraccyclines.
What does the following image show, what is the likely causative organism, how does it present and how would you treat?
Impetigo.
Characterised by a golden crust.
Usually caused by s.aureus but can be caused by strep.pyogenes or can a dual infection.
Can be treated with topical (fucidic acid) or oral antibiotics (flucloxacillin).
Also patient shouuld soak off the golden crust with soap and water.
What does the following image show, what is the likely causative organism, how does it present and how would you treat?
Ecthyma.
Start off as pustule or blister but become indurated (hardenned).
Signifys a deeper infection again caused by staph or strep.
It is more common in diabetics or those with immunosupression.
Needs a long course of oral antibiotics.
What does the following image show, what is the likely causative organism, how does it present and how would you treat?
Cellulitis
Gross oedema, erythema and heat.
Staph or strep.
Systemic antiobiotics oral or IV.
Worth checking for tinea pedis as this is a common portal of entry.
Bilateral cellulitis is very rare and therefore you should consider alternative diagnoses if the oedema is bilateral.
What does the following image show, what is the likely causative organism, how does it present and how would you treat?
Erysipelas
Well demarkated beefy red plaque on one side of the face.
Variant of cellulitis and is usally caused by strep.
Again treat with systemic antibiotics.
What does the following image show, what is the likely causative organism, how does it present and how would you treat?
Scalded Skin Syndrome
Fever and redness followed by peeling causing erosions on the face and body.
Caused by Staphylococcal toxins.
Identify the underlying cause may be something as trivial as simple impetigo.
Treatment is with IV flucloxacillin, fluids, analgesia and emollients.
Describe erythema nodosum, and state which infection it is associated with?
Red tender nodules on the shins.
Streptococcal infection
Which infections are erythema multiforme associated with?
HSV and Streptococcal
What infections is a purpuric rash associated with?
Post streptococcal in which case it is known as Henoch Schonlein Purpura
Meningococcal sepsis
Hepatitis C
What are the different hypersensitivity reactions to the streptococcal antigen?
Erythema Nodosum
Erythema Multiforme
Vasculitis and Glomerulonephritis
Guttate Psoriasis
What does the following image show, what is the likely causative organism, how does it present and how would you treat?
Necrotising Fasciitis
S.aureus and strep.
Very unwell, high fever, severe pain in the affect area, with the rash progressing rapidly over a few hours.
Emergency debridement involvement of plastics and a long course of IV antibiotics
What does the following image show, what is the likely causative organism, how does it present and how would you treat?
Cold sore
HSV
Vesicles usually on the lip but reappears at the same point.
Topical aciclovir can help if it is give immediately but it is a self limiting infection.
Note HSV 1 usually affects lips
HSV 2 usually affects the genitals but there is crossover
What does the following image show, what is the likely causative organism, how does it present and how would you treat?
Eczema herpeticum
HSV infection superimposed on eczema
Monomorphoc vesicles which crust or become eroded.
Treated with systemic aciclovir, IV if severe.
Carrys a mortality risk.
What does the following image show, what is the likely causative organism, how does it present and how would you treat?
Chicken Pox
Varicella Zoster Virus
Widespread vesicular rash, leading on to crusted papules as well as high fever.
Virus is transmitted in respiratory droplets and has an incubation of 14-17 days. Patients are contagious for one week from 2 days prior to the onset of the eruption.
In children mild and self limiting.
Internal organ involvement can happen in adults or immunosupressed in this group treat with systemic aciclovir.
What does the following image show, what is the likely causative organism, how does it present and what are the complications?
Shingles
VZV
VZV lies dormant in the dorsal root ganglion following primary infection. It may later reemerge causing an eruption of vesicles in a dermatomal distribution.
Usually settles on its own, but it can become superimposed with infection.
Also be wary of shingles on the nose as this implies involvement of the nasocilliary nerve these patients are likely to cause ocular involvement which can be sigt threatenning.
Also be wary of shingles around the external auditory meatus or pinnearas it may indicate the ramsay hunt syndrome (facial palsy, hearing loss and vertigo)
Other complications of shingles include post herpetic neuralgia and encephalitis.
What is the lesion, the causative organism and treatment?
Common Wart
Human Papilloma Virus
Cryotherapy
What is the lesion, the causative organism and treatment?
Mosaic Warts
Human Papilloma Virus
Curratage (difficult to treat)
What is the lesion, the causative organism and treatment?
Plain Warts (flatter and often coalesce)
Human Papilloma Virus
Cryotherapy
What is the lesion, the causative organism and treatment?
Filliform Wart (finger like projections)
Human Papilloma Virus
Cryotherapy or curratage
Note all warts are self limting although they are often treated as they take a long time to spontaneously heal.
What is the lesion, the causative organism, how does it present and what is the treatment?
Molluscum Contagiosum
Pox Virus
Umbilicated papules, common in children
It is self limiting and therefore not usually treated
