Bacterail Infections Flashcards
What virulence factors does staph have that confer pathogenic properties?
Receptors that allow it to bind fibrin which is found in abundance in wound surfaces and dermatitis
What diseases can staphylococcus aureus casuse
Impetigo
Cellulitis
Folliculitis
Folliculitis
- Follicular erythema (redness and inflammation of hair follicles)- sometimes pustular (bulging patch of skin filled with pus)
- May be infectious or non-infectious
Non infectious types are frictional Folliculitis and eosinophilc Folliculitis which is associated with HIV
- Why might recurrent cases of folliculitis arise and treatment
From nasal carriage of Staph aureus, particularly strains expressing Panton-Valentine Leukocidin (PVL)
- Antibiotics (usually flucloxacillin or erythromycin)
- Incision and drainage is required for furunculosis (abscess formation with pus and necrotic tissue in hair follicle)
What is the treatment for fosiculitis
- Antibiotics (usually flucloxacillin or erythromycin)
- Incision and drainage is required for furunculosis (abscess formation with pus and necrotic tissue in hair follicle)
What features might you see with Folliculitis
- Furunculosis
- Carbuncles
- Furuncles- deep follicular abscess
- Carbuncles- a collection of furuncles involving adjacent hair follicles. It’s more likely to lead to complications like cellulitis and septicaemia
Usually seen in infective cases
- What is pseudomonas folliculitis?
A bacterial infection of hair follicles after being exposed to contaminated water
Caused by hot tube use swimming pools and wet suits
Appears 1-3 days after exposure
Symptoms and treatment for pseudomonas Folliculitis
- Follicular erythematous papule
- ## Rarely- abscess, lymphangitis, fever
- Most cases are self-limited and no treatment is required
- Severe or recurrent cases can be treated with oral ciprofloxacin
Cellulitis
Infection of lower dermis and subcutaneous tissue
Tender swelling with I’ll defunded blanching erythema or Oedema
Caused by staphylococcus aureus and streptococcus pyogenes
Treat with antibiotics
Predisposing factor is Oedema
Impetigo
Superficial bacterial infection, stuck-on, honey-coloured crusts overlying an erosion
- Why do some patients develop recurrent staphylococcal impetigo or recurrent furunculosis?
-
S aureus establishes itself as a part of the resident microbial flora, esp in nasal flora
Patient may have a form of immune deficiency such as - hypogammaglobulinaemia
- HyperIgE syndrome- deficiency
- Chronic granulomatous disease
- AIDS
- Diabetes Mellitus
What bacteria causes impetigo
- Staphylococci- what kind of impetigo do they cause?Bullous because of the exfoliative toxins A & B that split the epidermis by targeting desmoglein I protein
- Streptococci- what kind of impetigo do they cause?Non-bullous (without blisters)
What parts of body does impetigo affect
Face
Peri oral
Ears nares
Treat with topical and sometimes systemic antibiotics
What is impetiginisation?
Superficial infection or impetigo in the context of atopic dermatitis
Doesn’t blister
Can occur due to HSV
Staph aureus
Panton Valentine Leukocidin Staphylococcus Aureus
A beta-pore forming exotoxin expressed by certain strains of S aureus
Causes Leukocyte destruction and tissue necrosis
What is it associated with morbidity, mortality and transmissibility wise PVLSA
Higher for all
What skin diseases does PVLSA cause
Often painful, >1 site, recurrent, present in contacts
- Recurrent and painful abscesses
- Folliculitis
- Cellulitis
What extracutaneous diseases can it cause PVLSA
- Necrotising pneumonia
- Necrotising fasciitis (top pic)
- Purpura fulminans (bottom pic)
What are the 5 Cs of contracting PVL staph?
- Close contact- e.g. hugging, contact sports
- Contaminated items- e.g. gym equipment, towels or razors
- Crowding- crowded living conditions e.g. military accommodation, prisons and boarding schools
- Cleanliness- of environment
- Cuts and grazes- having a cut or graze will allow the bacteria to enter the body
Treatment for PVLSA
- Consult local microbiologist and guidelines
- Antibiotics usually given, often tetracycline
- Decolonisation often occurs e.g.
- Chlorhexidine body wash for 7 days
- Nasal application of mupirocin ointment for 5 days
- Treatment of close contact
What bacteria causes syphilis
Treponema pallidum Treponema pallidum
How does the primary infection manifest? For syphilis
- With a chancre- painless ulcer with firm indurated border
- Painless regional lymphadenopathy 1 week after the primary chancre
- Chancre appears within 10-90 days of infection
Secondary syphilis
- Begins 50 days after chancre
- Malaise, fever, headache, pruritus, loss of appetite, iritis
Pityriasis rosea like Rash
Alopecia
Mucous patches
Lymphadenopathy
Residual primary chancre
Condylomata lata
Hepatosplenomegaky
What is lues maligna?
- Rare manifestation of secondary syphilis
- Pleomorphic skin lesions with pustules, nodules and ulcers with necrotising vasculitis
- More frequent in HIV manifestation
What happens in tertiary syphilis?
- Gumma skin lesions- nodules and plaques that extend peripherally while central areas heal with scarring and atrophy
- Mucosal lesions extend to and destroy nasal cartilage
Can also develop cardio disease and neurosyphilos (general paresis or tabes dorsalis)
Diagnosis and treatment for syphilis
- Clinical findings is main way
- Serology helps
- ## Strong index of suspicion is required in secondary syphilis
IM benzylpenicillin or oral tetracycline
Lyme disease
Annular erythema develops at site of the bite of a Borrelia burgdorferi-infected Ixodes tick
How does lymes manifest
- Initial cutaneous manifestation of erythematous papule at bite site in 75% of patients which progresses to annular erythema of >20cm
- 1-30 days after infection, fever and headache occurs
- Multiple secondary lesions develop that are similar to but smaller than initial lesion
- Neuroborreliosis can occur- what happens as part of this? (3)
- Facial palsy/other CN palsies
- Aseptic meningitis
- Polyradiculitis
- Arthritis- painful and swollen large joints (knee is most affected joint)
- Carditis
How to detect lymes and treatment
- Serology not sensitive
- Histopathology is non-specific
- High index of suspicion required for diagnosis with a basis of clinical features
Doxycycline amoxicillin and azithromycin given as treatment
Herpes simplex virus
Primary and recurrent vesicular eruptions
Occurs on orolabial and genital regions
When can transmission occur even HSV
Even during asymptomatic periods of viral shedding
How is HSV-1 typically spread?
Direct contact with contaminated saliva/other infected secretions
- Sexual contact
How is HSV-2 typically spread?
Sexual contact
Where does it travel from site of infection hsv
- Replicates at mucocutaneous site of infection
- Travels by retrograde axonal flow to dorsal root ganglia where it stays latent between flares
Describe the symptoms and how they progress HSV
- Symptoms occur within 3-7 days of exposure
- Preceded by tender lymphadenopathy, malaise, anorexia and maybe burning & tingling
- Then painful rouped vesicles on erythematous base develop
- These develop into ulcerations/pustules/erosions with a scalloped border
- Crusting and resolution within 2-6 weeks
What are the orolabial vs genital manifestations like? For HSV
- Orolabial lesions are often asymptomatic
- Genital involvement is often excruciatingly painful and can lead to urinary retention
What is the main systemic manifestation? For HSV
Aseptic meningitis in up to 10% of patients
What factors can cause reactivation of HSV? (5)
- Spontaneous
- UV
- Fever
- Local tissue damage
- Stress
What is a HSV emergency and when does it occur?
Eczema herpeticum that occurs in patients with atopic eczema
Monomorphic, punched out erosions (excoriated vesicles)
You can get HSV encephalitis which is fatal
IV acyclovir accompanied with antibiotic for superinfections with S aureus or Strep
What is herpetic whitlow?
HSV (1 more than 2) infection of digits- pain, swelling and vesicles (vesicles may appear later)
Often misdiagnosed as paronychia or blistering distal dactylitis caused by streptococci
Occurs in children
What is herpes gladiatorum?
HSV 1 involvement of cutaneous skin sites that reflect sites of contact with another athlete’s lesions
Seen most in contact sports
When does neonatal HSV arise?
Exposure to HSV 1 or 2 during vaginal delivery- risk higher when HSV acquired near time of delivery
Manifests from birth to 2 weeks
Seen in scalp or trunk
Manifest as vesicles or bullae erosions
Needs IV antiviral
Can cause death of neuro deficits
Can cause encephalitis which causes mortality in >50% without treatment
How can HSV manifest in immunocompromised patients?
Chronic enlarging ulcerations or erosions
- Verrucous lesions
- Exophytic lesions
- Pustular lesions
Can involve Resp or GI tract
How do we diagnose HSV and treat
Swab for polymerase chain reaction
- Don’t delay- PCR can take weeks to get back
- Oral valacyclovir or acyclovir 200mg 5 times daily in immunocompetent localised infection
- IV 10mg/kg TDS X 7-19 days
Pityriasis vesicolor
Hypopigmented, hyperpigmented or erythematous macular eruption +/- fine scale
Caused by malassezia spp
How does it develop and flare PV
- Begins during adolescence (when sebaceous glands become active)
- Flares when temps and humidity are high and also when there’s immunosuppression
Treatment for petyriases vesicolor
Topical azole
Dermatophytes
Fungi that live on keratin in our skin
What is the most common dermatophyte infection
Trichophyton rubrum
What fungus causes the most tinea capitis (fungal rash of the scalp)?
Trichophyton tonsurans
What is kerion?
- An inflammatory fungal infection that may mimic a bacterial folliculitis or a scalp abscess
- Scalp is tender and patient usually has posterior cervical lymphadenopathy
- Staphylococcus aureus
Frequently infected with staphylococcus aureus
What are causes of tinea pedis (fungal rash of the feet)?
Trichophyton rubrum causes Scaling and hyperkeratosis of plantar surface of foot
What are Id reactions?
- Aka dermatophytid reactions
- Are inflammatory reactions at sites distant from the associated dermatophyte infection- the primary reaction could be anywhere
What type of reactions can these include? Id reaction
- Urticaria
- Hand dermatitis
- Erythema nodosum
What are id reactions secondary to
strong host immunological response against fungal antigens
Candidiasis
Caused by Candida albicans
Predisposed by - Occlusion
- Moisture
- Warm temp
- Diabetes mellitus
How does candidiasis manifest
- Erythema
- oedema
- thin purulent discharge
What are the usual locations it can affect? Candiadis
- Usually an intertriginous infection affecting axillae, submammary folds, crurae and digital clefts
- Can affect oral mucosa
Mucosa
What is candidiasis a cimmmin cause id
Vulvovaginitis
What can happen to it in the context of immunocompromisation candidiasis
Can become systemic
Mucormycosis
Odema then pain then eschar
Fever headache proptosis,facial pain,orbital cellulitis and cranial nerves e dysfunction
Mucormycosis association
Diabetes’s
Malnutrition
Uraemia
Neutropenia
Medications such as steroids antibiotics or desferoxamjne
Burns
Hiv
Treatment of Mucormycosis
Aggressive debridement and anti fungal therapy amphoteracin
Scabies
Contagious infection caused by sarcoptes species
Femal mates burrows into upper epidermis layers her eggs and dies after one month
I red to flesh colored pruritic papules
Affects interdigital areas of digits volar wrists Axillary areas and genitalia
What does a diagnostic burrow consist of in scabies
Fine white scale
Hyperkeratosis
Crusted or Norwegian scabies
Pt presentation and treatment for scabies
Often asymptomatic immunocompromised
Treat with permethrin oral ivermectin
Two cycles of treatment needed
