Microbiology & Common Infections Flashcards by Kieran Ruthven

What % of people are permanently colonised with S. aureus?

60%

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Fibrinogen binding ClfA and ClfB are examples of what?

Adhesins

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Coagulase testing helps broadly differentiate what from what?

S. aureus (positive) from S. epidermidis (negative)

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Scalded skin syndrome is produced by toxins targetted against what?

Desmoglein-1, a protein involved in crossbridging of epidermis

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PVL is present in what % of clinical S. aureus isolates?

1-2%

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PVL is associated with what (3)

-Severe skin infection -Sepsis/necrotising fasciitis -Necrotising pneumonia

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PVL tends to be more common in hospital/community acquired MRSA?

Community

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S. pyogenes has what Gram stain?

Gram positive cocci

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How can S. pyogenes be differentiated from viridians group Strep (e.g. mutans)?

Haemolysis (Group A streps classically have beta haemolysis)

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Impetigo/cellulitis is a skin diseased caused by which group of Strep?

GAS

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Streptolysin S is associated with which condition?

Cellulitis

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What are common alpha-haemolytic Streps?

Pneumoniae, viridians

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Group A strep is a subclass of what type of strep?

Beta-haemolytic (clear)

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S. aureus may be further classified with what type of test?

Latex agglutination

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S. aureus has what air requirements?

Aerobic and facultative anaerobe (grows best in air)

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First-line antibiotic of choice in S. aureus infection?

Flucloxacillin

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Treatment options for MRSA

-Doxycycline -Co-trimoxazole -Clindamycin or vancomycin Check Tayside formularly too. NOT flucloxacillin

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Are coagulase negative staphs generally pathogens?

No, usually commensals

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What are the most “concerning” group of Streps?

Beta haemolytic strep (especially GAS)

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What’s the key clinical sign for NF?

Mismatch in what clinician sees and patient reports (e.g. mild erythema with extreme pain)

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Fournier’s Gangrene is a specifically severe type of what?

NF affecting the genitals

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Non-haemolytic streptococci include what species, and why are these clinically important?

Enterococcus, a cause of UTI

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Define the following terms: -Tinea capitis -Tinea barbae -Tinea corporis -Tinea manuum -Tinea unguum -Tinea cruris -Tinea pedis

Capitis = head Barbae = beard Corporis = body Manuum = Hand Unguum = Nail Cruris = Genitals Pedis = Feet

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What’s the commonest cause of contracting a fungal infection? What’s the second most common?

1st is contact with other infected humans. 2nd is contact with infected animals.

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Most common dermatophyte?

Trichophyton rubrum

Taking skin/scalp/nail clippings is the primary means of diagnosing ringworm, true/false?

False - culture can take up to 2 weeks. Diagnosis on clinical appearance and Woods light appearance.

Terbafine for scalp infection requires checking what?

Liver function

Candida most commonly affects which areas of skin and is termed what when these areas are infected?

Skin folds, candida intertrigo

Scabies parasite is a type of what? What is the technical name?

A type of arachnid mite. Called Sarcopetes scabei.

Norwegian Scabies is when the infection has what? What's the clinical importance?

Crusted over. HIGHLY infectious.

Treatment of scabies is with what?

Malathion lotion overnight (or benzyl benzoate, but NOT in children) and washed off next day

Lice is technically called what?

Pediculosis

Lice infestation is treated how?

Malathion lotion

Chickenpox & Shingles are both caused by what?

Varicella Zoster Virus

The characteristic appearance for a chickenpox/shingles rash is what?

Punched out papulovesicular

VZV establishes latency in which type of nerve? Where?

Sensory roots at dorsal root ganglion

VZV can reactivate multiple times. True/false?

False (only once)

Severe complications of chickenpox can include (5)

-Secondary bacterial infection -Pneumonitis -Haemorrhagic rash -Scarring -Encephalitis

What's the important contrast between clinical picture of shingles versus chickenpox?

Shingles is dermatomal

Shingles always presents in adults. True/false?

False (uncommon in \<10 but can occur)

Pain persisting for 4 weeks post shingles rash is termed what?

Post-herpetic nerualgia

Post-herpetic nerualgia is a particular concern in which groups of patients (2)?

-Elderly -Trigeminal nerve infected patients

Scarring is common in zoster. True/false?

False

Ramsay-Hunt Syndrome is what?

VZV reactivation from 7th nerve ganglion (facial). Presents with auditory canal and facial palsy. Can also cause deafness and permanent vertigo

The chickenpox vaccine is routine for children in the UK. True/false?

False

The chickenpox vaccine is routine for which group of patients?

70 year olds.

Primary gingiovostomatitis is a feature of which viral infection?

HSV

"A blistering rash at the vermillion border" could be indicative of which viral infection?

HSV

Which type of HSV is the routine cause of oral lesions?

Type 1

Which antiviral is useful in VZV and HSV?

Acyclovir

How does acyclovir work?

It is an analogue of guanosine which is incorporated and inhibits replication

Does acyclovir eliminate all virus particles?

No (latent remains)

Fleshy, firm, umbilicated, pearlescent nodules is indicative of which infection?

Molluscum contagiosum

Molluscum contagiosum is routinely treated with antivirals. True/false?

False - self-limiting, liquid nitrogen application used if needed

HPV causes which skin lesion?

Warts

Most common HPV serovars which cause warts/verrucas?

Types 1 to 4.

Most common HPV serovars which cause genital warts?

Types 6 to 11

Most common HPV serovars which cause cervical cancer?

Types 16 and 18

Gardasil protects against which HPV serovars?

6, 11, 16 and 18

Hand, Foot and Mouth disease is caused by which family of virus? What's a typical example of this family?

Enteroviruses. Typical example would be Coxsackie.

Slapped Cheek / erythema infectosium is caused by which virus?

Parovirus B19

Erythema infectosium / slapped cheek is typically diagnosed by antibody testing over skin swabbing. True/false?

True - test is specific parovirus B19 IgM

Orf is a virus/bacteria which is present in \_\_\_\_\_.

Virus. Present in sheep

Gummatous or CNS/CVD syphilis is indicative of which stage of infection?

Tertiary (can be fatal)

Syphilis is caused by which bacteria?

Treponema pallidum

Antibiotic of choice in syphilis?

Penicillin (injected)

Chancres are indicative of which stage of syphilis?

Primary

Snail track ulcers in the mouth are indicative of which stage of syphilis infection?

Secondary

Lyme disease is caused by which bacteria

Borrelia burgdoferi

Late presentation of Lyme disease symptoms include

Heart block, nerve palsy and arthritis

Therapeutic regimen of Lyme disease?

Amoxicillin or doxycycline if allergic

Ixodes tick bites can transfer the Borrelia bacteria immediately upon contact. True/false?

False - must be attached for 24 hours.

Asymptomatic tick bites always require antibiotic prophylaxis. True/false?

False

Erythema migrans is a buzzword for which disease/infection?

Lyme disease

Zika is carried by which organism vector?

Mosquito (Aedes aegypti)

Complications of Zika include (2)

-Microcephaply -GBS

List 3 skin commensals

S. epidermidis, Corynbacterium, propinobacter

Group B beta haemolytic strep are associated classically with which infection?

Meningitis in neonates

Staphs & Streps will both be covered by which antibiotic?

Flucloxacillin

The causative organism of type 2 NF is...

GAS infection

List some organisms worth treating if grown from a leg ulcer swab (3)

1) S. pyogenes (GAS), S. aureus 2) Other beta-haemolytic streps 3) Anaerobes

Fungus spreads in which layer of skin?

Stratum corneum

How are dermatophyte infections of scalp treated?

Terbafinine or itraconazole orally

Candida skin infection is diagnosed using which sample

Swabs from site

Which infection is this typical of?

Scabies

Haemorrhagic rash (as shown) is a potential complication of which infection?

Chickenpox

Which form of infection is this?

Ophthalmic zoster

Which form of infection is this?

Maxillary zoster

Geniculate zoster is AKA

Ramsay-Hunt Syndrome (7th nerve fascial palsy and irritation of the 8th nerve leading to deafness, vertigo and tinnitus)

The chickenpox vaccine is live/inactivated?

Live

What is this disease? What is the causative infection?

Erythema multiforme. Causative agent includes HSV, Mycoplasma pneumoniae

What is this disease? How is it treated?

Molluscum contagiosum - self-limiting but cryotherapy (Fleshy, firm, umbilicated lesions)

What is this? What is the causative agent?

Herpangina (blistering at back of mouth) caused by enteroviruses such as Coxsackie viruses

Hand, Foot & Mouth Disease is caused by which pathogen?

Coxsackie virus (enteroviruses)

Complication of parovirus / slapped cheek includes (3)

1) Abortion 2) Aplastic crisis (sudden drop in haemaglobin) 3) Chronic anaemia (if immunosuppressed)

What infection is this?

Orf (signular, fleshy, firm) - a lab diagnosis is not needed

Which stage of syphilis is this?

Primary (chancre)

What is this rash indicative of?

Lyme Disease (erythema migrans)