Exam 2 Flashcards
How is MTB transmitted?
Person-to-person via aerosol droplet nuclei
Who is the reservoir for MTB?
Humans only
Prosector’s Warts are indicative of inoculation with what disease?
MTB
MTB largely affects what age ranges?
Infants and older adults (bimodal age distribution)
MTB manifestations in infants/IMC? (2)
- Hematogenous dissemination
2. Meningitis
MTB manifestations in older pts? (2)
- Failure of immune sx
2. +/- reactivation of latent infection
Infection risk factor for children?
Close contact w/ infected caregiver
What are the causative agents of TB? (3)
- Mycobacterium tuberculosis»_space;
- Mycobacterium bovis (Consumption of unpasteurized milk/ contact w/ infected animals)
- Mycobacterium africanum (West African Counties, no animal reservoirs, spread by food)
Strain of Mycobacterium used to make TB, BCG vaccine?
Mycobacterium bovis, given in highly endemic areas
MTB characteristics (shape, cell wall, oxygen status, motility, heat sensitivity, growth) ?
- Bacillus
- Mycolic acid
- Obligate aerobe
- Non-motile
- Heat sensitive, killed by pasteurization
- Alveolar macrophage
MTB staining
- Acid Fast
- Ziehl-Neelsen or Kinyoun stains
- Cells resistant to staining and decolorization once stained
MTB virulence factors
No classic virulence factors or toxin, structure feature create issues for the pt
- Mycolic acid
- Cord factor - myoside,
- Lipoarabinomanna (LAM) - inhibits cell mediated immunity, scavenges ROI
CXR findings for TB?
Fibrotic and calcified tubercle
Risk of infection spread w/ latent TB?
No risk
Are pts w/ latent TB treated?
Yes
Are pts w/ reactivation or secondary TB infectious?
Yes
Cause of Miliary Tb? (2)
- Lypmhohematogenous spread of primary infection
2. Via latent focus w/ subsequent spread
Tests for DX of Tb? (5)
- XR consistent w/ TB
- Skin test reactivity
- Sputum stain/broth cx to detect acid fast bacteria
- Rapid blood test (release of IFN-Y)
- GeneXpert Rapid test for MTB and Rifampin resistance
Goal of tx for MTB?
- Recognize, isolate, and treat infected persons (Latent and active)
MAC characteristics (shape, cell wall, oxygen status, motility, growth)?
- Bacilli
- Acid fast, Weakly G+
- Aerobic
- Ubiquitous (water, soil, plants)
- Slow growing
MAC w/ person-to-person transmission?
NO
Pt isolation required w/ MAC infection?
No
MAC relationship w/ HIV pts?
Opportunistic pathogen. Leading cause of NTM infections in HIV+ pt
Lady Windermere’s syndrome is associated w/ what TB pathogen?
MAC
What gender/age range is Lady Windermere’s syndrome seen in?
Elderly, non-smoking female
Type of MAC disease in IMC (AIDs) pts?
Disseminated disease (no organ spared)
Findings/tests for NTM for dx? (3)
- Microscopy reveals acid fast bacteria and culture
- Must ecxlude other etiologies (Fungi, TB), sterile site isolation
- CXR w/ + pulmonary lesions
- Final ID via molecular techniques (PCR to determine 16S rRNA sequence)
MAC tx HIV- pts?
ABX until sputum cultures are negative for 1 yr
MAC tx in HIV + pt w/o infection?
Chemoprophylaxis w/ CD4 < 50 cell/uL, discontinue 3 months after CD4 > 100 cell/uL
MAC tx in HIV+ pt w/ MAC infection
- Lifelong (if w/o immune reconstitution)
- Begin tx for 2 weeks then anti-HIV HAART
Mycobacterium abscessus is especially difficult to treat in what disease population?
CF
MTB pathogenesis?
Granulomas (2-6 weeks post infection) → caseous lesions (fibrotic tubercle) → calcifies & seen on x-ray → disease stops
MTB infection outcomes? (5)
- Immediate resolution (no active TB) - innate immune system (alveolar macrophage) able to clear bacteria
- Primary disease
- Progressive primary (active) disease
- Latent infection (inactive bacteria, - signs/sx, not infectious, treatment necessary)
- Endogenous reactivation/secondary TB (+ signs/sx, infectious, insidious, lesions: caseous lesions → TB bacilli to bronchi → hematogenous spread
What is HAART?
Highly acute anti-retroviral therapy
Coryza, cough and conjunctivitis is concerning for what disease?
Measles
Koplick’s spots are diagnostic for what disease?
Measles
Mealse rash starts and spreads where?
Head, spread to body
When is a measles pt the sickest?
During rash/ highest fever (3-4 days after prodrome)
Acute symptomatic encephalitis is a complication associated with what disease?
Measles
also some associated w SSPE = subacute sclerosing panencephalitis
What complication is responsible for most deaths in measles pts?
Pneumonia
Is there a healthy carrier state associated with measles?
No, none known
Transmission of measles is via?
Respiratory droplets (highly contagious)
Is measles a disease of adulthood or childhood?
Primarily a disease of childhood (might be changing)
FA test for pt w/ measles will show?
Multinucleated giant cells
Largest preventative measure for measles?
MMR vaccine
also immune globulin BayGam for exposed non-immune subjects
MMR II is what type of vaccine?
Live, attenuated vaccine
Who should never receive MMR vaccine?
Pregnant, IMC
What % of population must be vaccinated to halt measles persistence?
95%
Rubella is also referred to as? (2)
- German Measles
2. “little red”
What age group often escaped rubella infection?
Children
Congenital rubella syndrome (CRS) is a complication due to what?
Maternal rubella infection during first trimester (worst prognosis earlier then infection, 1st month > 4th month)
Cataracts, hearing loss, and cardiac defects are sx of what?
Congenital rubella syndrome (CRS)
2 unique properties of HSV?
- Capacity to invade and replicate in CNS
2. Ability to establish latent infection
Shallow vesicles on erythematous +/- crusting and ballooning is concerning for?
HSV
Can the primary HSV infection be asymptomatic?
Yes
How does HSV become a latent virus?
Retrograde transport of virus through sensory neurons –> infection of dorsal root ganglia
What is the timeframe for completely clearing an HSV infection from the body?
None. HSV is for life!
Stress, menses, sunlights and nutrition are all triggers for what viral infection?
HSV
If a pt has a larger and more extensive initial outbreak with HSV, will their probability of recrudescence be higher or lower?
Higher
Will recrudescence of HSV occur in the presents of active humoral and cellular immunity?
Yes
Who is the reservoir for HSV?
Humans only
Can you transmitted HSV infection even if asymptomatic?
Yes
Are HSV-1 infection common in early life or later life?
Early life via casual contact
How are HSV-2 infections transmitted?
Sexual contact
Presence of enlarged or fused cells on Tzanck smear is concerning for what disease?
HSV
ACV (Acyclovir) is effective in treating HSV because viral enzyme thymidine kinase phosphorylates the drug for activation and then what?
Halts viral DNA replications b/c it lacks 3’-OH group
Will only get into infected cells when active
Varicella-zoster virus is responsible for what 2 disease states?
- Chickenpox
2. Shingles
Asymmetrical vesicular pruritic rash is concerning for what disease?
Chickenpox
Viral infection through conjunctiva or respiratory tract mucosa is concerning for what disease?
Chickenpox
Who is the only reservoir for chickenpox?
Humans
VZV infections peak during what seasons?
Winter-SPring
What age group has the highest incidence of VZV?
5-9 y/o
When is VZV pt most contagious?
1-2 before appearance of lesions and 4-5 days after
Are prodromal VZV present in older children and adults or younger children?
Younger children
VZV rash is primarily located where?
On the trunk
Is aspirin recommended in tx of chickenpox?
No, concerning for Reyes syndrome
TX for Chicken pox?
Sx relief - self limited
Acyclovir
Immune serum VariZig (high risk)
Varivax is the vaccine for what disease?
VZV
IS the VZV vaccine safe in pregnancy?
No
Will shingles cross midline?
No, unilateral dermatomal distribution
Shingles is recrudescence of what viral infection?
VZV
Searing, burning, stabbing lesions that don’t cross midline are concerning for?
Shingles
Most common complication fo shingles?
Postherpetic neuralgia
Can a pt present with shingles but never have had or been vaccinated against chicken pox?
No
Zostavax and Shingrix are vaccines against what?
Shingles
Is Zostavax or Shingrix a live vaccine?
Zostavax
Is Zostavax or Shingrix given in 2 doses?
Shingrix
Exanthem subitum, roseola infantum/6th disease are caused by what?
Human Herpes Virus-6 (HHV-6)
HHV-6 is dx by what? (2)
- Detection of AB by EIA
2. PCR
High fever w.o any obvious sources is concerning for what?
HHV-6
TX of HHV-6 does not require? (3)
- Isolation
- Anti-viral therapy
- Primary preventative measures
Fifth’s disease/ Erythema infectiosum is causes by?
Parvovirus B19
Prodrome of this disease is follow by maculopapular rash in “slapped cheeked” appearance?
Parvovirus B19
Arthralgia or arthritis follow maculopapular rash may be concerning for?
Parvovirus B19
Parvovirus B19 is most common in what seasons?
Later winter and spring
Virus that produces warts?
HPV
HPV 6 & II produce anogenital warts or cervical dysplasia and cancer?
Anogenital warts
HPV 16 & 18 produce anogenital warts or cervical dysplasia and cancer?
Cervical dysplasia and cancer?
Age range for Gardasil 9?
M/F 9-45
Dermatophytes require what for growth?
ketatin (hair, skin, nails)
Do dermatophytes infect mucosal surfaces?
No
What enzymes allows dermatophytes to inhabit keratinized regions of the body>
Keratinase
Dermatophyte test medium (DTM) allows for early detection of infection or can only be used to different source of dermatophyte?
Early detection
Arthroconidium is what?
The infective stage of disease for dermatophytes
Trichophytin is what? (2)
- Galactomannan peptide
2. Crude antigen of dermatophytes (CHO component = immediate response, Peptide component = delayed response)
How does 10% potassium hydroxide allow for visualization of fungi?
Digests human tissues, leaving fungal components intact
Dermatophytes utilize nitrogen compounds preferentially over carbs. DTM will turn what color?
Red (alkaline)
Dermatophyte test medium (DTM) is selective and differential for what?
Selective: Cyclohexamide and ABX
Differential: fermentation of sugars
Animal pathogens that may be transmitted to people are what?
Zoophilic
Antropholilic Dermatophytes are spread via what transmission?
Human to human
Soil to people transmission is what?
Geophilic
Geophilic dermatophytes will invade non-viable or viable keratinized tissue?
Non-viable
Fungi prefer dry or moist areas of the body?
Moist
Globally where are fungal infections more prevalent?
Tropics
Microconidia, macroconidia and sexual spores are infectious or non-infectious?
Infectious
Fragmented hypheal elements in hair, nails, outer skin are what?
Arthrospores
Lesions with inflamed edges and a central clearings are concerning for what infectious pathogen?
Fungi
Transmission pattern for arthrospores?
Person to persons
Are arthrospores infectious?
Yes
Microconidia is uni or multi cellular?
Uni
Macroconidia is uni or multicellular?
Multi
Classification for an allergic dermal reaction to fungal antigen occurring in areas devoid of organisms
Dermatophytid
Most common dermatophytid?
Athlete’s foot
How are dermatophytid reactions spread?
Itching
Will dermatophytid be present at only 1˚ or 1˚ and 2˚ sites?
Only primary
“Id reaction” is associated with what fungal infection?
Dermatophytid
What is an “id reaction” treated as?
An allergy
What is the most common trichophyton species?
T. mentagrophytes
Are trichophyton often fluorescent or not fluorescent?
Not fluorescent
What do all trichophyton species make?
Pencil-shaped macroconidia w/ thin walls
What 3 things do trichophyton produce?
Hyphae (spindle shaped), microconidia, macroconidia
What is the most common causative agent of tinea captitis?
M. canis
What disease is described as mostly a childhood disease that involves the hair and scalp?
Tinea capitis
What are the 2 types of ringworm infections?
Endothrix (infects throughout follicle)
Ectothrix
What infection is associated with certain species producing a black dot ringworm, intense inflammation, scarring/ permanent alopecia, and can be zoonotic?
Tinea capitis
With tinea capitis, infected hair can break off and lead to what?
Alopecia
If a patient presents with itching, peeling, and crackling of the skin in the toe webs/ soles of feet, what should you be concerned about?
Tinea pedis (most prevalent of dermatophytoses)
What are predisposing factors for tinea corporis and tinea cruris?
Diabetes, obesity, excessive perspiration
How are tinea corporis and tinea cruris transmitted?
Direct and indirect contact objects (towels, clothing, bed linens)
What is tinea unguium?
Onychomycosis (ringworm of the nail)
What infection is associated w/ the following:
- Finger/ toenails become discolored/ thick
- May be mistaken for psoriasis
- Usually has fungal involvement (Candida)
Tinea unguium
What are the most commonly encountered opportunistic mycoses?
Candidiases
What infection is associated with colonization of normal flora of the skin and mucous membranes?
Candidiases
What infection is associated with the following:
- Absence of competing normal flora
- Introduction to abnormal site
- “Pathologic” change in microenvironment
- Inborn or acquired immune defect
- Use of broad-spectrum abx
Candidiases
Although candida albicans does not have many virulence factors, all species are capable of attachment, and what is the most adhesive?
Germ tube more adhesive than yeast cell
How is a Candida infection diagnosed?
Direct microscopic exam
- Large G- cells
- Yeast cells
- Pseudohyphae
- True hyphae
Besides direct microscopic exam, how is a Candida infection diagnosed?
Cultures (germ tubes)
Histology
Serology
What is tinea versicolor aka?
Malassezia furfur
What fungi is described as microscopically having short, unbranched hyphae and somewhat spherical cells and also has yeast like colonies?
Malassezia furfur
If you see a “spaghetti and meatballs” arrangement on a microscopic exam, what fungal infection should you be suspicious of?
Malassezia furfur
What type of GF is required for growth of Malassezia furfur?
Lipophilic (fat, sebaceous glands)
In what populations is Malassezia furfur most commonly found?
Tropics, young adults
What fungal infection is associated with macular patches of depigmented or hyper pigmented skin that may enlarge and can lead to dandruff?
Malassezia furfur
How can Malassezia furfur be identified?
Microscopic exam in skin scrapings, KOH prep
What fungal infection is tinea nigra aka?
Hortaea werneckii
What fungal species is dimorphic and can grow in saturated salt solutions?
Hortaea werneckii
What fungal species is identified as a tropical disease, results in brownish lesions (melanin), and is identified with KOH and microscopy?
Hortaea werneckii
When is a bacterial skin infection considered complicated?
Pre-existing wound care Deeper tissues Requires surgery Unresponsive to therapy/ recurrent Associated w/ underlying disease
Recurrent infections raise concern over colonization with what?
Resistant bacteria or underlying issues
Although normally inoculum of bacteria (staph) introduced through breaks in skin is not large, what happens if a foreign body (splinter, stitches) is present?
Infectious dose drops dramatically
What disease is associated with the sebaceous follicles and is a noninfectious form of folliculitis?
Acne vulgaris
What is often the initial trigger for acne vulgaris?
Androgen hormones
What bacteria responsible for acne vulgaris is G+, anaerobic rod, and on normal skin flora (sebaceous glands)
Propionibacterium acnes
What does inflammatory acne develop?
When follicular contents rupture into dermis
papule > pustule > nodule
What is the usual cause of Folliculitis?
Staph. aureus
If a pt presents w/ mild pain, itching/ irritation with pustules or nodules surround hair follicles?
Folliculitis
If folliculitis is not responding to tx, what should be performed to r/o other possible causes?
Gram stain
r/o G- etiology or MRSA
What are the 2 primary pathogens responsible for superficial folliculitis?
Staph. aureus and Pseudomonas aeruginosa
Which pathogen is responsible for the majority of abscess-type infections, is G+, and coagulase-+ cocci in clusters?
(superficial folliculitis)
Staph. aureus
Which pathogen is described by the following: - G- rod - Opportunistic pathogen - Ubiquitous - Pyocyanin/ pyoverdin (superficial folliculitis)
Pseudomonas aeruginosa
P. aeruginosa is often the cause of what type of folliculitis?
“Hot tub” folliculitis
If a pt presents 8-48 hrs post exposure to contaminated water and is complaining of an itchy maculopapular rash with some pustules, what is the likely responsible pathogen?
Pseudomonas aeruginosa
A furuncle (boil) is an abscess caused involving a hair follicle and surrounding tissue caused by what pathogen?
S. aureus
What are clusters of furuncles with subcutaneous connections that extend into the dermis and subcutaneous tissue?
Carbuncles
What other sxs might accompany carbuncles?
Fever and prostrations
What populations are more commonly affected by furuncles and carbuncles?
Obese, immunocompromised, diabetic, elderly
If furuncles or carbuncles are > 5mm, do not resolve w/ drainage, are spreading, or occur in IMC/ subjects at risk of endocarditis, how are they treated?
Abx (effective against MRSA)
More aggressive combo therapy with rifampin if + fever/ multiple
What condition is a superficial skin infection with crusting or bullae and what is the most common pathogen cause?
Impetigo
Cause= steph, strep (or both)
What is the deeper, ulcerative form of impetigo?
Ecthyma
Moist environment, poor hygiene or chronic nasopharyngeal carriage of agents are RF’s for what disease?
Impetigo/ ecthyma
If a pt presents with clusters of vesicles that rupture and crust over around the nose and mouth, what should you be concerned for?
Non-bullous impetigo
What is the #1 cause of non-bullous impetigo?
S. aureus (with MRSA in 20%)
Strep. pyogenes co-infects frequently
In bullous impetigo, exfoliative toxin that disrupts epidermal cell connections results in vesicles enlarging to form what?
Bacteria-colonized fluid-filled bullae
What is the most common pathogen involved with bullous impetigo and what role does the toxin play?
S. aureus (specific strains)
Toxin does not disseminate beyond local sites of infection
A severe form of impetigo featuring deep invasion of the dermis caused by the same agent producing non-bullous impetigo is known as what?
Ecthyma
Lesions with hard crust that is deeper and thicker than impetigo underlying ulcerated tissue is known as what?
Ecthyma
Staphylococcal scalded skin syndrome is aka?
Ritter’s disease
Acute and extensive epidermolysis due to action of staph toxin (exfoliation) that splits the skin just beneath the granule cell layer is what?
Staphylococcal scalded skin syndrome
Why are the bullae in Staphylococcal scalded skin syndrome sterile (no bacteria or leukocytes)?
Due to toxin
Positive Nikolsky’s sign, skin peels easily, and desquamated areas look scalded fits the description for what condition?
Staphylococcal scalded skin syndrome
Is the mortality rate for scaled skin syndrome high or low?
Low
Erythema and edema to R LE (unitlateral) the appears deep w/in the dermis and has less distinct borders is concerning for erysipelas or cellulitis?
Cellulitis
Superficial cellulitis (erythema with raised lesions) w/ focal dermal involvement and distinct borders is concerning for what?
Erysipelas (st. Anthony’s Fire)
Most common pathogen for erysipelas?
Group A, B-hemolytic Streptococci, Strep pyogenes
How do erysipelas spread once dermis is infected?
Superficial lymphatic vessels
Will you always be able to pinpoint the source of cellulitis infection?
No, wound may not be evident
HEET (heat, erythema, edema, tenderness) is the hallmark for what bacterial skin infection?
Cellulitis
When treating cellulitis should you assume the infection is caused by a single pathogen?
No, may be mixed etiology
Why should NSAIDs be avoided in the treatment of cellulitis?
Can mask pain of developing myonecrosis (something more serious than cellulitis)
What is a warning sign that cellulitis infection might be necrotizing fascitis?
Out of proportion pain
Cellulitis pathogen associated w/ cat bite?
Pasteurella multocida
Redness, swelling warmth, pain + what signs/sx would make you concerned for a MRSA infection? (4)
- Fluctuance (evidence of fluid)
- Yellow/white center
- Central point (head)
- Draining pus or ability to aspirate pus w/ syringe
What gene can you screen for that might tell if you are Methicillin resistant?
MecA
Infections of the epidermis? (3)
- Erysipelas
- Impetigo
- Follicutlits
Infections of the dermis? (3)
- Ecthyma
- Furunculosis
- Cabunculosis
Infection of the superficial fascia? (1)
Cellulitis
Infection of the subQ tissue and fascia? (1)
Necrotizing fasciitis
Infection of the muscles? (1)
Myonecrosis (clostridial and nonclostridial)
Why is it difficult to dx NF w/o surgical intervention?
Initially overlying tissues appear unaffected
Why is muscle tissue spared from NF infection?
Generous blood supply
Type 1 NF pathogens are most common. What disease state disease state puts you at increased risk?
DM
If you have a hx of surgery, previous abscess or GI perforation are you at risk for Type 1 or Type 2 NF infection?
Type 1
Flesh eating bacteria or streptococcal gangrene more common in abdominal/groin area or the extremities?
Extremities
Pain out of proportion and skin color changes w/ bullae within 3-5 day of onset is concerning for?
Necrotizing fasciitis
What differentiates NF from cellulitis?
Failure to respond to ABX (cellulitis will respond w/in 24-48hrs to abx)
What is the tx for NF?
Surgical debridement/apmutation w/ IV ABX
Presence of no true pus, but brownish exudate and pain out of proportion/ rapid progression is concerning for?
NF
Gas gangrene is most caused by what pathogen?
Clostridium perfringens type A (90%)
- spore forming, G+, anaerobic bacillus
Gas gangrene primarily affects what tissue?
Muscle
Gas gangrene is also known as?
Clostridial myonecrosis
Skin that is tense/edematous, intensely tender, and crepitant (due to H2 gas) with bronze appearance is concerning for?
Gas gangrene
Rapid onset of pain ≤24 hrs following anaerobic cell/spore infection is concerning for?
Gas gangrene
Gram stain of tissue biopsy for gas gangrene will show what?
Muscle necrosis , gram variable rods, and tissue destruction
Hyperbaric oxygen therapy, surgery, and IV abx are tx for what dermal infection?
Clostridial myonecrosis
Causative agents for toxic shock syndrome? (2)
Staph aureus and strep pyogenes
Fever and sunburn like rash to entire body is concerning for what?
TSS
Early presentation for Strep TSS?
Soft tissue inflammation at site of skin infection
True or False: Pt’s w/ strep TSS are usually bacteremic and have NF?
True
Enterotoxin type B superantigen is associated with strep or staph TSS?
Staph
True or false: Pt’s with staph TSS are otherwise healthy w/ no pre-existing skin infections?
True
Which pathogen of TSS is associated with tampon use?
Staph
What pathogen is a burrowing mite that is the most serious of the mites, a close relative of ticks, and leads to scabies, crusted scabies, mange, and seven year itch?
Sarcoptes scabiei
What is the morphology of Sarcoptes scabiei?
Small mite w short legs
Is a male or female Sarcoptes scabiei fertilized on the skin surface, burrows into the epidermis, and completes its life cycle in 5 weeks then dies in the burrow?
Female
Does a male or female Sarcoptes scabiei have a shorter life span and remains on the skin surface or produces a shallow burrow?
Male
Where are the eggs of Sarcoptes scabiei laid and how soon after incubation do larva emerge?
Under the skin
Larva emerge after 4 days
How long after Sarcoptes scabiei hatch do adult mites develop?
2 weeks
How long after someone is infested with Sarcoptes scabiei does it take for sxs (itching) to develop?
First infestation = weeks
Re-infection = 24 hours
What causes the majority of clinical issues (intensely pruritic eruption that is worse at night) with Sarcoptes scabiei?
Burrowing
