Skin and Soft Tissue Flashcards

Question

S. aureus TYPE IINECROTIZING INFECTION

Answer 1

rare mostly in sick ppl -mostly due to community acquired MRSA -Rapid & serious - affects skin, fascia, subcutaneous and muscle tissue. - occur without a defined portal of entry or through an open skin wound or after surgery. -Large # of exotoxins cause decreased coagulation & fluid leakage in tissue. -Results in swelling and blister formation. with blockages in blood vessels that lead to tissue death - person goes into shock and dies.

Answer 2

-Causes impetigo, cellulitis, erysipelas & wound infections. -causes toxin related soft tissue infections. -Infection with GAS producing pyrogenic exotoxin -Damages plasma membranes of capillaries -Seen as diffuse red rash on upper chest - spreads to trunk & extremities -Followed by peeling of skin. -fever, sore throat & strawberry tongue If untreated, can result can affect the kidneys or heart or cause arthritis.

Answer 3

-rare,multisystem disease caused by GAS that makes pyrogenic exotoxin- SpeA, B or C. -Organism enters after minor bruise, injury, surgery or respiratory infection -Portal of infection can be unknown. -Children with chicken pox & elderly more at risk. -Toxin acts as a superantigen initiates massive proinflammatory response. -Same symptoms as Staph TSS - rapid multiorgan failure leads to shock & death.

Answer 4

-GAS is most common cause -Due to strains with M proteins & pyrogenic exotoxin A. -Enters thru surgical wound or trauma – sometimes no obvious point of entry. -starts as redness, swelling and pain out of proportion to signs of skin infection. -quickly progresses to fever, skin discoloration & swelling. Decreased blood supply= severe tissue damage & necrosis. Person goes into shock & dies.

Answer 5

due to direct inoculation of bacteria in skin. -mild skin infection, like folliculitis or more severe like skin and soft tissue infections -Infects burns, bed sores & wounds due to injuries or surgery gets directly into blood to cause bacteremia

Answer 6

as a result of Pseudomonas bacteremia. -Ecthyma gangrenosum. -Lesion due to bacterial invasion of dermal veins leading to hemorrhage & necrosis of skin. -Sore has purple-black center and is surrounded by a band of red

Answer 7

-can be harmless or be life threatening causing infective endocarditis -Mostly causes skin/soft tissue, bloodstream, & prosthetic device infections. -can be virulent & cause serious infections exactly like S. aureus -In superficial wounds – full ID with AST only if pure or predominating numbers -In deep wounds or sterile site- full ID with AST regardless of amount growing in culture

Answer 8

-Small-med, white, NH or weak BH. -GPC clusters, Catalase pos Staphaurex neg (*may be positive*), Tube coagulase neg (gold standard for lug) PYR pos, ORN pos (COMMOM CSMLS) -Use Vitek OX MIC result or KB with cefoxitin disk (30ug) as a surrogate to report oxacillin – Do not do OX screen - not reliable because CONS wont grow on media with salt -CLSI uses same interpretation breakpoints as S. aureus

Answer 9

Vibrio vulnificus: Type III necrosis -Exposure of open wound/or a wound obtained in seawater with organism. -Skin lesions with hemorrhagic bullae that progress to necrosis, septicemia and death.

Answer 10

Aeromonas: Type III necrosis -Found in brackish or fresh water -enters skin through open wound. -or if leeches used therapeutically because leeches have aeromonas in their gut -Starts with pain, swelling, hemorrhagic bullae, necrosis, gangrene with gas production, septicemia and death.

Answer 11

-pathogens arent always looked for but more so pt history Curved GNB/comma”- facultative anaerobe -MAC: V. vulnificus is LF, others are NLF -Oxidase pos, reduce nitrates to nitrites -Salt loving (halophilic) – can grow on media with high salt -MALDI, Vitek, API, Tube biochemicals

Answer 12

GNB (small coccobacilli)– facultative anaerobe Oxidase pos MAC: LF - Can’t grow on media with high salt MALDI, Vitek, API, Tube biochemicals

Answer 13

-Facultative, GNB or GNCB -Cause SSTIs after animal bite- dogs & cats. 5 serotypes but A & D cause disease =Virulence due to production of capsule & toxins -starts with redness & swelling then cellulitis with purulent discharge. -Rarely, becomes necrotizing infection. - osteomyelitis, septic arthritis, septicemia or endocarditis –but more in those with co-morbidities. **Does not grow on MAC** Oxidase pos, spot indole pos- ID by MALDI OR VITEK

Answer 14

Large gpb with spores, strict ANO2 -spontaneous with abdominal diseases – usually due to Clostridium septicum. -More often from severe traumatic wound –usually Clostridium perfringens -Produces multiple toxins- alpha toxin most virulent. -Causes clots in veins = decrease blood/O2 to tissue and pores in tissue cells so they lyse. -Produces DNAse, hyaluronidase, & hemolysin - all breakdown tissue -accompanied with foul smelling gas – gas gangrene Leads to shock & death unless treated or amputation.

Answer 15

-GNDC, can colonize the nose. -Rarely a direct cause of cellulitis - cause of indirect skin manifestation following septicemia or meningitis. - skin rash or Purpura fulminans (PF). -PF causes dermal micro clots in blood vessels leading to hemorrhagic skin necrosis, peripheral gangrene & shock Amputation & death may result.

Answer 16

Enterobacterales Acinetobacter spp. Stenotrophomonas maltophilia Enterococcus spp. (if predominating or pure) Anaerobes (from deep wounds or bites only)

Answer 17

Superficial Swabs (not optimal) – only when tissue or aspirate can’t be obtained. like when wounds wont close and can lead to unnecessary treatment -clean wound by irrigating with sterile saline to remove debris -roll swab 5 times focusing on pus or inflamed tissue -swab in Amies or Stuarts -NOT FOR ANO2

Answer 18

-Aspirates of pus or abscess fluid by needle or syringe. -Biopsies of infected wound tissue. -Both good for aerobic or anaerobic culture. -Portion of specimen placed in sterile empty container for aerobic culture. -Portion of specimen placed in an anaerobic transport tube. -For bite wounds best sample is aspirate pus from infected wound. -Don’t take specimens from fresh bite wounds- will have normal oral/resp flora introduced from bite but cultures can’t predict if these will cause infection.

Answer 19

-detection of IV catheter-associated bloodstream infections. -Short section of catheter that has been under the skin is aseptically cut off. -Collected into sterile container & sent to lab ASAP -Cultured by rolling tip across the agar surface using sterile forceps

Answer 20

done on all skin/wound specimens. -Quantitate & report pus, epithelial cells & any organisms seen because your workup is based on the # of these seen on the gram -epithelial cells indicates contamination of specimen with NSF. -WBCs is good indicator of infection. -Information regarding type of wound (surgical, traumatic pressure ulcer etc.) & location of wound important & should be on requisition.

Answer 21

where mycobacteria, zoonotic bacteria, fungus, virus, or parasites directly affect skin - Or organisms where skin manifestation of disease due to complications of a disseminated infection caused by that organism

Answer 22

less common -due to Corynebacterium diphtheriae or Corynebacterium ulcerans -dipthe transmitted p/p or surface very contagious -Ulcerans from infected animals/animal products *Only strains that acquire tox gene from bacteriophage cause respiratory form of Diphtheria. *Both toxigenic & non-toxigenic strains cause cutaneous form. -seen as a vesicle that becomes an ulcer with grey membrane both gpb clubbed dipth- urea neg ulcer- urea pos

Answer 23

you can use Swabs, aspirate, biopsy or skin membranous material -culture to media from bacterial isolation -ID with gram, colo morph and MALDI -PCR to detect dipth tox gene if ID is any cornye -if pos for tox gene- sent to National Microbiology Laboratory for confirmation by PCR and Modified Elek test

Answer 24

less common serovars L1 to L3 of Chlamydia trachomatis infects lymphatics Transmission = Sexual 1st stage- ulcers - painless - heals 2nd stage - moves to lymph nodes > puss filled buboes. they burst 3rd stage - Strictures/obstruction of lymph vessels -possible necrosis of genital tissue

Answer 25

based on history , clinical presentation and lab testing -men :Urine, urethral, throat or rectal swab, lesion swab bubo fluid -women-Urine, cervical, vaginal, throat or rectal swab, lesion swab, bubo fluid test with NAAT, any pos NAAT send to national laboratory to confirm for LGV genotype -culture not routinely done maybe at PHL

Answer 26

Treponema pallidum subspecies pallidum (not all treponema are pathogenic) -ANA corkscrew, motile GNB - hard to stain -transmitted sexually or mother-baby -2 stages: primary, 2ndary, latent and tert 1-chancres 2. red brown rash 3. gumma formation

Answer 27

sexually transmitted -forms lesion with soft edge = cancroid -if untreated becomes ulcer and causes lymph node buboes -tan yellow that you can push on agar -GNCB = school of fish *Oxidase: pos, Only X factor needed *MALDI or PCR

Answer 28

-branched beaded GPB -lung infection , skin and soft tissue -common one infecting SST - Actinomyces & Nocardia

Answer 29

Anaerobic, NOT acid fast Causes Actinomycoses: abscess of face & jaw that goes into deeper tissue. *Draining sinuses + yellow orange sulfur granules

Answer 30

strict aerobe, modified acid fast -Crumbly and looks like a molar tooth -Branching beaded GPB Causes Nocardiosis: Skin ulcer *Or Mycetoma-little abcesses under skin if on foot =Madura foot -black granules if fungus -red granules if Nocardia

Answer 31

Small GNB Rocky mountain spotted fever -maculopapular rash with petechiae -ticks, mites, lice, fleas

Answer 32

leptospirosis maculopapular rash that becomes hemorrhagic rodents and mammals

Answer 33

GNB Bartonellosis - Cat Scratch disease papule , lesions cat bites, sandflies, lice

Answer 34

streptobacillus monilformis GNB Spirillum minus GNB Spiral rat bite fever maculopapular or pustular rash on palms and soles rodent bites or contact with their feces

Answer 35

Tularemia maculopapular or vesicular rash ulceroglandular painless ulcer and painful swelling of the lymph node rabbits, rodent, bite from infected tick, flea , deerfly

Answer 36

small gpb erysipeloid painful red lesion with raised borders animals, animal meat, hides, saltwater fish handlers of above also at risk

Answer 37

Large GPB with spores anthrax cutaneous form starts a painless papules on face or arms, then they become vesicles leading to necrotic lesions with black centers coming in contact with animal or animal products with the spores

Answer 38

- Swabs from skin lesions or ulcers *Fluid, abscess aspirates *Tissue biopsy or Blood sample testing of growing organisms in BLS3 labs only -gram and histo direct stains -immunology /serology -PCR - single org or multiplexing -grow in culture and then MALDI

Answer 39

-Transmitted person-person or environment, food, animal or vector transmission *Organism seeds skin directly *Or as it travels through blood or lymphatics *Also, if travels from nearby area of infection

Answer 40

1.Cutaneous manifestations due to Mycobacteria in MTB complex 2.Buruli ulcer caused by Mycobacterium ulcerans & other ulcers caused by slow growing NTM 3.Leprosy caused by Mycobacterium leprae &Mycobacterium lepromatosis 4.Cutaneous infections caused by rapidly growing NTM

Answer 41

M. ulcerans: Buruli ulcer (Africa),Bairnsdale ulcer (Australia) -*In environment –transmitted by skin trauma. *Causes nodular lesions with or without ulceration .*Produces necrotizing immunosuppressive toxin – mycolactone. *able to infect underlying bone to cause osteomyelitis

Answer 42

M. leprae (Hansen’s bacilli): Leprosy strictly human pathogen and armadillo -droplet spread but only 5% carry leprosy -Chronic infection of skin, peripheral nerves & mucous membranes. *Paucibacillary form: < #s of organism & infected skin patches *Multibacillary form: > #s of organisms & infected skin patches

Answer 43

*Swab of lesion, vesicle or ulcer in Amies or Stuarts .*Aspirate of fluid from infected tissue. *Tissue samples are best sample. * blood Microscopy: acid fast stains ZN, Kinyoun, Auramine rhodamine Culture: To both Solid agar (LJ egg based or Middlebrook agar based) + broth (Middlebrook broth or broth included with automated instruments Identification: Biochemical tests, MALDI, PCR

Answer 44

Rashes (different types) *Lesions *Warts *Vesicles

Answer 45

take sample from spot where virus causes infection -SST lesion secretions Dacron/Rayon swabs -plastic or wire -all else use cell scrapings, tissue biopsy, body fluids -swab and tissue go in VTM/Universal UTM transport media (sucrose, proteins, antibiotics, buffers, gelatin & phenol red) -otherwise you would dilute .*fluid samples in sterile screw top that will not break when frozen & thawed* -Do not use UTM/VTM for these because will dilute the virus. *Place specimens for PCR – in its own manufacturer media

Answer 46

Process culture immediately *If there is a delay <72 hrs., store at 4, ship on a gel pack. *If delay is >72 hrs., freeze at -70oC. *Never freeze at -20oC because ice crystals form which damage the virus *Never freeze and thaw numerous times can damage the virus

Answer 47

1.Direct microscopic detection (direct fluorescence) 2.Molecular testing like PCR, multiplexing 3.Serological assays to detect viral Ags or Abs to the virus 4.Isolation of virus in cell culture with evidence of specific cytopathic effect

Answer 48

Tinea Versicolor due to Malassezia furfu -NF on skin -needs fat /oil to grow found around sebaceous gland -opportunistic causing dry patches -dandruff Lab Diagnosis: -Shine fluorescent woods lamp on skin & fungus will fluoresce *Microscopic exam of skin/hair specimen in 10%KOH shows“spaghetti & meatballs” = budding yeast & hyphae. *Won’t grow on culture media unless covered with oil – w/o oil cultures look negative

Answer 49

*Infections of keratinized tissue–skin, hair and nails *Dermatophytes or Candida spp. *Symptoms: redness, itching, scaling & ring like lesion (ringworm) *Named Tinea followed by the site where lesion is found. Tinea pedis = feet, Tinea capitis = hair, Tinea corporis = body skin -Transmission: direct/indirect contact with infected host. *Three genera infect different areas Microsporum infects skin and hair (not nails) Epidermophyton infects skin and nails (not hair) Trichophytoninfects hair, skin & nail

Answer 50

BSL2 in CL 2 Lab with PPE & Class II BSC Specimens: *Skin scraped from margin of lesion *Hair plucked, not cut, from edge of scalp lesion *Nails scrapings of nail bed :1. Microscopic exam directly on specimen: 10%KOH or Calcofluor white fluorescent stain *Look for 2 sizes of asexual reproductive cells-each a distinct shape Macroconidia & or Microconidia 2. Culture specimen on fungal media 3. Describe front and back of colony growing on plates 4. Lactophenol cotton blue of colony & examine microscopically for characteristic macro & or microconidia.

Answer 51

*Yeast skin infection caused by Candida spp.- C. albicans .*Affects warm, moist areas, especially in folds. *seen in infant diaper rash .*Can infect nails. *Causes red, itchy rash, skin can crack or blister. *Increased risk in diabetes, obesity, on antibiotics or immunocompromised.

Answer 52

Chronic infection of deep skin layers -may spread to muscle & bone but not usually blood or organs. *Environmental fungus in tropical areas enters skin trauma *Cause progressive non healing ulcers, draining sinus & tissue destruction *Eumycotic Mycetoma = mycetoma caused by fungus (examples: Madurella or Fusarium spp.) *Actinomycetoma=mycetoma caused by Actinomycetes, like Nocardia .*Fungal form causes black melanotic granules. *Are microcolonies of fungus discharged onto skin surface through sinus tracts. *Granules are expressed from draining lesions.

Answer 53

Fungal infection that spreads throughout the body. *affects organs, blood, CSF. * fatal in immunocompromised. *caused by dimorphic fungus, Aspergillus or a yeast.

Answer 54

Transmitted by inhaling spores, ingestion or inoculation of spore into skin -starts as a lung infection and rash -healthy people can overcome -immuno ppl get get chronic pulmonary infection - leads to granulomatous skin lesions which lead to systemic infections

Answer 55

BSL3 organisms use proper PPE & class II biological safety cabinet when processing .*Growing cultures only worked on in CL3 Lab Specimens: tissue biopsy, body fluid, sputum, blood Lab testing:*Antigen or Antibody detection: serological or immunodiagnostic techniques. *Molecular tests like PCR: *Direct Specimen Microscopy: detect yeast form in tissue. *Culture on fungal media 25C & 35C: may take weeks to grow (“Yeast in beast mold in cold”) *Microscopy of colony with LPCB to see characteristic dimorphic yeast or mold structures.

Answer 56

Free-living protozoan amoebae in soil and fresh water *Can cause Granulomatous Amebic Encephalitis (infects CSF & brain, when breathed in thru nose), Amebic Keratitis (Eye) & Cutaneous Acanthamoeba (Skin) -infection through open wounds -seen as abscesses, ulcers, nodules Staining skin biopsy by H & E, Periodic acid-Schiff (PAS), or calcofluor white. *Molecular can be done as well

Answer 57

Nematode round worms Hookworm: *Larvae gets in skin & burrows. *Visible under skin as a winding, threadlike, raised trail. *Rash, small bumps & blisters may also occur .Trematode flat worms like Schistosoma :*Cause irritation of skin where larval form enters through the persons skin.

Answer 58

Beg bugs Genus Cimex spp .Feed on blood, at night. Bites =skin rash & allergic reactions. Scabies Sarcoptes scabiei mite Burrows in surface skin. Causes itching & rash Lice Head Louse Pediculus Groin Louse Phthirus pubis Spread by close contact Causes itching, & sores

Answer 59

Parvo - slapped cheek rash Oral Herpes - cold sores Papillomas - plantar warts, filiform warts Roseola - cold followed by a rash 3-5 days later varicella chickenpox rubeola (measles)- paramyxovirus rubella - german measles nonpruritic Monkeypox othropoxvirus - rash with blisters Ebola, Marburg, Dengue Zoonotic viruses that cause severe bleeding under skin