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Clinical Microbiology > Miscellaneous infections > Flashcards

Miscellaneous infections Flashcards

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1
Q

Joint infections

A

Usually only occurs in one joint (monoarticular) and usually occurs in the knees and hips. There is direct extension of infected bone and is secondary to hematogenous spread. Can be used by an inflammatory response

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2
Q

Laboratory tests of joint fluids (3)

A
  1. Increased white blood cells
  2. Decreased glucose
  3. Increased protein
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3
Q

Specimen collection and processing of joint infections

A

Aspirate by needle and syringe. Inject specimen into anaerobic transport vial. If clotted, must grind, then prepare direct smear Can inoculate blood culture bottle, in addition to solid media. Includes nonselective media, enriched media (thioglycollate broth), and anaerobic media

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4
Q

Infection of prosthetic joints

A

Infection often occurs over a year after surgery- biofilms. Usually occurs due to normal skin flora

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5
Q

Specimen collection of bone marrow

A
  1. Cleanse puncture site
  2. Aspirate bone marrow
  3. If clotted, homogenize specimen in BSC
  4. Inoculate blood culture bottles and nonselective media
  5. Centrifuge lysis procedure (Isolator system) is recommend
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6
Q

Osteomyelitis

A

Due to hematogenous spread of the infectious agent and invasion of bone tissue, can occur from trauma or surgery. This often becomes a chronic infection. Underlying conditions put patients at risk- diabetes, bites, hospitalized patient, medical devices

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7
Q

Specimen collection and processing- osteomyelitis

A

Bone is removed at surgery or percutaneous biopsy- the infected bone is generally soft and necrotic. In BSC, grind specimen in sterile saline before inoculation of media. Place small bits of bone into solid media and enrichment broth

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8
Q

Selection of skin/tissue specimens

A

This depends on the extent and character of infection. A closed abscess is the specimen site of choice, culture is not recommended for dry, encrusted lesions. Tissues- specimens are usually sterile sites, collected from surgery, needle biopsy, and autopsy

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9
Q

Specimen collection from skin and tissue (6)

A
  1. Decontaminate skin, aspirate abscess contents with syringe
  2. Collect specimen from the advancing margin of the lesion.
  3. Burns must be extensively cleaned and debrided before collection.
  4. Place tissue sample into sterile container
  5. Swabs & aspirates use transport medium
  6. Labeling - give specific anatomic site; do not label specimen only as “wound.”
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10
Q

Aerobic transport of skin or tissue specimens

A

For aerobic only, submit in aerobic transport medium. This includes exudates from superficial lesions, open wounds, lacerations, or open abscesses

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11
Q

Anaerobic transport of skin and tissue samples

A

For anaerobic and aerobic requests- submit in anaerobic transport medium. Includes surgical aspirates, closed-abscess aspirates, and tissue biopsies

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12
Q

Processing of skin and tissue samples (5)

A
  1. Direct Gram stain
  2. Histological stain—helps determine tissue invasion
  3. Process sample in biological safety cabinet
  4. Enriched and selective solid media, as dictated by anatomical site of lesion. Broth media aid in isolation of facultative and anaerobic organisms.
  5. Quantitative tissue samples- primarily for infected burns
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13
Q

Direct Gram stain of skin and tissue samples

A

Determines quality of specimen. Look for bacteria. Neutrophils indicate presence of infection. Epithelial cells indicate contamination with skin flora

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14
Q

Skin infections (6)

A
  1. Pyoderma
  2. Cellulitis
  3. Impetigo
  4. Furuncle
  5. Carbuncle
  6. Erysipelas
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15
Q

Pyoderma

A

Skin infection, presence of pus (WBC)

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16
Q

Cellulitis

A

A bacterial infection, affects the deeper layer of skin and soft tissue

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17
Q

Impetigo

A

A highly contagious skin infection associated with children. Forms red, itchy lesions around the nose and mouth, which develop into vesicles that burst forming yellow crusted areas. Commonly caused by Staphylococcus or Streptococcus

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18
Q

Furuncle

A

Infection of the hair follicle; common name = boil

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19
Q

Carbuncle

A

A painful collection of furuncles that is connected under the skin.

20
Q

Erysipelas

A

A bacterial infection that is commonly caused by group A strep. It is a superficial form of cellulitis (in the upper dermis layer of the skin). Symptoms0 large red patches, swelling, pain

21
Q

Vesicles

A

small fluid filled blisters (sac, cyst)

22
Q

Bullae

A

large blisters, usually >5mm

23
Q

Draining Sinuses

A

Channel or passage way, abnormal passage from inside of the body to the outside

24
Q

Fistulas

A

Resulting from surgery or injury, an abnormal connection between organs or other tissues. Formation between hollow area and an organ.

25
Q

Necrotizing Fasciitis or Necrotizing Subcutaneous Infection (NSI)

A

Infection of the fascia – tissue lining under the skin that separate muscle and internal organs. Introduction by ulceration, infection (infected pox, blister) or trauma. 30% mortality when not diagnosed early

26
Q

Myonecrosis

A

Deep muscle tissue, leading to pain, cell death, gas gangrene= necrosis, sepsis, organ failure leading to death

27
Q

Myositis

A

Inflammation of the muscle, resulting from infection, injury, or autoimmune conditions.

28
Q

Clostridial Myonecrosis

A
  1. Clostridium perfringens (traumatic form, most common), 2. C. septicum (spontaneous form, most common),
  2. C.histolyticum, C. sordelli, C. sporogenes, etc.
    Traumatic – injury or trauma limiting blood supply. Spontaneous – Associated with immune dysfunction, colon cancer, rectal cancer other cancers
29
Q

Erythema Chronicum Migrans

A

Bull’s eye rash associated with Lyme disease. Lyme disease is the most common arthropod-borne (i.e., Ixodes tick) disease in the US. Causative agent - Borrelia burgdorferi

30
Q

Erythema Infectiosum

A

Slapped cheek rash associated with Fifth disease

31
Q

Erythema Infectiosum causative agents (4)

A
  1. Parvovirus B-19 – most commonly associated with 5th Disease
  2. S. pyogenes
  3. Syphilis
  4. Measles
32
Q

Bone marrow bacterial infections (2)

A
  1. Brucella abortus
  2. Mycobacterium tuberculosis
33
Q

Bone marrow fungal infections (2)

A
  1. Histoplasma capsulatum
  2. Blastomyces dermatitidis
34
Q

Necrotizing fasciitis causative agents (4)

A
  1. Group A streptococci
  2. Staphylococcus aureus
  3. Bacteroides sp.
  4. Clostridium sp.
35
Q

Why plate postmortem cultures?

A

Cultures must be taken no longer than 48hrs postmortem, best <24hr. Blood culture and sterile tissue are most helpful.
A single organism, typical pathogen, suggests true infection. Recovering skin flora suggests contamination from procedure

36
Q

Autopsy samples

A

Most internal organs (other than lungs) are previously uninfected and remain sterile for approximately 20 hours after death. 75% of all tissues obtained at autopsy should be sterile. >10^5 organisms/gram tissue indicates infection, While <10^5 organisms/gram tissue indicates colonization

37
Q

Optimal growth for mycobacteria

A

optimal growth for these is 30 degrees C

38
Q

Causes of wounds and abscesses (3)

A
  1. Bowel- lower GI flora
  2. Colon cancer
  3. Hospital-acquired infections (HAI, nosocomial)
39
Q

Types of wound infections (3)

A
  1. Tetanus- Clostridium tetani
  2. Wound botulism- Clostridium botulinum
  3. Fungal infections-Sporotrichosis, Phaeohyphomycosis, chromoblastomycosis, mycetoma, coccidiomycosis, & blastomycosis
40
Q

Surgical wound infection

A

Due to breakdown of skin barrier or the organism is introduced during surgery

41
Q

Main risk of intraabdominal abscess

A

Leads to secondary bacteremia

42
Q

Risk of bites

A

Infection with human or animal oral flora. Includes aerobic and facultative bacteria and anaerobes

43
Q

Infection of prosthetic devices

A

Infection occurs within 1 week to several years due to biofilm formation

44
Q

Infections in drug abusers

A

Source of infection includes contaminated materials or needles, or endogenous normal flora. There are factors contributing to increased risk of infection: malnourished, poor hygiene, lapses of consciousness, or aspiration. The most common infectious agent is S. aureus

45
Q

Complications of infection in drug abusers (2)

A
  1. Endocarditis: S. aureus, streptococci, enterococci, P. aeruginosa, Serratia marcescens
  2. Pneumonia: Prevotella sp., other anaerobic GNR, Peptostreptococcus sp., streptococci, S. aureus, aerobic GNR
46
Q

Predisposing factors of infection in diabetes patients (3)

A
  1. Peripheral neuropathy and decreased peripheral vascular circulation
  2. Acidosis predisposes patient to fungal infection
  3. Increased glucose levels can be immunosuppressive
47
Q

Types of infection in diabetes patients (6)

A
  1. Diabetic foot ulcer
  2. Chronic soft tissue infection
  3. Anaerobic cellulitis and fasciitis
  4. Necrotizing cellulitis
  5. Malignant otitis externa
  6. Fungal infections: Rhinocerebral mucormycosis, candidiasis

Clinical Microbiology (19 decks)

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