Wound & Skin Flashcards
1
Q
Normal skin biota
A
Inhibit pathogens: compete nutrient, decrease pH
Mostly GP: Staph, diphtheroid, Propionibacteria/Cutibacterium, Candida
Significant/transient: Staph. aureus
2
Q
Primary skin infection
A
- Dermatitis
- Pyoderma
- Cellulitis/Abscess
3
Q
Dermatitis
A
- Intertrigo: Epidermis, rash - Candida, S. aureaus - Baby, obesity
- Superficial candidiasis: Mucosa, mouth, genital - Candida - Antibiotic treatment, immunosuppressed
- Tinea: Keratinized surface (skin, nail, hair) - Mold - Cooler temp is a reason
4
Q
Pyoderma
A
- Folliculitis: Hair follicle - S. aureus, P. aeruginosa - Adults - Shaving, hot tubs
5
Q
Cellulitis & Erysipelas
A
- One of the most common skin and soft tissue infection
- Bac entry via breaches in the skin barriers
- Skin erythema, edema, warmth
- Cellulitis: deeper dermis & subcutaneous fat
- Erysipelas: Upper dermis and superficial lymphatis
6
Q
Skin abscess
A
- Painful, fluctuant, erythematous nodule
- Can develop via deep infection of a hair follicle: furuncle (boil) –> coalesce to form carbuncles
- Back of neck, face, buttocks
- Common in adults, body hair and obesity
- S. aureus (MRSA)
7
Q
Microbiology of primary skin infection
A
- Cellulitis:
- Beta-hem strep (A, B, C, G, F) and group A is most common
- Also S. aureus, GNR - Erysipelas
- Mostly beta-hemolytic strep
- Erysipethrix rhusiopathiae: meat/fish handler - Abscess
- > 75% due to S. aureus
- Can be caused by mixing culture
- Oral bacteria can be found in injection site
8
Q
Secondary
A
Bite, Burns, Diabetic Foot infection, Wound, Nodular lymphangitis, necrotizing fasciitis, gangrene
9
Q
Human bites
A
- Human oral bacteria: (aerobic, anaerobic) Stap. aureus, Streptococci
- Primary pathogens: S. aureus, Strep. (A, S, agninosis) , Clostridium, Eikenellea, Prevotella, Peptostreptococccis, Fusobacterium,
10
Q
Specimen processing
A
- Superficial Wound (non-sterile):
- Swab, aspirate, biopsy
- Gram stain & aerobic only - Deep Wound (sterile):
- Aspirate, biopsy, tissue
- GS, aerobic, ana, broth. Isolation of fastidious/ana organism - Tissue
- Biopsy, tissue
- GS, aero, ana, broth. Isolation fastidious/ana organism
11
Q
Specimen collection
A
Transport: deliver aspirate and tissues to the lab within 30 min - RT
12
Q
Primary agents of skin & soft tissue
A
Staphylococcus aureus Beta-hemolytic streptococci Pseudomonas aeruginosa Enterobacteriaceae Anaerobes
13
Q
Culture work up
A
- Read plate daily
- ID up to 3 organism if: PMN present, specimen from sterile site, no or low epi cells, organism seen on direct GS
- Minimal testing to indicate the type of microbiota for noninvasively collected specimen if: numerous of epi cells, no evidence of infection, more than 3 organism in the culture
14
Q
Skin flora
A
Diphtheroids Coagulase-negative staphylococcus Yeast Viridans groups strep Enterococci
15
Q
GI flora
A
GNR
Gram-positive aerobic organisms (including Yeast)
Anaerobes
16
Q
Oral/mouth flora
A
Diphtheroids Coagulase-negative staphylococcus Yeast Viridans group strep Enterococci Rothia Strep. anginosis (milleri) group Haemophilus spp. Lactobacillus Eikenella Capnocytophaga
17
Q
Potential Pathogens
A
Beta-hem streptococci S. aureus Pseudomonas aeruginosa Stenotrophomonas maltophilia Clostridium perfringens Actinomyces (hold plates 14 days) Unusual: Vibrio, Listeria, N. gonorrhoeae, bioterroism NLF GNR
18
Q
CFS - Specimen handling
A
- Micro. tube (tube 3) remain at RT prior to culture
- Do not refrigerate CSF unless for viral study (Haemophilus, Neisseria, S. pneumoniae) are sensitive to cold temp.
- Process CSF immediately (GS & culture = STAT test)
19
Q
CSF - Lab Routine test
A
- Smear & culture on concentrated CSF (cytocentrifuge): sediment for culture, supernatant for other tests (chem, PCR)
- Smear is used for: bacteria, fungi, WBC, RBC. Report of GS is positive
- Culture always must be cultured: inoculate onto BA, CA, BHI. If from shunt/drain: add anaerobic plate with 14 days incubation
20
Q
CSF culture - analysis
A
- If NG on media/BHI, continue reincubate for 3-7 days
- If Pos, proceed GS, spot test, MALD-TOF, do full ID and susceptibility
21
Q
Other Dx for CSF
A
- Direct CSF latex agglutination for: C. neoformans, H. influenzae, N. meningitis, E. coli, S. pneumoniae, Group B Strep.
- Direct: 16S rRNA for bacteria, 28S for fungal,
22
Q
Sterile eye fluid infection
A
- Endophthalmitis: bacterial/fungal infection in vitreous and aqueous humors
- Uveitis: infection caused by virus/parasite
23
Q
Endophthalmitis cause
A
- Exogenous: trauma, eye surgery, extension of keratitis. Aqueous –> vitreous
- Endogenous: bacteria, fungi seed the eye
24
Q
Endophthalmitis Dx
A
- Positive aqueous, vitreous, biopsy
- Small volume
25
Endophthalmitis pathogen
```
Coagulase-neg Staph
S. aureus, Strep
Viridans Strep
Bacillus cereus
Haemophilus influenzae, Moraxella catarrhalis
```
26
Peritonitis
- Inflammation of the peritoneum caused by an infection
- Dx: peritoneal fluid
- Types: Spontaneous bacterial, Peritoneal dialysis, Secondary and Peritonitis
27
Spontaneous bacterial peritonitis
- Unknown source: monomicrobic, often caused by aerobic
- GS; aerobic (anaerobic culture lower yield)
- Inoculate to blood culture bottle
- IDSA suggests: at least 10mL (not swabs of fluid)
- Culture neg but evidence of infection --> suspect fastidious, slow growth, fungi, etc.
28
Peritoneal dialysis associated peritonitis
- Evaluation of dialysis fluid
- Monomicrobic, aerobic
- Agents:
+ GP: Staph, Strep, Coryn
+ GN: E. coli, Klebsiella, Enterobacter
+ Anaerobes, fungi (<10%)
- Culture neg > 20% case
- 10-15mL of dialysate
- Additional test for fastidious & slow growth
29
Secondary peritonitis
- Caused by medical, accidental trauma
- Polymicrobic, anaerobic
- Agents:
+ GNR (ae/ana): Bacteroides, E. coli, Klebsiella
+ GP: Clostridium, Enterococcus, Bifidobacterium, Peptostreptococcus
+ GPC and yeast
- Dx: GS, aerobic/anaerobic culture. Blood culture is not helpful
30
Pleural space infection
- Fluid collected by thoracentesis
- GS, culture: Blood culture increase yield. Cell count, pH, protein, etc
- Community-acquired: S. anginosus group, S. aureus, anaerobes, Strep, Enterobacteria, S. pneumoniae
- HAI: Enterococcus, S. aureus, Strep (anginosus, pneumoniae), anaerobes.
31
Joint infection
- Common agent: S. aureus, Strep
- GNR: neonates, elderly
- Virus: parvovirus B19, rubella, Chikungunya
- Subacute/chronic infection: M. tuberculosis, Borreia burgdorferi, fungi
- Dx: collect synovial fluid --> GS, culture, cell count/diff
32
Prosthetic joint infection
- Knee, hip, shoulder, elbow
- Common: S. aureus, Coag-neg staph, S. epidermidis
- Others: Strep, enterococci, aerobic GNR, anaerobes
- Cutibacterium acnes (shoulder arthroplasty infection)
- Tissue culture: multiple specimens for aerobic, anaerobic culture
- Intraoperative or a combination of preoperative and intraoperative: yield the same organism --> evidence.
33
Intraamniotic infection
- Infection of amniotic fluid, membranes, placenta, etc.
- Migration of cervicovaginal flora thru cervix (polymicrobial: vaginal, enteric)
- Hematogenous spread from maternal bacteremia (monomicrobial: Listeria, S. aureus)
- Genital mycoplasms
- Others: anaerobes (Gardnerella vaginalis, Bacteroides), enteric GNR, Group B Strep
- Dx: clinical fever, elevated WBC, purulent fluid. Confirmed with positive GS, culture, low glucose
34
Hugh-Leifson O/F medium
- Fermenter: produce acid in both conditions (turn yellow)
- Oxidative: acid only in aerobic (turn yellow only opened tube, the other is green)
- Asaccharolytic: no media change (both green)
