Bacterial Infections Flashcards
Sources of osteomyelitis
hematogenous
contiguous
trauma, fx or surgery
Hematogenous - OA
spread through the blood (infection elsewhere in the body)
monomicrobial monomicrobial
Staphylococcus aureus
Contiguous - OA
Puncture wound, foot ulcer (concern with diabetes)
Infection is adjacent or near a bone
Polymicrobial: Gram + cocci, Gram – rods, anaerobes
Trauma, fx, or surgery
nosocomial infection
S. aureus
Risk factors of OA
-Diabetics Foot injury -Surgery -Artificial surfaces Joints Screws -IV drug users
Sx of OA
-Fever - develops in infection are hematogenous
-Chills
-Fatigue
-Localized pain** e.g. pt with hip replacement
-Inflammation (redness, swelling, heat, and pain)
-Infection due to trauma:
Purulent drainage from wound = cloudy and pus
Dx of OA
Blood sample:
Gram stain & culture (grow it)
Positive identification in about 50% of cases*
CBC: increase in WBC
ESR (erythrocyte sedimentation rate): increased
take DRAINAGE
Bone Biopsy: Gram stain & culture
Imaging- what it looks like but won’t tell you how to tx
Ab sensitivity test
what antibiotic the bacteria is sensitive to
NEED TO KNOW FOR MRSA
Tx of OA
Drainage- want this to have the infection out
Debridement- scrape out infection as possible
Surgery-
Long term IV antibiotics
Long term IV tx for OA
6 wks to 2 months
IV line
S. aureus -nafcillin -oxacillin MRSA -vanco
Staph a.
Most common cause of osteomyelitis
- hematogenous
- contiguous
- trauma/fracture/surgery
opportunistic pathogen
nosocomial infection
-device related
-postsurgical complications
Stap A. characteristics
gram-positive cocci gram stain - purple grape like clusters catalase + Coagulase +
why is biofilm important in OA?
allows it to attach to the surface
- difficult to grow in culture
- microbial community attached to a surface
- encased exopolysaccharide matrix or glycocalyx
- highly resistant to antibiotics and immune system
Heart valves and teeth
biofilm can attach to these surfaces
best tx of biofilm
debridement
replacement of the prosthetic
tx with antibiotics
GET RID OF BIOFILM right away!!!!
MRSA
- Methicillin Resistant Staphylococcus aureus
- mecA gene encodes PBP2a (pencillin-binding protein)
- Methicillin (beta lactams) can not bind to PBP2a, cell wall synthesis is not inhibited.
DOC for MRSA
vanco
staph a and enterotoxin
affect GI system
P. aeruginosa - OA
IV drug use
Puncture wounds
Characteristics of P. aeruginosa
Gram-negative rod Highly antibiotic resistant Characteristic color Characteristic sweet, grape like odor Forms a biofilm Alginate capsule
Pott’s disease
OA caused by TB
OA caused by salmonella
in children with sickle cell anemia
Reactive arthritis
autoimmune condition due to an infection at a different location in the body.
no infection present at the joint
due to infection somewhere else in the body
Reiter’s syndrome
classic reactive arthritis TRIAD: 1. inflammation of joints, polyarticular, knee 2. conjunctivitis 3. urethritis/cervicitis
Pathogens assoc. with Reactive arthritis
Usually presents 2-4 weeks after primary infection.
GI infection
Examples: Campylobacter jejuni, Salmonella, Shigella and Yersinia
STD:
Chlamydia- urethritis/cervicitis/conjuctivitis
Disease association to reactive arthritis
HLA-B27
Septic arthritis
inflammation due to infection of the joint. (suppurative, purulent, infectious)
pus-producing organism
synovial fluid will be cloudy - infection
pathogens involved in septic arthritis
gonococcal
nongonococcal
Sources of infection
Hematogenous
Contiguous- near the joint
Direct inoculation- antiinflammatory injection (unclean)
Joints affected in septic arthritis
knee 40-50%
hip 20-25%
ankle/shoulder/elbow 10-15%
wrist 10%
Risk factors for septic arthritis
History of arthritis Prosthetic joint - 2-10% of all recipients Gonorrhea Trauma Immunosuppressed IV drug users
Symptoms
Fever Joint pain -monoarticular -polyarticular- may be traveling Inflammation Limitation of movement- can't move joint
Dx for septic arthritis
Patient history very important: gonorrhea, any issues at the joint? Joint Fluid -Gram stain -Culture CBC: increase in neutrophils ESR CRP Imaging Techniques
Septic Arthritis : Gonorrhea
Neisseria gonorrhoeae -sexually transmitted Most common cause of septic arthritis in young, sexually active adults Gram negative, diplococci**** Fastidious Thayer-Martin Chocolate agar********* Pili: Attachment, Antigenic variation
Thayer-Martin Chocolate Agar
blood is lysed to release heme
Ab added to help niserria grow
Gonorrhea vs. stap a.
Most common cause of septic arthritis in young, sexually active adults
Other than this population=> think stap a.
Gonococcemia
spreading through blood stream
why in females > males (1-3% of women, lower for men)?
=> women tend to be asymptomatic for gonorrhea
Migratory joint - Gonoccemia
polyarticular
different joints at different times
SA - Early prosthetic joint infections!
<3 months
staph a.
SA - Delayed infection of prosthetic joint
>3 months
CoNs
-coagulase negative stapyloccocus e.g. staph epidermis
Staph a. - Septic arthritis
nongonoccocal
Adults
Children > 2 years old
Monoarticular
Other Nongonococcal pathogens- SA
Steptococcus sp.
P. aeruginosa - IV drug users
Gonorrhea in women - complication
PID
infertility
Staph. a. no culture
why no growth ? biofilm
SA - Lyme Disease
Pathogen: Borrelia burgdorferi
Early: bull’s eye rash
Disseminated: pain in joints, bones and muscles
Late: recurring arthritis, large joints
60-80% of untreated individuals develop arthritis
Tx of SA
Rapid destruction of the joint Drainage of infected joint Antibiotics Several weeks IV Gonococcal: ceftriaxone S. aureus: nafcillin or oxacillin MRSA: vancomycin
Surgery related SA
Prosthetic
—Tx: Surgery to replace joint + 6 weeks IV antibiotics
