Infection Flashcards
Hematogenous Osteomyelitis in (adults/children) occurs in the Metaphysis because
Children; hairpin turns of metaphyseal blood vessels slow blood flow, allowing bacteria to grow
Hematogenous Osteomyelitis in (adults/children) occurs in vertebral bodies and joints
Adults (no physeal barrier)
In children, the growth plate (physis) will serve as a barrier to infection, but even before skeletal maturity, Acute Osteomyelitis CAN spread to which select joints
Ankle (distal Fibula)
Elbow (Radial neck)
Shoulder (proximal Humerus)
Hip (proximal Femur)
*note that ALL are sites of RAPIDLY growing physes
Clinical presentation of hematogenous osteomyelitis
Pain/tenderness
Fever
Elevated ESR and CRP
Radiographic findings of osteomyelitis
- periosteal elevation/luncency
- Usually at major joints
- Takes 1-2 weeks to show changes on x-ray
What are the common causative organisms of osteomyelitis?
- Native joints: Staph aureus (gram +, catalase +, coagulase +)
- Implant joints: Staph epi (gram+, catalase +, coagulase -)
- Sickle cells: Salmonella (gram -)
Bacterial inoculation of rapidly growing joints (Hips and Knees) due to high blood supply, and thus increased possibility for bacterial seeding; Sternoclavicular joint can also be affected in IV drug users
Infectious (Septic) Arthritis
How is septic arthritis diagnosed?
- Exam findings: red, swollen, painful joint
- Joint aspiration
- WBC >50,000
- High PMN %
Tx for septic arthritis
surgical (irrigation & debridement; hip replacement)
What are the common causative organisms of septic arthritis?
- Staph aureus
2. Neisseria gonorrhoaea
What are the common causative organisms of prosthetic joint infection?
- staph. epidermidis (coag -)
2. P. acnes (only in shoulder replacement)
What algorithm can you use to evaluate aspirated synovial fluid in the setting of Joint Pain?
1) Blood? Yes (trauma, coagulopathy, tumor.) or No (next step)
2) If no, WBC >2K? Yes (inflammatory arthritis or septic arthritis (WBC >20K)) or No (trauma, osteoarthritis, AVN)
3) If yes to #2, test for crystals (rule out gout)
Pertinent Gram-negative ZOONOTIC rods for MSK infections
Brucella
Francisella
Pasteurella
Bartonella
“-ellas”
Pertinent Gram-positive ZOONOTIC rod for MSK infections
Bacillus anthracis
gram - zoonotic (cow, sheep, goat) rod transmitted through ingestion of contaminated milk (unpasteurized) or skin (butchering products)
Brucella
Brucella is facultative intracellular bacteria that survives within_____ and forms ______
macrophages; granulomas
What are the clinical and lab findings of brucella infection?
- Fever
- General Lymphadenopathy
- Splenomegaly
- Sacroiliac joint tenderness (lower back pain)
- Elevated WBCs, PMNs
- Elevated liver enzymes
gram - zoonotic (rabbit, deer) rod transmitted by ticks/flies or cutaneous exposure to animal tissue
Francisella tularensis
F. tularensis has a very low infectious dose and therefore can be a potential
bioterrorism agent
What are the clinical and lab findings of tularemia?
- Fever
- Non-healing ulcerated lesion
- Painful axillary lymphadenopathy
- Elevated WBCs, PMNs
- NORMAL liver enzymes
F. Tularensis grows within_____ and forms ______
macrophages; granulomas
Zoonotic bacteria associated with Granuloma formation
Brucella
Francisella tularensis
Treatment for Brucella and F. tularensis
Doxycycline, Streptomycin
gram - zoonotic (dogs, cats) rod transmitted by dog or cat bites; associated with complications such as osteomyelitis, endocarditis, meningitis); commonly seen in immunocompromised/diabetic patients
Pasteurella multocida
Zoonotic bacteria associated with bipolar staining (its core stains lighter than the edges) of capsule and no growth on MacConkey Agar
Pasteurella multocida
gram - zoonotic (cats) rod transmitted by cat scratches/bites; low virulence so usually self-limited
Bartonella henslea
Clinical findings of Bartonella infection
- fever
- Lymphadenopathy along scratch
Clinical finding for Bartonella in Immunocompromised hosts (AIDS)
Bacillary angiomatosis
Gram-positive zoonotic rod; SPORE-FORMING; human infection acquired via cutaneous exposure, inhalation/ingestion
Bacillus anthracis
What cutaneous disease is caused by Bacillus anthracis?
Pigmented eschar (scab) or necrotic lesion
What inhalation disease is caused by Bacillus anthracis?
Wool-sorters’ disease (hemorrhagic mediastinitis, pleural effusions, septic shock)
A SPIROCHETE bacteria that is transmitted by black-legged TICKS in spring/summer; causes lyme disease (borreliosis)
Borrelia burgdorferi
Symptoms/clinical presentation of lyme borreliosis
- Fever, chills
- ERYTHEMA MIGRANS (Bulls-eye rash)
- Facial palsy
- arthritis/joint pain
- swollen knee
How to diagnose Lyme Disease
ELISA
Western Blot
Treatment for Lyme Disease
Doxycycline
Amoxicillin
Which zoonotic bacteria are associated with ticks
Francisella tularensis
Borrelia burgdorferi
+ssRNA enveloped viruses that cause Dengue infection; insect-borne (mosquitoes)
Flavivirus
Severe fever illness with rash and “breakbone fever” (severe muscle/joint pain that feels like a broken bone); acute but self-limiting
Dengue Fever
Progression of Dengue fever; causes hemorrhagic shock
Dengue Hemorrhagic Fever
How does an infection of a DIFFERENT Dengue serotype result in a worsening of symptoms
Antibodies to the previous serotype DON’T neutralize the different serotype–> Activation of complement –> cytokine storm–> Shock and Hemorrhage
Zika and yellow fever viruses are what type of viruses?
flaviviruses
Coagulase-negative Staphylocci
S. epidermidis
S. saprophyticus
Coagulase-positive Staphylocci
S. aureus
S. aureus shows as ___________ on Mannitol Salt Agar
Gold/yellow
Findings of normal synovial fluid
- Clear
- <200 PMNs
- glucose levels equal to that in blood
Findings of synovial fluid during infection
- Cloudy
- > 20,000 PMNs
- 1/4 glucose level of blood
Findings of normal synovial fluid in rheumatoid arthritis
- Opalescent (less cloudy)
- 200-20,000 PMNs
- 1/2 glucose level of blood
Form of TB that occurs outside the lungs whereby disease is seen in the vertebrae, a kind of tuberculous arthritis of the intervertebral joints
Pott’s disease (aka. Spinal TB)
Gram-negative rod in GI tract; Lactose negative and H2S producer; Typhoid and Non-Typhoid species; can seed in bone marrow of SICKLE CELL patients early in childhood
Salmonella
IV drug use, catheters, open fractures, and sickle cell disease are risk factors of
Osteomyelitis