Blood Infections and Related Topics

Blood organisms can enter the bloodstream in various ways.
Transient presence without growth is called bacteremia.
- Brushing teeth or tooth extraction can cause bacteremia.
- Prophylactic antibiotics are sometimes given before exploratory surgeries.

Osteomyelitis (bone infection due to Staph aureus) can cause intermittent bacteremia and fever.
Damaged heart lining can lead to endocarditis.
Urinary catheterization commonly causes bacteremia.
Damaged tissue is susceptible to infection due to compromised immunity.
Septic arthritis is common in the elderly; joint warmth is a key sign and a medical emergency due to potential bone destruction.

Normal heart valves close tightly, producing clear heart sounds.
Damaged heart valves may not close properly, leading to a heart murmur (whooshing sound).

Prior strep pyogenes throat infections can result in antibodies that attack host tissue.
This can cause rheumatic fever, leading to inflammation and damage of heart valves.
Damaged valves are prone to colonization by low-virulence organisms, causing infectious endocarditis.
Infectious endocarditis often presents with low-grade, intermittent fevers.
The mouth is a common source of organisms causing infectious endocarditis.
Bacteremia can occur during tooth brushing or eating; organisms may settle on damaged heart valves.

Eric, a renal unit patient, presented with low-grade fever, malaise, anorexia, and weight loss.
Differential diagnosis included cancer, but the absence of respiratory symptoms and bowel changes made it less likely.
Examination revealed a slightly raised temperature and extensive gum disease.
A heart murmur indicated valve disease.
Eric was found to have Staph epidermidis in his bloodstream, likely infecting his heart valves.

Septicemia occurs when organisms actively grow in the bloodstream, leading to sepsis (a life-threatening condition).
Lymphangitis: A red streak extending from a wound towards the lymphatics suggests lymphatic spread.
Inflammation in the lymphatic is visible as a red line.
Enlarged lymph node may be palpable.

Common in catheterized patients, those with pneumonia or surgical wounds, and ICU patients.
Identifying the source of the organism is crucial.
- E. coli: Consider urinary tract infection (UTI).
- Staph aureus: Look for surgical wound infection.
- Strep pneumoniae: Check for pneumonia via chest X-ray.
- Pseudomonas: Suspect ventilator-associated infection in ICU patients.

Mortality is generally higher in Gram-negative sepsis due to endotoxin in the cell wall, which triggers a strong inflammatory response.
Gram-positive organisms also cause mortality due to molecules like lipoteichoic acid, which can cause inflammation.

Surgical wound infection: Staph aureus.
Urinary catheter: E. coli, but also consider other Gram-negatives like Klebsiella.
Ventilator-associated pneumonia: Pseudomonas (prefers plastic and humidified air).
Eric's case: Staph epidermidis biofilm on IV line used for renal dialysis, which spread to his heart valves.