Infections in Compromised Host

Question 1

What is a primary vs secondary immune defect? Give an example of each?

Answer 1

Primary - a congenital immune defect
i.e. Chronic granulomatous disease
Secondary - Acquired immune defect
i.e. Neoplasia causing obstruction, or neuropenia

Question 2

Why is a neoplasia causing an obstruction a problem?

Answer 2

I.e. prostate cancer -> prevents draining of urine and gives pathogens a place to live in urethra

Question 3

What can cause neutropenia and what are the most common pathogens we worry about?

Answer 3

Chemotherapy

Cause cause shetting of gut lumen / mucosa as well, allowing P. aeruginosa to invade.

We worry about Pseudomonas, aspergillis, and other opportunistic infections

Question 4

What are the common pathogens at the sites of burn wounds and surgical wounds?

Answer 4

Streptococcus, staphyloccus (normal skin flora)

Question 5

What is the most common pathogen from IV catheters?

Answer 5

Coagulase-negative staphylococci

Question 6

What bacteria cause problems in the setting of biliary tract obstruction, and what is a common complication?

Answer 6

Ascending cholangitis - infection of the bile ducts, often due to malignancies like pancreatic cancer

Bacteria: aerobic gram negative rods, anaerobes, GI enterococci

Question 7

Why is clinical diagnosis of neutropenic patients often difficult, and why is treatment of crucial?

Answer 7

Impaired immune response -> may not form obvious abscesses or have regular signs of infection (inflammatory signs are muted)

Treatment is crucial because the pathogen will disseminate quickly in the immunocompromised

Question 8

What is a typical empiric treatment regimen for neutropenic patients?

Answer 8

Must cover P. aeruginosa

Piperacillin/tazobactam or cefepime or imipenem

PLUS

Aminoglycoside like tobramycin

Question 9

Why is empiric use of vancomycin for neutropenic patients discouraged?

Answer 9

Pathogens are generally of lower immediate virulence -> can use in catheter-associated infection or proven gram + infection

Do not want to cause more resistance

Question 10

What is the most common form of antibody deficiency?

Answer 10

CVID - Common Variable Immunodeficiency - Leads to deficiency in Ig antibodies due to lack of T-cell activation of B ells

Question 11

What is the most important cause of a secondary defective in adaptive immunity?

Answer 11

Malnutrition, especially protein-energy malnutrition, as in kwashiorkor or marasmus

Question 12

What are four major immune defects associated with susceptibility to encapsulated organisms?

Answer 12

1. Multiple myeloma
2. Chronic lymphatic leukemia
3. Waldenstrom’s macroglobulinemia
4. Sickle cell disease

Question 13

What diseases cause defects in Cell-mediated immunity?

Answer 13

Hodgkin’s lymphoma, non-Hodgkin’s lymphoma, Chronic Lymphatic Leukemia (same as B cell), hairy cell leukemia.

Question 14

Why is CMI deficiency bad?

Answer 14

CMI is involved in a much wider array of pathogens than just encapsulated ones, and can lead to chronic opportunistic infections

Question 15

What are the 3 key pathogens of concern in humoral immune deficiency syndromes?

Answer 15

Encapsulated pyogenic bacteria

1. S. pneumoniae
2. H. influenzae
3. N. meningitidis

Question 16

Other than primary deficiencies, what else can cause defects in CMI?

Answer 16

Cytotoxic chemotherapy, corticosteroids, radiation, transplantion immunosuppression