Infection and Antibiotics

Infection and Antibiotics

Dale A. Dangleben, James Lee, and Firas Madbak

Test Taking Tip

Familiarize yourself with the table below for wound classification and general indication for antibiotic therapy.


Name factors that influence the development of infection:

Poor approximation of tissue, hematoma/seroma, hypothermia, long operation (>2 hours), excessive local tissue destruction/necrotic tissue, low blood flow, foreign body, dead space, and strangulation of tissues by tight sutures


Most common nosocomial infection:

Urinary tract infection (UTI)

How many colony-forming units (CFUs) are needed on urine culture to confirm a diagnosis of UTI?

>100,000 CFU

Most common nosocomial infection causing death:


Overall most common organism in surgical wound infections:

Staphylococcus aureus

Most common anaerobe in surgical wound infections:

Bacteroides fragilis

When do wound infection classically arise?

Postoperative day 5 to 7

Treatment for a wound infection:

Remove sutures/staples, culture wound, examine to rule out fascial dehiscence, leave wound open and pack, start antibiotics

Bacteria that will cause wound infection and fever within 24 hours after surgery:

Group A β-hemolytic Streptococcus and Clostridium perfringens

Organisms that can cause necrotizing soft tissue infections:

Group A β-hemolytic Streptococcus and Clostridium perfringens

Usual organism to cause necrotizing fasciitis:

Polymicrobial (anaerobes with gram-negative organisms)

Time period to wait before obtaining a CT scan to look for postoperative abscess:

>POD no. 7 (otherwise abscess may look like normal post-op fluid collection)

Findings on CT scan to indicate abscess:

Gas in fluid collection, fibrous ring surrounding fluid collection

Usual initial treatment for intraabdominal abscess:

Percutaneous drainage

Most common bacteria to cause a line infection:

Staphylococcus epidermidis

How many CFUs are needed from a central line culture to indicate line infection?

>15 CFU

In what instance should a central line be changed over a guidewire?

Fever without obvious external signs of infection (catheter tip culture should be sent)

A line changed over a guidewire can be left in place with what catheter tip culture result:

<15 CFU from previous line culture

A line change over a guidewire should be discontinued and a new line should be placed at a new site with this culture result:

>15 CFU from previous line culture

Term for blanching erythema from superficial epidermal/dermal infection:


Name the classic signs and symptoms of infection/inflammation:

Rubor (redness), calor (heat), dolor (pain), tumor (swelling)

Most common pathogen to cause bacterial meningitis in a patient with cerebrospinal fluid rhinorrhea:

Streptococcus pneumoniae

True or false: Prophylactic antibiotics have proven benefit to prevent bacterial meningitis in a patient with cerebrospinal fluid rhinorrhea?

False. Prophylactic antibiotics have shown no proven benefit and may predispose to meninigitis with antibiotic-resistant bacteria.

Empiric treatment for a patient with cerebrospinal fluid rhinorrhea who develops bacterial meningitis:

Vancomycin and an extended-spectrum cephalosporin (ceftriaxone, cefepime, or cefotaxime)

Term for infection/abscess formation in apocrine sweat glands:

Suppurative hidradenitis

Name the locations at which suppurative hidradenitis may occur:

Any site with apocrine glands: axilla, buttocks/perineum, and inguinal area

Most common organism involved in suppurative hidradenitis:

Staphylococcus aureus

What is the treatment for suppurative hidradenitis:

Antibiotics, incision and drainage, excision of skin for chronic infections

Microscopic finding associated with Actinomyces infection:

Sulfur granules

Antibiotic of choice for Actinomyces infection:

Penicillin G


Name clinical situations that require systemic antifungal therapy:

Candida endophthalmitis, osteomyelitis, septic arthritis, and endocarditis, or any patient with a single positive blood culture from an indwelling intravascular catheter

Treatment for mucocutaneous candidiasis:

Local clotrimazole or nystatin

Treatment for Candida isolated from a surgical drain:

Nothing, most likely represents colonization

Mechanism of action of voriconazole:

Prevents the production of ergosterol by acting as a selective inhibitor of the fungal cytochrome P-450 system

Mechanism of action of caspofungin:

Inhibits the synthesis of an essential fungal cell wall component; β-(1-3)-D-glycan

Mechanism of action of amphotericin B:

Increases permeability of the fungal cell membrane by binding ergosterol, which causes leakage of macromolecules and intracellular ions leading to cell death


True or false: Spontaneous bacterial peritonitis (SBP) is usually a polymicrobial infection?

False. SBP is a monomicrobial infection.

Most frequent organism responsible for SBP:

Escherichia coli followed by Klebsiella pneumoniae

True or false: SBP results from translocation of gut flora?

False. It is thought to be from the combination of impaired bactericidal activity of ascitic fluid, abnormal host defense, and intrahepatic shunting, which leads to prolonged bacteremia.

The ascitic fluid protein concentration associated with 10-fold increased risk of SBP:

<1 g/100 mL

Who should be admitted and treated for SBP?

All symptomatic patients with a peritoneal fluid polymorphonuclear count of 250 to 500 cells/μL

Current antibiotic regime for SBP:

Third-generation cephalosporin (cefotaxime)

What does cefotaxime not cover?



Which is the most likely blood-borne organism to be transmitted after a hollow bore needle stick?

Hepatitis B

Recommendation for a nonimmune health care worker exposed to hepatitis B:

Begin hepatitis B vaccination series and give hepatitis B immunoglobulin within 7 days of the exposure

Recommendation for a health care worker vaccinated against hepatitis B but whose immune status is unknown and is exposed to a patient with active hepatitis B infection:

Determine immune status. If anti-hep B antibody–positive—no intervention; If anti-hep B antibody–negative—hep B vaccine booster with hep B immunoglobulin

Aug 13, 2019 | Posted by in ABDOMINAL MEDICINE | Comments Off on Infection and Antibiotics
Premium Wordpress Themes by UFO Themes