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Questions and Answers
What is the most common route of entry for bacteremia?
Which of the following percentages represents the occurrence of bacteremia through abscesses?
What is a primary consequence of intravenous catheters?
What defines the intraluminal spread route of IV catheter-associated bacteremia?
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Which percentage is associated with surgical wound infections as a portal of entry for bacteremia?
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What is the definition of health care–acquired bloodstream infections (HA-BSIs)?
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Which type of bloodstream infection is associated with infections that develop before a patient is admitted to a healthcare facility?
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Which of the following can lead to the entry of bacteria into the bloodstream during transient bacteremia?
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What distinguishes extravascular bloodstream infections from intravascular bloodstream infections?
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Which of the following is NOT a major group of microbes that can be present during bloodstream infections?
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Study Notes
Bloodstream Infections
- Bloodstream infections (BSIs) are classified into two types:
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Health care–acquired BSIs (HA-BSIs): Infections occurring in a hospital or healthcare facility after 48 hours of admission.
- Include device-associated infections (DAIs) like central line-associated bloodstream infections (CLA-BSIs).
- Community-acquired bloodstream infections (CA-BSIs): Infections occurring outside of healthcare settings or within 2 days of admission.
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Health care–acquired BSIs (HA-BSIs): Infections occurring in a hospital or healthcare facility after 48 hours of admission.
- BSIs can be caused by various microorganisms, including bacteria, fungi, viruses, and parasites.
Bacteremia
- Bacteremia: Presence of bacteria in the bloodstream
- Can be transient, continuous, or intermittent.
- Transient bacteremia is often asymptomatic and caused by procedures involving non-sterile sites (e.g., dental procedures).
- Common portals of entry for bacteremia include:
- Genitourinary tract (25%)
- Respiratory tract (20%)
- Abscesses (10%)
- Surgical wound infections (5%)
- Biliary tract (5%)
Intravenous Catheter-Associated Infections
- Intravenous catheters (IVs) are commonly used in hospitalized patients for fluid, medication, and nutrition administration.
- Catheter colonization (bacteria or fungi) leads to infections and serious BSIs.
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IV catheter-associated bacteremia (or fungemia) occurs through two routes:
- Extraluminal spread: Organisms travel from the catheter entry site through the skin to the catheter tip.
- Intraluminal spread: Organisms migrate along the inside of the catheter to the catheter tip.
- The most common etiologic agents for IV catheter-associated BSIs are skin-dwelling organisms.
Fungal Bloodstream Infections
- Fungemia: Presence of fungi in the blood.
- Commonly occurs in immunosuppressed patients and those with serious illnesses.
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Candida albicans is the most common species causing fungal BSIs.
- Part of the normal flora in mucous membranes, but can become pathogenic in compromised individuals.
Candida spp.
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Candida albicans:
- A species within the genus Candida.
- Can exist as yeast, pseudohyphae, or hyphae depending on the environment.
- Is a significant opportunistic pathogen, responsible for many fungal infections.
- Pseudohyphae: Elongated yeast cells attached to one another, resembling hyphae.
- True hyphae: Long, tube-like structures with parallel sides, without constrictions.
- Candida spp. are the fourth most common cause of hospital-acquired BSIs in the United States, with a mortality rate of up to 50%.
- Other species include Candida glabrata, Candida parapsilosis, Candida tropicalis, and Candida krusei.
Pathophysiology of Invasive Candidiasis
- Adherence to surfaces: Candida albicans begins by adhering to surfaces before infection.
- Protease production: Candida albicans produce proteases, enhancing their ability to invade tissues.
- Phenotypic switching: Candida albicans can transition between different forms (yeast, pseudohyphae, and hyphae), promoting infection.
- Biofilm formation: Candida spp. form biofilms (extracellular polysaccharide material) that facilitate hematogenous spread and antibiotic resistance.
Diagnostic Techniques
- Blood culture: The gold standard for diagnosing invasive candidiasis.
- Drug susceptibility testing: Determines the effectiveness of antifungal drugs.
Management of Invasive Candidiasis
- Source control: Eliminating the source of infection (e.g., removing contaminated catheters, draining infected fluids).
- Early effective systemic antifungal treatment: Timely administration of antifungal medication.
References
- Pappas, P.G. et al. (2018). Invasive candidiasis. Nature Reviews Disease Primers doi:10.1038/nrdp.2018.26
- M. Tille, Patricia. "Bailey & Scott’s Diagnostic Microbiology Fourteenth Edition.” (2017), Chapters 62 & 67
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Description
This quiz covers the definitions and classifications of bloodstream infections (BSIs), including healthcare-acquired and community-acquired types. It delves into the causes, such as various microorganisms, and examines the concepts of bacteremia along with its different forms. Test your knowledge on this critical area of infectious disease management.
