All of the following organisms are included in the HACEK group, EXCEPT:

Appeared in: DSSSB October 2024

Explanation

Ehrlichia chaffeensis is not part of the HACEK group of bacteria.
It is an obligate intracellular, gram-negative bacterium transmitted by the lone star tick (Amblyomma americanum).
This pathogen is the causative agent of human monocytic ehrlichiosis, an acute, febrile, tick-borne illness.

Option B: Cardiobacterium hominis is a member of the HACEK group, representing the 'C' in the acronym.
Option C: Kingella kingae is a member of the HACEK group, representing the 'K' in the acronym.
Option D: Haemophilus species are members of the HACEK group, representing the 'H' in the acronym.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Identification of organisms belonging to the HACEK group as background academic context rather than a clinical decision trigger.
HACEK organisms are a significant cause of culture-negative infective endocarditis. Nurses should be aware that blood cultures for patients with suspected endocarditis may need prolonged incubation to detect these slow-growing organisms.
A patient history of recent dental procedures, poor dentition, or presence of prosthetic heart valves increases suspicion for HACEK endocarditis.
What if? If a patient with fever of unknown origin and a new heart murmur has blood cultures that are negative after 48 hours, the nurse should anticipate the healthcare provider will consider HACEK organisms and may request the lab to hold the cultures for an extended period (though modern systems often detect them sooner).

How to Approach the Question

First, identify the core subject of the question, which is the 'HACEK group' of organisms.
Note the keyword 'EXCEPT'. This means you are looking for the option that does not belong to the group.
Recall the mnemonic HACEK and the organisms it represents: Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, and Kingella.
Systematically evaluate each option against the mnemonic.
Cardiobacterium hominis ('C'), Kingella kingae ('K'), and Haemophilus species ('H') are all part of the HACEK group.
Ehrlichia chaffeensis does not fit the mnemonic and is therefore the correct answer.

Concept Tested & Keywords

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E6 Medicine Harrison 22e Part 1 p. 1307-1309

Practise the full DSSSB October 2024

Attempt every question from this paper in a timed mock, then review the full solution for each one.