Micro Minute 2

Introduction to the bacterium Bartonella henselae, a lesser-known but significant pathogen.
Commonly associated with various diseases in humans, particularly cat scratch disease.

Bartonella is one of the most common genera globally, comprising many recently described species.
Initially recognized for only two pathogenic species at the genus's foundation.
Currently includes many new and emerging human pathogens.
Named after Alberto Leonardo Barton, a Peruvian scientist.

In 1905, Barton identified a unique bacterium during a railway construction outbreak in the Andes.
The species he discovered was not B. henselae but was vital in founding the genus.
The species B. henselae honors Diane Hensel, a technologist who isolated it in the 1980s during an outbreak of bacillary angiomatosis among HIV patients.

B. henselae is a facultative intracellular pathogen, meaning it can replicate within and outside host cells.
Regional lymphadenopathy observed by Debrais in 1931 after cat scratches, leading to the identification of cat scratch disease (CSD).
CSD was further characterized as cat scratch fever, a prominent disease caused by B. henselae.
Confirmed in the 1990s as the cause of CSD through culture from lymph node tissue of patients.

B. henselae is notorious for infecting erythrocytes in cats and lymph nodes in humans.
Biological reservoir: cats and kittens; transmission occurs via scratches or bites and licking open wounds.
CSD is categorized as a zoonotic disease with transmission occurring from animals to humans.
Illustration depicts the life cycle in cats, showing how humans act as incidental hosts.

Cats develop chronic bacteremia, indicating they harbor the bacteria without showing any symptoms.
Despite being asymptomatic, cats can transmit B. henselae to humans through scratches or bites.

Symptoms for infected humans include:
- Bump or blister at the inoculation site.
- Fatigue and fever.
For most individuals, CSD is self-limiting.
High-risk groups:
- Immunocompromised individuals, particularly those with HIV, the elderly, and children.
- Implications for the HIV population include vascular angiomatosis leading to serious complications such as lesions in the brain and bones, with potential fatal outcomes.
The fatality rate is low overall but significantly higher in immunocompromised populations.

Gram-negative microorganism, staining pink/reddish in a Gram stain based on visual perception.
Morphology: primarily rod-shaped; occasionally noted to have a slight curved shape.
Lacks flagella but possesses pili, which are used for twitching motility.
An obligate aerobe, thriving optimally at 37 degrees Celsius, corresponding to human body temperature.
Fastidious grower, requiring specific conditions for laboratory cultivation.
Must grow on chocolate agar supplied with heme for effective growth.
Slow growth rate with a doubling time of approximately three hours, contrasting significantly with faster-growing bacteria like E. coli (20-30 minutes).

B. henselae defined as the causative agent of cat scratch fever, illustrating its relevance in human health, particularly regarding zoonotic transmission and high-risk populations.