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Cutibacterium acnes

life science Maturity 11-13 Next article →

*Cutibacterium acnes* is a type of bacterium that lives on human skin. It is a gram-positive, rod-shaped bacterium that grows relatively slowly. This organism is mostly commensal, meaning it lives on healthy people without causing harm. It is a major part of the normal skin flora found on most adults. However, it is also linked to several medical conditions. The most common is acne vulgaris, a chronic inflammatory disease.

Comedo acne 0001
Comedo acne 0001

These bacteria live primarily deep within the hair follicles and pores. To survive, they need specific nutrients to produce energy. They mostly eat fatty acids found in sebum, which is an oil produced by sebaceous glands. They also use cellular debris and metabolic byproducts from surrounding skin tissue. When sebaceous glands become hyperactive, they produce more sebum. This process is called sebaceous hyperplasia. If a follicle becomes blocked, the bacteria can grow and multiply very quickly.

As *C. acnes* grows, it performs several complex biological tasks. The bacteria secrete many proteins, including several digestive enzymes. These enzymes help the bacteria digest sebum to acquire nutrients. They can also destabilize the layers of cells that form the follicle walls. The rapid growth of the bacteria produces metabolic byproducts and bacterial debris. This buildup can trigger inflammation in the skin. This inflammation leads to the symptoms of acne and folliculitis.

Scientists have changed the name of this bacterium several times. It was originally identified as *Bacillus acnes*. Later, it was named *Propionibacterium acnes* because it generates propionic acid. In 2016, researchers reclassified it again due to new genomic studies. They used DNA G + C content and phylogenetic tree structures to distinguish it. This led to the creation of the new genus *Cutibacterium*. This new group includes species formerly known as *P. avidum* and *P. granulosum*.

Acne is a massive global health issue. It affects approximately 650 million people around the world. In the United States, more than 45 million individuals are affected. About 20% of all dermatologist visits are for acne-related issues. The bacteria often begin to colonize the skin 1 to 3 years before puberty. During puberty, the bacteria grow exponentially. This is why many teenagers and young adults experience breakouts. Doctors often treat this with antibiotics like erythromycin or doxycycline.

However, the bacteria are becoming harder to treat. Antibiotic resistance is a growing problem in North America and Europe. In 1979, resistance was at 20%, but it rose to 64% by the year 2000. Because of this, doctors often combine antibiotics with benzoyl peroxide. Some patients with severe acne use isotretinoin. Other treatments include salicylic acid, which is derived from white willow bark. Salicylic acid can reduce lipid synthesis in sebocytes, the cells that make sebum.

*C. acnes* can also be found in unexpected places. It has been found in the gastrointestinal tract and even in plants. A specific subtype called *Zappae* lives inside grapevines. This subtype diverged from human strains about 7,000 years ago. In humans, the bacteria can sometimes cause other problems. It is a common cause of endophthalmitis after cataract surgery. It has also been found in herniated discs and is linked to certain bone and eye conditions.

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File:Comedo acne 0001.jpg
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