Global number of deaths (A) and YLLs (B), by pathogen and GBD super-region, 2019 Ĭaused by Mycobacterium tuberculosis bacteria, one of the diseases with the highest disease burden is tuberculosis, which killed 1.4 million people in 2019, mostly in sub-Saharan Africa. In many cases, it is important to differentiate infection and colonization, which is when the bacteria are causing little or no harm. In some rare cases a pathogenic microbe can infect an entirely healthy person, but infection usually occurs only if the body's defence mechanisms are damaged by some local trauma or an underlying debilitating disease, such as wounding, intoxication, chilling, fatigue, and malnutrition.
#Bacterial phenomena symptoms skin
Some pathogens invade only the surface epithelium, skin or mucous membrane, but many travel more deeply, spreading through the tissues and disseminating by the lymphatic and blood streams. Pathogenic bacteria are specially adapted and endowed with mechanisms for overcoming the normal body defences, and can invade parts of the body, such as the blood, where bacteria are not normally found. The body has defence mechanisms that enable it to resist microbial invasion of its tissues and give it a natural immunity or innate resistance against many microorganisms. The blood and tissue fluids contain nutrients sufficient to sustain the growth of many bacteria. The body is continually exposed to many species of bacteria, including beneficial commensals, which grow on the skin and mucous membranes, and saprophytes, which grow mainly in the soil and in decaying matter.
By contrast, several thousand species are part of the gut flora present in the digestive tract. The number of these pathogenic species in humans is estimated to be fewer than a hundred. Most species of bacteria are harmless and are often beneficial but others can cause infectious diseases.
This article focuses on the bacteria that are pathogenic to humans. Pathogenic bacteria are bacteria that can cause disease.
Neisseria gonorrhoeae (small red dots) in pus from a man with a urethral discharge ( Gram stain)
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