Global InformationPathogenic bacteria information
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| Neisseria gonorrhoeae (small red dots) in pus from a man with a urethral discharge (Gram stain) |
Pathogenic bacteria are bacteria that can cause disease.[1] This article focuses on the bacteria that are pathogenic to humans. Most species of bacteria are harmless and are often beneficial but others can cause infectious diseases. The number of these pathogenic species in humans is estimated to be fewer than a hundred.[2] By contrast, several thousand species are part of the gut flora present in the digestive tract.[citation needed]
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. The blood and tissue fluids contain nutrients sufficient to sustain the growth of many bacteria. 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.
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. 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. 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. In many cases, it is important to differentiate infection and colonization, which is when the bacteria are causing little or no harm.
Caused 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.[4] Pathogenic bacteria contribute to other globally important diseases, such as pneumonia, which can be caused by bacteria such as Staphylococcus, Streptococcus and Pseudomonas, and foodborne illnesses, which can be caused by bacteria such as Shigella, Campylobacter, and Salmonella. Pathogenic bacteria also cause infections such as tetanus, typhoid fever, diphtheria, syphilis, and leprosy.
Pathogenic bacteria are also the cause of high infant mortality rates in developing countries.[5] A GBD study estimated the global death rates from (33) bacterial pathogens, finding such infections contributed to one in 8 deaths (or ~7.7 million deaths), which could make it the second largest cause of death globally in 2019.[6][3]
Most pathogenic bacteria can be grown in cultures and identified by Gram stain and other methods. Bacteria grown in this way are often tested to find which antibiotics will be an effective treatment for the infection. For hitherto unknown pathogens, Koch's postulates are the standard to establish a causative relationship between a microbe and a disease.
- ^ Ryan, Kenneth J.; Ray, C. George; Ahmad, Nafees; Drew, W. Lawrence; Lagunoff, Michael; Pottinger, Paul; Reller, L. Barth; Sterling, Charles R. (2014). "Pathogenesis of Bacterial Infections". Sherris Medical Microbiology (6th ed.). New York: McGraw Hill Education. pp. 391–406. ISBN 978-0-07-181826-1.
- ^ McFall-Ngai, Margaret (2007-01-11). "Adaptive Immunity: Care for the community". Nature. 445 (7124): 153. Bibcode:2007Natur.445..153M. doi:10.1038/445153a. ISSN 0028-0836. PMID 17215830. S2CID 9273396.
- ^ a b Ikuta, Kevin S.; Swetschinski, Lucien R.; Aguilar, Gisela Robles; Sharara, Fablina; Mestrovic, Tomislav; Gray, Authia P.; Weaver, Nicole Davis; Wool, Eve E.; et al. (21 November 2022). "Global mortality associated with 33 bacterial pathogens in 2019: a systematic analysis for the Global Burden of Disease Study 2019". The Lancet. 400 (10369): 2221–2248. doi:10.1016/S0140-6736(22)02185-7. ISSN 0140-6736. PMC 9763654. PMID 36423648.
- ^ "Tuberculosis (TB)". www.who.int.
- ^ Santosham, Mathuram; Chan, Grace J.; Lee, Anne CC; Baqui, Abdullah H.; Tan, Jingwen; Black, Robert E. (2013). "Risk of Early-Onset Neonatal Infection with Maternal Infection or Colonization: A Global Systematic Review and Meta-Analysis". PLOS Medicine. 10 (8): e1001502. doi:10.1371/journal.pmed.1001502. ISSN 1549-1676. PMC 3747995. PMID 23976885.
- ^ Hou, Chia-Yi (23 November 2022). "Bacterial infections linked to 1 in 8 deaths in 2019". The Hill. Retrieved 12 December 2022.