Serratia is a genus of Gram-negative, facultatively anaerobic, rod-shaped bacteria of the family Yersiniaceae. According to the List of Prokaryotic names with Standing Nomenclature (LPSN), there are currently 19 species of Serratia that are credibly published with accurate names as of 2020: S. aquatilis, S. entomophila, S. ficaria, S. fonticola, S. grimesii, S. liquefaciens, S. marcescens, S. microhaemolytica, S. myotis, S. nematodiphila, S. odoriferae, S. oryzae, S. plymuthica, S. proteamaculans, S. quinivorans corrig, S. rubidaea, S. symbiotica, S. ureilytica, S. vespertilionis. They are typically 1–5 μm in length, do not produce spores, and can be found in water, soil, plants, and animals. Some members of this genus produce a characteristic red pigment, prodigiosin, and can be distinguished from other members of the order Enterobacterales by their unique production of three enzymes: DNase (nucA), lipase, and gelatinase (serralysin). Serratia was thought to be a harmless environmental bacteria until it was discovered that the most common species in the genus, S. marcescens, is an opportunistic pathogen of many animals, including humans. In humans, S. marcescens is mostly associated with nosocomial, or hospital-acquired, infections, but can also cause urinary tract infections, pneumonia, and endocarditis. S. marcescens is frequently found in showers, toilet bowls, and around wet tiles as a pinkish to red biofilm but only causes disease in immunocompromised individuals. Aside from S. marcescens, some rare strains of the Serratia species S. plymuthica, S. liquefaciens, S. rubidaea, and S. odoriferae have been shown to cause infection such as osteomyelitis and endocarditis.
Aeromonas is a genus of Gram-negative, facultative anaerobic, rod-shaped bacteria that morphologically resemble members of the family Enterobacteriaceae. Most of the 14 described species have been associated with human diseases. The most important pathogens are A. hydrophila, A. caviae, and A. veronii biovar sobria. The organisms are ubiquitous in fresh and brackish water.
Aeromonas veronii is a Gram-negative, rod-shaped bacterium found in fresh water and in association with animals. It can be a pathogen of humans and a beneficial symbiont of leeches. In humans A. veronii can cause diseases ranging from wound infections and diarrhea to sepsis in immunocompromised patients. Humans treated with medicinal leeches after vascular surgery can be at risk for infection from A. veronii and are commonly placed on prophylactic antibiotics. Most commonly ciprofloxacin is used but there have been reports of resistant strains leading to infection. In leeches, this bacterium is thought to function in the digestion of blood, provision of nutrients, or preventing other bacteria from growing.
Elizabethkingia meningoseptica is a Gram-negative, rod-shaped bacterium widely distributed in nature. It may be normally present in fish and frogs; it may be isolated from chronic infectious states, as in the sputum of cystic fibrosis patients. In 1959, American bacteriologist Elizabeth O. King was studying unclassified bacteria associated with pediatric meningitis at the Centers for Disease Control and Prevention in Atlanta, when she isolated an organism that she named Flavobacterium meningosepticum. In 1994, it was reclassified in the genus Chryseobacterium and renamed Chryseobacterium meningosepticum(chryseos = "golden" in Greek, so Chryseobacterium means a golden/yellow rod similar to Flavobacterium). In 2005, a 16S rRNA phylogenetic tree of Chryseobacteria showed that C. meningosepticum along with C. miricola were close to each other but outside the tree of the rest of the Chryseobacteria and were then placed in a new genus Elizabethkingia named after the original discoverer of F. meningosepticum.
Aeromonas salmonicida is a pathogenic bacterium that severely impacts salmonid populations and other species. It was first discovered in a Bavarian brown trout hatchery by Emmerich and Weibel in 1894. Aeromonas salmonicida's ability to infect a variety of hosts, multiply, and adapt, make it a prime virulent bacterium. A. salmonicida is an etiological agent for furunculosis, a disease that causes sepsis, haemorrhages, muscle lesions, inflammation of the lower intestine, spleen enlargement, and death in freshwater fish populations. It is found worldwide with the exception of South America. The major route of contamination is poor water quality; however, it can also be associated stress factors such as overcrowding, high temperatures, and trauma. Spawning and smolting fish are prime victims of furunculosis due to their immunocompromised state of being.
Cupriavidus pauculus is a Gram-negative, nonfermentative, motile bacterium of the genus Cupriavidus and family Burkholderiaceae isolated from water from ultrafiltration systems and bottled mineral water. C. pauculus is associated with human infections.
Aeromonas australiensis is a Gram-negative, anaerobic bacterium from the genus Aeromonas isolated from an irrigation water system in Western Australia.
Aeromonas bivalvium is a Gram-negative, oxidase- and catalase-positive, motile bacterium with a polar flagellum of the genus Aeromonas isolated from bivalve molluscs.
Aeromonas diversa is a Gram-negative, facultative anaerobic bacterium of the genus Aeromonas isolated from the leg wound of a patient in New Orleans.
Aeromonas encheleia is a Gram-negative, motile bacterium of the genus Aeromonas isolated from European eels in Valencia, Spain.
Aeromonas eucrenophila is a Gram-negative bacterium of the genus Aeromonas isolated from fresh water and infected fish. A. eucrenophila is a pathogen of fish, and it causes diarrhoea in humans.
Aeromonas fluvialis is a Gram-negative, oxidase- and catalase-positive, facultatively anaerobic, non-spore-forming bacterium of the genus Aeromonas isolated from water from the Muga River in Girona in northeastern Spain.
Aeromonas molluscorum is a Gram-negative, oxidase- and catalase-positive, motile bacterium with a polar flagellum of the genus Aeromonas which was isolated from bivalve molluscs.
Aeromonas rivuli is a Gram-negative, oxidase- and catalase-positive, non-spore-forming bacterium with a polar flagellum of the genus Aeromonas isolated from Westerhöfer Bach in Harz in Germany.
Aeromonas simiae is a Gram-negative, oxidase- and catalase-positive motile bacterium of the genus Aeromonas, with a polar flagellum, isolated from the faeces of a healthy monkey.
Aeromonas tecta is a Gram-negative bacterium of the genus Aeromonas isolated from stool of a child with diarrhoea, a healthy patient, and environmental sources.
Psychrobacter aquimaris is a Gram-negative, non-spore-forming, nonmotile bacterium of the genus Psychrobacter which was isolated from the South Sea in Korea.
Shewanella decolorationis is a gram-negative, dye-decolorizing bacterium first isolated from activated sludge of a waste-water treatment plant. It is motile by means of a single polar flagellum. The type strain is S12T. Its genome has been sequenced.
Myroides odoratimimus is an obligate aerobic, gram negative bacterium. Although it has been isolated from a range of bodily fluids, it is a rare opportunistic pathogen. Myroides species are commonly found in the environment. Infections can occur following contact with contaminated water. In this context, pericardial effusion, pericarditis, pneumonia, soft tissue infection, septic shock, and urinary tract infection were already associated with these microorganisms. However, neurological infections were rarely reported in literature.
Xenophilus azovorans is a bacterium from the genus Xenophilus which has been isolated from soil in Switzerland.
