Escherichia coli (E. coli) è un batterio gram-negativo a forma di bastoncello che si localizza comunemente nella parte inferiore dell'intestino degli organismi a sangue caldo (endotermi). La maggior parte dei ceppi di E. coli è innocua e rappresenta una parte importante di un tratto intestinale umano sano. Tuttavia, alcuni ceppi possono essere causa di malattie nell'uomo, tra cui diarrea, infezioni del tratto urinario, malattie respiratorie e polmonite.

Il nome definisce la forma e il luogo dove si trova questo batterio:

• Escherichia si riferisce al nome del genere e deve il suo nome a Theodor Escherich, pediatra e batteriologo tedesco-austriaco che ha scoperto questo batterio.
• coli si riferisce al fatto che questo batterio si trova nel colon

È un anaerobo facoltativo  che può sopravvivere sia in ambienti ricchi di ossigeno (aerobi) sia in ambienti poveri di ossigeno (anaerobi) in grado di sfruttare vari composti organici come fonte di carbonio ed energia o, in determinate condizioni, di eseguire la fotosintesi. 

Alcuni ceppi patogeni (che generano malattie) di E. coli, come l'E. coli O157:H7, emettono tossine che possono provocare gravi malattie. Questi ceppi sono spesso associati a epidemie di origine alimentare e possono essere trasmessi attraverso l'acqua o il cibo contaminati, oppure tramite il contatto con persone o animali infetti.

A cosa serve e dove si usa

I batteri E. coli sono spesso impiegati nella ricerca biologica e genetica, in quanto possono essere facilmente coltivati in laboratorio e la loro genetica può essere modificata. Sono anche utilizzati nell'industria per la produzione di prodotti farmaceutici come l'insulina.

Studi

Brumwell A, Sutton G, Lantos PM, Hoffman K, Ruffin F, Brinkac L, Clarke TH, Adams MD, Fowler VG Jr, Fouts DE, Thaden JT. Escherichia coli ST131 Associated with Increased Mortality in Bloodstream Infections from Urinary Tract Source. J Clin Microbiol. 2023 Jun 20:e0019923. doi: 10.1128/jcm.00199-23.

Abstract. Escherichia coli sequence type 131 (ST131) is a globally dominant multidrug-resistant clone, although its clinical impact on patients with bloodstream infection (BSI) is incompletely understood. This study aims to further define the risk factors, clinical outcomes, and bacterial genetics associated with ST131 BSI. A prospectively enrolled cohort study of adult inpatients with E. coli BSI was conducted from 2002 to 2015. Whole-genome sequencing was performed with the E. coli isolates. Of the 227 patients with E. coli BSI in this study, 88 (39%) were infected with ST131. Patients with E. coli ST131 BSI and those with non-ST131 BSI did not differ with respect to in-hospital mortality (17/82 [20%] versus 26/145 [18%]; P = 0.73). However, in patients with BSI from a urinary tract source, ST131 was associated with a numerically higher in-hospital mortality than patients with non-ST131 BSI (8/42 [19%] versus 4/63 [6%]; P = 0.06) and increased mortality in an adjusted analysis (odds ratio of 5.85; 95% confidence interval of 1.44 to 29.49; P = 0.02). Genomic analyses showed that ST131 isolates primarily had an H4:O25 serotype, had a higher number of prophages, and were associated with 11 flexible genomic islands as well as virulence genes involved in adhesion (papA, kpsM, yfcV, and iha), iron acquisition (iucC and iutA), and toxin production (usp and sat). In patients with E. coli BSI from a urinary tract source, ST131 was associated with increased mortality in an adjusted analysis and contained a distinct repertoire of genes influencing pathogenesis. These genes could contribute to the higher mortality observed in patients with ST131 BSI.

Wirth T, Falush D, Lan R, Colles F, Mensa P, Wieler LH, Karch H, Reeves PR, Maiden MC, Ochman H, Achtman M. Sex and virulence in Escherichia coli: an evolutionary perspective. Mol Microbiol. 2006 Jun;60(5):1136-51. doi: 10.1111/j.1365-2958.2006.05172.x. 

Abstract. Pathogenic Escherichia coli cause over 160 million cases of dysentery and one million deaths per year, whereas non-pathogenic E. coli constitute part of the normal intestinal flora of healthy mammals and birds. The evolutionary pathways underlying this dichotomy in bacterial lifestyle were investigated by multilocus sequence typing of a global collection of isolates. Specific pathogen types [enterohaemorrhagic E. coli, enteropathogenic E. coli, enteroinvasive E. coli, K1 and Shigella] have arisen independently and repeatedly in several lineages, whereas other lineages contain only few pathogens. Rates of evolution have accelerated in pathogenic lineages, culminating in highly virulent organisms whose genomic contents are altered frequently by increased rates of homologous recombination; thus, the evolution of virulence is linked to bacterial sex. This long-term pattern of evolution was observed in genes distributed throughout the genome, and thereby is the likely result of episodic selection for strains that can escape the host immune response.

Barnich N, Darfeuille-Michaud A. Adherent-invasive Escherichia coli and Crohn's disease. Curr Opin Gastroenterol. 2007 Jan;23(1):16-20. doi: 10.1097/MOG.0b013e3280105a38.

Abstract. Purpose of review: The identification of mutations in the nucleotide oligomerization domain 2-encoding gene in patients with Crohn's disease suggests a link between the innate immune response to invasive bacteria and the development of Crohn's disease. Herein, we review reports concerning the association of pathogenic Escherichia coli with the intestinal mucosa of Crohn's disease patients. Recent findings: Adherent-invasive E. coli were isolated from ileal biopsies of 36.4% of patients with ileal Crohn's disease. Adherent-invasive E. coli colonize the intestinal mucosa by adhering to intestinal epithelial cells. They are also true invasive pathogens, able to invade intestinal epithelial cells and to replicate intracellularly. Adherent-invasive E. coli strains replicate extensively into macrophages inducing the secretion of very large amounts of tumor necrosis factor-alpha. Similar pathogenic E. coli strains were recently associated with granulomatous colitis of Boxer dogs. Interestingly, high levels of E. coli outer membrane protein C antibodies are present in 37-55% of Crohn's disease patients and reactivity to outer membrane protein C is associated with increased severity of Crohn's disease. Summary: As the infection cycle of adherent-invasive E. coli could depend upon the ability of these pathogenic bacteria to colonize the gastrointestinal tract of genetically predisposed Crohn's disease patients, antibiotics which could eradicate the bacteria, or probiotics which could substitute them in the gastrointestinal tract, could be of therapeutic value in ileal Crohn's disease.

Tazzyman SJ, Hall AR. Lytic phages obscure the cost of antibiotic resistance in Escherichia coli. ISME J. 2015 Mar 17;9(4):809-20. doi: 10.1038/ismej.2014.176. 

Abstract. The long-term persistence of antibiotic-resistant bacteria depends on their fitness relative to other genotypes in the absence of drugs. Outside the laboratory, viruses that parasitize bacteria (phages) are ubiquitous, but costs of antibiotic resistance are typically studied in phage-free experimental conditions. We used a mathematical model and experiments with Escherichia coli to show that lytic phages strongly affect the incidence of antibiotic resistance in drug-free conditions. Under phage parasitism, the likelihood that antibiotic-resistant genetic backgrounds spread depends on their initial frequency, mutation rate and intrinsic growth rate relative to drug-susceptible genotypes, because these parameters determine relative rates of phage-resistance evolution on different genetic backgrounds. Moreover, the average cost of antibiotic resistance in terms of intrinsic growth in the antibiotic-free experimental environment was small relative to the benefits of an increased mutation rate in the presence of phages. This is consistent with our theoretical work indicating that, under phage selection, typical costs of antibiotic resistance can be outweighed by realistic increases in mutability if drug resistance and hypermutability are genetically linked, as is frequently observed in clinical isolates. This suggests the long-term distribution of antibiotic resistance depends on the relative rates at which different lineages adapt to other types of selection, which in the case of phage parasitism is probably extremely common, as well as costs of resistance inferred by classical in vitro methods.