E-coli

Página 1

General features

Gram negative

Perittichous

Rod shaped

Facultative anaerobe

Obtains energy by oxidation and reduction of organic sources

Common inhabitant of intestines of all warm blooded animals

frequently a harmless commensal

some variants cause diseas

Part of micro biome

Number of bacterial cells 10x that of mammalian cells

Essential for development, homeostasis, digestion and immune development

E-coli is ubiquitous in micro biomes of mammals and birds

Presence of E-coli in water is indication of faecal contamination

Key role in biosynthesis of vitamin K

Versatile pathogen

Commensal , carried by most vertebrates

Infection may be opportunistic or caused by specific pathogens

Infections group into

Intestinal

Extra-intestinal

Pathogenic E-coli further grouped into pathotypes on bases of clinical signs

Diarrheagenic E-coli

Extra pathogenic E-coli

Not all can be conveniently grouped

Virulence factors

Adhesions such as pili and fimbriae allow attachments to host cell

Flagella important for motility

Some fibril types strongly associated with virulence

Nutrient scavenging systems for hostile environments

Toxins that act on gut or systemically

Secrete systems that deliver host proteins to alter function/structure of host cells

Bacterial components that activate innate immunity lipopolysaccharide from E-coli is a potent simulator of inflammation

Horizontal gene transfer

Conjugation

Sex pills reaches from cell to cell

Transfers plasmids

Transformation

DNA released into environment

Taken up by new cell

Transduction

Bacterial phage transfers DNA from one

Evolution of virulence and role of horizontal gene transfer

Major driver in pathogenic diversity in E coli

Pathogenicity islands are regions of DNA acquired into the genome encoding ???

Toxins

Enterotoxins important in ETEC

Damage enterocytes leading to diarrheoa

Shiga-like toxins act on blood vessels and endothelial cells

Encoded by bacteriahage

Stx toxins

Coli carry STEC

EHEC are a class of STEC

EHEC carried asymptomatically in cattle

Toxin doing human infection may cause haemorrhage in gut or damage kidneys

Pigs affected by 138 O139 and O141 serotypes

Toxin has range of effects in ????

Secretion systems

Gram bacteria have type 1 and type 2 secretion systems

May be energy dependent

Type 3 and 4 have needle like protein which allows insertion of secretion into a host cell

LEE T3SS

T3SS encoded on LEE operon is associated with colonisation of gut in cattle and enteritis in humans

Doesn't mediate cell invasion but translocates its own receptor to enterocytes

Allows binding to gut

Effectors injected into the host cell cause???

Disease is usually result of virulence factors working in concert

Most disease is consequence of several factors

EHEC systems allow survival in gut are essential

Attachment requires adhesions s

????

German 2011 beansprout E-coli outbreak

O104 is EAEC that causes persistent diarrhoea

German isolate acquired Stx toxin genes so became persistent

Infection was common in women 15-50 - unusual as often children and elderly

Extra-intestinal disease

Caused by ExPEC

ExPEC include neonatal meningitis, urinary tract and avian pathogenic pathotypes

???

APEC

Important endemic disease in both layer and broiler sectors

Major cause of mortality in young broilers - resp and systemic disease

Though cause between 2-4% mortality in UK broiler flock

Reproductive tract infections in mature layers

Common clinical presentations are diverse

Respiratory distress with inflammation of air sacs

Fibrous or caseous deposits around visceral organs

Reproductive tract infection with inflammation and fibrinous and caseous deposits on ovaries or egg peritonitis SPS

Accumulation of fluid in abdomen

Mastitis

E-coli mastitis in housed cattle over winter

Bacteria infect udder and strong inflammatory response leads to inflammation

Excessive response to LPS can lead to systemic????

E-coli and AMAR

Sentinel for AMR

??