Enterobacteriacaea Flashcards
General features of Enterobacteriacaea
- stain, shape
- 3 antigens used in serotyping
- Many genera: all gram negative bacilli
- present in gut to soil and water “coliforms” (ferment lactose)
- 3 antigens used in serotyping (is where antigen binds -> determined by colour production)
- O antigen = somatic (part of cell wall ->LPS)
- H antigen = flagellar
- K antigen = capsular (or pili)
Genera within Enterobacteriacaea (10)
- E. coli
- Shigella
- Salmonella
- Klebsiella
- Proteus
- Yersinia
- Citrobacter
- Edwardsiella
- Enterobacter
- Serratia
Features, habitat & resistance of Enterobacteriacaea
Features: aerobic to faculatively aerobic
-oxidase neg
-Catalase pos
-glucose fermented to acid (& sometimes gas)
-majority motile
-grow well on artifical media
Habitat: alimentary tract of humans (part of normal flora) -> generally opportunistic pathogens
Resistance: no special features but more resistant than most vegetative bacteria to drying
-resistance to antibiotics readily acquired by plasmids and resistance now widespread
-family divided into tribes, which are divided into genera and species
Escherichia coli
- where found
- features
- resistance
- Found in gut (esp. large intestine, but some specialised strains can adhere to small intestine)
- vast majority non pathogenic commensals (except if they get into wounds)
- ferment lactose
- indol positive
- antimicrobial resistance major issue!
E.coli main disease syndromes
- Gastroenteritis (various forms; esp. neonates)
- Septicaemia (esp. neonates)
- Environmental mastitis (mammory gland)
- Urinary tract infections
- Wound infections
Gastroenteritis
- Caused by certain serotypes
- various mechanisms
- enterotoxigenic strains (ETEC)
Enterotoxigenic strains of E. coli (ETEC)
- have adhesions that allow bacteria to adhere to enterocytes in small intestine (i.e. Pili called K88)
- different in different animal species
- -result in watery “secretory” diarrhoea
- e.g. calves, lambs, foals, piglets, children under 5 most susceptible
- responsible for traveller’s diarrhoea
Other strains of E. coli
- enteropathogenic
- enteroinvasive
- enterohaemorrhargic
- enteroadherant
Shigella
- what infect
- species & subtypes
- what they induce
- Infect humans & non-human primates
- non-lactose fermenting, indole not produced, MR test positive, VP test neg, citrate not utilised
- 4 species & subtypes
- important enteric pathogen, associated w/ poor hygiene
- produce cytotoxins and enterotoxins
- induce colitis (inflammation of colon) and bloody diarrhoea
- sometimes encode neurotoxins
- severe gastroenteritis -> locally invasive type with necrotic ulcers
Salmonella
- features
- causes 3 things
- habitat
- Only one true species = S. enterica
- motile
- can invade cells
- non lactose fermenting
- important cause of eneritis, septicaemia, abortion
- important zoonotic infections (mainly food borne)
- now often multiple drug resistant
- Habitat: GI tract of humans and animals
3 types of Salmonella (+ 2 examples)
- Host adapted: specific disease in a particular animal and has low virulence in other animals
e. g. S. Typhi (Typhoid fever) and S. Paratyph (A & C) - Partially Host adapted: Infection in host of origin & also a limited no. of other species
e. g. S. Cholerase-suis (pig: necrotic enteritis & septicaema - occasionally infects humans) & S. Paratyphi B (human) - Not Host-Adpated: The majority: cause diseases in many species (and zoonotic)
e. g. S. Typhimurium (all species, some multiple drug resistant overseas) & S. Chester (all species)
Classification of Salmonella
- Serovars determined on basis of multiple O (somatic) antigens and H (flagella) anigens (Kauffman-White scheme)
- Additional strain typing traditionally done by “Phage typing” (viruses that infect bacteria) -> pattern of lysis after incubation defines the phage type of the isolate
Salmonella associated with humans
-S.Typhi & S. Typhimurium
- how adapted are they
- what they cause
- transmission
- drug resistance
S. Typhi
- host adapted
- causes typhoid or typhoid fever - is a severe septicaemic disease
- mainly person to person transmission
- long term carriers (i.e. Typhoid mary)
- now often Chloramphenicol resistant
S. Typhimurium
- Not host adapted
- Common and important
- enteritis (and sometimes with septicaemia)
- food-borne zoonosis
- multiple drug resistance
Klebsiella
- features
- what it can ferment
- resistance
- What it can cause
-Slimy capsule, non-motile
-Lactose fermenting, produce gas from glucose
-sporadic infections
-now often drug resistant (extended spectrum beta lactamase strains)
Causes;
-Respiratory infections
-Metritis
-Mastitis
-Enteritis
-Urinary tract infections
Proteus (e.g. P. mirabilis)
- where found
- what it can ferment
- odour (what from)
- features of infection (3)
-Found in soil & water
-non-lactose fermenting
-urease positive (hydrolyses urea to ammonia = fishy smell)
-swarming motility on agar
-resistant organism
Features of infection;
-Urinary tract infections
-Otitis externa (middle ear infection)
-Septicaemia in neonates
-Gastroenteritis in humans
*sporadic infection only
