Enterobacterales - Ross University Veterinary Medicine PDF

Enterobacterales Dr. Ricardo Gutiérrez Cruz, MSc., Ph.D. Assistant Professor of Microbiology [email protected] Summer 2024 BACTERIA Enterobacterales Enterobacterales General features Gram-negative rods (coccobacilli) Strait, cylindrical, rounded ends Non-sporulating Simple nutritional requir...

Enterobacterales Dr. Ricardo Gutiérrez Cruz, MSc., Ph.D. Assistant Professor of Microbiology [email protected] Summer 2024 BACTERIA Enterobacterales Enterobacterales General features Gram-negative rods (coccobacilli) Strait, cylindrical, rounded ends Non-sporulating Simple nutritional requirements Facultative anaerobes (fermenters → acid) Nitrate -> nitrite* Motile (peritrichate flagella) / non-motile Oxidase – (lack cytochrome C oxidase)* Over 40 genera Over 180 species Enterobacterales Enterobacterales G R A M N E G AT I V E B A C T E R I A Gram-negative No enterobacteria Enterobacterales Enterobacterales MacConkey Agar Enterobacterales Enterobacterales ENTEROBACTERIACEAE PLANTS SOIL WATER Enterobacterales COLIFORMS No taxonomic significance Refer to Enterobacteriaceae that ferment lactose (lactose +) They are used as enteric contamination markers E. coli is the ideal fecal contaminant indicator Lactose + (production of acid & gas) Coliforms: Escherichia coli Klebsiella spp. Enterobacter spp. Citrobacter spp. Enterobacterales PATHOGENICITY Pathogenicity Uncertain Unknown significance for animals (appox. 17 genera) Opportunistic Opportunistic pathogens for animals (approx. 8 genera) Pathogens Major pathogens for animals (approx. 3 genera) Klebsiella & Proteus E. coli, Salmonella & Yersinia Escherichia coli ENTEROBACTERIACEAE Escherichia coli Type species of the family. Present in the intestine of most animal species: 107-109 organisms/g in feces. + - Rapid acquisition from the environment Survives in the environment, but it usually does not multiply Concentration is higher at the large intestine ENTEROBACTERIACEAE Escherichia coli Commensals E. coli Members of the microbiota (benefits). No virulence factors (VFs) present, or some strains may have VFs but not specific for their host. Example: E. coli strains from bovines that are human pathogens (EHEC) Diarrheagenic/ Intestinal (DEC or InPEC) Economically important pathogens of neonatal piglets, calves, and lambs. Post-weaning diarrheal infections are also important in swine. Extraintestinal (ExPEC) Urinary tract, umbilicus, blood, lung, and wounds in any location (e.g. mastitis). Based on genotypic and phenotypic traits ENTEROBACTERIACEAE Escherichia coli FYI Flexible gene pool: Up to 1 million bp difference E. coli genome size ranges from 4.5-5.5 Mbp Etcheverria et al., 2016 ENTEROBACTERIACEAE Escherichia coli Virulence factors 1. Capsule 2. Endotoxin (lipid A) → septicemias / toxemia in coliform mastitis 3. Fimbriae (some are adhesins) → attachment 4. Flagella 5. Siderophores → invasive strains 6. Enterotoxins → Heat LT, ST, EAST1, 7. Other toxins: Shiga-like toxin, hemolysins ENTEROBACTERIACEAE Escherichia coli Serotyping 1. Capsule: K antigens (polysaccarides) 2. Somatic: O antigens (sugar side-chains of LPS) 3. Flagellar: H antigens 4. Fimbriae: F antigens (proteins) International typing scheme uses O and H antigens: - 181 O-antigens - 53 H antigens E.g.: E. coli O157:H7 ENTEROBACTERIACEAE Escherichia coli Commensals E. coli Diarrheagenic/ Intestinal (DEC or InPEC) Extraintestinal (ExPEC) 6 major intestinal pathogroups : 1. Enterotoxigenic E. coli (ETEC) 2. Enteropathogenic E. coli (EPEC) 3. Enterohemorrhagic E. coli (STEC/VTEC included) 4. Enteroaggregative E. coli (EAEC) 5. Enteroinvasive E. coli (EIEC) 6. Diffusely-adherent E. coli (DAEC) in diarrheic and healthy animals More associated with humans Others emerging pathogroups: AIEC, EAHEC, EAggEC… ENTEROBACTERIACEAE Escherichia coli ETEC: Enterotoxigenic E. coli 1. Important pathogens of calves, piglets & lambs 2. Host specificity (sp. & age) 3. Key virulence factors: enterotoxins and adhesins Enterotoxins: STa (heat-stable toxin a) : piglets & calves STb (heat-stable toxin b) : piglets LT (heat labile toxins) : piglets EAST1 (enteroaggregative heat-stable enterotoxin 1) Adhesins: F4 (K88) : piglets F5 (K99) : piglets, calves & lambs F6 (987P) : piglets F17: calves & lambs F18 : piglets F41 : piglets, calves & lambs AIDA-I (non-fimbrial) : piglets ENTEROBACTERIACEAE Escherichia coli ETEC: Enterotoxigenic E. coli PATHOGENESIS These actions lead to accumulation of Cl-, HCO3 - and Na+ ions and water in the intestinal lumen ENTEROBACTERIACEAE Escherichia coli ETEC: Enterotoxigenic E. coli Adherence step Host-specificity of ETEC Presence/absence of fimbriae genes Expression of fimbriae receptors in intestinal lining Age-dependent Lower expression Over-expression ENTEROBACTERIACEAE Escherichia coli ETEC: Enterotoxigenic E. coli Severe watery diarrhea (non-bloody). Results in dehydration, listlessness, metabolic acidosis, and death Noninflammatory secretory diarrhea Diarrhea is mostly observed in the first few days after birth and affects one or more animals in a group: - Up to the 6th week in piglets 1st week in calves Up to the first 10 days of life in lambs ENTEROBACTERIACEAE Escherichia coli ETEC in piglets ETEC presentations in piglets 1. Neonatal diarrhea (colibacillosis) 2. Post-weaning diarrhea (PWD) ENTEROBACTERIACEAE Escherichia coli ETEC in piglets (neonatal diarrhea) Altered equilibrium between maternal immunity and infection pressure vs ETEC infection Lowering of maternal immunity Sow: sick, first delivery Piglet: low birth weight; other infection Too many piglets per sow Increase infection pressure Low hygiene Presence of ETEC diseased piglets Appearance of new type ETEC strain ENTEROBACTERIACEAE Escherichia coli ETEC in piglets (postweaning diarrhea) After weaning, the change in the intestinal environment of piglets, mainly due to dietary changes, results in an alteration of the composition of the indigenous flora ENTEROBACTERIACEAE Escherichia coli ETEC in piglets 1. Neonatal diarrhea (colibacillosis) 2. Post-weaning diarrhea (PWD) F4 receptors expressed F6r & F41r F18r F5r Newborn Neonatal ETEC F4; F5; F6; F41 STa; STb 8w 3w Weaning Neonatal till weaning ETEC F4 LT; STa; STb; EAST1 Post Weaning diarrhea (PWD) F4; F18 LT; STa; STb, EAST1 ENTEROBACTERIACEAE Escherichia coli ETEC in piglets 1. Neonatal diarrhea (enteric colibacillosis) Newborn (