Module 4 (Gram-negative And Facultative Anaerobic Rods) Flashcards
➢ These microbes constitute the major microflora of the gastrointestinal tract
➢ They have the ability to become
opportunistic microbes in almost all
species of animals
➢ Predisposition to septicemic diseases, enterotoxigenic diarrhea and edema disease
Escherichia
Species of Escherichia associated
with animal infections
• E. coli
• Colibacillosis of fowls
• E. coli infection of swine
(Swine Colibacillosis)
• E. coli infection of cattle
(Colibacillosis of Cattle)
• E. coli infection of lambs
(Colibacillosis of lambs)
• E. coli infection of horses
(Colibacillosis of horses)
• E. coli infection of horses
(Colibacillosis of horses)
• E. coli infection of dogs
• E. coli infection of poultry
• E. coli infection of Rabbits
Morphology, staining features
and cellular composition of Escherichia
➢ Gram-negative rods
➢ Non-spore former, some strains are capsulated
➢ Strains are motile by means of peritrichous flagella (H-antigens)
➢ Invasive strains possess capsular polysaccharides (K-antigens)
➢ K antigens inhibit attachment of the pathogen to phagocytic cells and ingestion by host cells
Growth characteristics of Esherichia
• The organism grows on all ordinary media
• Some strains are aerobes while some are facultative anaerobes
• Positive for indole, nitrate and urease
• Does not ferment sorbitol (E. coli 0157: H7)
Reservoir of Infection Escherichia
• Environment infected with fecal
materials
• Carrier animals
Transmission of Escherichia
• Feco-oral route
Strains of Escherichia associated with animal infections
(Diarrhea and Colibacillosis)
- Enterotoxigenic strains (ETEC) - neonatal piglets, and weanlings
- Entero-invasive strains (EIEC) – neonates that received inadequate amount of colostrum
- Enteropathogenic strains (EPEC) – diarrhea in animals with attaching and effacing lesions in the intestinal tract
- Enterohemorrhagic strains (EHEC)- associated with Edema and enterotoxemia and it involves release of a vasotoxin
- Colibacillosis of fowls- debilitation and chronic diarrhea
- Extra-intestinal pathogenic E. coli (ExPEC)
• Marked by debilitation and chronic
diarrhea
• Fulminating septicemia
• Complicated by respiratory infections
• Associated with salpingitis,
synovitis and panophthalmitis
Colibacillosis of fowls
▪ Marked by colonic malabsorption
3 Distinct manifestations
• Neonatal E. coli enteritis (1-4 days old piglets)
• Weanling enteritis (enteritis occurs shortly after weaning, entero-toxemia cases)
• Edema disease (diarrhea, associated with age, change in feed)
E. coli infection of swine
(Swine Colibacillosis)
➢ Enteric disease (white scours) in
calves during the first week life
E. coli infection of cattle
(Colibacillosis of Cattle)
• Enteric form occurs in lambs 2-8
days old
• Caused by the proliferation of
entero-pathogenic, non-invasive
strains of E. coli in the upper small intestines
E. coli infection of lambs
(Colibacillosis of lambs)
• Accounts for approximately 1% of
abortion cases
• Observed in mares and about 25%
in infected foals
E. coli infection of horses
(Colibacillosis of horses)
• Bacteremia implicated in
“fading puppy syndrome”
E. coli infection of dogs
➢E. coli is rarely implicated in avian
diarrheal diseases
E. coli infection of poultry
• Cellulitis accompanied by dysentery and high mortality
E. coli infection of Rabbits
Virulence Factors of Escherichia
➢ Surface structures expressed as O (somatic), K (Capsular), H (flagellar) and F (fimbrial) antigens attack complement cascade
➢ Plasmid- encoded heat-labile (LT) and heat-stable (ST) enterotoxins
➢ Edema disease toxin
➢ Vasotoxin (edema disease)
➢ Lipopolysaccharide from the outer membrane
➢ Adhesins (adherence to target cells of the GI tract)
➢ Siderophores, Shiga-like toxins (verotoxin)
➢ Cytotoxic necrotizing factors
➢ Hemolysin
Laboratory diagnosis of Escherichia
Samples: Stools
Agent identification
➢ Bacterial isolation (MacConkey, Minca medium and E media
➢ Quantification of E. coli in the small intestines
➢ ELISA for ST and LT enterotoxin
➢ DNA probes for genes encoding enterotoxins
➢ PCR specific for E. coli trait
➢ Detection of genes associated with EPEC
Treatment of Escherichia
• Apramycin
• Chloramphenicol
• Spectinomycin
• Gentamycin
• Trimethoprim-sulfamethazole
• Ceftiofur
• Correction of fluid and electrolyte imbalance
Prevention and Control for Escherichia
➢Vaccination of gilts and sows with
fimbrial K88 antigens
➢Administration of heat-inactivated
bacterins
➢Good husbandry practice
• These are pathogens of the
gastrointestinal tract of animals
• The species of the genus cause
some septicemic infections
Salmonella
Species of Salmonella associated with animal infections
➢ S. typhimurium
➢ S. agona
➢ S. dublin
➢ S. anatum
➢ S. worthington
➢ S. newport
➢ S. Abortus-equi
➢ S. Abortus-ovis
➢ S. gallinarum
➢ S. pullorum
➢ S. heidelberg
➢ S. Abortus-suis
➢ S. montevideo
➢ S. Saint-paul
➢ S. panama
➢ S. arizona
Morphology, staining features and
cellular composition of Salmonella
• Gram-negative
• Non-capsulated short rods
• With peritrichous flagella (majority of strains)
• Some carry fimbriae (S. gallinarum and S. pullorum)
• There is one capsular type (Vi, virulence) though most do not possess capsules
• LPS, O-antigens and antigenic determinants on surfaces of flagella (H-antigens) (Kauffman-White serologic classification
Growth characteristics of Salmonella
➢ Aerobic but some are facultative
anaerobes
➢ Use citrate as a carbon source
➢ Produce gas from glucose
Reservoir of infection of Salmonella
• Soil, water, vegetation and animal feeds
• GI tract of warm and cold-blooded animals
• Carrier animals
Transmission of Salmonella
➢ Feco-oral route
➢ Ingestion
➢ Through the yolk, horizontal
transmission and Argasid ticks (Pullorum and fowl typhoid)
Establishment of infection to
Salmonella
Phase I. Colonization of the Intestine
(mediated by adhesins)
Phase II. Invasion of the intestinal epithelium (inflammatory response with PMN influx and diarrhea sets in if immune response wanes)
Phase III. Stimulation of fluid exsorption
Diseases associated with Salmonella
- Salmonellosis in cattle
- Salmonellosis in swine
- Salmonellosis in horses
- Salmonellosis in dogs and cats
- Salmonellosis in sheep and goats
- Salmonellosis of poultry
- Pullorum/Bacillary white diarrhea
- Fowl typhoid
Etiologic agent/s: S. dublin, S. typhimurium, S. montevideo, S. Saint-paul
• Infect young animals (4 to 6 months old)
• Feedlot cattle are susceptible
• Septicemic in nature or limited to the GI tract
• Pneumonia is acquired hematogenously
• Abortion is common
• Decreased in milk production
• Foul smelling diarrhea
• Fever, depression, anorexia and weakness
• Death of calves in a day or two
Salmonellosis in cattle
Etiologic agent: S.Cholera-suis,S.typhimurium
• Acute, fulminating septicemia or chronic debilitating disease in feeder pigs
• Stress-associated infection
• Purplish areas on the ears, rump and abdomen
• High fever and anorexia
• Postmortem lesions (petechiae, pneumonia, thickening and necrosis of the intestinal mucosa
Salmonellosis in swine
Etiologic agent: S. Abortus-equi, S. typhimurium, S. heidelberg)
➢ Diarrhea with severe abdominal pain, septicemia and colic
Salmonellosis in horses
Etiologic agent/s: S. typhimurium,
S. panama
• Very uncommon
• Due to noso-comial infection
• Abortion, stillbirths
Salmonellosis in dogs and cats
Etiologic agent/s: S. abortus ovis, S. Dublin, S. montevideo, S. typhimurium
Salmonellosis in sheep and goats
Etiologic agent: S. pullorum, S. typhimurium, S. anatum, S. Newport
➢Fatal among chicks (first 2 wks of life)
➢Infects the embryo before egg is hatched
➢Associated with the failure of eggs to hatch
➢Death is due to septicemia
Pullorum/Bacillary white diarrhea
Etiologic agent: S. gallinarum
➢Acute septicemic disease of adult chickens
➢Paresis, anemia, wing drooping
Fowl typhoid
Clinical signs of salmonellosis in
Poultry
➢ Diarrhea, Septicemia, Weakness
➢ Wing drooping
➢ hyperexcitability
➢ Drowsiness
➢ Paresis and joint swellings
➢ Anemia and Hemorrhages
➢ Leukocytosis
➢ Multiple small necrotic area
➢ Enlarged spleen (PM)
Other disease entities caused by
Salmonella
- Paratyphoid (Infectious enteritis of pigs)
Etiologic agent: S. typhimurium - Avian Arizoonosis
Etiologic agent: S. arizonae - Paracolon infection of turkeys
➢maintained in turkey flock via infected eggs
➢Have R plasmids
Virulence Factors of Salmonella
➢ O (somatic) Antigen
➢ H (flagellar) Antigen
➢ Vi (Virulence) Antigen
➢ Invasins (sip, Salmonella invasion protein in pathogenicity islands in the chromosomes)
➢ Adhesins (fimbria encoded genes, fim; plasmid encoded
fimbriae, pef; and long polar fimbriae, lpf)
➢ Toxins (LT-like toxin with phospholipase A activity)
➢ Siderophores (removes iron from iron-binding proteins of host)
➢ Salmonella virulence plasmids (svp)
➢ RNA polymerase containing RPOs that regulate acid tolerance (survival at < 5.0 pH) LPS and Salmolysin (Sly A)
Laboratory diagnosis of Salmonella
Samples: Feces, intestinal scrapings, milk of infected cows, blood samples, spleen and bone marrow)
Preferred culture media
➢Bacterial isolation (MacConkey Agar, XLD agar, Hektoen Enteric Media, Brilliant Green Agar)
Agent
Identification
➢Determination of somatic and flagellar antigens
➢Salmonella-specific DNA probes and primers for PCR
Treatment for Salmonella
➢ Ampicillin
➢ Cirofloxacin
➢ Enrofloxacin
➢ Amikacin
Prevention and Control for Salmonella
➢Elimination of carriers
➢Proper hygiene and sanitation
➢No effective vaccines
➢ Large, non-motile bacteria
➢ Produce sticky colonies when plated on nutrient media
➢ Normal flora of the vestibule, urethra and clitoris
➢ Frequently encountered in infections of the respiratory, intestinal and urogenital tracts
KLEBSIELLA