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Enteric Bacteria PowerPoint PPT Presentation


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Enterobacteriaceae Gram negative bacilli ferment glucose oxidase (-). Enteric Bacteria. Escherichia Enterobacter Klebsiella Serratia Citrobacter. Proteus (usually nonpathogenic) Shigella Salmonella. Normal Flora vs. Pathogens. COLIFORMS. NON-COLIFORMS. Lactose Fermentation?. yes.

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Enteric Bacteria

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Enteric bacteria l.jpg

EnterobacteriaceaeGram negative bacilli

ferment glucose

oxidase (-)

Enteric Bacteria


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Escherichia

Enterobacter

Klebsiella

Serratia

Citrobacter

Proteus (usually nonpathogenic)

Shigella

Salmonella

Normal Flora vs. Pathogens

COLIFORMS

NON-COLIFORMS


Enterobacteriaceae coliform or non coliform l.jpg

Lactose Fermentation?

yes

no

normal flora

pathogen

Enterobacteriaceae: Coliform or non-coliform?


Obligate enteric pathogens l.jpg

Shigella dysenteriae

Salmonella typhimurium

http://www.mpg.de/news02/news0209.htm

http://www.co.boulder.co.us/health/hpe/FactSheets/salmonella.htm

Obligate Enteric Pathogens


Escherichia coli o157 h7 l.jpg

http://www.quarks.de/milch/06.htm

Escherichia coli O157:H7

http://www.jfha.or.jp/saikin/shashin/o157.html


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Eosin Methylene Blue (EMB) Agar

E. coli

http://www.cat.cc.md.us/courses/bio141/labmanua/lab3/embeacolony.html

E. aerogenes

S. Typhimurium

P. aeruginosa


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Electrons from carbos(or other food source)

Electron carriers

NO3-, SO42-,CO2

O2(Aerobic respiration)

Pyruvic acid

(Anaerobic respiration)

(Fermentation)

Black, J.G (2002) Microbiology: Principles and Explorations 5th Ed. Fig. 5.21


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Fermentation Pathways

Glucose(or other sugar)

Butyric acid, butanol,isopropyl alcohol,acetone & CO2

Propionic acid,acetic acid,& CO2

Pyruvic acid

Butyric-butylicfermentation

Propionic fermentation

Black, J.G (2002) Microbiology: Principles and Explorations 5th Ed. Fig. 5.11

Butanediol& CO2

Ethyl alcohol& CO2

Acetic aid,succinic acid,ethyl alcohol,

CO2 & H2

Butanediolfermentation

Lactic acid

Alcoholic fermentation

Mixed-acidfermentation

Homolactic acidfermentation


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API 20 E Test Strips


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Sugar Fermentation

  • Melibiose

  • Amygdalin

  • Arabinose

  • Sorbitol

  • Rhamnose

  • Sucrose

  • Glucose

  • Mannitol

  • Inositol

Must use additional reagents to GLU to see result


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Catabolic Enzymes

  • Beta galactosidase

  • Arginine dehydrogenase

  • Lysine decarboxylase

  • Ornithine decarboxylase


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Citrate Utilization

blue indicates citrate utilization and alkaline by-products


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Sulfur Reduction

CH2

SH

CH3

cysteine desulfurase

H2S

COOH

+

CH

H2N

CH

COOH

H2N

(hydrogen sulfide)

(alanine)

(cysteine + sodium thiosulfate)

Fe++ (in medium)

FeS

(iron sulfide)

(black ppt)


Nitrogen fixing l.jpg

H2N

NH2

urease

2 NH3

+

CO2

C

(ammonia)

O

(urea)

Nitrogen Fixing


Tryptophan indole reaction l.jpg

H2O +

H2N

Tryptophan deaminase

(indole)

COOH

CH2

CH

N

(tryptophan)

N

+

NH3

(ammonia)

+

CH3

C = O

(pyruvic acid)

COOH

Tryptophan - Indole Reaction

Must add Kovac’s reagent to see result


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Acetoin Reaction

Must add KOH and α-naphthol to see result


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Gelatinase(s)

  • Large group of proteolytic enzymes

  • Degrade collagen

  • Metalloproteases

  • Virulence factors


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API Test : Sample Prep

  • Pick ONE SINGLE colony (no agar)

  • Emulsify colony by pipetting up and down in small amount of liquid


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Inoculating API Test Strips

Overlay with mineral oil:

  • ADH, LDC, ODC, H2S, & URE

  • Fill tubules & cupules:

  • CIT, VP & GEL

  • (see pg. 223 in lab manual)


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Reading API Test Strips

  • Use chart on pp. 225-8 in manual to determine results

  • Record + or – results for each test

  • Add + results in oval below tests

  • Record 7-digit code and look up ID


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Why did we inoculate withPseudomonas aeruginosa?


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