Part 1: Enteric Gram-Negative Rods (Enterobacteriaceae)

• These are large, heterogenous, and gram - rods

• Gram - bacilli or coccobacilli

Enterobacteriaceae

Where is the natural habitat of Enterobacteriaceae?

intestinal tracts of humans and animals

What do we see when we grow Enterobacteriaceae in SBA and CAP?

large, moist, and gray colonies

What are the two commonly used terms for Enterobacteriaceae?

1. enterics

2. coliforms

What are the common aerotolerance of Enterobacteriaceae?

1. facultative anaerobes

2. aerobes

Enterobacteriaceae ferments a wide range of carbohydrates, but they all ferment what specific carbohydrate

glucose

Enterobacteriaceae does not usually produce cytochrome c oxidase which is why they are oxidase -, except for?

plesiomonas

Enterobacteriaceae can reduce nitrate to nitrite because they have the enzyme nitrate reductase, except for two which are?

1. photorhabdus

2. xernorhabdus

Enterobacteriaceae are usually motile at room temperature using peritrichous flagella except for what?

1. klebsiella

2. shigella

3. yersinia

All Enterobacteriaceae are catalase + except for what?

shigelladysenteriae type 1

What do we use to organize the Enterobacteriaceae family? this is where we group them based on their biochemical characteristics and is further divided into genera and species

tribes

Who and when did they create tribes?

Ewing (1963)

This tests’ result is the blackening of the colony or medium

H2S Test

What are the two mediums you can use for H2S test?

1. triple sugar iron (TSI) agar

2. lysine iron agar (LIA)

When using TSI for H2S test, what are the genera that results to a positive reaction or blackening of the colony or medium?

• salmonella

• proteus

• arizona

• citrobacter

• edwardsiella

When using LIA for H2S test, what are the genera that results to a positive reaction or blackening of the colony or medium?

• salmonella

• arizona

• citrobacter

• edwardsiella

In the urease test in tribe, what are the two categories?

1. rapid urease producing

2. slow urease producing

In the urease test in tribes, what are the rapid urease producers?

• proteus

• providencia

• morganella

In the urease test in tribes, what are the slow urease producers?

• citrobacter

• klebsiella

• enterobater except E. gergoviae

• yersinia

• serratia

In tribes, these are the deaminase producers

• proteus

• providencia

• morganella

In tribe, these are the Lysine Decarboxylation (LDC) positive

• klebsiella

• escherichia

• edwardsiella

• serratia

• salmonella except S. paratyphi A

• hafnia

In tribe, these are the Lysine Decarboxylation (LDC) negative

• proteus

• providencia

• morganella

• citrobacter

• yersinia

• enterobacter except E. aerogenes and E. gergoviae

• shigella

For the pathogenesis and spectrum of diseases, what are the two categories?

1. opportunistic pathogens

2. intestinal pathogens

• This is under pathogenesis and spectrum of diseases in Enterobacteriaceae

• This is a part of the intestinal microbiota of humans and animals

• They can still cause serious extraintestinal opportunistic disease

opportunistic pathogens

• This is under pathogenesis and spectrum of diseases in Enterobacteriaceae

• They are also referred to as primary pathogens

• They can cause diseases even to immunocompetent people

intestinal pathogens

• This is under pathogenesis and spectrum of diseases in Enterobacteriaceae

• This is under opportunistic pathogens

• This is an example of a specie that is normally a part of the bowel microbiota, but when placed on other places of the body, it can cause UTI, septicemia, and meningitis on neonates

E. coli

What is an example of opportunistic pathogen except for E. coli?

• citrobacter

• enterobacter

• klebsiella

• proteus

• serratia spp.

• This is under pathogenesis and spectrum of diseases in Enterobacteriaceae

• This is under intestinal pathogens

• This specie causes typhoid fever or enteric fever

salmonella typhi

• This is under pathogenesis and spectrum of diseases in Enterobacteriaceae

• This is under intestinal pathogens

• This causes dysentery

shigella

What are the three virulence and antigenic factors of Enterobacteriaceae?

1. O antigen

2. H antigen

3. K antigen

• This antigen is also called as somatic antigen

• This is heat stable

• It is located on the cell wall

O antigen

• This antigen is known as flagellar antigen

• This is heat labile

• Is commonly found in the surface of flagella

• Responsible for motility

H antigen

• This antigen is also known as capsular antigen

• Heat stable polysaccharide

• Commonly found in encapsulated species

• Examples are E. coli and Salmonella enterica

K antigen

What is the IMVC for E. coli?

++--

Who and when did they discover E. coli?

Escherich (1885)

E. coli is also known as what 2 common names?

1. colon bacillus

2. golden bacillus

• This is a member of the opportunistic pathogens under Enterobacteriaceae

• Facultative anaerobe

• Glucose fermenter

• Gram - bacilli

• Oxidase -

• Can grow in MAC

E. coli

E. coli can grow on two media, what are these?

1. MAC

2. Eosin Methylene Blue (EMB) agar

When E. coli grows in MAC, what do we see?

pink with precipitated bile salts

When E. coli grows in EMB, what do we see?

green metallic sheen

E. coli is used as the what in contaminated water testing?

primary marker

What are the virulence factors of E. coli?

O, H, and K antigens

E. coli is the most common cause of gram - (blank) infections

nosocomial

What are the common illnesses caused by E. coli

UTI, bacteremia, neonatal meningitis, and nosocomial infections

Aside from glucose and lactose, what are the other carbohydrates that E. coli can ferment?

trehalose and xylose

E. coli can produce indole (indole +) from using what?

tryptophan

E. coli can ferment glucose through the use of what pathway?

mixed acid pathway

To ferment glucose in E. coli, what should be the corresponding results for IMVC?

methylene red + and voges-proskauer -

E. coli does not produce?

• H2S

• DNase

• urease

• phenylalanine deaminase

E. coli does not use what as its sole carbon source?

citrate

What are the two divisions under E. coli?

1. urogenital E. coli

2. gastrointestinal pathogens

• This is a member of gastrointestinal pathogens under E. coli

• Diarrhea in adults especially in children

• The most common cause of infant bacterial diarrhea

• Also causes diarrheal disease/traveler’s disease

• Produces heat-labile enterotoxin

enterotoxigenic E. coli

What is the MOT for enterotoxigenic E. coli?

consumption of contaminated food or water

What increases the risk factor for developing enterotoxigenic E. coli?

achlorhydria

What are the common symptoms for having enterotoxigenic E. coli?

• watery diarrhea

• abdominal cramps

• nausea (sometimes)

• no vomiting or fever

• This is a member of gastrointestinal pathogens under E. coli

• Also known as infantile diarrhea

• Has O serogroup and H antigen

enteropathogenic E. coli

What are the common symptoms when you have enteropathogenic E. coli?

• low-grade fever

• malaise

• vomiting

• diarrhea

In enteropathogenic E. coli, what is the role of O serogroup?

cause of diarrhea

In enteropathogenic E. coli, what is the role of H antigen

intestinal infection

When you have enteropathogenic diarrhea, what does your stool look like?

watery with mucus but no blood

• This is a strain of E. coli under Gastrointestinal pathogens

• This is characterized by producing dysentery, direct penetration, invasion, and destruction of intestinal mucosa

• It is similar to shigellosis

• Its MOT is fecaloral route

• It is non-motile

• It cannot ferment lactose

• It cannot decarboxylate lysine

enteroinvasive e. coli

What is the MOT for enteroinvasive E. coli?

person to person fecaloral route

• This is a member of gastrointestinal pathogens under E. coli

• This was discovered in 1982 during the outbreak of hemorrhagic diarrhea and colitis

• This is characterized by hemorrhagic diarrhea, colitis, and HUS

• It cannot ferment sorbitol within 24 hours

• Its biochemical test is MUG assay

enterohemorrhagic E. coli

What does HUS mean?

hemolytic uremic syndrome

What does MUG assay mean?

4-methylumbelliferyl-B-D-glucoronide

HUS is characterized by what?

• low platelet count

• hemolytic anemia

• kidney failure

What are the two verotoxins under MUG assay?

1. verotoxin I

2. verotoxin II

• This is a verotoxin under MUG assay

• Is similar to shiga toxin

• Causes damages to vero cells

verotoxin I

What is another term for vero cells?

african green monkey kidney cells

• This is a verotoxin under MUG assay

• This is similr to shiga toxin and verotoxin I

• Also known as STEC

verotoxin II

What does STEC mean?

shiga toxin producing E. coli

Enterohemorrhagic E. coli is characterized by what stool?

• watery diarrhea

• bloody diarrhea

• abdominal cramps

• low-grade fever or no fever at all

In MUG assay, it detects what enzyme and then cleaves it to produce a fluorescent product?

B-glucoronidase

In MUG assay, how many percent of strains of enterohemorrhagic E. coli produces B-glucoronidase?

92%

• This is a strain of E. coli under Gastrointestinal pathogens

• This talks about diarrheal syndromes and UTIs

• DAEC and EAEC

enteroadherent E. coli

What does DAEC mean in enteroadherent E. coli?

diffusely adherent E. coli

What does EAEC mean in enteroadherent E. coli?

enteroaggregative E. coli

• This is under enteroadherent E. coli

• It causes diarrhea by adhering to the surface of intestinal mucosa

enteroaggregative E. coli

What are the extraintestinal infections that can be caused by enteroadherent E. coli?

• septicemia

• meningitis in neonates

What are the three other escherichia species?

1. E. hermannii

2. E. vulneris

3. E. albertii

• This is another specie of escherichia

• Yellow-pigmented

• Isolated using CSF, wounds, and blood

E. hermannii

• This is another specie of Escherichia

• Yellow-pigmented

• Isolated through infected wounds

E. vulneris

• This is another specie of Escherichia

• Causes diarrheal syndrome in children

E. albertii