What are Gram Negative, Oxidase negative bacilli

G- single rods 

Ferment glucose 

Oxidase negative 

Reduce nitrates to nitrites 

Facultative aerobes 

Soil and GI tract of mammals

Potential Pathogens 

-Escherichia, Morganella, Proteus, Enterobacter....?

Shigella

Salmonella

Yersinia

Motile

No lactose fermentation

Endogenous

Nosocomial

UTIs 

Wound/burn/surgical infections

Motility

-move up urethra or uterers

Urease

-degrade uric acid (increase ph)

Fimbriae

-adhesion to eptihelium -(transitional?)

IgA proteases 

Hemolysins

Klebsiella Pneuomoniae

Common on skin, pharynx, or Gi tract

Community:

-pneumonia in alcoholics

-High fatality

Nosocomial

-UTIs and wounds 

-Chronically ill/immunosuppressed

Endogenous, fomite, direct

K. Pneumoniae Virulence Factors 

Capsule (K antigens)

-polysaccharide

-many serotypes

-anti-phagocytic

-complement resistant

-fast capsule regeneration=increased virulence 

-thicker capsule=increased virulence

Pili

-Attachment to epithelium 

-Anti-phagocytic

Enterobacter

(E. Cloacae and E. aerogenes)

Bacteremia

lower respiratory tract infections

skin infections 

UTI's 

Deep tissue

-Endocarditis, osteomyelitis

Nosocomial 

-prolonged hospitlatization (ICUs)

-prior treatment with antibiotics 

-immunosuppression

E. Cloacae Virulence Factors

-Adhesin

-Siderophore

-Complement resistance 

-Alpha-hemolysin

-Tissue Invasins

Rare

Found in freshwater and on fish; sometimes in GI tract 

Gasteroenteritis, wound infections, sepsis

Contact with infected fish, contaminated water or endogenous

Very Dangerous (50 fatality for sepsis)

Emerging infection

Edwardsellosis in fish

-Chinook salmon, channel catfish, eel, tilapia, flounder

Virulence factors for Edwardsiella Tarda

Hemolysin

Epithelial invasins 

Phagocytic killing 

Complement resistance 

Dermatotoxins

- cause erthema and edema

Escherichia Coli- Enterobacteriae 

Serotypes

Over 700 serotypes

-O antigen of LPS

H=flagellar antigen 

K= capsular antigen 

Escherichia Coli 

Different serotypes can cause

UTIs 

Neonatal meingitis

Gastroenteritis

-5 different types

E. Coli UTI's

Uropathogenic E.coli (UPEC)

Virulence Factors

-P fimbriae 

*Attach to uroepithelium

Type I fimbriae

adherence to uroepithelium

Siderophores

Hemolysins

K antigen

-capsular antigen 

-Decreases phaocytosis and complement lysis

E. Coli

Gastroenteritis 

5 classes

*Different serotypes pathogenesis

**i dont think i have to know them....**

Infant's and traveler's diarrhea

Profuse, watery diarrhea;

may have fever, comiting, headache

Lasts 3-4 days 

Self Resolving 

(ETEC)

Fibriae

-attach to cells in small intestine

Heat-labile enterotoxin (LT) 

*Similar to cholera toxin

-binds to G protein in intestinal epithelium 

-upregulates cAMP

-Release of water and ions into lumen of intestine

Heat-stable Enterotoxin (ST)

-Very small, several types

-increase cytosolic cAMP

-Release of water and electrolytes

Enteroinvasive E. Coli (EIEC)

Like Shigella infections

Dysentery:

-Diarrhea containing blood and mucus

-Fever 

-Cramps

-Vomiting

Virulence Factors for EIEC

Adhesin

-outer membrane protein

Invasion of epithelial cells

-induces inflammation and destruction of epithleium 

No exotoxins

Enteropathogenic E. Coli (EPEC)

Leading cause of infant diarrhea in 3rd World 

Usually children 

-Profuse watery diarrhea with mucus 

-Fever

-Vomiting and abdominal pain

Lasts 1-3 days 

Dangerous in infants 

EPEC adherence factor (EAF)

-Adherence to intestinal epithelum 

Intimin 

-adhesion 

NO EXOTOXINS**

Can invade host cells

-Signs and Symptoms caused by inflammation

Enteroaggregative E. Coli (EAEC)

Persistent diarrhea in young children 

-Non-bloody diarrhea

Not well studied or understood

Virulence Factors for EAEC 

Adherence to epithleium 

Enteroaggregative ST toxin (EAST)

-Heat-labile

-Functions like ETEC ST toxin

Hemolysin

Hemorrhagic colitis 

-seve abdominal pain

-bloody diarrhea

-vomiting

-little to no fever

5 to 10 days

Usually self-limiting 

Can progress to hemolytic uremic syndrom (HUS)

Treatment 

-supportive care

-if HUS: transfusions, dialysis 

Verotoxin/Shiga toxin (Stx)

-same toxin as in Shigella

-on plasmid

-inactivates ribosomes in vascular epithelium 

-hemorrhaging 

-if kidneys are effected=HUS

Adehsion to intesting epithelium by fimbriae 

Shigella

4 species

-s. boydii

-S. dysenteriae

-s. flexneri

-s. sonnei

All pathogens 

Different world wide distributions

Fecal-oral route 

-Shed bacteria during illness and 1-2 weeks after

-few bacteria needed to cause infection (10-200)

Dysentery:

-bloody diarrhea, fever, stomach cramps, vomiting

-Lasts 2-3 days; recovery in 5-7

-S. dysenteriae outbreaks in 3rd world

**5-15% mortality 

Pathogensis of Shigella 

Ingested

Survives gastric juices; travels to large intestine 

Attach, enter and spread thru epithelium 

Destruction/inflammation of epithelium 

-Mucosal layer is ulcerated 

-Leakage

*blood *mucas *inflammatory elements

-Absorption of water is inhibited 

Virulence Factors of Shigella

Cell invasion 

Inter- and intra- cell movement 

Toxin (not in all cases)

Invasions 

Movement

**maybe ability to survive gastric juices and adhesion to epithelium as well....

At 37 C VirF is expressed

VirF induces expression of VirB 

VirB induces expression of mxi, spa, ipa

Mxi, Spa, Ipa assmeble into Mxi-Spa complex 

Mxi-Spa activated when Shigella contacts epithelium Secretes IpaB, IpaC, Ipaa

Ipa proteins induce endocytosis 

Ipa proteins induce escape endosome

Can move inside cell or between cells 

Intracellular 

-bacteria travel along actin filaments 

Intercellular 

-Use IcsA

Shiga toxin= verotoxin

S. dysenteriae and E.coli O157:H7

Attacks vascular endothelium 

-B subunit binds Gb3 on vascular endothelium 

-complex enters cell 

-A subunit modifies rRNA 

Endothelium cannot renew

hemorrhage 

Starts with bloody diarrhea

Fever, V/D, bruising, paleness, decreased urine

Attacks small vessels of kidney, lungs, digestive tract

-hemolytic uremic syndrome (HUS)

Treatment 

-dialysis, antibiotics, transfusions

Death rate 5-15% 

Treatment for Shigella

Ampicillin

Tremethroprim/sulfamethoxazole (bactrim)

Ciprofloxacin

Some antibiotic strains exist 

Antidiarrheal meds can make illness worse

2463 serotypes

Horrible nomenclature 

-2 SPECIES: Senterica and S. bongori

--divided into subspecies 

---- divided into serotypes

Habitat

-Gi tract of humans and animals 

-Can be found in water sewerage, soil 

Transmission 

-fecal oral 

-contaminated food/water

Main human pathogens

-S. Typhimurium (dysentery)

-S. typhi (typhoid fever)

Not typhus 

Effects 21.5 million people around the world

No Tx

--20% death rate

S. Typhi lives only in humans