CH. 6 Bacteria - Gram Negative Rods

Pseudomona

• Found: soil, sea/fresh water, colonizes plants & animals

• Important decomposer & bioremdiation

• Freq contam: Home & clinical

• Aerobic resp - DO NOT ferment carbs

• Make: oxidase, catalase

• Many make: water soluble pigments

Pseudomonas Aeruginosa

• Widespread distribution 

• Inhabits: Soil & water

• Opportunistic pathogen: infect lungs, skin, eyes & ears 

• Can cause: Pneumonia, corneal disease, otitis media,UTI, abscesses, endocarditis, meninigitis, bronchopneumonia

• Esp: immunocompromised - untreated HIV & cystic fibrosis 

• Most common pathogen hospitalised pt (>1 week)

• Cause: serious & life threat nosocomial infection 

• Character: grapey odour & fluorescent green blue colony colour - ID in sputum or pus 

• Multidrug resistant

Escherichia Coli 

• Common normal gut microflora component (aerobic & non-fastidious bacterium)

• Used: indicator - fecal contam (food & water)

• Coliform count: colonies of E.coli cultured from sample 

• Lots of E.coli strains (150) - life threatening infections (bowel & genito-urinary tract - kidneys too)

• E.Coli strain 0157:H7: produces exotoxin (shiga toxin)

• Infection from: contaminated unpasteurized milk/ undercooked ground beef → hemorrhagic diarrhea 

• Children, elderly & immunocompromised: infection → hemolytic uremic syndrome (HUS) & acute kidney failure

E.Coli - Strain - Enterotoxigenic

• Cause: severe diarrhea d/t heat labile & heat stable toxin 

• Stim: secretion & fluid loss

• Has fimbriae

E.Coli - Strain - Enteroinvasive

• Cause: inflamm disease of L.I

E.Coli - Strain - Enteropathogenic

• Linked: wasting from infantile diarrhea

E.Coli - Enterohemorrhagic

• O157:H7 strain

• Cause: hemorrhagic syndrome & kidney damage

• ID: 100 cells

Other Coliforms

• Klebsiella pneumoniae: 

• Enterobacter sp.

• Serratia marcescens 

• Citrobacter sp

Klebsiella pneumoniae

• Norm inhab: respiratory tract

• Large capsule

• Cause: nosocomial pneumonia, meningitis, bacteremia, wound infections and UTIs

Enterobacter sp

•  UTIs, surgical wounds

Serratia marcescens 

• Prod: red pigment

• Causes pneumonia, burn and wound infections, septicemia and meningitis

Citrobacter sp

• opportunistic UTIs and bacteremia

Salmonella & Shigella 

• Well devel V.F, 1 pathogens, not normal human flora 

• Some G.I involvement & diarrhea but often affect other systems

Salmonella Enterica 

• Cause: Typhoid Fever (serious, common, epidemic form of diarrhea ~ asso. w/ poor sanitation 

• Typhoid: major toll on human history (eg: Mesoamerican Aztec civilization: collapsed after typhoid epidemic) 

• Typhoid epidemics - ended in areas w/ effective sanitation systems (seperation of sewage & drinking water, monitoring food contami)

• S.enterica spread: faecal oral route - fecally contam water & food 

• Attacks: liver & range of symptoms: mild febrile illness → severe diarrhea, septicemia, ulcerated intestine, peritonitis, septic shock & death 

• Still lots of cases in war zones, failed states & impoverished/uderdevel areas

Salmonella Typhi

 Most serious pathogen; causes typhoid fever; human host

Salmonella Cholerae-Suis

 Zoonotic pathogen found in swine.

Salmonella Enteritidis

• Includes 1,700 different serotypes,

• classified based on variations in O, H, and capsular antigens.

Salmonella Species - General Characteristics

• Flagellated

• Ferments glucose

• Resistant to chemicals such as bile and dyes

Typhoid Fever - Transmission & Carriers

• Ingestion of fecally contaminated food or water

• Occasionally spread by close personal contact

• Infectious dose (ID): 1,000–10,000 cells

Carriers:

• Asymptomatic carriers 

• Chronic carriers shed bacilli from the gallbladder

Typhoid Fever - Pathogenisis

• Bacilli adhere to the small intestine, causing invasive diarrhea → septicemia

Typhoid Fever - Treatment & Prevention

Treatment:

• Chronic infections treated with chloramphenicol or sulfa-trimethoprim

Prevention:

• 2 vaccines → temporary protection

Animal Salmonelloses - Characteristics

• Enteric fevers, Salmonella food poisoning, Gastroenteritis

Characteristics:

• Less severe than typhoid fever, but more common

• Caused: various serotypes of Salmonella enteritidis

• Zoonotic in origin, but humans can become carriers

Animal Salmonelloses - Infection Source

• Cattle, poultry, rodents, reptiles

• Animal and dairy products

• Fomites contaminated with animal intestinal flora

Shigella & Bacillary Dysentery

• Shigellosis - incapacitating dysentery 

• Shigella dysenteriae, S. sonnei, S. flexneri, S. boydii

• Human parasites

• Invades the villus of the large intestine

• Perforate the intestine or invade the blood 

• Enters Peyer’s patches, triggering an inflammatory response

• Produces endotoxins and exotoxins

Shigella and Bacillary Dysentery - Treatment

Treatment:

• Fluid replacement

• Ciprofloxacin or sulfa-trimethoprim

Brucella