Micro - Gram negative Bacteria

Gram negative cell wall

Inner membrane
Periplasmic space containing:
- Thin peptidoglycan
Outer membrane (contains LPS)

Outer membrane of gram negatives

Contains:
Lipopolysaccharide (LPS)
Porin proteins

Endotoxin - becomes toxic when released during infections

Lipid portion of gram negative outer membrane contains

Functions as receptors and blocking immune response

Function of outer membrane of gram negatives

Porin proteins

Proteins in the upper layer of the outer membrane of gram negative cells - regulate molecules entering and entering the cell

Aerobic Gram-Negative Bacilli

- Non spore forming
- Found in LI (enteric), respiratory, zoonotic, soil, water
- Most not medically important; some true pathogens, some opportunists
- All have LPS outer membrane - release endotoxin

Pseudomonas and Burkholderia

Aerobic gram negative bacilli - opportunistic pathogens

Brucella and Francisella

Aerobic gram negative bacilli - zoonotic pathogens

Bordetella and Legionella

Aerobic gram negative bacilli - mainly human pathogens

Pseudamonas, Burkholderia, Bordetella, Francisella, Alcaligenes

Gram negative rods - Aerobes that do not ferment carbohydrates

Escherichia, Kleisiella, Citrobacter, Enterobacter

Gram negative rods - Facultative anaerobes that do ferment carbohydrates: Lactose fermenters

Salmonella, Shigella, Proteus, Providencia, Morganella, Hafnia, Edwardsiella, Serratia, Yersinia

Gram negative rods - Facultative anaerobes that do ferment carbohydrates: Oxidase-negative

Haemophilus and Pasteurella

Gram negative rods - Facultative anaerobes that do ferment carbohydrates: Oxidase-positive

Bacteriodes

Gram negative rods - Obligate anaerobe

Pathogenic gram negative bacilli

- Pseudamonas Aeriguinosa
- Bordetellsa pertussis
- Legionella spp.
- Escherichia coli
- Escherichia coli O157:H7

Pseudomonas aeruginosa

Gram-negative bacilli most known for complication of burns, skin rashes, corneal ulcers, meningitis, endocarditis, complication of CF, UTIs

Bordetella pertussis

Gram-negative bacilli most known for whooping cough

Legionella spp.

Gram-negative bacilli most known for pneumonia

Escherichia coli

Gram-negative bacilli most known to cause acute diarrhea and UTIs

Escherichia coli O157:H7

Gram-negative bacilli most known for acute diarrhea, colitis, and Hemolytic uremic syndrome

Salmonella typhi

Gram-negative bacilli most known for septicemia and typhoid fever

Salmonella spp.

Gram-negative bacilli most known to cause acute diarrhea

Shigella spp.

Gram-negative bacilli most known to cause neuron damage, acute diarrhea and bacillary dysentery

Yersinia pestis

Gram-negative bacilli most known to cause the Bubonic plague, and pneumonic plague

Plague!!

Haemophilus
Blood-loving Bacilli

- Gram negative pleomorphic rods
- Fastidious (sensitive to drying, temp extremes and disinfectants)
- Grows on chocolate agar ** (needs special techniques to grow on blood agar)

Haemophilus influenzae (H. influenzae)

Gram negative coccobacillus most known for bacterial meningitis, bacteremia, and pneumonia; less serious infections - conjunctivitis, epiglottitis, cellulitis, sinusitis, otitis media, and infectious arthritis

Vaccination against the b serotype

Decreases 90% of disease incidence by H. infuenzae

Meningitis caused by H. influenzae

Fever, vomiting, stiff neck and neurological impairment are symptoms of this disease

90% fatality

Fatality rate in untreated cases of H. influenzae

Alcoholism, poor nutrition, cancer or diabetes

Predisposing factors for H. influenzae induced pneumonia

Resemble those of pneumococcal pneumonia

Symptoms of H. influenzae induced pneumonia resemble those of which infection

Isolation and use of special medial for nutritional requirements

How to diagnose the bacterial cause of pneumonia (H. influenzae)

cephalosporins

Treats pneumonia causes by H. influenzae

Klebsiella

Enterobacteria species that can cause pneumonia

Impaired host defenses
*cause most of the deaths from healthcare associated infections

How would an enterobacteria (Klebsiella) or other gram negative rods cause pneumonia?

Repeated chills, bloody jelly-like sputum, cough, chills, SOB, fever, chest pain, cyanosis

Signs and symptoms of Klebsiella pneumonia

blood-tinged sputum

Symptom of pneumococcal pneumonia that differentiates it from Klebsiella pneumonia

1-3 days

Incubation period of Klebsiella pneumonia

Klebsiella pneumonia

Gram-negative rod with large capsule, produces big mucoid colonies

- Normal microbiota of GI tract and can be found in mouth an throat

Secretions transmitted by contact, or medical equipment (ventilators); Organism colonizes throat ->- travels to lung via inhaled air and mucus --> adhesions aid in colonization
*capsule = virulence factor

How is Klebsiella Pneumonia contracted?

Very old or very young, compromised immune system (alcoholics, hospital pts, institutionalized pts)

Who is typically effected by Klebsiella?

antibiotic/antimicrobial resistance/multi-drug resistance

Strains of bacteria circulating in hospitals, nursing homes often display

Bordetella purtussis

Causative agent of Pertussis; gram-negative rod

cells are inhaled, attached to ciliated cells of respiratory epithelium - colonize upper throat, trachea, bronchi and bronchiole where they release toxins: PT, ACT, TCT)

** Highly contagious

How is Pertussis contracted?

Pertussis toxin (PT)

An A-B endotoxin; B attaches to receptors, A moves through cytoplasmic membrane cAMP; yields increased mucus, decreased killing ability of phagocytes, release of lymphocytes into bloodstream ineffectiveness of natural killer cells

Adenylate cyclase Toxin (ACT)

lyses leukocytes; catalyzes ATP to cAMP

Tracheal cytotoxin (TCT)

causes release of fever-inducing IL-1; toxic to ciliated epithelial cells

whooping cough

Pertussis is also known as

Yes- but still endemic in many countries including U.S.
* Causes half a million deaths annually globally

Is Pertussis preventable by vaccine?

- Highly contagious
- Spread by respiratory secretions/inhaling airborne droplets
- Most infective during catarrhal stage
- Classically fx infants; most fatalities <1yr old
- Mild infxn in older children/adults; may be mistaken for common cold

Hallmarks of pertussis

- Catarrhal stage: Microlide abx (ineffective in paroxysmal stage)
- Intensive support therapy for infants
- DTaP vaccine (Diptheria, Tetanus and acellular pertussis vaccine) + booster (Tdap)

Treatment and prevention of pertussis

Legionella pneumophila; gram- negative rod - facultative intracellular parasite; survives well in warm freshwater containing protozoa (house the bacteria) includes cysts

Legionnaires' disease (type of pneumonia) is caused by which bacteria?

headache, muscle aches, high fever, confusion, shaking chills, dry cough produces sputum, sometimes blood; SOB, GI issues (25% of cases), slow recovery - weakness and fatigue for weeks

Signs and symptoms of Legionnaires' Disease

inhaling aerosolized water with organism - promoted uptake by alveolar macrophages

-Bacteria survive by preventing phagosome-lysosome fusion; multiply within macrophages

-Alvolar cell necrosis and inflammatory response lead to abscesses, pneumonia, pleurisy and bacteremia

-Fatal respiratory failure in 15% of hospitalized cases

*** No direct person-to-person spread

How is Legionaires' contracted?

Yersinia pestis
* Gram negative rod

Which organism is responsible for the plague?

Biofilms in digestive tract of infected fleas - vomit into wounds

How is yersinia pestis spread?

Bubonic plague
Septicemic plague
Pneumonic plague

What does Yersinia pestis cause?

Escherichia coli

Most common aerobic and non-fastidious bacterium in the gut

virulence by plasmid transfer - others are opportunists

How does E. coli spread?

Pathogenic strains of E. coli

- Enterohemorrhagic (EHEC)

- Enterotoxigenic (ETEC)

- Enteroinvasive (EIEC)

- Enteropathogenic (EPEC)

- Enteroaggregrative (EAEC)

- Shigella-toxin (STEC)

Enterohemorrhagic E. coli (EHEC)

Causes hemorrhagic colitis leading to hemolytic uremic syndrome and kidney damage

Enterotoxigenic E. coli (ETEC)

Causes severe diarrhea due to heat-liable toxin and heat-stable toxin - stimulate secretion and fluid loss; also has fimbriae

* cause diarrhea in infants of developing countries, also visitors
* High infectious dose

Enteroinvasive E. coli (EIEC)

Causes inflammatory disease of large intestine

* cause disease in young children in developing countries

Enteropathogenic E. coli (EPEC)

Linked to wasting form of infantile diarrhea
* Greatest cause of mortality among babies
* Protected by antibodies in breast milk
* Low infectious dose

Enteroaggregrative E. coli (EAEC)

Common cause of pediatric diarrhea

* Fx children, travelers, AIDS patients

Shigella toxin E.coli (STEC)

food borne strains; epidemics involving groung beef, unpasteruized milk, bean sprouts

* initial source is often untreated cow manure
* low infectious dose; can also spread by direct contact

Amongst humans

Most clinical cases of E. coli are transmitted how?

~ 70% of traveler's diarrhea
- 50-80% of UTIs

Generally, E. coli causes

- Oral abx - effective in early phases of infection
- OTC tx for sx relief
--- Lorapremide aka Imodium - slows gut motility; but can retain pathogen for longer
--- Bismuth salicylate (pepto-bismol) more effective; counteracts enterotoxin provides an antimicrobic effect

How is E. coli treated?