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The Gram-Negative Bacteria of Medical Importance. Chapter 20. Gram Negative Bacteria. Cocci. Family Neisseriaceae. Gram-negative cocci Residents of mucous membranes of warm-blooded animals Genera include Neisseria , Moraxella , Acinetobacter 2 primary human pathogens

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The Gram-Negative Bacteria of Medical Importance


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    1. The Gram-Negative Bacteria of Medical Importance Chapter 20

    2. Gram Negative Bacteria Cocci

    3. Family Neisseriaceae • Gram-negative cocci • Residents of mucous membranes of warm-blooded animals • Genera include Neisseria, Moraxella, Acinetobacter • 2 primary human pathogens • Neisseriagonorrhoeae • Neisseriameningitidis

    4. Neisseria • Gram-negative, bean-shaped, diplococci • No flagella or spores • capsules on pathogens • pili • Strict parasites, do not survive long outside of the host • Aerobic or microaerophilic • Pathogenic species require enriched complex media and CO2

    5. Neisseriagonorrhoeae • Causes gonorrhea, an STD • Virulence factors: pili, other surface molecules, IgA protease • Strictly a human infection • In top 5 STDs • Does not survive more than 1-2 hours on fomites • Infection is asymptomatic in 10% of males and 50% of females

    6. Neisseriagonorrhoeae http://www.staysafe.co.nz/index.html

    7. gonorrhea • Males – urethritis, yellowish discharge, scarring & infertility • Females – vaginitis, urethritis, salpingitis (PID), common cause of sterility & ectopic tubal pregnancies • Extragenital infections – anal, pharygeal, conjunctivitis, septicemia, arthritis

    8. gonorrhea Potential scar tissue blockage infertility

    9. gonorrhea Potential for PID (pelvic inflammatory disease)

    10. Gonorrhea in newborns • Infected as they pass through birth canal • Eye inflammation, blindness • Prevented by prophylaxis after birth

    11. Gonorrhea diagnosis

    12. Neisseriameningitidis • Virulence factors – capsule, pili, IgA protease • Many strains exist • Prevalent cause of meningitis • Disease begins when bacteria enter bloodstream, pass into cranial circulation, multiply in meninges; very rapid onset; endotoxin causes hemorrhage and shock; can be fatal • Treated with penicillin, chloramphenicol • Vaccines exist

    13. Neisseriameningitidis Spread of bacteria from a nasopharyngeal infection to blood and CSF

    14. The Gram-Negative Bacilli of Medical Importance Chapter 20

    15. Septic Shock-Endotoxic shock • LPS (lipopolysacchardide) Component of Gram negative cell wall is a potent immune stimulant. • May lead to circulatory failure, tissue damage and death Release of LPS as bacteria breaks apart

    16. Aerobic Gram-Negative Bacilli • Pseudomonas – an opportunistic pathogen • Brucella & Francisella – zoonotic pathogens • Bordetella & Legionella – mainly human pathogens • Alcaligenes – opportunistic pathogen

    17. Pseudomonas • small gram-negative rods with a single polar flagellum, produce oxidase & catalase • highly versatile metabolism

    18. Pseudomonas aeruginosa Single polar flagellum

    19. Pseudomonas aeruginosa • common inhabitant of soil & water (ubiquitous-wide spread) • intestinal resident in 10% normal people • grapelike odor • greenish-blue pigment (pyocyanin) • resistant to soaps, dyes, quaternary ammonium disinfectants, drugs, drying • frequent contaminant of ventilators, IV solutions, anesthesia equipment • opportunistic pathogen

    20. Pseudomonas aeruginosa • common cause of nosocomial infections in hosts with burns, neoplastic disease, cystic fibrosis • Can cause: pneumonia, UTI, abscesses • Septicemia can lead to: endocarditis, meningitis, bronchopneumonia • Corneal ulcers from contaminated lens solutions • Ear infections (Otitis) “swimmer’s ear” • Skin rash (contaminated hot tubs, saunas, swimming pools) • multidrug resistant

    21. Pseudomonas aeruginosa Skin rash/eruption

    22. Pseudomonas aeruginosa Multiple drug resistance Staphylococcus aureus Pseudomonas aeruginosa

    23. Brucella • tiny gram-negative coccobacilli • 2 species • Brucellaabortus (cattle) • Brucellasuis (pigs) • Brucellosis (synonyms=malta fever, undulant fever, & Bang disease) – a zoonosis transmitted to humans from infected animals • fluctuating pattern of fever –weeks to a year • combination of tetracycline & rifampin or streptomycin • animal vaccine available (efforts underway to eradicate from cattle herds and swine) • potential bioweapon

    24. Brucellosis Undulating fever

    25. Francisellatularensis • causes tularemia, a zoonotic disease of mammals endemic to the northern hemisphere, particularly rabbits • transmitted by contact with infected animals, water & dust or bites by vectors • headache, backache, fever, chills, malaise & weakness • 10% death rate in systemic & pulmonic forms • intracellular persistence can lead to relapse • gentamicin or tetracycline • attenuated vaccine available • potential bioterrorism agent

    26. Bordetellapertussis • minute, encapsulated coccobacillus • causes pertussis or whooping cough, a communicable childhood affliction • acute respiratory syndrome • often severe, life-threatening complications in babies • reservoir – apparently healthy carriers • transmission by direct contact or inhalation of aerosols • May be relatively common in adults (as chronic cough) and be misdiagnosed as a cold or the flu

    27. Bordetellapertussis • virulence factors • receptors that recognize & bind to ciliated respiratory epithelial cells • toxins that destroy & dislodge ciliated cells • loss of ciliary mechanism leads to buildup of mucus & blockage of the airways • Hacking coughs followed by abrupt deep inhalation (whoop) • Vaccine does not give long-term immunity so adults and older children can have a recurrence

    28. Pertussis Prevalence increasing due to decrease in vaccination rate in children as a result of concern over its publicised vaccine side effects

    29. Alcaligenes • live primarily in soil & water • may become normal flora • A. faecalis – most common clinical species • isolated from feces, sputum, & urine • occasionally associated with opportunistic infections – pneumonia, septicemia, & meningitis

    30. Legionellapneumophilia

    31. Legionellapneumophila • widely distributed in water • 1976 epidemic of pneumonia afflicted 200 American Legion members attending a convention in Philadelphia & killed 29 (source was a contaminated air-conditioning system) Legionnaires disease • Most prevalent in males over 50 • nosocomial disease in elderly patients • Symptoms: fever, cough, diarrhea, abdominal pain, pneumonia fatality rate of 3-30% • azithromycin

    32. Enterobacteriaceae Family • enterics • large family of gram-negative bacteria • many members inhabit soil, water, & decaying matter & common occupants of large bowel of humans & animals • all members are small, non-sporing rods • facultative anaerobes, grow best in air • cause diarrhea through enterotoxins • divided into coliforms (lactose fermenters) and non-coliforms (non lactose fermenters)

    33. Dichotomous Key for the Enterobacteriaceae

    34. Diarrheal Disease • Two Mechanisms • Toxigenic • Organism itself does not invade the tissue • Enterotoxins released which cause cells to increase secretion secretory diarrhea • Invasive • Microbes breakdown epithelial cells and form ulcerations. May see bleeding • Fluid and electrolyte loss may result in dehydration…death. • Diarrheal disease = 40% of infectious diseases • 18% of death worldwide

    35. Nosocomial Infections Nosocomial infections from Gram negative enterics

    36. Coliforms- Ferment lactose. (normal enteric flora but may cause infections) Noncoliforms- Do not ferment lactose. (some are normal enteric flora others are true pathogens…Salmonella, Shigella)

    37. Escherichia coli • most common aerobic & non-fastidious bacterium in gut • enterotoxigenicE. coli causes severe diarrhea due to heat-labile toxin & heat-stable toxin – stimulate secretion & fluid loss; also has fimbrae • enteroinvasiveE. coli causes inflammatory disease of the large intestine • enteropathogenicE. coli linked to wasting from infantile diarrhea; O157:H7 strain causes hemorrhagic syndrome & kidney damage

    38. Escherichia coli • pathogenic strains frequent agents of infantile diarrhea – greatest cause of mortality among babies • causes ~70% of traveler’s diarrhea • causes 50-80% UTI • indicator of fecal contamination in water

    39. Escherichia coli O157:H7 The Ready-To-Eat Spinach outbreak of ‘06

    40. E. Coli 0157:H7 outbreak • September 28, 2006 : 187 people infected in 26 states (97 hospitalized…29 developed HUS) 2006 Spinach-associated outbreak 1-4 5-9 10-14 15 +

    41. Newer Outbreaks • Nestle Toll House cookie dough (E. coli) June 2009) http://www.cdc.gov/ecoli/2009/0630.html (72 cases in 30 states) • Ground beef (E. coli) ( July 2008) http://www.cdc.gov/ecoli/june2008outbreak/ (49 cases in 7 states) • Pepperoni pizza (E.coli) (Oct-Nov 2007) http://www.cdc.gov/ecoli/2007/october/103107.html (21 cases in 10 states)

    42. Other coliforms • Klebsiellapneumoniae– normal inhabitant of respiratory tract, has large capsule, cause of nosocomial pneumonia, mennigitis, bacteremia, wound infections & UTIs • Enterobacter – UTIs, surgical wounds • Serratiamarcescens – produces a red pigment; causes pneumonia, burn & wound infections, septicemia & meningitis • Citrobacter – opportunistic UTIs & bacteremia

    43. Capsule of Klebsiella pneumoniare

    44. Noncoliform lactose-negative enterics • Proteus • Salmonella & Shigella

    45. Proteus • Swarm on surface of moist agar in a concentric pattern • Cause UTI, wound infections, pneumonia, septicemia, & infant diarrhea

    46. Salmonella • S. typhi – typhoid fever – ingested bacilli adhere to small intestine, cause invasive diarrhea that leads to septicemia. Asymptomatic carriers perpetuate and spread the bacteria. • S. enteritidis – 1,700 serotypes (varieties)-salmonellosis – can be zoonotic(fecal contamination of food products) (1/3 of all chickens have Salmonella) • Food Poisoning-gastroenteritis for 2-5 days

    47. A recent Salmonella in peanut butter outbreak(Late 2008 through 2009)

    48. Phases of Typhoid Fever Invasion Septicemia

    49. Shigella • Shigellosis – bacillary dysentery • S. dysenteriae, S. sonnei, S. flexneri & S. boydii • Invades large intestine, can perforate intestine or invade blood (septicemia) • Virulence factors: endotoxin & exotoxins • Treatment – fluid replacement & ciprofloxacin & sulfa-trimethoprim Patches of mucus and blood