GRAM NEGATIVE BACTERIA Flashcards
(8 cards)
Aerobic/microaerophilic, motile, helical/vibrioid-
Flagellated, no axial filaments. Most are harmless. Campylobacter spp.- among most common causes of diarrheal illness in the US and other developed countries.
May lead to septicemia. Acquired orally. Invades intestinal epithelia Helicobacter pylori- responsible for >85% of gastric and duodenal ulcers.
Spirochetes:
spiral bacteria, axial filament. Most are free-living
Treponema pallidum- syphilis. Sexually transmitted. No growth on any laboratory media. Borrelia recurrentis- Relapsing fever. Tick borne.
B. burgdorferi- Lyme disease. Tick borne. Headache, stiff neck, arthritis.
Aerobic rods and cocci
Pseudomonas aeruginosa- Inhabit soil, water, plants and animals (moist areas). Motile, many pigments, metabolically active (many enzymes) but may use few of the common nutrients and grow on anything. Extremely invasive and toxigenic in compromised patients (weakened ability to resist infectious agents)
Nosocomial infections: Urinary tract infections (UTI), septicemia, abscesses, burns, wounds. Legionella spp.- Ubiquitous in warm, moist environments.
L. pneumophila- Legionellosis, Legionnaires disease (pneumonia-like). Many toxins. Spread by aerosols. Asymptomatic infections common in all age groups.
Neisseria spp.- diplococci. Pathogenic species usually associated with leukocytes (neutrophils in particular).
N. gonorrhoea- gonorrhea. No capsule. Pili on virulent forms. Highly toxic LPS.
N. meningitidis- found only in humans. Inhalation, pili attach, invasion to blood, fulminant infection, circulatory collapse, meningitis
Brucella spp.- Obligate parasites of animals (incl. humans). Often found intracellularly (survives phagocytosis). Transmitted by ingestion or passage through skin or mucous membranes.
Undulant fever (Brucellosis)- chronic, and involves many tissues. Endotoxin mediated.
Bordetella pertussis- Whooping cough, infant immunizations have been very effective. Respiratory transmission. Pertussis toxin and other toxins. Relatively non-invasive.
Francisella tularensis- Tularemia (ulcers, necrotic lesions, fever, malaise). Entry through abrasions following animal contact, insect bite, ingestion or inhalation. Highly infectious and toxic.
Facultative anaerobes 1
Enteric bacteria- natural habitat for most is intestinal tract.
Some are normal flora and cause incidental disease; some are regularly pathogenic Escherichia coli- Common intestinal inhabitant. UTI’s and food poisoning (traveler’s diarrhea);
spread by fecal contamination. LPS and many other toxins (heat stable and labile toxins). Salmonella- Common in many animals. Transmitted to humans by oral route.
Enteric (typhoid) fever, bacteremia, and enterocolitis. Invasive (gut to blood) and toxigenic.
Shigella- Humans only. Shigellosis (dysentery) and traveler’s diarrhea.
LPS, exotoxins, and enterotoxins (interfere with nutrient uptake). Appearance in blood is rare.
Klebsiella pneumoniae- Normal flora of respiratory or GI tract. Diseases similar to E. coli, and pediatric septicemia, pneumonias in the immunocompromised, esp. chronic alcoholism
Serratia marcescens- Normally free-living. Very opportunistic. Nosocomial infections- UTI’s and respiratory tract infections (RTI)
Proteus spp.- UTI’s, wound infections, and infant diarrhea. Highly motile. Yersinia pestis- Many toxins. Multiply rapidly in blood and other tissues.
Bubonic plague: Rats ➡️Fleas ➡️ Humans. Pneumonic plague: Respiratory aerosols. Enterobacter cloacae and E. aerogenes- common inhabitants of soil, water, & animals.
Nosocomial infections- UTI and sepsis.
Facultative anaerobes 3
Vibrio-
curved rods (comma shapes). Among most common inhabitants of surface waters. Vibrio cholerae- cholera. Contaminated water, poor sanitation. Potent enterotoxin.
V. parahaemolyticus- A halophile. Gastroenteritis from raw or poorly cooked fish and shellfish
Pasteurella- primarily animal pathogens. Transmitted to humans by dog or cat bite.
P. multocida- in humans, local lymphadenopathy, followed by widespread infection, septicemia and
chronic respiratory infection. Toxigenic.
Haemophilus influenza- Non-encapsulated may be normal flora. Encapsulated is pathogenic. Spread by
inhalation. Meningitis and earache in infants and children; laryngotracheitis. RTI in children and adults.
Facultative anaerobes 4
Anaerobic, straight, curved, and helical rods
Bacteroides- Normal intestinal flora. Peritonitis, following puncture wounds Fusobacteria- Normal oral flora. Dental abscesses
Facultative anaerobes 5
Obligate intracellular parasites-
reproduce only in host cells
Rickettsia- Most are arthropod borne. Multiply in endothelial cells of many organs & cause necrosis
R. prowazeckii- epidemic typhus. Grows in cytoplasm
R. rickettsia- Rocky Mountain Spotted Fever. Grows in nucleus
Coxiella burnetti- Q fever. Inhalation. Influenza, pneumonia, hepatitis, encephalopathy.
Chlamydia spp. - Cannot synthesize ATP. Persistent parasites. Blindness, respiratory disease, venereal disease.
Facultative anaerobes 5
NO CELL WALL:
Mycoplasma
Very small. Often normal flora of mouth, gut and urogenital tract. Can be intracellular parasites. Atypical
pneumonia and urethritis, esp. in compromised host, post-partum disease. Toxigenic.
