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33 Cards in this Set

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Streptococcus pyogenes

- Also called group A streptococci


- Lyse red blood cells via beta-hemolysis


- Strep throat, ear infections, impetigo


- Can lead to scarlet fever, rheumatic fever, acute glomerulonephritis and streptococcal toxic shock syndrome


- Frequently isolated from the upper respiratory tract of healthy adults

Streptococcus pneumoniae

- Encapsulated strains are very invasive


- Used in Griffith's experiments


- Reduced lung function, called pneumonia, results from the accumulation of recruited phagocytic cells and fluid


- Still sensitive to vancomycin

Pneumonia

- Kills about 5 million children per year


- Common nosocomial infection


- At least 80 different causes (not a single disease)

Corynebacterium diphtheriae

- Cause of diphtheria


- Enters the host form airborne droplets, infecting the tissues of the throat and tonsils


- Pathogenic strains carry a lysogenic bacteriophage whose genome encodes an exotoxin called diphtheria toxin


- Causes formation of a pseudomembrane: a combination of damaged host cells and C. diphtheriae cells


- Gram positive


- Non-motile


- Aerobic

Diphtheria Toxin

- Exotoxin


- Inhibits protein synthesis in the host, leading to cell death

Bordetella pertussis

- Causative agent of pertussis (whooping cough)


- Produces both an exotoxin (which induces cAMP synthesis) and an endotoxin


- Up to 50 million cases worldwide and 250,000 deaths


- Cases in the U. S. are rising due to lower vaccination rates and prevalence of the bacteria

Pertussis Exotoxin

- Induces synthesis of cAMP which is partially responsible for the vents that lead to host tissue damage in pertussis

Mycobacterium tuberculosis

- Causative agent of tuberculosis


- Subject of study by Robert Koch


- Gram-positive


- Acid-fast


- Widespread, airborne transmission


- 1.5 million deaths per year


- Bacteria survive and grow within macrophages in the tubercles to evade the immune system


- Cell membrane has unique lipids and glycolipids that are toxic to eukaryotic cells, and form a hydrophobic protective barrier


- Treated with a 6-9 month course of antibiotics


- Problems with multi drug resistance


- Resistance is a problem because cellular components contribute to extended antibiotic treatment times


- Granulomas arise if the disease is not controlled, leading to extensive destruction of lung tissue

Mycobacterium leprae

- Causative agent of leprosy, also known as "Hansen's disease"


- Intracellular pathogen


- Gram-positive


- Acid-fast


- Lepromatous leprosy characterized by folded, bulblike lesions on the body


- Causes loss of limbs


- Around 250,000 new cases per year, mostly in Africa, Indian subcontinent and Brazil


- Transmitted by direct contact of nasal secretions as well as an airborne route but is not highly contagious


- Very long incubation time


- Blood test has been developed



Tuberculoid Leprosy

- Mild, non progressive form


- Damaged nerves and areas of the skin bordered by nodules

Lepromatous Leprosy

- Progressive


- Large numbers of M. leprae develop in the skin cells killing the skin tissue


- Progressive loss of facial features and appendages


- Disfiguration

Meningitis

- An inflammation of the meninges, the membranes that are the protective covering of the central nervous system, that is, the spinal cord and brain


- Several different microorganisms, including certain viruses, bacteria, fungi, and protists, can cause meningitis

Neisseria meningitidis

- Causative agent of infectious meningitis


- Gram negative


- Obligate aerobe


- Coccus


- Infection is airborne or by close contact


- May lead to meningococcemia


- Vaccinations are available


- Treatment is via rapid antibiotic delivery


- The bacteria is able to cross the blood-brain barrier resulting in release of neurotoxins that cause paralysis

What are the most common causes of bacterial meningitis?

- Streptococcus pneumoniae


- Neisseria meningitidis (meningococcal meningitis)


- Haemophilus influenzae

Meningococcemia

A condition which causes tissue destruction, shock, and in 10% of cases, death as a result of N. meningitidis bacteremia

Staphylococcal Infections

- Major cause of bacterial disease


- Acne, boils, pimples, impetigo, pneumonia, osteomyelitis, caryatids, meningitis and arthritis


- Staphylococcus (Firmicutes) are normal inhabitants of the upper respiratory tract, skin, gut, and genital tract


- Pyogenic (pus-producing) cocci


- Peptidoglycan layer and teichoic acid contribute to pathogenicity


- Coagulase positive Staphylococcus aureus is the most important human pathogen in this group


- Divided into slime producers (pathogenic) and non slime producers


- Many virulence genes are carried on plasmids


- Common nosocomial infections


- Can be spread to pretty much any area of the body


- Common form of food poisoning

Staphylococcus aureus

- Produces the virulence factor coagulase


- Produces leukocidin, a protein that destroys white blood cells


- Certain strains cause toxic shock syndrome (TSS)


- MRSA (methicillin resistant Staph. aureus) exists as well as VRSA (vancomycin-resistant)


- Normal treatment is penicillin or cephalosporin

Coagulase

- Virulence factor produced by Staphylococcus aureus


- An enzyme that converts fibrin to fibrinogen, forming a localized clot. Clotting induced by coagulase results in the accumulation of fibrin around the bacterial cells, making it difficult for host immune cells to contact the bacteria and initiate phagocytosis

Toxic Shock Syndrome (TSS)

- Associated with high absorbency tampons


- Staphylococcus aureus


- High fever, rash, vomiting, and death


- Seen in both men and women and is typically initiated by staphylococcal infections following surgery


- Symptoms result from an exotoxin called toxic shock syndrome toxin-1 (superantigen)

Toxic Shock Syndrome Toxin-1

- Exotoxin produced during toxic shock syndrome


- Superantigen that recruits large numbers of T cells to the site of infection


- The major inflammatory response that results is fatal in about 70% of cases

Helicobacter pylori

- Gram negative


- Highly motile


- Spiral-shaped bacterium


- Associated with chronic gastritis


- Forms ulcers in the gut that can rupture, bleed, and result in death


- Adheres to mucous-secreting cells under the mucous layer


- Produces urease leading to ammonia production


- Treatment involves both antibiotics and drugs to decrease stomach acid


- Up to 50% of the world's population is infected


- A correlation exists between lack of helicobacter and asthma, which suggests that they are actually important tin the development of the immune system

Neisseria gonorrhoeae

- Gram negative


- Betaproteobacteria


- Obligate aerobe


- Cannot survive away from mucous membranes


- Only transmitted by intimate person-to-person contact


- Can be passed vertically, from mother to fetus


- Utilizes type IV pili to attach to host cell


- Interaction with host cell receptors allow the bacteria to enter host cells


- May be asymptomatic in females (and lead to pelvic inflammatory disease which can lead to sterility)


- Infects urethral canal in males and causes pus-like discharge


- May cause blindness in infants


- Large number of antigenic variation


- Birth control increases the pH of the vagina which means lactic acid bacteria normally found in the adult vagina fail to develop, and this reduces competition for colonization by the bacteria


- Produces an endotoxin but not an exotoxin


- Treatment: cell wall inhibitors and translation inhibitors

Treponema pallidum

- Causative agent of syphilis


- Gram negative


- Spirochaete


- Transmitted through sexual contact or from mother to fetus during pregnancy


- Obligate intracellular parasite


- Cannot be cultured in a lab and is difficult to research


- Has glycolytic enzymes, but no TCA cycle or oxidative phosphorylation


- Easily treatable with penicillin, no antibiotic resistance


- Imports ATP


- Estimated that there are 12 million new cases a year


- Kills about 100,000 people per year


- Initially causes chancres, but can progress to attack the CNS (to cause neurodegenerative disorders) and cardiovascular system

Chlamydia trachomatis

- Gram negative


- Non-proteobacteria


- Obligate intracellular parasite (when not inside the host cell, it is metabolically inert)


- Leading cause of bacterial STDs (est. up to 4 million cases per year in the U.S. alone!)


- Nongonococcal urethritis


- Difficult to detect


- Elementary bodies outside of the host cell: thought to be metabolically inert


- When they enter the host cell they become reticulate bodies which are metabolically active


- Can be transmitted to the newborn in the birth canal


- If left untreated, can lead to infertility in women

Lyme Disease

- Arthropod-transmitted bacteria


- Humans are accidental hosts while arthropods are the reservoir (natural hosts)


- Tickborne, affects humans and other animals


- Headache, backache, chills, fatigue, bull's eye rash


- Chronic infections lead to arthritis, neurological problems, and heart damage

Barrel burgdorferi

- Causative agent of Lyme Disease


- Tickborne, affects humans and other animals


- Spirochaete


- Has 21 different plasmids (circular as well as linear) that are important for pathogenicity


- Chronic conditions are difficult to treat because the bacteria is able to cross the blood-brain barrier


- Linear chromosome (one of only a handful of bacteria that have this as opposed to a circular chromosome)


- Treatable with tetracycline or penicillin

Yersinia pestis

- Causative agent of the Plague


- Gram negative


- Facultative aerobic


- Rod-shaped


- Can be spread by infected flea, direct contact with infected animals or inhalation


- Multiply in the blood and lymph


- Enlarged lymph nodes = "buboes"


- Without treatment, death occurs in 3-5 days


- Hide in phagocytic cells


- Injects effectors in host cells to help it establish its infection


- Treatable with streptomycin


- Importance of the Type Three Secretion System

Pneumonic Plague

Kills within 48 hours

Septicaemic Plague

- Spread through the blood stream


- Does not form buboes

Vibrio cholerae

- Causative agent of cholera


- Gram negative


- Proteobacteria


- Comma shaped


- Characterized by profuse diarrhea


- Water- or food-borne


- Release cholera toxin (an enterotoxin) in the small intestine


- Adheres to intestinal cells and secretes choleragen, an AB exotoxin


- The A subunit enter intestinal epithelial cells and activates adenylate cyclase via ADP-ribosylation. This results in hyper-secretion of water and chloride ions form the cells


- Ingesting over 10^8 bacteria causes the disease (less is required if it is food-borne)


- There are 1.4 to 4.3 million cases and 28,000 to 142,000 deaths worldwide every year


- Electrolyte therapy and fluid is required to avoid death

Food-Borne Bacterial Diseases

- Similar to water-borne


- About 4 million cases per year


- Result in 11,600 hospitalizations and 238 deaths in Canada


- Food poisoning (food intoxication): the ingestion of toxins


- Occurs when there is enough bacteria in the food to establish an infection

Clostridium botulinum

- Gram positive


- Endospore-forming


- Rod-shaped


- Inhabits soil or water, but produces endospores which can contaminate food


- Botulinum toxin is a neurotoxin


- Often associated with home canning


- Treatment is with an antitoxin

Escherichia coli

- Most strains are not pathogenic


- There are six categories of diarrheagenic E. coli


- Treatment is with fluids and antibiotics such as doxycycline and trimethoprim-sulfamethoxazole