Final: - Cocci, + Bacillus Flashcards
Neisseria characteristics
Neisseria are Gram-negative diplococci that are fastidious and require enriched media and an atmosphere rich in CO2 for growth. Pathogenic strains are usually encapsulated.
Neisseria virulence factors
Neisseria species have several virulence factors: fimbriae and capsules aid attachment to mucous membranes and resistance to phagocytosis; LPS endotoxin causes fever, inflammation, and toxic shock; protease destroys secretory IgA; penicillinase destroys penicillin.
N. gonorrhoeae characteristics
Neisseria gonorrhoeae is primarily an STD but can also infect newborns during birth, causing ophthalmia neonatorum (prevented by silver nitrate or antibiotics). It attaches to mucous membranes and can spread to joints, endocardium, or meninges.
N. gonorrhoeae immunization and treatment
There is no vaccine for gonorrhea, and infections do not provide lasting immunity. Penicillin was once the treatment of choice, but penicillinase-producing strains are now common, requiring combination antibiotics for multiple STDs.
N. meningitidis characteristics
Neisseria meningitidis causes epidemic meningococcal meningitis. Carriers are asymptomatic but transmit the bacteria by droplets. The infection may progress from pharyngitis to blood infection and meningitis.
N. meningitidis immunization and treatment
Immunization with a capsular polysaccharide vaccine is used, particularly during epidemics. Chemotherapy involves penicillin or chloramphenicol, with rifampin or tetracycline used prophylactically for close contacts.
Bacillus characteristics
Bacillus species are Gram-positive, catalase-positive, endospore-forming rods commonly found in soil. Only two species are pathogenic: B. anthracis (anthrax) and B. cereus (food poisoning).
B. anthracis virulence factors
Bacillus anthracis has a polypeptide capsule to prevent phagocytosis and exotoxins that cause edema, cell death, and toxic shock.
B. anthracis types
Bacillus anthracis causes three types of anthrax: gastrointestinal anthrax (ingested contaminated meat), cutaneous anthrax (wounds), and pulmonary anthrax (inhaled spores causing severe shock and possible death).
B. anthracis treatment and immunization
Immunization for B. anthracis is given to high-risk individuals, using a live spore vaccine for animals and a purified toxoid for humans. Treatment includes penicillins, tetracyclines, or ciprofloxacin.
B. cereus food poisoning
Bacillus cereus causes food poisoning similar to S. aureus, where spores in food germinate and produce enterotoxins. Symptoms are rapid and include vomiting and diarrhea.
Clostridium characteristics
Clostridium species are Gram-positive, catalase-negative, endospore-forming rods, often found in soil. They are anaerobic and produce potent toxins causing tissue infections and food intoxications.
Clostridium virulence factors
Clostridium species produce toxins such as collagenase, hyaluronidase, DNase, and lecithinase that cause tissue destruction and gas formation in infections.
Gas gangrene and Clostridium species
Clostridium perfringens, novyi, and septicum cause gas gangrene, where endospores enter wounds, germinate, and produce gas and toxins leading to tissue necrosis.
Clostridium gas gangrene treatment
Treatment includes debridement (removal of infected tissue), antibiotics (cephalosporins or penicillins), and sometimes hyperbaric oxygen therapy.
Clostridium difficile colitis
Clostridium difficile can cause antibiotic-associated colitis, especially after broad-spectrum antibiotics wipe out normal intestinal flora. The bacteria produce toxins that inflame the colon and cause diarrhea.
Tetanus and Clostridium tetani
Clostridium tetani produces tetanospasmin, a potent neurotoxin that causes prolonged muscle contractions (lockjaw) and can be fatal if not treated promptly. Tetanus is prevented by vaccination (DTP).
Botulism and Clostridium botulinum
Clostridium botulinum causes botulism, a food intoxication where botulinum toxin paralyzes muscles, leading to respiratory failure. Foodborne botulism is caused by improperly canned foods.
Infant botulism and Clostridium botulinum
Infant botulism occurs when infants ingest Clostridium botulinum spores from honey or unprocessed foods, leading to the production of botulinum toxin in the intestines.
Wound botulism
Wound botulism occurs when Clostridium botulinum spores enter a wound and produce botulinum toxin, leading to paralysis similar to foodborne botulism.
Clostridium perfringens food poisoning
Clostridium perfringens causes food poisoning when spores sporulate in the intestines, producing enterotoxins that lead to diarrhea, but it is not usually fatal.
Listeria monocytogenes characteristics
Listeria monocytogenes are Gram-positive rods, motile with 1-4 flagella, and cause listeriosis. It can cause mild symptoms in healthy individuals but is dangerous to immunocompromised individuals, pregnant women, and newborns.
Listeria monocytogenes transmission and treatment
Listeria is foodborne, typically from contaminated dairy or meat products, and can grow at refrigerator temperatures. Treatment typically includes ampicillin or trimethoprim-sulfamethoxazole.
Corynebacterium diphtheriae characteristics
Corynebacterium diphtheriae are pleomorphic rods that cause diphtheria. The bacteria produce a toxin that causes throat inflammation, a grayish pseudo-membrane, and can lead to heart and kidney damage.
Diphtheria transmission and treatment
Corynebacterium diphtheriae is contracted through airborne droplets. Treatment includes antitoxin, antibiotics, and sometimes physical removal of the pseudo-membrane.
Mycobacterium characteristics
Mycobacterium are acid-fast, filamentous rods that are slow-growing and resistant to germicides and drying due to their waxy coat. Two primary pathogenic species are M. tuberculosis and M. leprae.
M. tuberculosis characteristics
Mycobacterium tuberculosis causes tuberculosis, primarily affecting the lungs. It is transmitted by airborne droplets and can remain dormant in the body, reactivating later, especially in immunocompromised individuals.
M. tuberculosis treatment and immunization
Tuberculosis treatment requires long-term use of multiple drugs to prevent resistance. The BCG vaccine, derived from M. bovis, is used in some countries to prevent tuberculosis.
M. leprae characteristics
Mycobacterium leprae causes leprosy, affecting skin and peripheral nerves. The disease has a slow onset, with an incubation period of 3-5 years. It can cause disfiguring lesions in the advanced stages.
M. leprae transmission and treatment
Transmission of M. leprae is not fully understood, but it may be spread by direct contact or through respiratory droplets. Treatment for leprosy involves multi-drug therapy over several years.
