Lecture 11 notes
Lecture 11 notes BIO 4405
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This 5 page Class Notes was uploaded by Mary Moore on Saturday September 24, 2016. The Class Notes belongs to BIO 4405 at Mississippi State University taught by Heather Jordan in Fall 2016. Since its upload, it has received 24 views. For similar materials see Pathogenic Microbiology in Biology at Mississippi State University.
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Date Created: 09/24/16
Clostridium species characteristics They are found in abundant amounts in soil, water, sewage They are part of the normal microbial flora They are large gram positive rods (notice that this is not the “standard” gram positive shape as gram positive usually means cocci shaped bacteria) They do form spores They are anaerobic (or grow without oxygen) First type of Clostridium: C. perfringens (perfringens = “breaking through”) They have the common Clostridium species characteristics above, except its spores are rarely observed in vivo or in vitro (it rarely forming spores differentiates it from the other Clostridium types of bacteria) Non-motile, rapidly spreading growth on lab media Double zone of hemolysis on blood agar (meaning Produces numerous “lethal toxins” and enzymes. One it produces is the Alpha toxin – a lecithinase (Phospholipase C) that lyses red blood cells, platelets, and leukocytes. The alpha toxin causes massive hemolysis, increased vascular permeability and bleeding, tissue destruction, hempatic toxicity, and myocardial dysfunction. *to remember the alpha toxin is produced by C. perfringens, Alpha toxin is a phospholipase C (they both have the same beginning letters, C and P; If you can remember C. perfringens produces a phospholipase C, just remember the phospholipase C is an alpha toxin) Diseases caused by C. perfringens: Gastroenteritis (or Clostridial food poisoning) o Usually due to eating meat products, such as chicken, turkey, or beef, that has been contaminated with soil or dust spores o It has a short incubation period (8 to 24 hours) o Includes abdominal cramps and diarrhea, but no fever, nausea, or vomiting is present o Clinical course lasts 24 to 48 hours (self-limiting: once toxin is out of the body, symptoms subside) o Due to the action of a heat-labile exterotoxin (superantigen) o Holding contaminated food at temperatures less than 60C allows spores, that survived during cooking, to germinate and grow, but refrigerating after cooking can prevent bacterial growth and reheating food at 74C can destroy the heat-labile enterotoxin Soft tissue infections o Cellulitis can develop in wounds: Fasciitis (suppurative myositis) – a buildup of pus in the muscle planes; also not pain generally Myonecrosis (gas gangrene) – most common disease caused by C. perfringens Pain, edema, cellulitis Present of gas in tissues (gas gangrene) Hemolysis, jaundice, and blood tinged exudates are common Shock and death can ensue. High mortality rate Abundant of rectangular gram-positive rods and absence of inflammatory cells (because most are lysed by clostridial toxins) Diagnosis and Treatment of C. perfringens Labs only performs a confirmatory role in diagnosing suspected Clostridial soft-tissue infections because antibiotics must be given immediately The detection of gram-positive rods from tissue and absence of leukocytes under a microscope can diagnosed C. perfringens It is simple to culture, but culture is not commonly used to diagnose Clostridial food poisoning Treatment of severe soft-tissue infections must be treated with surgical debridement and high- dose penicillin therapy Replacement of fluids or Tylenol is given for food poisoning Although exposure to C. perfringens is difficult to avoid, proper wound care and use of diseased- preventative antibiotics helps to prevent infections Second type of Clostridium: C. tetani (tetani = related to “tension”- the locking of muscles or jaw in a disease) Motile (remember C. perfringens was non-motile) Drumstick-shaped spores Spores are widespread in soil – usually enter through wound It is difficult to grow in culture because it is extremely sensitive to oxygen toxicity Germination of spores is favored by necrotic tissue and poor blood supply Causes the disease tetanus or “lockjaw” Produces two toxins: o Tetanolysin – oxygen labile hemolysis (type II toxin) (allows the organism to survive longer) o Tetanospasmin- plasmid-encoded (plasmid is non-coagulated- meaning it cannot turn a nontoxic strain into a toxic strain), heat-labile neurotoxin (A-B toxin) It is the major cause of disease symptoms It binds to specific receptors on the surface of motor neurons and is taken up by receptor-mediated endocytosis. It is then carried to the central nervous system where the endosome becomes acidified, resulting in the release of the light chain portion of the toxin into the cytosol The light chain is a zinc endopeptidase that cleaves proteins involved with the release of the inhibitory neurotransmitters glycine and gamma-aminobutyric acid (GABA). This causes spastic paralysis and toxic binding is irreversible. Diseases caused by C. tetani Generalized tetanus o It is violent spasms that occur in the masseter muscles (one of the facial muscles)- lockjaw or trismus o One of its characteristics is a sardonic smile (or grimace), known as Risus sardomicus o Includes drooling, sweating, irritability, and persistent back spasms (opisthotonos) o In more severe cases, it includes cardiac arrhythmias and respiratory failure o A high mortality rate is associated with this Neonatal tetanus –an infections of the umbilical stump that become generalized o It is almost a disease found only in developing countries o It has a mortality rate of over 90% o To recover functions, it requires regeneration of nerve endings Diagnosis and Treatment of C. tetani Diagnosed by clinical presentation by microscope detenction and culture results Treatment includes o Wound debridement and proper wound care o the use of metronidazole or penicillin, but penicillin inhibits GABA activity, which can lead to central nervous system excitability o Passive immunization with human tetanus immunoglobulin o Vaccination with tetanus toxoid, a series of three shots of toxoid followed by a given booster every 10 years Third type of Clostridium: C. botulinum (botulus = “sausage”) It is found in soil and dust It is clinical used for Botox or injection to prevent grinding of teeth, chronic headaches, Parkinson’s disease, etc. The production of the botulinum toxin (an A-B toxin) causes disease symptoms – a.k.a. the most toxic substance known to man o It’s non-toxic heavy chain serves as a receptor and light chain is released after acidification of endosome, like with tetanospasmin o To differ from Tetanospasmin, the botulinum neurotoxin includes protective proteins, remains at neuromuscular junction, and cleaves proteins involved in the release of acetylcholine Diseases caused by C. botulinum Foodborne botulism (an intoxication) o Usually due to eating food with the toxin in it o Involved with home-canned foods, especially vegetables o Includes blurred or double vision, fixed dilated pupils, dry mouth, constipation, and abdominal pain, but NO fever is associated o Can even include respiratory paralysis o Recovery time can be from a few months to a year o As it’s mortality rate used to be 70%, it has then decreased to 5%-10% Infant botulism (a toxin-infection) o It is the most common form of botulism in the U.S. o In infants, the neurotoxin is established in the GI tract (infants younger than 1 year don’t have complex normal flora yet) o Includes constipation, weak cry, “failure to thrive”. If the disease progresses, further symptoms of flaccid paralysis and respiratory arrest can be seen o Often associated with the consumption of spore containing honey Treatment of C. botulism Proper sterilization and canning of canned and vacuum sealed-foods Honey shouldn’t be given to babies younger than a year old Treatment includes ventilatory support, gastric lavage and use of metronidazole or penicillin, and the use of trivalent botulinum antitoxin Fourth and final type of Clostridium: C. difficile (difficile = “difficult”) Associated with antibiotic-associated diseases, such an antibiotic-caused diarrhea It produces two toxins: o Toxin A (enterotoxin) Chemotactic for neutrophils Cytopathic effect, disrupting tight junctions, increased permeability of intestinal wall, and diarrhea o Toxin B (cytotoxin) Causes actin to depolymerize (destruction of cell structure) Surface-layer proteins that help attach C. difficile to intestinal epithelium Diagnosis and Treatment of C. difficile It’s toxins are found in stool of an infected patient with its associated symptoms Discontinuation of the antibiotic-associated (clindamycin, fluoroquinolones) Includes the use of oral metronidazole or vancomycin Proper sanitation and cleaning of hospital rooms as spores can contaminate the rooms *On slide 21, Asymptomatically colonized patients are found to be protected against toxins Aerobic, non-spore forming gram positive rods Three types can be differentiated by clinical presentation and microscopic morphology: o Listeria monocytogenes o Corynebacterium diphtheriae o Mycobacterium Listeria monocytogenes Facultative anaerobic with tumbling motility and cold growth (rare in pathogens) and can grow in high salt Short rods appear single, in pairs, or in short chains Weak β-hemolysis on blood agar Grows in macrophages and cells lining the GI tract (found in the GI tract of animals) Associated with newborns, the elderly, pregnant women, immunocompromised people Can survive proteolytic enzymes, stomach acid, and bile salts Adheres to host cells via internalin proteins (InlA, InlB) and escapes from phagosomes via activation of a type II exotoxin (Listeriolysin) and two different phospholipase C enzymes Humoral immunity is unimportant because It is intracellular It has a high mortality rate of 20%-30% for foodborne diseases Disease caused by Listeria monocytogenes Mild gastroenteritis – mild influenza-like symptoms with possible gastroenteritis, can be confused with a 24-hour flu Septicemia – often in pregnant women; history of chills and fever or more acute high grade fever and hypotension Neonatal disease o Early onset- before birth Can result in abortion, a stillbirth, or premature birth Granulomatosis infantiseptica – disseminated abscesses and granulomas in multiple organs (high mortality rate if not treated promptly) o Late onset – soon after birth 2 to 3 weeks after birth Meningitis or meningoencephalitis with septicemia Meningitis in adults – most common form of Listeria in adults o Found in patients with organ transplants or cancer and pregnant women with meningitis o It has a high mortality rate of 20% to 50% o Significant neurological sequelae in among survivors Diagnosis and Treatment of Listeria monocytogenes A gram stain of cerebrospinal fluid typically shows no organisms, this differentiates it from other causes of meningitis Must be distinguished from pneumococcus, enterococcus, and Corynebacterium Beta hemolysis on sheep blood agar, positive CAMP test, characteristic motility, cold enrichment Gentamicin with penicillin or ampicillin; also trimethoprim-sulfamethoxazone is effective
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