Chapter 19: Gram Positive, Pathogenic Bacteria Flashcards

Question

How is Streptococcus agalactiae pathogenic?

Answer 1

Capsule is not protective (unlike S. pyogenes) Often infects newborns without specific antibodies Produces enzymes (proteases, hemolysins, hyaluronidase, etc.) whose roles are not yet understood

Answer 2

Associated with neonatal bactermia, meningitis, and pneumonia Older, immunocomprimised patients also at risk

Answer 3

Diagnosis- ELISA test used to identify group B streptococcus Treatment-Penicilin G is the drug of choice Prevention- immunization of women can protect future children

Answer 4

Alpha-hemolytic Streptococci (incompletely break down RBCs, WBCs, etc.) Lack group specific carbohydrates- cannot be classified using Lancefield system Many produce a green pigment when grown on blood media Inhabit mouth, pharynx, GI tract, genital tract, and urinary tract One cause of dental caries and dental plaque- Stick to dental surfaces via dextarn If enter the blood can cause meningitis and endocarditis

Answer 5

Streptococcus pneumoniae Gram positive cocci that most commonly form pairs Form unpigmented, alpha hemolytic colonies on blood agar

Answer 6

Polysaccaride capsule (required for virulence) Phosphorylcholine- stimulates cells to phagocytize the bacteria Protein adhesin- mediates binding of cells to epithelial cells of pharynx Secretory IgA protease- destroys IgA (anitbodies found in the pharynx) Pneumolysin- binds to cholesterol in the cytoplasmic membranes of epithelial cells, producing pores that result in cell lysis

Answer 7

Pneumococcal pneumonia- bacteria multiply in the alveoli, damaging the alveolar lining, allowing fluid, RBCs, and leukocytes to enter the lunds Sinusitis and otitis media- bacteria can invade the sinuses and middle ear causing pus and inflammation Bacteremia and endocarditis- colonize in the blood and heart Pneumococcal meningitis- spread to the meninges

Answer 8

Diagnosis- gram-stain of sputum smears, confirmed with Quellung reaction (anti-capsular antibodies cause the capsule to swell) Treatment- penicillin Prevention- vaccine made from purified capsular material

Answer 9

Previously classified with group D streptococcus- reclassified as a separate genus Gram positive, unencapsulated, catalase negative, non-hemolytic Forms short chains and pairs Can grow up to 45 degrees Celsius, pH 9.6, and can grow in the presence of salt and bile Found in the human colon where it is rarely pathogenic- may introduce disease if found in a different area Enterococcus faecalis and Enterococcus faecium

Answer 10

Important cause of nosocomial infections Difficult to treat because enterococci often are resistant to antimicrobials Prevention in health care setting is difficult- patients often have weakened immune systems

Answer 11

Gram positive bacilli that occur singly, in pairs, or in chains Normally dwells in soil, is facultatively anaerobic Form endospores and posess and protective capsule composed of polyglutamic acid which inhibits phagocytosis (not polysaccharides) Pathogenic strains produce anthrax toxin containing three polypeptides: Edema factor, Protective antigen, and Lethal factor

Answer 12

Primarily a disease of herbivores (zoonoses) Humans contract via one of three routes- inhalation of spores (most deadly), incoluation of spores through break in skin, ingestion of spores Category A bioterror agent

Answer 13

Bacillus anthracis only causes anthrax Three clinical manifestations Gastrointestinal anthrax- rare in humans, results in intestinal hemorraging and death Cutaneous- produces a painless, swollen, black, crusty ulcer called an eschar which releases a toxin in blood Inhalation- rare in fever, high fever, aches, labored breathing, high mortality rate

Answer 14

Diagnosis- large, nonmotile Gram-positive bailli in lung or skin sample Treatment- ciproflaxacin and many other antimicrobials Prevention- control of disease in animals, effective vaccine available (requires multiple doses and boosters)

Answer 15

Gram positive, anaerobic, endospore-forming bacillus Ubiquitous in soil, water, and gastrointestinal tracts of animals and humans Endospores allow for survival in harsh conditions Ability to secrete potent toxins- histolytic, enterotoxins, and neurotoxins 4 important species- C.perfringens, C.difficile, C. botulinum, and C. tetani

Answer 16

Produces toxins that can cause irreversible damage to body Food poisioning- abdominal cramps and watery diarrhea, lasts for less than 24 hours, occurs through ingestion of contaminated meat Gas gangrene- trauma introduces endospores into body where they germinate in anaerobic environment of deep tissues (extremities) Endospores germinate and cause necrosis, produce gaseous watse (results in bubbling or crakcing cells)

Answer 17

Diagnosis- presence of minimum bacterial load in food or feces, gas gangrene self diagnostic Treatment- food poisoning is self limited, gas gangrene requires removel of dead tissue and administering antitoxins and antimicrobials Prevention- dfficult to prevent because organism is so common, reheating food can destory toxin

Answer 18

Very difficult to treat Common member of intestinal microbiota Opportunistic pathogen in patients taking broad-spectrum antimicrobial drugs Minor infections result in self-limiting explosive diarrhea May cause pseudomembranous colities (sections of colon wall slough off) which can follow the use of broad spectrum antibiotics Toxin A causes diarrhea and Toxin B is cytotoxic to colon cells (life threatening)

Answer 19

Diagnosis- isolation of organism from feces of immnoassay Treatment- discontinue causative antimicrobial drugs to resolve minor infections, serious cases treated with vancomycin or metronidazole New, more pathogenic strain Prevention- proper hygiene to limit nosocomial infections

Answer 20

Common in soil or water Botulism results when the endospore germiantes and produces potent neurotoxins Seven known botulinum toxins, A through G

Answer 21

Acetylcholine is a neurotransmitter that mediates communication between neurons and othe cells Botulism prevents the release of acetylcholine into the synaptic cleft, resulting in the prevention of muscular contraction (flaccid paralysis)

Answer 22

Botulism in an intoxation, not an infection 3 Manifestations: Foodborne botulism (canned food, preserved fish)- results from ingestion of toxins, death can result from asphyixation Infant botulism (honey)- results from ingestion of endospores- "Failure to thrive" Wound botulism- contamination of wound by endospores

Answer 23

Diagnosis- symptoms are diagnostic Treatment- administer neutralizing antibodies against botulism toxin, administer antimicrobial durgs in infant botulism cases Prevention- proper canning of food, infants under one year should not eat honey

Answer 24

Obligately anaerobic Ubiquitious in soil, dust, and GI tract of animals and humans Tetanus results when endospores germinate and produce tetanus toxin- tetanospasmin

Answer 25

Blocks the release of inhibitory neurotransmitters leading to constant contraction of muscles

Answer 26

Diagnosis- characteristic muscle contraction Treatment- administer immunoglobulin against tetanus toxin, administer antimicrobial drugs, active immunization with tetanus toxoid Prevention- immunization with tetanus toxoid, five doses beginning at 2 months of age, followed by a booster every ten years of life

Answer 27

Gram positive, low G+C, non-spore-forming coccobacillus Ubiquitous in nature; found in soil, water, mammals, birds, fish, and insects Enters body in contaminated food and drink Motility at lower temperatures through flagella and due to actin polymerization at 37 degrees Celsius within a human cell Intracellular pathogen

Answer 28

Virulence is directly related to the bacteria's ability to live and spread within cells Unique ability to survive over a wide range of temperatures from 4 to 40 degrees Celsius Causes an uncommon but potentially serious type of food-borne infection known as listeriosis E.g.- Listeria monocytogenes

Answer 29

Listeria is acquired by ingestion, must find and adhere to the small intestine mucosa to infect it Highly motile due to flagella at lower temperatures (20- 25°C) Actin-based tumbling motility in human cells Uses host cell actin to move within and between host cells Polymerizes actin molecules into long stiff actin filament tails that propel the bacteria into cytoplasm

Answer 30

Listeria binds to the surface of a phagocytic cell and triggers its own endocytosis Adherence and invasion is mediated by membrane proteins internalins Once inside the human cell’s phagosome, Listeria synthesizes a pore-forming cytotoxin, called Listeriolysin O (LLO) It also produces two other enzymes, phosphatidylinositol- specific phospholipase C (PI-PLC) and phospholipase C (PC-PLC) All enzymes help Listeria to escape from phagosome

Answer 31

Listeria is initially endocytized The intracellular bacteria escapes the phagosome and reproduces within the phagocyte The bacteria then polymerizes the host cell’s actin filaments at one end to form a “tail” that propels it through the cytoplasm into pseudopods A neighboring cell then endocytizes the pseudopod Listeria once again “tunnels” its way out of the phagosome and continues its intracellular existence

Answer 32

L. monocytogenes is rarely pathogenic in healthy adults Causes high mortality in individuals developing systemic infection Most deaths involve fetuses, newborns, or immunocompromised adults One of the few microbes that can cross the placenta and blood brain barrier, results in miscarriage, stillbirths, or severely infected newborn Immunocompromised adults can develop meningitis, and death Very difficult to control during food processing as it can multiply over wide range of temperatures Incubation period very long from 11-70 days

Answer 33

Diagnosis- Presence of bacteria in the cerebrospinal fluid, characteristic tumbling motility (only at room temp.), Rarely seen in Gram stain Can be cultured by cold enrichment technique Treatment-Antimicrobial drugs like penicillin and erythromycin inhibit Listeria Resistant to tetracycline and trimethoprim Prevention-Difficult because organism is ubiquitousAt-risk individuals should avoid certain foods like raw vegetables, unpasteurized milk, soft cheeses, cole slaw, etc.

Answer 34

Smallest free-living microbes, pleomorphic Lack cytochromes, enzymes of the Krebs cycle, and cell walls Most have sterols in their cytoplasmic membranes Classified as low G+C, gram positive bacteria according to genetic classification, even though they stain pink with Gram stain Require various growth factors from a host or supplied in laboratory media Can colonize the mucous membranes of the respiratory and urinary tracts

Answer 35

Attaches to epithelial cells lining the respiratory tracts of humans Causes primary atypical pneumonia (walking pneumonia) Early symptoms not typical of other types of pneumonia Not usually severe enough to require hospitalization Not seasonal Spread by nasal secretions among people in close contact Diagnosis difficult Mycoplasmas are small and difficult to detect Difficult to prevent Patients often infectious without signs or symptoms Erythromycin or tetracycline No vaccine available

Answer 36

Three other mycoplasma associated with human diseases M. hominis, M. genitalium, and Ureaplasma urealyticum Often colonize the urinary and genital tracts of newborn girls M. genitalium and U. urealyticum cause inflammation of the urethra (urethritis), Treated by erythromycin or tetracycline M. hominis can cause pelvic inflammatory disease in women, Treated by clindamycin

Answer 37

High G+C, pleomorphic, non-endospore forming bacteria Ubiquitous on plants, animals Colonize on skin and respiratory, gastrointestinal, urinary, and genital tracts Bacteria divide by binary fission (snapping division) to form characteristic V-shapes and palisade arrangements Distinctive feature is presence of metachromatic granules Corynebacterium diphtheriae causes diphtheria

Answer 38

Corynebacterium diphtheriae is transmitted from person to person via respiratory droplets or skin contact Bacteria contains a lysogenic bacteriophage that codes for diphtheria toxin Toxin contains two polypeptides One polypeptide binds to a growth factor receptor on cells triggering the endocytosis of the toxin Inside the cell, proteolytic enzymes cleave the toxin, releasing the second polypeptide into the cytosol Enzymatically destroys elongation factor, a protein required for the synthesis of polypeptides in eukaryotes Results in complete stoppage of polypeptide synthesis and cell death

Answer 39

Infections in immune and partially immune individuals are asymptomatic or result in mild respiratory disease Disease most severe in non-immune patients resulting in diphtheria Sore throat, fever, pharyngitis Oozing of fluid composed of intracellular fluid, blood clotting factors, leukocytes, bacteria, and dead cells This fluid thickens into a pseudomembrane Adheres to tonsils, uvula, palate, pharynx, and larynx Blocks the respiratory passages resulting in death by suffocation Cutaneous diphtheria results in formation of pseudomembrane on skin Toxin can get absorbed into the blood, leading to coma and death

Answer 40

Diagnosis Initial diagnosis on the basis of presence of pseudomembrane Elek test – immunodiffusion assay in which antibodies against toxin react with the toxin in the sample Culture on Loffler’s medium reveals typical colonial morphology Treatment Antitoxin administration to neutralize the toxin Penicillin or erythromycin Prevention By vaccination Administered as part of DTaP vaccine

Answer 41

High G+C, non-endospore forming pathogen Cell wall contains a way lipid called mycolic acid in cell wall, results in a number of unique characteristics Slow growth Protection from lysis after phagocytosis Capacity for intracellular growth Resistance to Gram statning, stain acid fast, detergents, many antimicrobial drugs, and dessication

Answer 42

Grows on differential medium Lowenstein-Jensen agar Virulent strands of M. tuberculosis have a cell wall component called cord factor- produces strands of daughter cells that remain attached to one another in parallel alignment, inhibits migration of neutrophils Pathogen not particularly virulent- only %5 of infected people develop disease, Kill 50% of untreated patients Two main species: M. tuberculosis and M. leprae

Answer 43

Tuberculosis- respiratory disease Cases are declining in US due to better living conditions, pandemic in other regions of the world Remains one of the top three killers of people worldwide today Nearly 2 billion people are currently infected

Answer 44

Primary TB- results from initial infection, formation of tubercles Secondary TB- reestablishment of active infection after period of dormancy Disseminated TB- results when infection spreads throughout body

Answer 45

85% of infections remain in lungs Primary infection involves the formation of small, ahrd nodules in the lungs 5 Stages of Infection: 1. Bacteria infects the respiratory tract via inhalation- minimum dose is 10 cells, baceteria have adhesive pili that attach to extarcellular human protein laminin 2. Macrophages in the alveoli of ungs phagovytize the pathogens but unable to digest them as the bacteria prevents the fusion of phagosome and lysosome 3. Bacteria replicate freely within the host cells, gradually killing them, release chemokines, bacteria are released from dead cells are phagocytized by other macrophages, asymptomatic stage 4. Infected macrophages present antigen to T lymphocytes, which produce cytokines to trigger inflammation, tightly appressed macrophages surround site of infection, forming a tubercle 5. Other cells deposit collagen fibers enclosing the infected macrophages within the tubercle, infected cells in the center die, releasing M. tuberculosis and producing caseous necrosis (liquid), center may become filled with air as a tuberculous cavity If immune system able to kill all the mycobacteria, it subsequently deposits calcium around the tubercle, known as Ghon complexes

Answer 46

The bacteria ruptures the tubercle, and re-establishes active infection Bacteria sperad through lungs via bronchioles Reactived TB found commonly in immunosuppressed individuals

Answer 47

Results when some macrophages carry the pathogens via the blood and lymph to variety of sites Bone marrow, spleen, kidneys, spinal cord, brain Common name for TB in the early 1900s-consumption-reflected wasting of body due to involvement of multiple sites

Answer 48

Tuberculin skin test (PPD) Inject 0.1mL of cell wall antigens into the skin, appearance of induration (swelling) within 24-72 hours is positive Many false positives and false negatives Chest X-rays identify individuals with active disease Presence of acid-fast cells and cords in sputum

Answer 49

Common antimicrobials (penicillin, erythromycin) are ineffective, mycobacterium grows so slowly taht drugs are cleared from body before being effective Combination therapy used for months to treat disease- combination of Isoniazid, rifampin, pyrazinamide, and ethambutol for two months followed by isoniazid and rifampin alone for 4 months Development of multi-drug resistant strins (MDR)- have to be treated with fluoroquinolones in combination with kanamucin for more than 2 yeras Extensively drug resistant TB (XDR-TB)- resistant to all TB anti-microbials

Answer 50

Cases in US show a strong correlation with the age, sex, and recent immigration history of a patient High rates in new immigrants from areas of South Asia, South America, and Africa, also in AIDS patients Directly Observed Treatment, Shortcourse (DOTS)- ingestion of TB medications is observed by a responsible person, lowers rate of drug-resistant TB and the rate of tuberculosis relapse Prevention- BCG vaccine (composed of attenuated M. bovis strain), administered to children in all developing countries, efficicay studies vary

Answer 51

Leprosy- caused by Mycobacterium leprae Bacteria do not grow in cell-free culture, armadillos only other host Bacteria grow best at 30 degrees Celsius, showing preference to grow in cooler regions of the body, like peripherlal nerve endings and skin in fingers, toes, etc. Becoming relatively rare Transmitted via person to person contact or break in skin Two different forms: Tuberculoid leprosy, and lepromatous leprosy

Answer 52

Non-progressive form of disease Strong cell-mediated immunity is able to kill infected cells Regions of skin lose sensation due to nerve damage

Answer 53

Develops in patients with weak CMI Bacteria multiply in skin and nerve cells, gradually destroying tissue and leading to progressive loss of facial features, fingers, toes, etc. Incubation period up to several years Transmitted via person-to-person contact, not particularly virulent

Answer 54

Diagnosis- based on signs and symptoms of disease, Leprosy antigen skin test Treatment- combination of antimicrobial drugs (clofazimine, rifampin, or dapsone for 12 months), lifelong treatment is sometimes needed Prevention- limiting exposure to the pathogen, BCG vaccine provides some protection

Answer 55

Mycobacterium avium-intracellulare Opportunistic pathogen Most common mycobacterial infection among AIDS patients in the US Infections result from ingestion of contaminated food or water Can affect almost every organ and result in massive organ failuer Treatment is difficult due to the dissmeinated nature of the infection

Answer 56

Caused by M.ulcerans, an emerging pathogen present in swamps Produces a potent toxin mycoalcton that destroys cells beow the skin Treatment- Rifampina and Streptomycin

Answer 57

Small, gram positive rods often found on the skin Produce propionic acid as a by product of fermenation of carbohydrates Propionibacterium acnes msot commonly involved in human infections- causes acne in 85% of adolescents and young adults May be an opportunistic pathogen Many cases require no treatment Antimicrobial drugs help control bacterium Retinoic acid- derivative of Vitamin A, can inhibit formation of oil

Answer 58

Common inhabitant of soils rich in organic matter Cell wall contains mycolic acid and stains acid-fast Appear like long hyphal cells- diagnostic Produces opportunistic infections in numerous sites Pulmonay infections, Cutaneous infections (may produce a myceotma characterized by swelling, pus, and sores), CNS infections Prevention involves avoiding exposure to bacterium in soil

Answer 59

Characterized by hypha-like, gram positive cells Member of surface microbiota of human mucous membranes Colonies form visible concretions resembling grains of sand known as "sulfur granules"- actually contain calcium phosphate Opportunistic infections- respiratory, gastrointestinal, urinary, and female genital tracts, sometimes cause dental carries Actinomycosis- results when bacteria enter breaks in the mucous membrane, formation of absecesses connected by channels in skin or mucous membranes Diagnosis difficult as other orgniams cause similar symptoms

Chapter 19: Gram Positive, Pathogenic Bacteria Flashcards

(84 cards)