Flashcards
Gram-Positive Cocci
Cards in this deck (124)
- 1What are some key concepts regarding species and strains?1. a frequently used threshold is that strains of a species should show >95% average nucleotide identity (ANI) among themselves and < 95% ANI when compared to strains from a different species
2. a technique used before whole genome sequencing became widespread was DNA-DNA hybridization and the species cutoff was arbitrarily set at 70% hybridization: 70% DNA-DNA hybridization translates precisely to 95% ANI in genomic sequence data - 2What are the clinically important genera of gram-positive cocci discussed in class?- streptococcus
- enterococcus
- staphylococcus - 3What is the purpose of the catalase test with regards to gram-positive cocci?separates Staphylococcus from Streptococcus AND Enterococcus
- 4What is the catalase reaction?hydrogen peroxide -----> water + hydrogen gas
- 5What is the enzyme that causes a catalase reaction to occur?catalase
- 6What are the common features of gram-positive cocci?- immunoreactivity of the GM+ cell wall
- capsules
- superantigens
- exotoxins
- extracellular pathogens
- antibiotic resistance - 7What are the microbe resistance molecular patterns of the immunoreactive cell wall of gram+ cocci?- peptidoglycan fragments
- teichoic and lipoteichoic acids - 8What are superantigens?microbial products that have the ability to promote massive activation of immune cells, leading to the release of inflammatory mediators that can ultimately result in hypotension, shock, organ failure and death (dis-regulate CD4 T cells and proinflammatory molecules)
- 9What are examples of host responses that are affected by the extracellular pathogens of gram+ cocci?- humoral immunity
- neutrophils, opsonic antibodies - 10What are the types of Streptococcus we discussed in class?Lancefield Groups A, B, C, D, F, & G
Viridans Streptococci
S. pneumoniae - 11What are some common characteristics of Streptococci?- gram + cocci
- morphology: chains of varying lengths, but can be diplococci
- catalase negative
- widely distributed in nature
- inhabit of the mucosal surfaces of man and animals
- majority are saprophytic and nonpathogenic but some are opportunistic or overt pathogens - 12What are saprotrophs?an organism that feeds on or derives nourishment from decaying organic matter
- 13What are opportunistist bacteria?take advantage of an opportunity not normally available, such as a host with a weakened immune system, an altered microbiota (such as a disrupted gut microbiota), or breached integumentary barriers
- 14What are the basic culture requirements to grow Streptococci?blood agar for 24-48 hours in 5% CO2 in air
- 15What are the types of hemolysis that are produced by Streptococci colonies on blood agar?1. incomplete alpha hemolysis
2. complete beta hemolysis
3. no gamma hemolysis - 16What is the sole fermentation end-product of gram + cocci? and this allows them to live in what type of environment?1. lactic acid
2. highly acidic environments - 17What are the fluid clinical specimens that you can see chain streptococci?bood, pus, CNF, ect.
- 18What is the Lancefield system of identification?is based on the antigenic characteristics of the group-specific cell wall polysaccharide (or teichoic acid) extracted from bacterial cells using acid or enzymes
- 19What type of bacteria is the Lancefield system intended for?beta hemolysis streptococci
- 20Why is the Lancefield test not applicable for alpha-hemolysis?it will interact with the Lancefield antigens and cause misdiagnosis
- 21What are the serological and biochemical tests used for the identification of Streptococci species?1. latex agglutination test
2. detection of carbohydrate fermentation types
3. Lancefield test - 22How is identification made via the Lancefield test? (the specifics of the lab test)1st: the wall polysaccharide (Lancefield antigen) is extracted from the cells using dilute acid or enzymes
2nd: after neutralization, the soluble antigen is detected with antibodies bound to latex beads - 23What is the only organism of the Lancefield A group?Streptococcus pygenes
- 24What are the identification tests and results for the Lancefield A bacterium?1. gram stain: gram+
2. catalase test: negative
3. blood agar: beta hemolysis
4. A disk on blood agar: susceptible for bacitracin
5. Lancefield test
6. produce PYR - 25What is the envelope composition of the A group bacterium?capsule, cell wall, peptidogylcan layer, cytoplasmic membrane and many cell-surface and secreted proteins involved in the pathogenesis
- 26What is the acid produced by the capsule of the Lancefield A bacterium?hyaluronic acid
- 27What are the components of the cell wall to remember of the Lancefield A bacterium?protein antigens and group-specific carbohydrate
- 28What are the group-specific carbohydrates of the Lancefield A bacterium?N-acetylglucosamine
rhamnose - 29What is the composition of the peptidoglycan layer of the Lancefield A bacterium?N-acetylglucosamine
N-acetylmuramic acid
oligopeptide - 30Pyrogenic exotoxins of Lancefield A bacterium cause what biological effects in the host cell?- mediated pyrogenicity
- enhancement of delayed hypersensitivity and susceptibility to endotoxins
- cytotoxicity
- nonspecific mitogenicity for T cells
- immunosuppression of B cell function
- production of scarlatiniform rash - 31What is the principal virulence factor of the Lancefield group bacteria?M protein
- 32What are some general characteristic features of the M protein?- alpha helical coiled-coil fibrillar protein which has a domain-like structure
- amino acid sequence of the extracellular portion is highly variable - 33What are the class I M protiens?share extracellular epitopes but strains do not produce opacity factor
- 34What is the opacity factor?lipo-proteinase, increase opacity of serum, binds fibronectin
- 35What is G3PD?located at cell surface, acts as an adhesion
- 36What is enolase?located on cell surface, binds plasminogen
- 37What is the class II M protein?lack shared extracellular epitopes, but strains produce opacity factor
- 38What class M protein causes rheumatic fever?class I
- 39What diseases result from local infection with Lancefield A bacterium and its products?- scarlet fever (superantigens)
- streptococcal pyoderma (impetigo)
- desquamation occurs - 40What diseases result from invasion of Lancefield A bacterium?- erysipelas
- necrotizing fasciitis
- sepsis - 41What are two post-streptococcal diseases? (autoimmune diseases)1. acute rheumatic fever
2. acute glomerulonephritis (complete resolution of illness) - 42What are the immunogens of the Lancefield group A bacterium?M-protein, Lancefield antigen, hyaluronic acid capsule, cytoplasmic membrane
- 43Why is a GAS infection cause autoimmunity and molecular mimicry in acute rheumatic fever?it induces antibodies that are heart, skeletal muscle and CNS reactive
- produce protected antigens - 44What are characteristics of GAS immunity?- type specific to GAS M type
- anti-M antibodies are opsonic (promote phagocytosis)
- antibody to streptolysin O follows infection - 45What is the only Lancefield group B Streptococcus?Streptococcus agalactiae
- 46What are the key identification test and results for the Lancefield group B bacterium?- gram stain (gram +)
- + hippurate hydrolysis
- Lancefield test (beta hemolysis)
- resistant to bacitracin - 47What is the envelope composition of the Lancefield group B bacterium?- capsular polysaccharides
- type specific proteins
- group B polysaccharides
- lipotechoic acid
- peptidoglycan layer
- cell membrane - 48What are the capsular polysaccharides of the GBS bacterium?sialic acid
galactose
glucose
glucosamine - 49What is sialic acid important in the invasion of the GBS bacterium?deactivates the complement cascade
- 50What is the important virulence factor of the GBS bacterium?the capsule
- 51What are the capsule serotypes of the GBS bacterium that are commonly associated with colonization and disease?Ia, Ib, II, III and V
they are all heavily sialated - 52What are the pathogenicity modes of action for the GBS bacterium?- colonize the anus in a neonate
- colonize the vagina in a pregnant women and infect the neonate
- travel via the placenta to the mother and attack the mother's brain - 53What is the epidemiology associated with GBS infection in the vagina and rectum?10%-30% of women (worry about in the 3rd trimester)
colonization is dynamic (episodic carriage) - 54What is the disease presentation in early onset GBS infection?-disease in infants younger than 7 days (80%)
- ascending infection of amniotic fluid, aspiration leading to invasive disease
- perinatal transmission can occur across intact membranes - 55What is the disease presentation of late onset GBS infection?- disease appearing between 1 week and 3 months postpartum (20%)
- vertical transmission: mother to infant
- horizontal transmission: nosocomial and community - 56What is the CDC recommendation for prenatal GBS site cultures?vaginal and rectum
- single swab or two swabs
- through anal sphincter
- self collection an option - 57What is the CDC recommendation for prenatal GBS culture timing?at 35 and 37 weeks pregnant
- 58What are the 3 instances when the CDC recommends intrapartum antibiotics for GBS?1. women whose culture results are unknown at the time of delivery (risk-based approach)
2. women with GBS bacteriuria in any concentration during their current pregnancy
3. who previously gave birth to an infant with early onset GBS disease - 59What are the key disease manifestations of GBS in neonates?septicemia
pneumonia
meningitis - 60What is the key disease manifestation of GBS in pregnant woment?meningitis
- 61What are the key factors of immunity in GBS infections?- type-specific anti-capsular antibodies are protective
- functional classical and alternative classical pathways are required
- opsonophagocytosis
- terminal sialic acid on capsule prevents classical activation
- conjugate polyvalent capsule vaccine under development - 62What are the general characteristics of Lancefield Group C, F, & G Streptococci?- heterogeneous group of bacteria
- mostly beta hemolytic, but may be alpha or gamma
- strains within a species may possess different Lancefield antigens
- Group C and F are now considered to constitute a single subspecies
- comparison of the complete genome sequence of Group G demonstrates it is closely related to S. pyogenes - 63What is the single subspecies that is comprised of Lancefield Group C and G?Streptococcus dysgalactiae subsp equisimilis
- 64What the characteristics of the S. anginosus or S. milleri group?- often exhibit Lancefield antigens A, C, F, or G but can be distinguished by their small colonies they produce on sheep blood agar
- residents of the mouth and GI tract with the ability to cause abscesses and systemic infections
- unique ability to cause abscesses - 65What the epidemiology of a S. anginosus or S. milleri group infection?- part of the resident microbiota of the oropharynx, GI and GU tracts
- microaerophilic or anaerobic
- may form 'minute' colonies
- some produce large zones of beta hemolysis similiar to GAS - 66What are the key derterminants of pathogenicity in Lancefield group bacteria?- M or M-like proteins
- hyaluronic acid capsule
- IgG-binding protiens
- fribronectin-binding proteins
- plasminogen-binding proteins
- C5a peptidase
- hyaluronidase
- streptokinase
- streptolysin and Streptodornase (Dnase)
- may have pyrogenic exotoxins - 67What are the pathogenicity factors of Lancefield bacteria?- opportunistic pathogens
- pharyngitis sometimes followed by AGN by NEVER ARF
- skin and soft tissue infections
- puerperal infections
- bacteremia, pneumonia & meningitis
- septic arthritis
- endocarditis
- Strep. toxic shock-like syndrome (group G) - 68What are some diseases that increase in an individual to a Lancefield group disease?- chronic pulmonary/cardiac disease
- diabetes
- malignancy
- alcoholism - 69What are the identification tests and results of Streptococcus pneumoniae?- gram stain (morphology: gm+, bullet shaped diplococci)
- catalase negative
- quellung test: swollen capsule
- alpha hemolysis
- optochin sensitive (detergent) - 70What is a unique feature of S. pneumoniae cell wall and its impact on the host cell it invades?contains a chlorine-binding protein
- present in the cytosol and only released when cell lysis occurs causing a MASSIVE inflammatory response causing damage - 71What are the clinical characteristics of S. pneumoniae?- most common form of bacterial pneumonia
-nasopharynx is the reservoir
- carrier rate may be as high as 60% in children
- not all capsule types are equally invasive
- rarely a primary infection
- PM neutrophil is major line of defense
- opsonic antibiodies important
- emerging penicillin resistance - 72What are the diseases of S. pneumoniae?pneumonia
otitis media
meningitis - 73What are the characteristics of the immune response of S. pneumoniae?- naturally acquired immunity is high - opsonic antibodies
- artificially acquired immunity - polyvalent capsular polysaccharide vaccine
-23 capsule types protect against 90% of pneumococcal infections (only 60% effective)
- antibodies are capsule type-specific
- maternal transfer of IgG antibody for 3-5 weeks postpartum
- conjugate vaccine (7 valent) for those under 2 yrs old
- vaccine has induced serotype shifts - 74Where area of the body is Viridans Streptococci commensal to?oropharynx
(oral cavity is site of entry into the bloodstream then the heart and brain) - 75What disease does Viridans Streptococci cause?subacute bacterial endocarditis
(involves abnormal valves) - 76What is a biotype?organisms that differ by 1 or 2 biochemical tests
- 77What genus of bacteria consists of Lancefield D?Streptococcus and Enterococcus
- 78What are the species of Lancefield D Enterococcus?E. faecalis
E. faecium - 79What are the species of Lancefield D Streptococcus?S. gallolyticus
S. infantarius - 80What are the key features of Lancefield Group D Streptococci and Enterococci?- grow at 45 degrees Celcius and are viable up to 60 degrees
- grow in 40% bile
- grow in high salt concentrations (enterococci)
- hydrolyze esculin (a coumarin glucoside)
- usually alpha or non-hemolytic
- typical streptococcal wall
- Lancefield antigen is a glycerol LTA - 81Which of the Lancefield Group D genus grows in 6.5% NaCl?Enterococci
- 82Which of the Lancefield Group D genus hydrolyze starch?Streptococcus
- 83Which of the Lancefield Group D genus is PYR positive?Enterococci
- 84What are the epidemiological characteristics of Lancefield Group D bacteria?- opportunistic pathogens
- commensals of the G.I. tract
- many inhabit skin, upper respiratory and GU tracts - 85What are the diseases associated with Lancefield Group D Streptococci?- bacteremia
- native & prosthetic valve endocarditis - 86What are the diseases associated with Lancefield Group D Enterococci?- important nosocomial infection
- UTI
- biliary tract infection
- septicemia
- wound infection
- intra-abdominal abscess
- endocarditis - 87What is the last antibiotic defense against gram + bacteria?vancomycin
- 88What are the antibiotic characteristics associated with Lancefield Group D bacteria?- intrinsic resistance to many antibiotics (beta-lactams)
- acquired resistance to gentamycin and vancomycin via transposons and plasmids
- to date seen predominately in E. faecium - 89What is a Van A resistant strain?resistance to Vancomycin and Teicoplanin
acquired via transposon - 90What is a Van B resistant strain?resistance to Vancomycin only
acquired via plasmid - 91What are the clinically significant species of Staphylococcus?S. aureus
S. epidermidis
S. saprophyticus - 92What are the morphological and metabolic characteristics of Staphylococcus?- GM+ cocci grape-like clusters
- catalase positive
- produce pigments
- may be beta-hemolysis - 93What color pigment is produced with S. aureus?gold
- 94What color pigment is produced with S. epidermitis?white
- 95What is the epidemiology of S. aureus?episodic colonizer
pathogen - nasal carriage (anterior nares) in about 50% of humans - 96What is the epidemiology of S. epidermidis?commensal - skin and mucous membranes
- 97What is the epidemiology of S. saprophyticus?episodic colonizer
transient - the mucocutaneous area of the anal-urogenital area - 98What does a positive coagulase test mean?presence of coagulase
Staphylococcus genus
coagulase enzyme will cleave the plasma creating a clot (time specific test) - 99Which of the Staphylococci species ferments mannitol?S. aureus
- 100What species of Staphylococci is not resistant to novobiocin?S. epidermis
- 101What species of Staphylococci is resistant to novobiocin?S. saprophyticus
- 102What are the two factors that predispose an individual to a Staphylococci infection?1. breach skin/mucosa
2. reduced host response - 103What are key characteristics of antibiotic resistance in Staphylococci species?- vancomycin resistance is emerging
- serious epidemiologic and therapeutic problems
- resistant to a wide range of antibiotics
- plasmid and bacteriophage-mediated
- extended resistance to semi-synthetic B-lactams
- acquisition of the mecA gene - 104What are beta-lactamases?- extracellular enzymes
- probably several types
- usually inducible but can be constitutive
- encoded on plasmids but can be chromosomal - 105What is a key characteristic of the envelope compositions of S. aureus?-gram + cell wall
-extensively crosslinking
-remain viable on inanimate objects for months
-loose capsule - 106What are the determinants of pathogenicity of S. aureus?- coagulase enzyme
- toxins
- IgG binding protein (protein A) - 107What are characteristics of community-acquired MRSA?- not hospital acquired clones that have spread into the community
- susceptible to a lot of antibiotics - 108What does community-acquired MRSA produce that contributes to its pathogenicity?- mecA cassette
- produce Panton-Valentine Leukocidin (PVL)
- phenol-soluble modulins
- toxins - 109What are phenol-soluble modulins?novel class of factors that induce cytokine synthesis
- 110What is the pathogenesis of S. aureus?- abscess formation is characteristic
- cutaneous infections
- pneumonia
- bacteremia-endocarditis
- osteomyelitis
- septic arthritis
- toxic shock syndrome
- food poisoning - 111What are the two coagulase negative Staphylocci (CNS) bacteria?Staphylococcus epidermidis
Staphylococcus saprophyticus - 112What is the common disease associated with S. epidermidis?prosthetic devise infections
- 113What is the common disease associated with S. saprophyticus?UTI in sexually active young women
- 114What are the basic characteristics of Bacillus cereus?aerobic gram-positive spore-forming rod
- 115What is the enteric form of Bacillus cereus?heat stable protease-resistant enterotoxin
ingestion - 116What is the diarrheal form of Bacillus cereus?heat-liable enterotoxin
ingestion - 117What are the basic characteristics of Clostridium perfringens and C. difficile?anaerobic, gram-positive, spore-forming rods
- 118What does enterotoxigenic mean?food poisoning and GI tract disease
- 119What are the characteristics of pathogenicity of C. perfringens?- enterotoxin - producing type A strains
- 3rd most common cause of food poisoning
- meat contamination
- requires ingestion of 10x8 - 10x9 bacteria
- mild, self-limiting gastroenteritis
- acute abdominal pain and foamy, foul-smelling diarrhea - may be nauseated by NO vomiting - 120What strain type of C. perfringens causes acute necrotizing disease?beta toxin producing type C strains
- 121What are the two diseases associated with C. difficile?antibiotic-associated colitis
pseudomembraneous colitis - 122What are the 3 toxins produced by C. difficile?1. A (cytotoxic & fluid accumulation) CDA
2. B (cytotoxic & inhibits protein synthesis) CBB
3. CDT a binary toxin that ADP ribosylates actin - 123Where is C. difficile a major problem?nosocomial
patients receiving broad-spectrum antibiotics - 124What is dysbiosis?microbial imbalance or maladaptation on or inside the body, such as an impaired microbiota
- disease as a result of an upset of the host microbiome
- a fecal transplant might be a good idea (restore resident microbiome)
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- Flashcards on Gram-Positive Cocci, created by Kerra Washington on 12/11/2018.
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- Kerra Washington · Nov 2018
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- Nov 13, 2018
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