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Microbiology
FA complete review part 1 Cellular, Genetics, and Categories
Question | Answer |
---|---|
What is the function of flagellum? | Motility |
What is the function of Pilus/fimbriae? | Mediate adherence of bacteria to cell surface; sex pilus forms during conjugation |
What is the chemical composition of a spore? | Keratin-like coat; dipicolinic acid; peptidoglycan , DNA |
Which type of bacteria have spores? | Gram (+) only |
What is the main function or purpose of a spore? | Survival: resists dehydration, heat, and chemicals |
What is the composition of a CAPSULE? | Organized, discrete polysaccharide layer |
What it the function of a capsule? | Protects against phagocytosis |
What cellular structure is in charge of protecting against phagocytosis? | Capsule |
Composed of loose network of polysaccharides? | Glycocalyx |
What is the function of Glycocalyx? | Mediates adherence to surface, especially foreign surfaces |
What is the the exception of Capsule? | Poly-D-glutamate on B anthracis |
What are the 3 main components of the Outer membrane? | 1. Outer leaflet 2. Embedded proteins 3. Inner leaflets |
What is the composition of outer leaflets of the outer membrane? | Endotoxin (LPS/LOS) |
Phospholipids is the main component of which part of the outer membrane? | Inner leaflet |
What kind of bacteria is the only one with outer membrane? | Gram negative only |
What are the role of porins in the outer membrane? | Transport across the membrane |
What is the role of Lipid A? | Induces TNF and IL-1 |
What is the space between cytoplasmic membrane and outer membrane in gram (-) bactria? | Periplasm |
What is in the middle of the Periplasm? | Peptidoglycan |
What is the function of the periplasm? | Accumulates components exiting gram (-) cells, including hydrolytic enzymes |
What is the composition of the Cell wall? | Peptidoglycan is a sugar backbone with peptide side chains cross-linked by transpeptidase |
What is the main function of the cell wall? | Net-like structure gives rigid dsupport, protects against osmotic pressure damage |
What are the two roles of the Cytoplasmic membrane? | 1. Site of oxidative and transport enzymes; PBPs involved in cell wall synthesis 2. Lipoteichoic acids induce TNF-alpha and IL-1. |
What are the main components of the cytoplasmic membrane? | - Phospholipid bilayer sac with embedded proteins and other enzymes - Lipoteichoic acids (gram (+) only) extend from membrane to exterior |
What cell envelope structures are exclusive of gram (-) bacteria? | Outer membrane (Endotoxin/LPS, porin), and Periplasmic space |
Lipoteichoic acid is unique to gram _________ bacteria. | Positive |
What is another way to refer to spherical morphology? | Coccus |
Coccus gram negative bacteria: | 1. Moraxella catarrhalis 2. Neisseria |
What are common pleomorphic (no cell wall) gram negative bacteria? | Anaplasma, Ehrlichia, Chlamydiae, Rickettsiae, Mycoplasma, and Ureaplasma |
Which bacteria is identified with Giemsa stain? | Rickettsia, Chlamydia, Trypanosomes, Plasmodium, Borrelia |
A bacteria with a thick peptidoglycan layer will stain what color? | Violet |
Thin peptidoglycan wall bacterial stains __________________, in color. | Pink or red |
Which bacteria do not stain well do to lack of peptidoglycan wall due to decreased muramic acid? | Legionella, Rickettsia, Chlamydia, Bartonella, Anaplasma, and Ehrlichia |
What is similar in Mycoplasma and Ureaplasma? | NO cell wall |
Cell wall too thin to be visualised is seen in: | Treponema and Leptospira |
Mycobacteria does not stain well because: | Cell wall has high lipid content |
What condition is diagnosed with Periodic acid-Schiff stain? | Whipple disease |
What is primarily stained with Periodic acid-Schiff stain? | Glycogen and mucopolysaccharides |
Acid-fast bacteria most commonly include: | Mycobacteria and Nocardia |
Ziehl-Neelsen stain is also known as: | Carbol fuchsin |
What substance is stained with Ziehl-Neelsen stain? | Mycolic acid in cell wall |
What bacteria or organism are stained with Ziehl-Neelsen stain? | Acid-fast bacteria and Protozoa |
Identification of Cryptosporidium oocysts with stain is done with: | Ziehl-Neelsen stain |
What stain is used in Cryptococcus neoformans identification? | India ink stain |
What stain is used in fungi? | Silver stain |
For what is Silver stain used? | Fungi, Legionella, and H. pylori |
What is the main function of Selective media? | Favors the growth of particular organisms while preventing growth of other organisms |
What is a common example of a Selective media? | Thayer-Martin agar |
What is Indicator (differential) media function? | Yields color change in response to the metabolism of certain organisms |
MacConkey agar is an example of ___________________media. | Indicator (diffencital) |
How is the color change indicated by a differential media? | Due to changes in pH |
What is the media used in H. influenzae? | Chocolate agar |
What are components of Chocolate agar? | Factors V (NAD+) and X ( hematin) |
Media made of Factor V (NAD+) and X (hematin). | Chocolate agar |
What type of media is used for Neisseria species? | Thayer-Martin agar |
In Thayer-Martin media, the growth of gram positive organism is done with _______________. | Vancomycin |
What antibiotics are included in Thayer Martin agar to inhibit growth of gram negative bacteria, except Neisseria? | Trimethoprim and Colistin |
Nystatin is used to inhibit __________ growth in Thayer Martin agar. | Fungi |
Media used for B. pertussis | Bordet-Gengou agar |
What is the component of Bordet-Gengou agar? | Potato extract |
What is the components of Regan-Lowe medium? | Charcoal, blood, and antibiotic |
What organism uses Regan-Lowe medium? | B. pertussis |
Tellurite agar + Loffer medium are used for _________________ growth. | C. diphtheriae |
Agar used to M. tuberculosis? | Lowenstein-Jensen agar |
M. pneumoniae uses ___________ agar and requires _____________. | Eaton agar; Cholesterol |
What media is used by Lactose-fermenting enterics? | MacConkey agar |
Fermentation caused in a MacConkey agar culture, turns colonies __________ (color) | Pink |
What media is often used by E. coli growth? | Eosin-methylene blue (EMB) |
What is the color of E. coli colonies been cultured with EMB? | Green metallic sheen |
What characteristic media is used by Legionella? | Charcoal yeast extract agar buffered with cysteine and iron |
Sabouraud agar is used to grow cultures of __________. | Fungi |
What are common examples of Anaerobes? | Clostridium, Bacteroides, Fusobacterium, and Actinomyces israelii. |
What are enzymes are lacking in Anaerobic? | Catalase and/or superoxide dismutase |
What are some key features used to describe and identify anaerobes? | 1. Foul-smelling (short-chain FAs) 2. Difficult to culture 3. Produce gas in tissue |
Where in the body are anaerobes usually part of the normal flora? | GI tract |
Which class of antibiotics are ineffective to anaerobes? | Aminoglycosides |
What is the characteristic definition of Facultative anaerobes? | May use O2 as a terminal electron acceptor to generate ATP, bu can also use fermentation and other O2-independent pathways |
Which class of bacteria are a mixed of anaerobes and anaerobes? | Facultative anaerobes |
What are some common Facultative anaerobes? | Streptococci, staphylococci, and enteric gram (-) bacteria |
What are the two classes of INTRACELLULAR bugs? | Obligate and Facultative |
What organisms are Obligate intracellular? | RIckettsia, Chlamydia, Coxiella |
Which class of organism rely on host ATP? | Obligate intracellular |
List of Facultative intracellular bacteria: | 1. Salmonella 2. Neisseria 3. Burcella 4. Mycobacterium 5. Listeria 6. Francisella 7. Legionella 8. Yersinia pestis |
Salmonella, Mycobacterium, Listeria, Legionella, and Yersinia pestis are examples of _______________________ bacteria | Facultative intracellular |
What are the most common Encapsulated bacteria? | Streptococcus pneumoniae, H. Influenzae type b, Neisseria meningitidis, E. coli, Salmonella, Klebsiella pneumoniae, and group B Strep |
What is the role of the capsules of "Encapsulated" bacteria? | Serve as antiphagocytic virulence factor |
Capsular polysaccharide + protein conjugate = | Antigen in vaccines |
What mnemonic is used for Encapsulated bacteria? | Please SHINE my SKiS |
how are encapsulated bacteria cleared from body? | Opsonized and cleared by the spleen |
Which type of patients are at higher risk of encapsulated bacterial infections? | Asplenics |
Available vaccines for Encapsulated bacteria (3): | 1. N. meningitidis 2. S. pneumoniae 3. H. influenzae type b |
What is the purpose of Encapsulated bacteria vaccines composition? | Polysaccharide capsule is conjugated to carrier protein, in order to enhance immunogenicity by promoting T-cell activation and subsequent class switching |
Mnemonic used for Urease- positive organisms: | Pee CHUNKSS |
Pee CHUNKS stands for: | Proteus, Cryptococcus, H. pylori, Ureaplasma Nocardia Klebsiella S. epidermidis S. saprophyticus |
Urease positive organism predispose to which type of kidney stone? | Struvite |
Which urease (+) organism most commonly predisposes to Struvite formation? | Proteus |
What is the function of Urease? | Hydrolyses urea to release ammonia and CO2 ---> increase in pH |
What is the function of Catalase? | Degrades H2O2 into H2O and bubbles of O2 before it can be converted to microbicidal products by the enzyme myeloperoxidase |
What immunodeficiency is often have higher risk of catalase (+) organism infections? | Chronic granulomatous disease |
Examples of Catalase (+) organisms: | Nocardia, Pseudomonas, Listeria, Aspergillus, Candida, E. coli, Staphylococcus, Serratia, B cepacia, and H pylori |
Nocardia, Pseudomonas, E. coli, H. pylori, Serratia, and H. pylori are all ___________ positive organisms | Catalase |
C cepacia is __________ positive | Catalase |
Yellow "sulfur" granules seen with: | Actinomyces israelii |
What color pigment is seen with S. aureus? | Yellow |
Blue-green pigment is associated with: | P. aeruginosa |
Color pigment associated with Serratia? | Red |
What infections are associated with S. epidermidis biofilm production? | Catheter and prosthetic device infections |
What are some biofilm-producing bacteria? | S. epidermidis, Viridans streptococci, P. aeruginosa, and nontypeable H. influenzae. |
Dental plaques, infective endocarditis ar due to biofilms produced by ______________________. | Viridans streptococci |
What conditions are associated with P. aeruginosa biofilm production? | 1. Ventilator-associated pneumonia 2. Contact lens-associated keratitis 3. Respiratory tree colonization in CF patients |
What is the purpose of Bacterial virulence factors? | Promote evasion of host immune response |
What organism has Protein A virulence factor? | S. aureus |
IgA protease is a virulence factor seen with: | S. pneumoniae, H. influenzae type b, and Neisseria |
Which virulence factor binds to Fc region of IgG? | Protein A |
After binding, what actions are prevented by Protein A? | Opsonization and phagocytosis |
What is the function virulence factor IgA protease? | Enzyme that cleaves IgA, allowing bacteria to adhere to and colonize mucous membranes |
M protein helps prevent _____________. | Phagocytosis |
What kind of bacteria expresses M protein virulence factor? | Group A streptococci |
What is a possible underlying reason for the autoimmune response seen in acute rheumatic fever? | M protein |
Shares similar epitopes to human cellular proteins (molecular mimicry) | M protein |
What is another name for Type III secretion system? | Injectisome |
What is an injectisome? | Needle-like protein appendage facilitating direct delivery of toxins from certain gram (-) bacteria to eukaryotic host cell |
What is the process of bacterial Transformation? | Competent bacteria can bind and import short pieces of environmental naked bacterial chromosomal DNA |
Besides IgA protease virulence factor, the SHiN bacteria, undergo ______________________ readily. | Transformation |
What can prevent transformation? | Adding deoxyribonuclease degrades naked DNA |
What are the two types of conjugation? | 1. F+ x F- 2. Hfr x F- |
Which plasmid contains genes for sex pilus and conjugation? | F+ |
What is transferred via the sex pilus? | Single strand of plasmid DNA |
What is a plasmid? | Small, extrachromosomal DNA molecule within a cell |
What kind of DNA is NOT transferred in Conjugation? | Chromosomal DNA |
What is Hfr? | Plasmid that has incorporated the F+ plasmid |
How is conjugation of chromosomal DNA possible? | Using Hfr only |
What are the two modes of Transduction? | Generalized and Specialized |
What mode of Transduction is referred as a packing "error"? | Generalized |
What is generalized transduction? | Lytic phage infects bacterium, leading to clava of bacterial DNA. |
Which transduction mode is referred as an "excision" event? | Specialized |
What kind of phage is used in Specialized transduction? | Lysogenic |
Transduction mode in which host and phage DNA break into little pieces? | Generalized |
Newly formed phage capsids in Generalized transduction contain bacterial DNA , which then: | Infects other bacteria and creates then a recombinant DNA |
In Specialized Transduction, instead of cleavage of bacterial DNA, it: | Viral DNA from the lysogenic phage incorporates in bacterial DNA |
What is the difference in newly created phage capsids between Generalized and Specialized transduction? | In specialized, all the new phage capsids contain recombinant bacterial and viral DNA, which creates genes different from donor and recipient |
Which are the 5 bacterial toxins aht are encoded in a lysogenic phage? | Group A strep erythrogenic toxin Botulinum toxin Cholera toxin Diphtheria toxin Shiga toxin |
What is Transposition? | Segment of DNA that can "jump" from one location to another, can transfer genes form plasmid to chromosome and vice versa |
What is the most common way to transfer plasmid with multiple antibiotic resistance among species? | Transposition |
What are some key features of Spores? | 1. Lack metabolic activity 2. Highly resistant to heat and chemicals 3. Core contains dipicolinic acid |
What temperature of an autoclave should be in other to kill spores? | 121 C for 15 minutes |
Where are the endotoxins most likely located? | Outer cell membrane of most gram (-) bacteria |
What is the main component of Endotoxins? | Lipid A component of LPS |
Where are the genes located in a Endotoxin? | Bacterial chromosome |
What are the most common clinical effects of an endotoxin? | Fever, shock (hypotension), and DIC |
What is the MOA of endotoxins? | Induce TNF, IL-1, and IL-6 |
What are the most typical diseases produced by Endotoxins? | Meningococcemia; Sepsis by gram (-) rods |
Which are more toxic, Exotoxins or Endotoxins? | Exotoxins |
Do exotoxins or endotoxins, produce antitoxins? | Exotoxins |
Which can resist higher temperatures, exotoxins or endotoxins? | Endotoxins |
How are exotoxins used in vaccines? | Toxoids produced are used as vaccines |
What are the most typical exotoxin produced diseases? | Tetanus, botulism, and diphtheria |
Which exotoxin producing organism inhibit protein synthesis? | Corynebacterium diphtheriae, Pseudomonas aeruginosa, Shigella spp., and Enterohemorrhagic E. coli. |
Which bacteria's exotoxins inactivate elongation factor 2 (EF-2)? | Corynebacterium diphtheriae and Pseudomonas aeruginosa |
What is C. diphtheriae clinical manifestation? | Pharyngitis with pseudomembranes in throat and severe lymphadenopathy (bull neck), myocarditis |
What is P. aeruginosa exotoxin? | Exotoxin A |
What is the clinical manifestation of Endotoxin A? | Host cell death |
What is the mechanism of action of EHEC and Shigella spp toxins? | Inactivate 60S ribosome by removing adenine form rRNA |
Which organisms' toxin inhibit protein synthesis by inactivating the 60S ribosome? | Shigella spp and EHEC |
Which organism has Shiga-like toxin? | EHEC |
What is the clinical manifestation of Shiga toxin? | 1. GI mucosal damage --> dysentery 2. Enhance cytokine release, causing HUS |
What is a clinical difference of how Shigella and EHEC toxins act? | EHEC does not invade host cells |
HUS is caused by which two organisms? | Shigella spp and EHEC |
Which endotoxin containing organisms act by increase in fluid secretion? | ETEC, Bacillus anthracis, and Vibrio cholerae |
What are the two exotoxins found in Enterotoxigenic E. coli? | 1. Healt-LABILE 2. Heat- STABLE |
MOA of Heat-Labile ETEC exotoxin? | Over activates adenylate cyclase (increase cAMP --> increase Cl- secretion in gut and water efflux |
Overactivates guanylate cyclase (increase cGMP) --> decrease resorption of NaCl and water n gut. | Heat-stable toxin of ETEC |
What is the mode of action of Anthrax toxin? | Mimics adenylate cyclase |
Which toxin is know to permanent activating Gs? | Cholera toxin |
What organism is responsible for edematous border of black eschar in cutaneous anthrax? | Bacillus anthracis |
Voluminous "rice-water" diarrhea | Vibrio cholerae infection |
What organism causes Whooping cough? | Bordetella pertussis |
What is the mode of action of Pertussis toxin? | Inactivates the inhibitory Gi --> activation of adenylate cyclase and increase of cAMP. |
What is the analogue condition of Whooping cough in adults, called? | "100-day cough" |
Pertussis toxin inhibits the _______________ ability. | Phagocytic |
Which exotoxin interferes with optimal phagocytic activity? | Pertussis toxin |
Which two common exotoxins inhibit the release of neurotransmitters? | Tetanospasmin and Botulinum toxin |
What is the MOA of C. tetani and C. botulinum neurotoxins? | Proteases that cleave SNARE, a set of protein required for NT release via vesicular fusion |
What NT release is inhibited by Tetanospasmin? | Inhibitory (GABA and glycine) NTs form Renshaw cells in spinal cord |
GABA and glycine release is inhibited by _________________. | Tetanospasmin |
What are the classic signs of Tetanus? | Spastic paralysis, risus sardonicus, and trismus (lockjaw) |
What NT release is inhibited by Botulinum toxin? | Stimulatory ACh signal at Neuromuscular junction |
What are the clinical findings of Botulism? | Flaccid paralysis |
Which organisms' toxins lyse cell membranes? | Clostridium perfringens and Streptococcus pyogenes |
What are the two associated exotoxins with Strep pyogenes? | 1. Streptolysin O 2. Erythrogenic exotoxin A |
What is the MOA of alpha toxin in C. perfringens? | Phospholipase that debrades tissue and cell membranes |
What is the name of the enzyme used in Alpha toxin? | Lecithinase |
What organism causes "gas gangrene"? | Clostridium perfringens |
What are the most common clinical manifestations of Clostridium perfringens? | 1. Degradation of phospholipids --> myonecrosis ("gas gangrene") 2. Hemolysis ("double zone") |
What are antibodies against Streptolysin O? | ASO |
What titer levels are used to Dx rheumatic fever caused by S. pyogenes? | ASO titers |
Streptococcus pyogenes ANTIBODIES cause ________________. | Rheumatic fever |
Streptococcus pyogenes immune complexes cause _______________________. | Poststreptococcal glomerulonephritis |
What organisms have supertantiges causing shock exotoxins? | S. aureus and S. pyogenes |
What is the mode of action of TSST-1 and Erythrogenic exotoxin A? | Cross-links B region of TCR to MHC class II on APCs outside ot the antigen binding site |
What is the result of the cross link process of TCR and MHC II in superantigens? | Overwhelming release of IL-1, IL-2, IFN-gamma, and TNF-alpha ----> shock |
What are the clinical manifestation of S. aureus Toxic shock syndrome? | Fever, rash and shock |
Exfoliative toxin of S. aureus causes ---> | Scalded Skin Syndrome |
What is characteristic manifestation of S. pyogenes Toxic Shock syndrome? | Fever, rash, shock, and Scarlet fever |
What is the composition of LPS? | O antigen + core polysaccharide + lipid A |
What is the toxic component of LPS composition? | Lipid A |
What are the 3 main effects of LPS? | 1. Macrophage activation (TLR4/CD14), 2. Complement activation 3. Tissue factor activation |
ENDOTOXINS is a menemoconc to remember what characteristic of endotoxins? | E- edema N- nitric oxide D- DIC/Death O- outer membrane T- TNF-alpha O- O antigen + core polysaccharide + lipid A X - eXtremely heat stable I- IL-1 and IL-6 N- neutrophil chemotaxis S- Shock |
Scarlet Fever is caused by which bacteria exotoxin? | S. pyogenes |
Gram positive Aerobic Bacilli: | LIsteria, Bacilus, and Corynebacterium |
Clostridium is an important represent of: | Anaerobic Gram positive bacili |
Nocardia is: | Aerobic gram positive branching filamentous bacteria |
Which is the most common Gram (+) branching filament anaerobic bacteria? | Actinomyces |
Which bacteria have NOVOBIOCIN sensitivity testing? | S. saprophyticus and S. epidermidis |
Which specie of Staphylococcus is Novobiocin positive? | S. epidermidis |
Group A strepto: | S. pyogenes |
What is the MC representant of Group B strep bacteria? | S. agalactiae |
Which are the 2 most common representations of Viridans streptococci? | S. mutans and S. mitis |
Viridans streptococci has no_____________. | Capsule |
Which streptococci categorie has Optochin testing? | Partial hemolytic streptococcus |
S. pneumonia is Opsonin ____ or positive. | Sensitive |
What type of sensitivity is used in Group A and Group B streptococci? | Bacitracin sensitivity |