Step 1 - Micro 2

denniskwinn's version from 2015-04-25 16:08


Question Answer
Gram + CocciStaphy, Strep
Gram - CocciNeisseria
Gram + bacillusClostridium, Corynebacterium, Bacillus, listeria, Mycobacterium (acid fast)
Gram - bacillusE. Coli, shigella, salmonella, Yersinia, Klebsiella, Proteus, Enterobacter, Serratia, Vibrio, Campylobacter, Helicobacter, Pseudomonas, Bacteriodes, Haemophilus, Legionella (silver) , Bordetella, Yersinia, Francisella, Brucella, Pasteurella, Bartonella, Gardnerella
Branching Filamentous bacteriaOnly gram + = Actinomyces, Nocardia (weakly acid fast)
Pleomorphic bacteriaonly gram - = Rickettsiae, Chlamydiae (Giemsa)
Spiral bacteriaSpirochetes - leptospira, Borrelia (Giemsa), Treponema
Bacteria with no cell wallMycoplasma
Things that don’t gram stain wellThese Rascals May Microscopically Lack Color - Treponema, Rickettsia, Mycobacteria, Mycoplasma, Legionella, Chlamydia
Treponemes stainingdark field micro & fluorescent ab staining
Giemsa stainBorrelia, Plasmodium, trypanosomes, chlamydia
PAS stainstains glycogen, mucopolysaccharides - used to diagnose whipple’s disease ( Tropheryma whippelii)
Ziehl - Neelsen stainAcid-fast organism
India ink stainsCryptococcus neoformans (mucicarmine can also be use to sta
H. Influenzae special cultureChocolate agar with factors V & X
N. Gonorrhoeae special cultureThayer-martin (or VPN) media - vancomycin (inhibits gram+) - polymyxin & nystatin (inhibit fungi)
B. Pertussis special cultureBordet-Gengou (potato) agar
B. Diptheriae special cultureTellurite plate. Loffler’s media
M. Tuberculosis special cultureLowenstein-Jensen Agar
M. Pneumoniae special cultureEaton’s agar
Lactos-fermenting entericsPink colonies on MacConkey’s agar (fermentation produces acid, turning plate pink); e. Coli is also grown on eosin-methylene blue (EMB) agar as blue-black colonies with metallic sheen
Legionella special cultureCharcoal yeast extract agar buffered with cysteine
Fungi special cultureSabourauds’s agar
Obligate aerobesNagging Pests Must Breathe - Nocardia, Pseudomonas aeruginosa, Mycobacterium tuberculosis, Bacillus
P. AeruginosaAerobe seen in burn wounds, nosocomial pneumonia & pneumonias in cycstic fibrosis patients
Obligate anaerobesCan’t Breathe Air - Clostridium, Bacteroides, Actinomyces - lack catalase or superoxide dismutase = oxidative damage - normally flora in GI tract, pathogenic elsewhere -
Obligate intracellular bugsstay inside cell when its Really Cold - rickettsia, chlamydia - can’t make own ATP
Facultative intracellular bugsSome Nasty Bugs May Live FacultativeLy - Salmonella, Neisseria, Brucella, Mycobacterium, Listeria, Fransicella, Legionella
Encapsulated bacteriaKapsules Shield SHiN - Klebsiella pneumoniae, Salmonella, Strepto pneumoniae, Haemophilus influenzae type B, Neisseria meningitidis. - capsule =antiphagocytic virulence factors
Urease positive bugsParticular Kinds Have Urease - Protease, Klebsiella, H. Pylori, Ureaplasma
Novobiocin & Staph Saprophyticus = resistant, Epidermidis is Sensitive
Strep & OptochinViridan is resistant, Pneumoniae is Sensitive
Strep & Bactitracingroup B are resistant, group A are sensitive
TSST inducesT cell activation
Protein AS. Aureus virulence - binds Fc region of Ig - prevents opsonization & phagocytosis
IgA proteaseEnzyme that cleaves IgA. Secreted by S. Pneum, H. Flu type B & Neisseria - in order to colonize respiratory mucosa
M proteinmade by group A strep - helps prevent phagocytosis
Exotoxin sourcePolypeptide secreted from Certain species of some gram+ & gram - bact: such as?
Endotoxin source1. LPS structural from outer cell membrane of most gram - bacteria & Listeria 2. Leads to fever & shock, low toxicity - activate TNF & IL-1 3. Poorly antigenic 4. Poorly antigenic 5. No vaccine 6. Stable at 100C 5. Typically in Meningococcemia, sepsis from gram - rods
Exotoxin vaccinestoxoids used as vaccines - induces high-titer antibodies aka antitoxins
Exotoxin diseasesTetanus, botulism, diptheria
Superantigens1. bind directly to MHC II & T-cell receptor simultaneously, activating large numbers of t cells to stimulate release of IFN gamma & IL- 2 2. S. Aureus & s. Pyogenes
S. Aureus superantigen1. TSST-1 superantigen → toxic shock syndrome (fever, rash, shock). 2. Other toxins include enterotoxins that cause food poisoning as well as exfoliatin which → staph scalded skin syndrome
ADP ribosylating A-B toxinsinferfere with host cell funtion. B (binding) component binds to a receptors on surface of host cell, enabling endocytosis. A (active) component then attaches an ADP-ribosyl to a host cell protein altering protein fxn.
Corynebacterium toxininactivates elongation factor (EF-2) - → pharyngitis & pseudomembrane in throat . . (Pseudomonas aeruginosa's exotoxin A also inhibits EF-2)
Vibrio choleraeA-B toxins - ADP ribosylation of G protein stimulates adenyly cyclase increasing pumping of Cl- into gut & decreasing Na absorption. Water moves into gut lumen = rice water diarrheaa
E. ColiHeat - labile toxin stimulates adenylate cyclase - heat-stable toxin stimulates guanyl cyclase - both cause watery diarrhea - (labile like the Air, stable like the Ground)
Bordetella pertussisIncreased cAMP by inhibiting Galpha1 -→ whooping cough, inhibits chemokine receptor causing lymphocytosis
Clostridium perfringens toxinalpha toxin → gas gangrene - get double zone of hemolysis on blood agar
Clostridium tetani toxinblocks the release of inhibitory neurotransmitters GABA & glycine → “lockjaw”
C. Botulinum toxinblocks Ach release - → anticholinergic symptoms - CNS paralysis, esp cranial nerves. 2. Spores found in canned food, honey - → floppy baby
Bacillus anthracis toxinEdema factor - part of the toxin complex is adenylate cyclase
Shigella toxinShiga toxin (also produced by E. Coli O157:117) cleaves host cell rRNA - also enhances cytokine release causing HUS
S. Pyogenes toxinStreptolysin O is a hemolysin - antigen for ASO antibody, which is used in the diagnosis of rheumatic fever
Cholera toxin action permanently activates Gs (turns the “on” on) - → rice water diarrhea
Pertussis toxin actiondisables G causing whooping cough (turns “off” off) - also inhibits chemokine receptors
E coli (ETEC) toxin actionHeat-labile toxin - acts via ADP ribosylation - permanently activates endogenous adenylate cyclase
Bacillus anthracis toxin actionedema factor = a bacterial adenylate cyclase ( ↑cAMP)
Endotoxin actions1. Heat stable 2. Activates macrophages (IL-1, TNF, NO) 3. Activates complement (C3a, C5a) 4. Activates Hageman factor (DIC)
Peptidoglycan Fxn & Chem compRigid support, protects against osmotic pressure / Sugar backbone with cross-linked peptide side chain
Cell wall/cell membrane (gram positives) Fxn & Chem compMajor surface antigen / Peptidoglycan for support, techoic acid induces TNF & IL-1
Outer membrane (gram negatives) Fxn & Chem compSite of (LPS); major surface antigen
Plasma membrane Fxn & Chem compSite of oxidative & transport enzymes - lipoprotein bilayer
Ribosome Fxn & Chem compProtein synth / 50S & 30S subunits
Periplasm Fxn & Chem compSpace b/w cytoplasmic & outer membrane in gram - bacteria - contains many hydrolytic enzymes, including beta lactamases
Capsule Fxn & Chem compprotects against phagocytosis / usually polysaccharide (except bacillus anthracis - which contains D-glutamate)
Pilus/Fimbria Fxn & Chem compMediate adherence of bacteria to cell surface; sex pilus forms attachment b/w 2 bacteria during conjugation / made of glycoprotein
Flagellum Fxn & Chem compMotility / made of protein
Spore Fxn & Chem compProvides resistance to dehydration, heat & chems - Keratin- like coat made of dipicolinic acid
Plasmid Fxn & Chem compcontains a variety of genes for antibiotic resistance, enzymes & toxins - made of DNA
Glycocalyx Fxn & Chem compmediates adherence to surfaces, especially foreign surfaces - made of polysaccharide
Cell wall layers out to in Gram +Capsule, Peptidoglycan, membrane
Cell wall layers out to in gram -Capsule, Endotoxin/LPS. Peptidoglycan, periplasmic space, membrane
Mycoplasma membranecontains sterols & have no cell wall
Mycobacteria membraneContains mycolic acid - high lipid content
Legionella stainingsilver stain
Silver stain used forFungi, Legionella
Quellung reactionfor encapsulated bacteria - will swell when anticapsular antisera added
Actinomyces israeliiproduces yellow granules due to pus inside the cell
Staph aureus pigmentyellow pigment
Pseudomonas aeurginosa pigmentblue-green pigment
Serratia marcescens pigmentred pigment
Lag phase of bact growthmetabolic activity without division
Log phase of bact growthrapid cell division
Stationary phase of bact growthnutrient depletion slows growth. Spore formation in some bacteria
Death phase of bact growthprolonged nutrient depletion & buildup of waste leads to death
Bact transformationTake up DNA from environment (aka competence) - s.a. S. Pneum, H flu B, Nesseria
Bact F+ X F- conjugationF+ has genes required for conjugation & send their plasmid over - plasmid genes only
Bact Hfr X F- conjugationF+ plasmid can become incorporated into chromosome of Hfr cell - more than plasmid can transfer
Bact generalized transductionA “packaging” event - lytic phage infects bacterium, leading to cleavage of bacterial DNA & synth of viral proteins. Parts of bact chromosome DNA may become packaged in viral capsid. Phage infects another bacterium, transferring these genes.
Bact specialized transduction“excision” evet - lysogenic phage infects becterium; viral DNA incorporated into bacterial chromosome. Bacterial genes flanking phage may come with it - DNA is packaged into phage viral capsid & can infect another bacterium
Bact transposition transductionSegment of DNA that can “jump” from one location to another, can transfer genes from plasmid to chromosome & vice versa. When excision occurs, may include some flanking chromosomal DNA which can be incorporated into a plasmid & tranferred to another bacterium
Bact toxins encoded in lysogenic phagesABCDE - shigA-like toxin, Botulinum toxin (certain strains), Cholera toxin, Diptheria toxin, Erythrogenic toxin of Strep pyogenes
Alpha-hemolytic bacteriagreen ring around colonies on blood agar = Strep pneumoniae (catalase -, optochin sensitive), & Viridans strep (catalase -, optochin resistant)
Beta-hemolytic bacteriaclear area of hemolysis on blood agar = S. Aureus (catalase,coagulase +), strep pyogenes, strep agalactiae, listeria monocytogenes (tumbling motility, meningitit in newborns, unpast milk)
Catalasedegrades H2O2 before it can be converted to microbicidal products by the enzyme myeloperoxidase - staph
Coagulasemade by S. Aureus
Protein A virulence factor In s. Aureus - binds Fc Ig stopping complement
TSST superantigen that binds MHCII & TCR→polyclonal T-cell activation
S. Aureus pathophysProtein A →: 1. Inflamm disease (skin infection, organ abcsesses, pneumonia) 2. Toxin-mediated disease (toxic shock syndrome -TSST-1, scalded skin syndrome, rapid onset food poisoning) 3. MRSA
S. EpidermidisInfects prosthetic devices & IV catheters via adherent biofilms. Component of normal skin flora; contaminates blood cultures
S. PneumoniaMost common cause of MOPS - meningitis, otitis media, pneumonia, sinusitis 2. Rusty sputum, Post splenectomy infection in sickle cell anemia & splenectomy 3. Encapsulated in IgA protease
Viridans group strepalpha hemolytic 2. Normal flora of oropharynx - cause dental caries 3. Cause subacute bacterial endocarditis 4. Optochin resistant
Strep Pyogenes (GAS)1. Pyogenic -pharyngitis, cellulitis, impetigo 2. Toxigenic - scarlet fever, toxic shock syndrome 3. Immunologic -rheumatic fever, acute gloermulonephritis 4. Bactitracin sensitive - Ig to M protein enhance host defenses 5. ASO titer detects recent S. Pyogenes infection
Strep agalactiae (GBS)Bactitracin resistant, Beta-hemolytic: → pneumonia, meningitis & sepsis, mainly in babies!!
Enterococci (GDS)1. Faecalis, faecium - normal colonic flora 2. Penicillin G resistant 3. Cause UTI & subacute endocarditis. 4. Variable hemolysis 5. Heartier than GDS
Lancefield groupingbased on differences in C-carbohydrate on bacterial cell wall.
VREvancomycin resistant enterococci - an important cause of nosocomial infection
Strep bovis (GDS)colonizes gut - can cause bacteremia & subacute endocarditis in colon cancer patients
Corynebacterium diptheriae1. exotoxin encoded by Bita-prophage = inhibits protein synth via ADP ribosylation of EF-2 2. Pseudomembranous pharyngitis (grayish white membrane) + lymphadenopathy 3. Lab diagnosis based on gram + rods w/blue & red granules 4. Toxoid vaccine prevents diptheria
Bacterial sporesOnly certain gram+ rods from spores when nutrients are limited (at end of stationary phase) - spores highly resistant to destruction by heat & chems. Must autoclave to kill spores.
Spore forming gram + bacteria in soilBacillus anthracis, Clostridium perfringens, C. Tetani . . . Other spore formers - B. Cereus, C. Botulinum
C. Botulinumproduces preformed, heat-labile toxin that inhibits ACh release at NM junction - causing botulinism
C. Perfringensproduces an alpha toxin (lecithinase - a phospholipase) that can cause myonecrosis (gas gangrene) & hemolysis
ClostridiaGram +, spore forming, obligate anaerobic bacilli
C. Tetaniproduces tetanospasmin, exotoxin causing tetanus - blocks glycine release (inhibits) from Renshaw cell in spinal cord - → spastic paralysis, trismus (lockjaw) & risus sardonicus
C. Difficilleproduces a cytotoxin - exotoxing that kills entorcytes - causing pseudomembranous colitis- often secondary to antibiotic use, esp clindamycin or ampicillin - 2. Treat with metronidazole