Microbiology - Block 2 - Part 1
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2015-06-17 14:42
Bacteriology
| Question | Answer |
|---|---|
| Molecule in the cell wall of bacteria that is the target of beta-lactam drugs | Peptidoglycan |
| Sometimes used as sites of attachment | Pilus/Finbria |
| Bacteria that absorbs Gram stain | Gram Positive |
| Bacteria that do not absorbs Gram stain | Gram Negative |
| Bacteria that has a thick cell wall containing large amounts of peptidoglycan along with Teichoic acid and Lipoteichoic acid | Gram Positive |
| Bacteria that has a thin cell wall containing peptidoglycan and an outer membrane composed of Lipopolysaccharide (LPS) | Gram Negative |
| Outer membrane of Gram negative | Lipopolysaccharide (LPS) |
| Holes in the Lipopolysaccharide that allow substances to reach the bacteria cell walls | Porins |
| Lipopolysaccharide (LPS) is also known as | Endotoxin |
| The toxic component of Lipopolysaccharide (LPS) | Lipid A |
| This antibiotic cannot pass through the porins of Gram negative bacteria to target the peptidoglycan and is therefore not a viable treatment antibiotic for Gram negative bacteria | Vancomycin |
| Bacteria that are Gram positive | Thick Cell Wall |
| Bacteria that are Gram negative | Thin Cell Wall |
| The structure of peptidoglycan is composed of these glycan subunits | n-Acetylmuramic Acid (NAM) and n-Acetylglucosamine (NAG) |
| The peptide sequence that is targeted by vancomycin | D-Alanine - D-Alanine |
| Transpeptidase-carboxypeptidase enzymes are also known as | Penicillin-Binding Proteins |
| Formation of these help certain bacteria survive harsh conditions and are highly resistant to dessication, chemicals, hot/cold temps | Endospores |
| The two important genera of bacteria that form spores | Bacillus and Clostridium |
| Beta-lactum drugs work best at this phase of bacterial growth | Log Phase |
| 2O2- + 2H+ > H2O2 + O2 | Superoxide Dismutase |
| 2H2O2 > 2H2O + O2 | Catalase |
| O2 necessary, use only aerobic respiration and die in absence of O2 | Obligate aerobes |
| Pseudomonas, Mycobacterium are examples of | Obligate aerobes |
| Require lesser amounts of O2 - 5 to 10% | Microaerophiles |
| Campylobacter, Helicobacter are examples of | Microaerophiles |
| Can use both aerobic respiration (using O2) and fermentation/anaerobic respiration (without O2) | Facultative anaerobes |
| Enterobacteriaceae is an example of | Facultative anaerobes |
| Cannot use O2 and will die when exposed to O2 | Obligate anaerobes |
| Clostridium, Bacteroides are examples of | Obligate anaerobes |
| Bacteria that live outside of a cell | Extracellular bacteria |
| Vibrio cholera is an example of this life style | Extracellular bacteria |
| Can survive both outside or inside host cells. Intracellular bacteria escape antibodies (present in extracellular environment), can only be eliminated by a cellular immune response. Have adapted mechanisms to escape host killing mechanisms once internalized | Facultative intracellular bacteria |
| Grows inside macrophages, induces its’ own uptake & blocks lysosomal fusion | Legionella |
| Grows inside macrophages, destroys phagosome, inhibits lysosomal fusion, escapes and grows in cytoplasm of macrophage | Mycobacterium tuberculosis |
| Cannot survive outside host cells | Obligate intracellular bacteria |
| Chlamydia is an example of this type of bacteria life style | Obligate intracellular bacteria |
Gram Stain and Morphology
| Question | Answer |
|---|---|
| The genus of bacteria and the type of antibiotic to be used is indicated by | Gram Stain |
| Gram +, Cocci, chain | Streptococcus |
| Gram +,Cocci, cluster | Staphylococcus |
| Gram +, Cocci, pairs | Streptococcus pneumoniae |
| Gram -, Cocci, pairs | Neisseria |
| Gram +, Bacilli, chain | Bacllus anthracis |
| Gram +, Bacilli, with terminal spores | Clostridium tetani |
| Gram -, Vibrio, isolated with flagellum | Vibrio cholera |
| Gram -, Coccobacilli, isolated/pairs | Bordetella pertussis |
| Gram +, Coccobaclli, pairs | Corynebacterium diptheriae |
| Gram -, Spiral, isolated | Helicobacter pylori |
| Gram +, Bacilli, isolated | Clostridium Botulinum |
| Gram o , Coccobaclli, pairs | Klebsiella pneumoniae |
Bacteria Genetics
| Question | Answer |
|---|---|
| Genes directing transfer of plasmid to other cells | Fertility plasmid |
| Genes for antibiotic resistance | Resistance plasmids |
| Genes for toxin production | Exotoxin Plasmids |
| Plasmids that can integrate into bacterial chromosome | Episomes |
| Genes the can copy themselves and then excise themselves from the chromosome leaving a copy where they were and insert into another part of the chromosome or into a plasmid | Transposons |
| The genes that encode many virulence factors are clustered together. Examples include genes encoding adhesins, invasins, and exotoxins are adjacent to one another | Pathogenicity Islands |
| The process by which bacteria transfer genes from one cell to another by cell-to-cell contact | Conjugation |
| There is one-way transfer of DNA from a donor (or male) cell to a recipient (or female) cell through | Sex Pilus |
| The sex pilus forms this between the two bacteria | Conjugation Bridge |
| Many conjugative plasmids carry genes for this | Antibiotic Resistance |
| The transferred F plasmid integrates into the chromosome | High-frequency Recombinant (Hfr Cell) |
| Controls conjugation | Fertility factor (F plasmid) |
| Transfer of genes from one cell to another via phage-vector, no cell-to-cell contact occurs | Transduction |
| A phage picks up bacterial DNA by error and transfers the DNA into another bacteria | Transduction |
| Only undergo lytic replication | Virulent Phages |
| Can undergo both types of replication | Temperate Phages |
| Uptake of naked DNA from the environment by competent cells | Transformation |
Bacteria Pathogenessis
| Question | Answer |
|---|---|
| A microorganism capable of causing disease | Pathogen |
| One that rarely causes disease in an immunocompotent host but can cause serious infection in immunocompromised individuals | Opportunistic Pathogen |
| Is the ability of a microorganism to cause disease | Pathogenicity |
| One that lives in a certain niche in the host and is unharmful there. May be pathogenic when introduced into other areas of the body | Commensal |
| Is a quantitative measure of pathogenicity | Virulence |
| Attributes possessed by disease-causing microorganisms that aid in their colonization of host tissue and establishment of infection | Virulence Factors |
| Entry into host tissue, Adherence to host cells, Evasion of primary host defenses, Growth in numbers are in this stage of infection | Colonization |
| Invasion accompanied by inflammation and production of toxins, enzymes – damage host tissue are in this stage of infection | Production of Disease |
| Prevents bacteria from being carried away by mucus or washed swept away by fluids using pili/fimbriae in this stage of infection | Adherence to Host Surfaces |
| Capsules and IgA proteases, biofilm production, intracellular survival of bacteria, antigenic variation and inactivation of complement are measures used by bacteria in this stage of infection | Evasion of Primary Host Defenses |
| Variable expression of antigens that constantly change the presentation of the bacteria to the immune system | Antigenic Variation |
| Neisseria meningititis, Haemophilus influenzae type b, Streptococcus pneumoniaeall are encapsulated and produce IgA proteases which can cause this if it can get into the CSF | Meningitis |
| Cells of immune system and antibiotics cannot penetrate this structure produced my a group of bacteria | Biofilm |
| Secreted into the surrounding environment | Exotoxin |
| Polypeptides, antigenic, can be converted to toxoids, A-B subunit toxins | Extoxin |
| An integral part of the cell wall of only Gram negative bacteria | Endotoxin |
| Structural part of cell wall (outer membrane). Found only in Gram negative bacteria and released into host circulation following bacterial cell lysis | Endotoxin |
| Subjecting exotoxins to low heat and chemicals (eg. Formaldehyde) in the laboratory environment inactivates them. Looses toxicity but retains antigenicity | Toxoid |
| Dimeric endotoxin structure | A-B Subunit Exotoxin |
| Subunit that binds the exotoxin to specific receptors on target cells | B Subunit |
| Subunit that enters the host cell and exerts toxic effect | A Subunit |
| A-B subunit toxin that inhibits protein synthesis by binding to EF-2 | Diphtheria Toxin |
| A-B subunit toxin that activates cAMP | Cholera Toxin |
| Cholera toxin increases cAMP by binding to | Adenylate Cyclase |
| Toxin that inhibits of protein synthesis by ADP-ribosylation of host elongation factor (EF-2). Primarily targets heart/nerves/epithelium | Diphtheria Toxin |
| Toxin inhibition of protein synthesis by ADP-ribosylation of elongation factor (EF-2). Primary target is the liver | Pseudomonas Exotoxin A |
| Inhibits protein synthesis by interfering with 60S ribosomal subunit | Shiga and Shiga-like Toxin |
| Stimulates adenylate cyclase by ADP-ribosylation of GTP binding protein. Hypersecretion of fluids and electtrolytes from intestinal epitthelium. Profuse watery diarrhea | Cholera Toxin |
| Stimulates adenylate cyclase by ADP-ribosylation of GTP binding protein. Watery diarrhea. | Heat Labile Toxin (LT) |
| Stimulates guanylate cyclase. Watery diarrhea | Stable toxin (ST) |
| Heat labile toxin (LT) and Stable toxin (ST) are produced by | Enterotoxigenic E.coli |
| ADP ribosylation of Gi (inhibitory G protein - negative regulator of adenylate cyclase) causing increased cAMP | Pertussis Toxin |
| EF = edema factor = adenylate cyclase, LF = lethal factor, PA = protective antigen. Decreases phagocytosis; causes edema, kills cells | Anthrax Toxin |
| Toxin causes cell membrane damage and leakage of cell membrane | Cytolysins |
| Has lecithinase activity which damages cell membranes | Alpha Toxin (Clostridium perfringens, Myonecrosis “gas gangrene”) |
| Inserts into membrane to form pores which causes cell membrane to become leaky | Alpha Toxin (Staph aureus) |
| Toxins that inhibit normal neuron function or transmission | Neurotoxin |
| Blocks release of inhibitory neurotransmitters glycine & gamma-amino butyric acid (GABA). Inhibits neurotransmission in inhibitory synapses. Results in muscle spasms, spastic paralysis | Tetanus Toxin |
| Blocks release of acetylcholine from peripheral cholinergic neurons. Results in flaccid paralysis | Botulinum Toxin |
| Cause non-specific activation of T-helper lymphocytes. Bind and link MHC-II molecule (of antigen-presenting cell) with T-cell receptor (on T-helper cell) outside of the peptide binding groove. Large numbers of T cells are activated irrespective of their specificity for the antigen which leads to massive amount of cytokines secreted | Superantigens |
| Pyrogenic, Fever, rash, shock, capillary leakage. Endotoxin enhancer which increases susceptibility to LPS | Toxic Shock Syndrome Toxin (TSST-1) |
| Toxic shock syndrome toxin is produced by | Staph aureus |
| Pyrogenic, Fever, rash, shock, capillary leakage. Endotoxin enhancer which increases susceptibility to LPS, Cardiotoxicity | Erythrogenic/Pyrogenic Toxin |
| Erythrogenic/pyrogenic toxin is produced by | Strep pyogenes |
| Inject the exotoxins they produce directly into host target cells using this system. Toxin evade the antibodies because it directly enters a host cell | Type III Secretion System |
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