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Stack #567520
Microbiology
| Question | Answer |
|---|---|
| CLUE: These Rascals May Microscopically Lack Color (don't Gram stain well). | These/TREPONEMA Rascals/RICKETTSIA May/MYCOBACTERIA Microscopically/MYCOPLASMA Lack/LEGIONELLA PNEUMOPHILA Color/CHLALMYDIA |
| 4 stages of the bacterial growth curve? | LAG: Metabolic activity w/o division. LOG: rapid cell division. STATIONARY: nutrient depletion slows growth. Spore formation in some bacteria. DEATH: prolonged nutrient depletion & buildup of waste products lead to death. |
| Source of exotoxin? | gram + and - organisms |
| Source of endotoxin? | outer cell membrane of most gram negative bacteria and Listeria. |
| Are toxins secreted from exotoxins or endotoxins? | exotoxins |
| Chemistry of an exotoxin? | polypeptide |
| Chemistry of an endotoxin? | Lipopolysaccharide |
| Genes located on exotoxins? | plasmid or bacteriophage |
| Genes located on endotoxins? | bacterial chromosome |
| Toxicity level of an exotoxin? | toxicity level is high (fatal dose is 1 ug). |
| Toxicity level of an endotoxin? | Toxicity level is low (fatal dose is hundreds of micrograms). |
| Clinical effects of exotoxins? | toxic shock (increased cytokines); watery diarrhea; gas gangrene; |
| Clinical effects of endotoxins? | Fever & shock |
| Mechanism of action of exotoxins? | Acts on 60s ribosomes as a protein synthesis inhibitor; Acts at elongation factor 2; ADP ribosylates activate tissue adenylate cyclase to increase cAMP. |
| Mechanism of action of endotoxins? | TNF & IL-1 |
| Antigenicity of exotoxins? | Induces high titier antibodies called antitoxins. |
| Antigenicity of endotoxins? | Poorly antigenic |
| Are exotoxins used as vaccines? | YES, these are used as vaccines. |
| Are endotoxins used as vaccines? | NO, these are NOT used as vaccines. |
| Heat stability of exotoxins? | Destroyed rapidly at 60 degrees c (except staphylococcal enterotoxin). |
| Heat stability of endotoxins? | Stable at 100 degrees C for 1 hour. |
| Typical diseases exotoxins produce? | Tetanus; Botulism; Diptheria. |
| Typical diseases endotoxins produce? | Meningococcemia; Sepsis(gram negative rods) |
| Which bacterial virulence organisms promote immune responses? | S aureus (protein A); IgA protease; Group A streptococcal M proteins |
| How does S aureus (protein A) attack the immune system? | Binds Fc region of Immunoglobins. |
| How does IgA protease attack the immune system? | It cleaves IgA; Their polysaccharide capsules also inhibits phagocytosis; It is secreted by S pneumonia, H influenzae and Neisseria. |
| How does Group A streptococcal (M protein) attack the immune system? | Helps prevent phagocytosis. |
| What is the DIAGNOSIS of a 55 yo man who smokes and drinks heavily and presents with a new cough and flu like symptoms. Gram stain shows no organisms. Silver stain of sputum shows gram negative rods. | Legionella pneumonia |
| After taking clindamycin, the patient develops toxic megacolon and diarrhea. What is the DIAGNOSIS? | Clostridium difficile overgrowth. |
| A 25 year old man presents with 3 days pf fever,chills, and a painful, swollen knee. What is the DIAGNOSIS and CAUSATIVE AGENT? | Septic arthritis; N gonorrhoeae. |
| 19 year old femal college student presents with vaginal itching and thick, curdy discharge. What is the CAUSATIVE AGENT? | Candida albicans |
| 30 year old woman returns from a camping trip and complains of watery diarrhea and cramps. What is the CAUSATIVE AGENT? | Giardia lamblia |
| An alcoholic vomits gastric contents and develops foul smelling sputum. What organisms are most likely? | Anaerobes |
| Middle aged male presents with acute onset monoarthritic joint pain and bilateral Bell's palsy. What is the likely disease and how did he get it? | Lyme disease; Bite from Ixodes tick. |
| Urinary analysis (UA) shows WBC casts. What is the diagnosis? | Pyelonephritis |
| Patient presents with a thorn prick with ulcers along the lymphatic drainage. What is causing the infection? | Sporothrix schenckii |
| 25 yo college student has a burning feeling in his gut after eating. Biopsy of gastric mucosa showas gram negative rods. What is the likely organism? | Helicobacter pylori |
| 32 yo male has "cauliflower-like" skin lesions. Tissue biopsy s hows broad based budding yeasts. What is the likely organism? | Blastomyces |
| A breast feeding woman suddenly develops redness and swelling of her right breast. On examination a fluctuant mass is noticed. What is the DIAGNOSIS? | Mastitits caused by S aureus |
| A 20 yo college student presents with lymphadenopathy, fever, and hepatosplenomegaly. His serum agglutinates sheep RBCs. What celll is infected? | B cell (EBV; infectious mononucleosis). |
| After 3 hours of eating custard at a picnic, everyone began to vomit. After 10 hours, they felt better. what is the organism? | S aureus (produces performed enterotoxin)/ |
| Infant becomes flaccid after eating honey. What organism is likely and what is the MOA? | Clostridium botulinum; inhibited release of ACh. |
| A man presents with squamous cell carcinoma of the penis. He had exposure to what virus? | HPV |
| Patient develops endocarditis 3 weeks after receiving a prosthetic heart valve. What organism is suspected. | S epidermidis |
| Meaning of superantigens? | Exotoxins which bind directly to MHC 2 and T cell receptor simultaneously, activating large numbers of T cells to stimulate release of IFN-gamma and IL 2. |
| Name 2 superantigens. | S aureus & S pyogenes |
| Define S aureus | TSST-1 superantigen which causes toxic shock syndrome (Fever, rash, shock). Other S aureus toxins include entertoxins which causes food poisoning & exfoliatin which causes staphylocccal scaleded skin syndrome. |
| Define S pyogenes | Scarlet fever-erythrogenic toxin causes toxic shock-like syndrome. |
| Meaning of ADP ribosylating A-B toxins. | This toxin interferes with host cell function. B(binding) component binds to a receptor on surface of host cell,enabling endocytosis. A(active) component then attaches and ADP-ribosyl to a host cell protein (ADP ribosylation), altering protein function. |
| Name 4 ADP ribosylating A-B toxins. | Corynebacterium diphtheriae; Vibro cholerae; E coli; Bordetella pertussis |
| Define Corynebacterium diptheriae. | This toxin inactivates elongation factor (EF-2) and is similar to Pseudomonas exotoxin A. It also causes pharyngitits and pseudomembrane in throat. |
| Define Vibrio cholerae. | This toxin causes ADP ribosylation of G protein stimulates adenylyl cyclase; increases pumping of CL- into gut and decreases Na+ absorption; Water moves into gut lumen and causes voluminous rice -water diarrhea. |
| Define E coli (Hint: Labile like the Air, stable like the Ground!) | This heat labile toxin stimulates Adenylate cyclase and stimulates heat stable toxin Guanylate cyclase; these both cause watery diarrhea. |
| Define Bordetella pertussis. | Increases cAMP by i nhibiting G-alpha 1; causes whooping cough; inhibits chemokine receptor, causing lymphocytosis. |
| Define Clostridium perfringens. | Alpha toxin causes gas gangrene; produces a double zone of hemolysis on blood agar. |
| Define C tetani | Blocks the release of inhibitory neurotransmiters GABA and glycine; causes "lockjaw". |
| Define C botulinum | Blocks the release of acetylcholine; causes anticholinergic symptoms, CNS paralysis, esp cranial nerves; spores found in canned food, honey (causes floppy baby syndrome). |
| Define Bacillus anthracis. | 1 of the toxins in this toxin complex is adenylate cyclase. |
| Define Shigella | Shiga toxin, which is also produced by E coli 0157:H7, cleaves host cell rRNA; also enhances cytokine release causing HUS. |
| Define S pyogenes | Contains Streptolysin O, a hemolysin and antigen for ASO antibody, which is used in the diagnosis of rheumatic fever. |
| Define endotoxin. | A lipopolysaccharide found in cell wall of gram negative bacteria; "N-dotoxin is a part of the gram N-egative cell wall." Is heat stable; |
| 3 Functions of endotoxins | 1.Lipid A part acts on macrophage: stim IL-1(fever),TNF(fever/hemorr tissue necrosis)& NO(hypoten/shock) 2.Activates complement pathway: Stim C3a->hypoten/edema & C5a->Neu trophil chemotaxis. 3.Acts on Hageman factor: stim coagulation cascade->DIC |
| Which bacteria produce pigments | S aureus-> yellow pigment Pseudomonas aeruginosa-> blue green pigment. Serratia marcescens-> red pigment |
| What color and form of gram (+) organisms produce? | Purple/blue; Cocci and Rods/Bacilli |
| Describe 2 gram (+) cocci catalase reactions. | Cocci (catalase (+)clusters): Staphylococcus; Cocci (catalase (-) chains): Streptococcus |
| What are the 4 gram (+) rods/bacilli which stain? | Clostridium (anaerobe); Corynebacterium; Listeria; Bacillus. |
| Which organism has a coagulase response? | Staphylococcus |
| Describe the coagulase responses. | staphylococcus:-> S aureus-->COAGULASE (+) S epidermidis-->COAGULASE (-) and Novobiocin sensitive; S saprophyticus-->COAGULASE (-) and Novobiocin resistant. |
| Name 3 types of hemolysis reactions. | PARTIAL hemolysis->shows GREEN->ALPHA response; COMPLETE hemoloysis-> shows CLEAR->BETA response; No hemolysis->GAMMA response. |
| Which organism will show hemolysis? | Streptococcus |
| Describe gamma response. | No hemolysis of catalase (-) streptococcus causes this response-> enterococcus (E faecalis) & Peptostreptococcus (anaerobe) |
| Describe beta response. | Complete hemolysis of catalase (-) streptococcus response cause 2 responses: Group A (S pyogenes)->bacitracin sensitive. & Group B (S agalactiae)->Bacitracin resistant |
| Describe alpha response. | Due to partial hemolysis of catalase (-) streptococcus; Causes 2 general responses: S pneumoniae-> Capsule (+) quellung reaction optochin sensitive bile soluble Viridans streptococci/S mutans: No capsule Optochin resistant Not bile soluble |
| Hint: NO StRES | NOvobiocin: SaprophyTicus is Resistant; Epidermidis is Sensitive |
| Hint: OVRPS (overpass) | Optochin--Viridans is Resistant; Pneumonia is Sensitive. |
| Hint: B-BRAS | Bacitracin--group B strep are Resistant; group A strep are Sensitive. |
| What is the color and form of gram negative organisms. | Stains pink; Cocci/ Coccoid(rods)/ Rods |
| Name & describe gram (-) cocci organisms. | Neisseria meningitidis: Maltose fermenter & N. gonorrhoeae: Maltose nonfermenter |
| Name coccoid/rod gram (-) organisms. | Haemophilus influenzae; Pasteurella; Brucella; Bordetella pertussis |
| What does gram (-) rod organisms produce? | Lactose |
| Describe gram (-) rods lactose fermenters. | Fast fermenters: Klebsiella E coli Enterobacter Slow fermenters: Citrobacter Serratia |
| What does lactose NON-fermenters produce? | Oxidase |
| Which organism is Oxidase (+)? | Gram (-) Pseudomonas |
| Which organisms is Oxidase (-)? | Gram (-)'s Shigella, Salmonella, & Proteus. |
| Which media do you use to culture H influenza? | Chocolate agar with factors 5 (NAD) and X (hematin). |
| Which media do you use to culture N gonorrhoeae? | Thayer-Martin media |
| Which media do you use to culture B pertussis? | Bordet-Gengou (potatoes)agar |
| Which media do you use to culture C diphtheriae? | Tellurite plate and Loffler's media |
| Which media do you use to culture M tuberculosis? | Lowenstein-Jensen agar |
| Which media do you use to culture Lactose-fermenting enterics? | MacConkey's agar (shows Pink colonies) |
| Which media do you use to culture Legionella? | Charcoal yeast extract agar buffered w/increased iron & cysteine. |
| Which media do you use to culture Fungi? | Sabouraud's agar |
| What stains congo red? | Amyloid protein which shows apple-green birefringence in polarized light b/c of Beta pleated sheets. |
| Giemsa stains what organisms? | Stains Borrelia, Plasmodium, trypanosomes & Chlamydia |
| PAS (Periodic Acid-Schiff) stains what? | Stains glycogen & mucopolysaccharides Used to diagnose Whipple's disease. |
| Ziel-Neelsen stains what? | Stains acid fat bacteria. |
| India ink stains what? | Stains Crytococcus neoformans. |
| Silver stain, stains what? | Stains Fungi & Legionella |
| Define transformation. | Any DNA taken up directly from environment by competent prokaryotic and eukarytotic cells. |
| Define conjugation (F+ x F-) | F+ plasmid contains genes required for the conjugation process. Bacteria w/o this plasmid are termed F-. Plasmid is replicated & transferred through pilus from F+ cell. involves DNA plasmid only; there is no transfer of chromosomal genes. |
| Define conjugation (Hfr x F-) | F+ plasmid can become incorporated into bacterial chromosomal DNA (Hfr); Replication of incorporated plasmid DNA may include some flanking chromosomal DNA. Involves transfer of plasmid and chromosomal genes. |
| Define generalized transduction. | Lytic phage infects bacterium-> cleavage of bacterial DNA and synthesis of viral proteins; Parts of bacterial chromosomal DNA may become packaged in viral capsid; Phage infects another bacterium transferring these genes. |
| Define specialized transduction. | Lysogenic phage infects bacterium; viral DNA incorporated into bacterial chromosome; when phage DNA is excised, flanking bacterial genes may be excised with it; DNA is packaged into phage viral capsisd and can infect another bacterium. |
| Define transposition. | Segment of DNA that can jump from one location to another, transferring genes from plasmid to chromosome and visa versa; excision may include flanking chromosomal DNA, which can be incorporated into a plasmid and trasferred to another bacterium. |
| Define lysogeny. | Method of viral reproduction where the bacteriophage nucleic acid of the bacteria is integrated into the the genome of the host cell. This newly integrated genetic material is called a prophage. |
| Define the ABCDE's of lysogeny. | shigA-like toxin; certain strains of Botulinum toxin; Cholera toxin; Diphtheria toxin; Erythrogenic toxin of Strptococcus pyogenes. |
| What are obligate aerobes? Hint: "Nagging Pests Must Breathe" | These organisms use an O2 dependent system to generate ATP: Nocardia Pseudomonas aeruginosa Mycobacterium tuberculosis Bacillus |
| What are obligate ANaerobes? Hint: "Anaerobes know their ABC's" | Actinomyces, Bacteroides, and Clostridium: These organisms lack catalase &/or superoxide dismutase and are susceptible to oxidative damage; they are short chain fatty acids and smell foul; difficult to culture; produces gas in tissues (CO2 and H2). |
| Where in the body is anaerobes considered normal flora? What drug is ineffective against them. | Considered normal in the GI tract and pathogenic elsewhere. AminO2glycosides are ineffective against anaerobes b/c these antibiotics require O2 to center into the bacterial cell. |
| Where is P aeruginosa more likely seen. | Burn wounds, nosocomial pneumonia, pneumonias in CF patients. |
| What part of the lungs does M tuberculosis prefer to live? | The apices of the lung which has the highest Po2. |
| Name 2 types of intracellular bugs. | Obligate intracellular bugs & Facultative intracellular bugs. |
| Describe Obligate intracellular organisms. Hint: "These bugs stay inside when it is REALLY COLD"' | Obligate intracellular bugs: Rickettsia & Chlamydia. These bugs can't make their own ATP. |
| Decribe Facultative intracellular bugs. Hint: "Some Nasty Bugs May Live FacultativeLY". | Salmonella, Neisseria, Brucella, Mycobacterium, Listeria, Francisella, Legionella, Yersinia. |
| If a bacteria is encapsulated what reaction will be noticed? Hint: NOT "swellung" | A positive QUELLUNG reaction (capsule swells when specific anticapsular antisera is added). |
| Give examples of organisms with a positive quellung reaction. | Streptococcus pneumoniae; Haemophilus influenzae(esp B serotype); Neisseria meningitidis; Klebsiella pneumoniae. |
| What benefits do encapsulated bacteria have. | Their polysaccharide capsule is an antiphagocytic virulence factor. The capsule serves as an antigen in vaccines (Pneumovax, H influenzae B, meningococcal vaccines). Their conjugation with protein increase immunogenicity and T-cell dependent response. |
| Name urease positive bugs. | H pylori; Proteus; Klebsiella; Ureaplasma |
| Describe the resistance of bacterial spores. | Are highly resistant to destruction by heat & chemicals; Have dipicolinic acid in their core; Have no metabolic activity; must autoclave to kill spores. |
| Name gram (+) spores. | Found in soil: Bacillus anthracis; Clostridium perfringens; C tetani Other: B cereus; botulinum |
| Which bacteria form spores? | Certain gram (+) rods form this when the nutrients are limited (at end of stationary phase). |
| Name 2 alpha-hemolytic bugs. What color is the hemolysis. | 1.Streptococcus pneumoniae (catalase negative and optochin sensitive). 2.Viridans streptococci (catalase negative and optochin resistant). Forms a green ring around colonies on blood agar. |
| Name 4 Beta-hemolytic bugs. | S aureus: (catalase & coagulase +); S pyrogens/group A strep:(catalase - & bacitracin sensitive); S agalactiae/group B strep: (catalase - & bacitracin resistant); Listeria monocytogenes:(tumbling motility, meningitis in newborns, unpasterized milk). |
| What color does Beta-hemolysis form. | Clear area of hemolysis. |
| What organisms make catalase? | Staphlococci b/c they have more "staff". (strep does not!) S aureus makes coagulase. S spidermidis and S saprophyticus does not. |
| Describe how catalase inhibits bacteria. | It degrades H2O2 (an antimicrobial product of PMNs. H2Os is a substrate for myeloperoxidase. |
| What does Staph aureus make. | Makes coagulase and toxins. |
| What is the MOA of Staphylococcus aureus? | Protein A (virulence factor) binds Fc-IgG, thus inhibing complement fixation and phagocytosis. |
| What diseases are associated with Staphylococcus aureus. | Skin infections, organ abscesses, pneumonia; TSST-1 syndrome, exfoliative scalded skin syndrome, rapid onset food poisoning (enterotoxins).MRSA causes noscomial & community acquired infections. Resistant to Beta-lactams due to altered penicillin bp's. |
| Describe MOA of TSST (TSST-1 toxin). | A superantigen that binds to MHC 2 and T-cell receptor resulting in polyclonal T-cell activation. |
| What is the cause of S aureus food poisoning? | Preformed toxins |
| What causes acute bacterial endocarditis and osteomyelitis. | Staphylococcus aureus |
| What diseases is Streptococcus pyogenes associated with? Hint 1: "PHaryngitis gives you rheumatic PHever & glomerulonePHritis". Hint 2: "no RHEUM for SPECCulation" | Pyogenic(pharyngitis, cellulitis, impetigo); Toxigenic(scarlett fever, toxic shock syndrome); Immunologic (rheumatic fever-(Subcutaneous nodules, Polyarthritis,Erythema marginatum, Chorea, Carditis); Acute glomerulonephritis). |
| Describe features of Streptococcus pyogenes(group A Beta hemolytic streptococci). | Bacitracin sensitive; antibodies to M protein enhance host defenses against S pyogenes but, can give rise to rheumatic fever; ASO titer detects recent S pyrogenes infection. |
| What are the most common causes of Streptococcus pneumoniae? Hint: MOPS | Meningitis; Otitis media (children only); Pneumonia; Sinusitis. "Most OPtochin Sensitive" |
| What organism is associated with sepsis in sickle cell anemia and splenectomy? | Pneumococcus (rusty sputum). |
| Which organism is encapsulated & has IgA protease. | Streptococcus pneumoniae |
| What disease does Group B strep cause? | Pneumonia, Meningitis and Sepsis mostly in babies. |
| What are the characteristic features of Group B streptococci? | Bacitracin resistant and Beta-hemolytic. |
| What diseases does Staphylococcus epidermidis cause? | Infects prosthetic devices & catheters; Component of normal skin flora; contaminates blood cultures. |
| Name and describe the resistance of enterococci bacteria. | Enterococcus faecalis, E faecium, S durans, & S avium. Penicillin G resistant. Causes UTI & subacute endocarditis. Lancefield group D (grouping based on differences of C carbohydrates on the bacterial cell wall). Hemolysis is variable. Includes VRE. |
| What medium does enterococci grow in? | Grows in 6.5% NaCl. |
| What is the definition of entero? | intestine |
| What is the meaning of faecalis? | feces |
| What is the meaning of strepto? | twisted chains |
| What does coccus mean? | Berry |
Created by:
dbee
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