Microbiology Flashcards
Candida Albicans Histo
Yeast and Pseudohyphae Q ID: 109
What vaccines are conjugated polysaccharides?
S pneumo
H influenzae
N meningitis
What fungi characterized by small ovoid bodies WITHIN macrophage?
Histoplasmosis: disseminated disease in immunocomp’ed (HIV)
systemic (fever, weight loss)
pulm: hilar adnopathy, cavitary lesions upper lobes Hepatosplenomegaly
oral ulcers
lymphadenopathy
Q267: Aspergillus: hyphae showing V branchingCryptococcus: extracelluar. large, polysaccharide capsuleCoccidiodes: spherules containing microspores
Elderly man with fever, malaise, myalgia, headache, with other family members same sx = dx? What are elderly prone to developing after this? Most common orgs that cause the secondary infection?
- Influenza (lots ppl in family have) 2. Secondary bacterial pneumonia = S. pneumoniae, S aureus, Haemophilus
What is the only virus that is ssDNA and nonenveloped?
Parvovirus - Fifth’s disease- Aplastic anemia in sickle cell - Hydrops fetalis
What organism is best visualized using silver stain, cultured on buffered charcoal yeast extract medium with L-cystine and Fe, and can be nosocomially spread? How is it spread?
Legionella - contaminates water supplies, water-based cooling systems in hospitals.
What organism characterized by SPHERULES packed with ENDOSPORES?
Coccidioides: - endemic to southwestern US (Cali, Arizona, NMexico, Texas)
hyphae at 20-30 -> inhalation of spores -> spherules containing endospores at 37/body temp -> dissemination of endospores
Sx: - pulmonary disease + erythema nodosum - Immunocompromised: pulm, extra pulm, meningitis
Microorganisms and Regions they are Endemic
Coccidiodes: southwestern US Histo: Ohio and Mississippi - bird, bat dropping, cavingCryptococcus: pigeon droppings
Maculopapular Rash on face that spreads to trunk and extremities + postauricular LAD
Rubella (Measles would also have that rash)
What is the monospot test? What does it differentiate?
Monospot (+): EBV infection = heterophile Ab detected by agglutination of sheep or horse RBC: Monospot (-) = CMV mononucleosis instead
Congenital rubella
sensorineural hearing losscataractscardiac malformations (PDA)
Presentation of C. botulinum?
3D’s: Diplopia Dysphagia Dysphonia
Acquired toxin:
Food Borne: preformed toxin in bad bottles of food
Wound Borne: toxin production in wound
Infant Borne: toxin in honey - spores ingested that then mature
Function of Pilus
- Attachment to cell surface. 2. Conjugation thru sex pilus
What do the following Hep B markers represent? HBsAg, HBcAg, HBeAgAnti-HBs, Anti-HBc IgM and IgG, Anti-HBe
HBsAg = acute infection, persists > 6 mo = chronic inf.
HBcAg = antigen associated with core of HBV
HBeAg = marker for viral replicability and transmission
Anti-HBs = resolution of acute infection, immunity
Anti-HBc IgM = present during window phase
Anti-HBc IgG = present after recovery vs. present without anti-HBs in chronic infection; not present after vaccination
Anti-HBe = present after recovery; if present in chronic indicates low viral replicability
What kind of RNA virus is infectious and can induce protein synthesis?
SS+ RNA (single stranded, positive sense) = Rhinovirus. Q1373
Resistance to Aminoglycosides (Gentamicin, etc) mediated by?
Bacterial transferase enzymes inactivate drug by acetylation, phosphorylation, adenylation. Drug normally inhibits formation of initiation complex and cause misreading of mRNA.
Resistance to Penicillin mediated by?
- beta-lactamase2. altered penicillin binding protein
Resistance to Tetracycline mediated by?
Eecrease uptake or increase efflux out of bacterial cells by plasmid-encoded transport pumps
Resistance to Fluoroquinolones mediated by?
chr encoded mutation in DNA gyrase.
Resp Infections in Children (Q1667)
Croup - barking, brassy cough - parainfluenza (paramyxovirus)
Epiglottitis - drooling, difficulty swallowing - H. flu
Diptheria - pharyngeal pseudomembrane - C. diptheria
Bronchiolitis - wheezing - resp syncytial virus.
What does the Thayer-Martin selective medium isolate and how?
N. gonorrhea
Vanco = inhibit G+
Colistin (Polymyxin) = inhibit G
Nystatin = inhibit fungi
Trimethoprim = inhibit G- other than Neisseria, such as Proteus
What medication needs an acidic environment to kill M tuberculosis?
Pyrazinamide - active inside phagolysosomes.
How does Hep B replicate?
dsDNA -> + ssRNA template -> dsDNA reverse transcriptase DNA polymeraseQ376
How do you treat S. epidermis?
Vanco + Rifampin or GentamicinMost are methiciilln resistant.
H. flu type B causes what?
invasive disease - sepsis, meningitis, pneumonia, epiglottitis.
What viral-encoded protein would change if the virus were to gain the ability to infect human epithelial cells?
Glycoprotein - mediates attachment to target host cell plasmalemma receptors
Antibodies to polyribosyl-ribitol-phosphate (PRP) provides protection against?
Epiglottitis. Hib vaccine = PRP component of Hib capsule conjugated to diptheria toxin
What microbe causes pityriasis versicolor?
Malassezia furfur. KOH = spaghetti and meatballs
What response does inactivated vaccine vs live vaccine generate?
Inactivated = humoral Live = CD8
What does influenza vaccine help inhibit?
Viral entry into cell. Antibody against hemagluttinin antigen preventing it from interacting with cell receptors.
What cause of inflammatory diarrhea can be transferred from animals to humans?
Campylobacter
Anerobes above the diaphragm vs. below?
Above - ClindamycinBelow - Metronidazole
How does vibrio cholerae cause rice watery diarrhea? What would you expect to see on stool microscopy?
GN, oxidase positive, comma-shaped rod grows on alkaline media
Cholera toxin - permanently activates Gs - inc. cAMP. No leukocytes or erythrocytes visualized on microscopy since it does not invade mucosa or cause cell death…
Why do cephalosporins NOT work against nongonoccocal urethritis?
Caused by Chlamydia or Ureaplasma Urealyticum. Chlamydia - lacks peptidoglycan within cell wallUreaplasma Urealyticum - lacks a cell wall entirely
Ecoli virulence factors?
- P fimbrae - UTI - allows adhesion to uroepithelium
- K capsule - Pneumonia, Neonatal Meningitis - prevents phagocytosis and complement mediated lysis
- LPS - bacteremia and septic shock 4. Enterotoxins (ETEC and EHEC)
What is mucormycosis? What species cause it?
Mucormycosis
Pt: ketoacidotic diabetic and leukemic pts
Sx: infection of blood vessel walls -> paranasal sinuses, cribriform plate, frontal lobe abscesses -> facial pain, headache, black necrotic eschar, cn involvement
Dx: Mucor - nonseptated hyphae branch at wide anglesRhizopus -septated hyphae branch at 90 degrees (vs. aspergillus is 45)
Tx: Amphotericin B
Dimorphic Fungi
molds with hyphae (ambient temp, 25-30) and yeasts/single cell (body temp, 37)
Sporothri schenckii Coccidioides immitis Histoplasma capsulatum Blastomyces Dermatitidis Paracoccidiodes Brasiliensis Q103
Daptomycin - Use, mech, toxicities
Used for invasive MRSA infections. (can’t use against GN orgs bc doesn’t penetrate their outer cell membrane; can’t use against pneumonia bc inactivated by pulm surfactant)
Mech: disrupts bacterial membrane and membrane potential by creating transmembrane channels Tox: Myopathy, increased CPK
How does HBV vs. HCV increase risk of HCC?
HCV - chronic inflam -> regenerative hyperplasia -> increases chance of genetic mutations
HBV - even when not active hepatitis, HBV inserts DNA into host genome (main cause of the increased risk) -> production of HBx protein -> stimulate cell prolif and suppress p53
Amphotericin B - how does it cause toxicity?
Binding to cholesterol in membrane. Preferentially binds ergosterol but can bind cholesterol.
What drugs can precipitate serotonin syndrome when given with antidepressants?
Linezolid
Ondansetron
Tramadol
Triptans
What causes spasms and muscle rigidity in neonate with unsterile umbilical cord cutting? What should have been done to prevent this?
Tetanus! Maternal Immunization - IgG antibodies can cross the placenta.
How do pufferfish cause sx?
Tetrodotoxin - binds to Na channels - inhibit Na influx and conduction of action potential
Major virulence factor of GAS
M protein - prevents phagocytosis
Name 3 bacterial virulence factors
IgA protease - S. pneumo, H. flu, Neisseria Protein M - GAS - prevents phagocytosis Protein A - S. aureus - prevents opsonization and phagocytosis
What three drugs that inhibit dihydrofolate reductase and what are they used for?
Trimethoprim - combined with Sulfamethaxazole against bacterial dihydrofolate reductase Methotrexate - cancer drug; targets rapidly dividing cellsPyrimethamine - antimalarial; + sulfadiazine for toxo bc inhibits parasitic dihydrofolate reductase.
What microbe is associated with wool sorting?
Bacilius Anthracis!
Woolsorter inhalation of spore -> pulm anthrax -> fever, pulm hemorrhage mediastinitis, shock Unique features of anthrax:
- polypeptide capsule - D glutamate instead of polysaccharide
- “medusa head” colonies on culture
- Anthrax toxin - edema, lethal factor, protective antigen
What adverse effect is associated with ethambutol?
Optic neuritis - color blind, dec. visual acuity, central scotoma.
What drug for HIV induces hyperglycemia?
Protease inhibitor Other adverse effects: lipodystrophy, inhibition of cytochrome p450 (ritonavir)
How do you diagnose tetanus?
H&P
MOA of raltegravir?
Inhibits HIV integrase. Inhibits integration of HIV into genome of the host cell. (Q8371 picture)
What antifungal inhibits cell wall synthesis?
Caspofungin - inhibits cell wall synthesis by inhibiting synthesis of beta-glucan. Use: Invasive Aspergillosis, Candida
Pathogenesis of Diptheria?
Toxin inhibits EF2 by ADP-ribosylation, this inhibiting protein synthesis.
Ways to distinguish S. pneumoniae from other bacteria in the lab?
GP diplococci Catalase negative. Capsule present Optochin sensitive. Bile Soluble - lysed in bile.
Lesion associated with Pseudomonas Aeruginosa infection?
Ecthyma gangrenosum = cutaneous necrotic lesion after Pseudomonas invades perivascularly, and releases destruction exotoxins -> insufficiency of blood flow to patches of skin which become edematous and necrose.
What virus does NOT acquire their envelope from the plasma membrane, but from the nuclear membrane?
Herpes Viruses: HSV 1 HSV 2 VZV (HHV3) EBV (HHV4) CMV (HHV5) HHV6 - roseola HHV7 - less common cause of roseolaHHV8 - Kaposi sarcoma
Ganciclovir and Zidovudine together will cause what adverse effect.
Bone Marrow suppression - neutropenia
How does Shigella invade the GI mucosa?
Gain access thru the M cells of Peyer’s patch in the ileum thru endocytosis. Then shigella lyses the endosome, multiples, and spreads laterally -> causing cell death, ulceration, hemorrhage, diarrhea.
Dx of pt who has bronchial asthma complicated by recurrent pulmonary infection and bronchiectasis; eosinophilia on labs?
Aspergillus Fumigatus
Allergic Bronchopulmonary Aspergillosis
Tx for recurrent C diff
Fidaxomin –| RNA polymerase - impair protein synthesis, bacteriCIDAL - oral, minimal systemic absorption
Most common cause of Bacterial Meningitis
S. pneumo = GP diplococcci
What glycoprotein of HBV is NONinfectious?
HbSAg - noninfective envelope glycoprotein forms spheres and tubules 22 nm in diameter.
Amphotericin B toxicity
Renal toxicity - - HypoK, HypoMg
What microbe is associated with subacute sclerosing pancencephalitis?
Measles - SSPE develops in years after infection. Absent matrix protein -> replicates intracellularly within neurons and oligodendrocytes -> inflam, demyelination, gliosis
Mycobacteria grow in “serpentine cords” or parallel chains due to what?
Cord Factor - Virulence factor - induces release of TNF alpha - neutrophil inhibition - inhibits macrophage maturation.
Causes of painful vs. painless genital ulcers?
Painful - Chancroid (Haemophilus Ducreyi)- HSV-2
Painless - Primary Syphillis (chancre), Lymphogranuloma Venereum - painless genital ulcer -> painful lymphadenopathy (buboes) - Chlamydia Trachomatis
What antiviral agent does NOT require intracellular phosphorylation to be active?
Foscarnet –| viral DNA polymerase (pyrophos analog)
Cidofovir –| viral DNA polymerase (nucleoside monophosphate)
Both indicated for CMV retinitis when ganciclovir fails; Acyclovir-resistant HSV
What bacteria have no cell wall?
Mycoplasma.
What picornavirus is acid-labile?
Rhinovirus - gets destroyed by stomach acid - does not infect GI tract. Just common cold!
Recent vacation + Fever, Pneumonia, GI, CNS sx =
Legionnaires’ DiseaseWill see hyPOnatremia!
What are the HIV structural genes and proteins they code for?
Env - gp120 = attachment - gp41 = fusion and entry
Gag - p24 = capsid
Pol- reverse transcriptase - protease - integrase
Anal Ulcer in HIV(+) most likely what?
Squamous Cell Carcinoma - HPV!
Efflux Pumps depend on what to pump antibiotics out?
H gradientATP Na gradient.
What DNA viruses do not replicate in the nucleus?
Poxvirus - carries own DNA dependent RNA polymerase
What are the DNA viruses?
HHAPPPPy Hepadna = HBV Herpes Adenovirus Parvo Papilloma = HPV Polyoma = JC, BK Poxvirus = Smallpox, Cowpox, Molluscum Contagiosum
What the DNA virus characteristics and exceptions?
dsDNA - except parvo ss and linear
Linear - except papilloma, polyoma - circular- and hepadna - circular and incomplete
Iscosahedral - except poxReplicate in the nucleus - except pox
What family of virus most likely to cause aseptic meningitis?
Picornavirus - Enteroviruses (Echo, Coxsackie)
Protein synthesis inhibitors - what do they do?
Buy AT 30, CCEL at 50.
30S inhibitors:
Aminoglycosides - inhibit formation of initiation complex
Tetracycline - inhibit tRNA binding
50S inhibitors:
Chloramphenicol - peptidyl transferase inhibitor Clindamycin - inhibit translocation
Erythromycin (Macrolides) - inhibit translocation “macroslides”
Linezolid- inhibit bacterial initiation complex
What protein synthesis inhibitor is bacteriocidal?
Aminoglycoside
Aspergillus MIcroscopy
Septate hyphae - 45 degrees “Acute angles for aspergillus”Conidiophore with radiating chains of spores.
Giardia Lamblia - what’s it look like?!
Trophozoite - owl eye nucleus!! Cysts in the stool Presents as malabsorption - fatty rich Ghirardelli chocolates. Does not cause invasive disease.
What are the presentations of Aspergillous?
Aspergillomas in Lung Cavity, esp after TB infection
Allergic Bronchopulmonnary Aspergillosis - assoc. with asthma, cystic fibrosis - causes bronchiectasis and eosinophilia
Invasive Aspergillosis - esp immunocompromised, chronic granulomatous disease Virulence = HEMATOGENOUS spread.
What GP cocci synthesize dextrans from glucose? And what do they normally cause?
Viridans strep - S. mutans and S. sanguinis
- Dental Caries
- Subacute bacterial endocarditis at damaged heart valves (fibrin-plt aggregates)
Host cell receptor/Virion protein binding specificities: - HIV- EBV- Parvovirus B19
HIV: CD4 and gp120
EBV: CD21 and gp350
Parvovirus: Erythrocyte P-antigen and parvovirus B19
Culture requirements for H. flu? Can be grown with what species?
Chocolate agar with factor V (NAD+) and X (hematin)
Grown with S. aureus: - actively secretes NAD+- beta hemolysis -> hematin release from RBC.
Immune Mechs against Giardia? What immunodeficiencies are predisposed to infection?
- CD4 2. IgAIgA deficiencyX-linked agammaglobulinemiaCVID
What mediates MRSA resistance to naficillin?
Altered penicillin binding protein.
HIV pt with impaired renal vision who gets a prescribed _____ and then develops seizure, Hypoca, HypoMg
Foscarnet
What virus causes hepatitis and has a high mortality rate among pregnant women?
HEV: fecal-oral route. Nonencapsulated ssRNA virus.
Associated with waterborne epidemics.
Mild severity, no chronic hepatitis.
Does cause high mortality in pregnant patients!
What do the toxins of Clostridium Difficile do?
Toxin A = enterotoxin binds to brush border - causes the inflammation and secretions
Toxin B = Cytotoxic = CYTOSKELETAL disruption via actin depolymerization = pseudomembranous colitis
What are the NNRTI?
Nevirapine EfavirenzDelavirdine
What is Reye Syndrome?
Aspirin in pts 5-14 yo + some infection 1. Hepatic Dysfunction: microvesicular steatosis. 2. Encephalopathy: hepatic dysfxn -> hyperammonia.
Mechanisms of action of Acyclovir?
Nucleoside analog -> viral thymidine kinase -> cellular enzyme phos to acyclovir triphosphate -> incorporate into newly synthesized viral DNA and terminate DNA synthesis.
What is the most common outcome of HBV infection?
Complete resolution after acute hepatitis with mild/subclinical sx. Could also - chronic hepatitis +/- cirrhosis and HCC- fulminant hepatitis with massive liver necrosis.
Hepatitis B Virus - mechanism of injury?
Presence of viral HbSAg and HbCAg on cell surface stimulate CD8 cytotoxic T cell to destroy infected hepatocytes. IS NOT cytotoxic on its own.
Enterococci usually develops after what?
GU manipulation (cystoscopy, surgery)
Timeframe of TB infection
First week: intracellular bacterial proliferation
2-4 weeks after: Th1 response, IFNgamma, etc
Legionella Classic Presentation
Pneumonia + High Fever + GI sx (diarrhea) + Headache/Confusion
Pt: Smoker, Water Source
Labs: HypoNaSputum stain showing lots of PMN, but no bacteria
Dx: Urine antigen
Tx: Resp Fluoroquinolone (Levofloxacin), Macrolide (Azithromycin)
Cave exploration + Pulm Sx
HISTOPLASMOSIS. Pt: bird/bat droppings, Ohio and Mississippi valleys
Histo: macrophage filled with histoplasma (smaller than an rbc)
Encapsulated yeast
Cryptococcus!
What drug resistance is mediated by decreased bacterial catalase-peroxidase activity?
INH!
Where does Kaposi Sarcoma occur? Gross and Histo?
Kaposi Sarcoma: skin and GI tract
Reddish/violet, flat maculopapular lesion
Hemorrhagic nodule
Spindle-shaped tumor cells with small-vessel proliferation.
Cryptosporidium causes what?
Severe watery diarrhea in AIDS pts. Transmission: Oocysts in water. Gross colonoscopy: Nonulcerated inflammation, with basophilic clusters on surface of intestinal mucosal cells. Dx: Oocysts on acid-fast stain
Unexplained oral thrush in an otherwise healthy person suggests?
HIV
Most likely outcome of HCV infection?
Chronic stable hepatitis. Second most common is chronic hepatitis progressing to cirrhosis.
Mechanism of Zidovudine
Nucleoside RT inhibitor: inhibits 3’-5’ phosphodiester bond formation. AZT has a amido group in place of 3’OH.
Competitively binds to reverse transcriptase -> bc no 3’OH -> DNA chain termination.
What bacterial factor mediates adherence to cell?
Pili
What antibiotic binds to 23sRNA of 50s ribosome?
Macrolide (erythromycin, azithromycin, clarithromycin)Clindamycin Prevent translocation
Linear erythematous rash shortly after hiking trip = ?
Poison Ivy (Contact dermatitis) = Type IV Hypersensitivity
How do dsDNA viruses replicate?
All replicate in the nucleus except poxvirus. DNA dependent DNA polymerase = replication of viral genomeDNA dependent RNA polymerase = transcription of viral DNA -> mRNA exported to cytosol -> translated by cellular ribosomes into viral proteins. Note: RNA dependent DNA polymerase = RT Nomenclature: the “dependent” part is what the polymerase is acting on.
What pathogen has trophozoites with phagocytosed RBCs?
Entamoeba HistolyticaPt: fecal-oral route - cysts in water, country with poor sanitationoral-anal contact - homosexuals
Sx: bloody diarrhea, abd pain, cramping
Histo:
- trophozoites with phagocytosed RBCS
- Cysts with up to 4 nuclei
What histological feature characterizes Rabies infection?
Negri bodes - eosinophilic cytoplasmic inclusions in the hippocampal neurons.
Why give PCN with Probenecid? What other combination is similar to this?
Probenecid - inhibits RT secretion of PCN, most cephalosporins, and other weak acids.
Imipenem + Cilastatin. Cilastatin - inhibits renal dehydropeptidase in PCT which would inactivate imipenem.
Both Probenecid and Cilastatin, directly or indirectly, inhibit RT secretion of the drug.
All RNA viruses replicate in the ______, except _____ and _____.
All RNA viruses replicate in the cytoplasm, except influenza and retroviruses.
HIV pt with abd pain, GI complaints. Bx shows mucosal ulcerations and erosions. Histo shows large cell with ovoid nuclei and basophilic deposits.
CMV Colitis - reactivated in setting of HIV. “Owl eye”
HSV Tzanck test shows
Multinucleated giant cells with intranuclear cowdry A inclusions.
Opportunistic causes of diarrhea in HIV pts
- Cryptosporidium - chronic, watery diarrhea- acid-fast cysts seen in stool - esp when CD4 <200
- CMV colitis - mucosal ulcers and erosions- owl eye nuclei - large ovoid nuclei with centralized intranuclear inclusions
- MAC- necrotizing and non-necrotizing granulomas- acid fast bacilli
