ph 162a midterm 1

penicillin

beta-lactam that inhibits peptidoglycan cross-linking by binding PBPs

penicillin (type)

bactericidal

penicillin (target)

bacterial cell wall synthesis

tetracycline

Binds the 30S ribosomal subunit and blocks tRNA attachment (protein synthesis inhibitor

tetracycline (type)

bacteriostatic

ciprofloxacin (type)

bactericidal

sulfonamides (type)

bacteriostatic

acyclovir (type)

antiviral

AZT - Zidovudine (type)

antiviral

fluconazole (type)

antifungal

ciprofloxacin

inhibits DNA gyrase/topoisomerase IV (DNA synthesis)

sulfonamides

antimetabolite that blocks folate synthesis

acyclovir

Guanosine nucleoside analogue activated by viral kinases; terminates DNA chain and inhibits viral DNA polymerase (treats herpes viruses)

AZT (Zidovudine)

Nucleoside reverse transcriptase inhibitor that blocks HIV replication.

Fluconazole

antifungal that inhibits ergosterol synthesis by disrupting lanosterol

cocci

spherical-shaped bacteria

bacilli

rod-shaped bacteria

Gram-positive

thick PG cell wall, no outer membrane, stains PURPLE with Gram stain

Gram-negative

think PG plus outer membrane with LPS, stains PINK with Gram stain

Ziehl-Neelsen (acid-fast) stain

type of staining method where carbol fuchsin is retained by waxy, lipid-rich cell walls even after acid decolorization (used for mycobacterium)

flagella

external appendages that provide motility

pili

hairlike appendages for attachment or DNA transfer during conjugation

virulence factor

bacterial product/structure that enhances pathogenicity but isn’t essential for basic growth

type III secretion system

needle-like apparatus in Gram-negative bacteria that injects effect proteins into host cells to alter signaling and immunity

pathogen

microorganism that causes disease by invading and damaging the host

commensal bacterium

lives on/in the host without harm

ex. of virulence factors

cholera toxin and capsules

cholera toxin

disrupts cell signaling and causes diarrhea

capsules

protect bacteria from being phagocytosed by immune cells

vibrio cholerae

colonizes the small intestine and produces cholera toxin

vibrio cholerae toxin

increases cAMP in host cells, causing water and ions to leave the cells which leads to watery diarrhea and dehydration

selective toxicity

drug harms microbes more than the host

why is selective toxicity important to antimicrobial therapy

allows treatment without killing host cells

broad-spectrum antibiotics

act on many types of bacteria (gram - and +). useful clincially before the exact pathogen is known but can disrupt normal flora and promote resistance by applying broad selective pressure for resistance genes on both pathogen and commensal microflora

narrow-spectrum antibiotics

target specific bacteria. less disruptive and lower resistance risk but require knowing the pathogen first

how do beta-lactam antibiotics work

block enzymes that cross-link PG in cell walls, leads to bacterial death

how do bacterias acquire resistance in beta-lactam antibiotics work

making beta-lactamase enzymes (encoded on plasmids), changing the target PBPS, or using efflux and permeability barriers

how does completing full antibiotic course limit spread of resistance

all bacteria (targeted by antibiotic) are killed and prevented partially resistance ones from surviving and spreading

3 mechanisms of antibiotic resistance

mutation in drug targets, enzymes that inactivate drugs (beta-lactamase),efflux pumps that remove drugs 

3 mechanisms of action of antibiotics

block cell wall synthesis, block protein synthesis, block nucleic acid synthesis or metabolism

prions

abnormal proteins that cause transmissible disease

viroids

infectious RNA molecules in plants that don’t encode proteins

bacteriophage

virus of bacteria that can follow a lytic or lysogenic cycle

oncogenic virus

viruses that contribute to cancer development (ex. HPV, HBV, HCV, HTLV, Herpesviruses)

viral tropism

specific tissues or cell types a virus can infect

capsid

protein coat made of capsomeres surrounding the viral genome

envelope

lipid membrane surrounding some viruses, often with protein spikes

cytopathic effect

observable changes in cultured cells due to viral infection (ex. swelling, lysis, syncytia)

steps of viral replication cycle

attachment, penetration, replication of genome/synthesis of proteins, assembly/maturation, release

budding

used by enveloped viruses (slow, cell may survive)

lysis

bursts the cell (typical of naked viruses)

acute

rapid infection, cleared (ex. influenza)

latent

virus hides and can reactivate (ex. herpes simplex)

chronic

long-term infection with ongoing replication (ex. hepatitis B)

viral growth curve

eclipse, latent, after the latent period

eclipse period

virus is inside cells, but hasn’t created new virions yet

latent period

new virions are assembled but haven’t left the cell

after the latent period

virions leave the cell and can be detected extracellularly

lytic cycles in bacteriophages

phage replicates and kills the host cell

lysogenic

phage DNA integrates into the host genome and stays there until triggered to excise, then enters lytic phase

virioids

small, naked RNA molecules that infect plants

prions

misfolded proteins that spread by changing normal proteins into abnormal forms

ex. of prion diseases

Creutzfeldt-Jakob disease

oncogenic virus

viruses that cause cancer

ex. of oncogenic virus

HPV (cervical cancer), HBV/HCV (liver cancer), HTLV (T-cell leukemia)

role of reverse transcriptase in retroviruses

copies viral RNA into DNA so retroviruses can integrate into host genome

influenza (-ssRNA)

needs RdRp in the virion

dengue (+ssRNA)

uses host ribosome first, then makes RdRp to replicate its genome

HIV (retrovirus)

brings reverse transcriptase

herpsevirus (dsDNA)

uses host polymerases, sometimes its own DNA polymerase

4 main groups of protozoa based on locomotion

amoebas, flagellates, cilates, apicomplexans

plasmodium spp

malaria

trypanosoma brucei

sleeping sickness

trypanosoma cruzi

chagas disease

leishmania spp

leishmaniasis

anopheles mosquito

transmits malaria

tsetse fly

insect transmits African sleeping sickness

triatomine (“kissing bug”)

insect transmits Chagas disease

sandfly

insect transmits leishmaniasis

Giardia lamblia

protozoan parasite that is transmitted by contaminated food or water instead of an insect vector

3 types of leishmaniasis

cutaneous (skin ulcers), mucocutaneous (nose/mouth destruction) , visceral (kala-azar, affects spleen/liver)

3 strategies to prevent malaria transmission

bed nets, indoor insecticide spraying, antimalarial drugs

absorption

virus recognizes and binds to specific receptors on the host cell’s surface. determines host range and tissue tropism (which species or cells the virus can infect)

penetration

fusion, endocytosis, injection

replication

viral genome and synthesis of viral proteins

maturation/assembly

viral genomes are packaged into new capsids

virus family for ebola

filoviridae

virus family for HIV

retroviridae

virus family for rabies

rhabdoviridae

virus family for dengue

flaviviridae

two groups of helminths that cause human disease

cestodes and trematodes

IgG

type of antibody produced by the immune system in response to an infection

direct detection

detects for actual pathogen (bacteria, virus, antigen, or nucleic acid)

indirect detection

detects for immune response to the pathogen (ex. antibodies)

ex. of indirect detection

ELISA for IgG

ex. of direct detection

PCR, gram stain, rapid antigen test

oncogenic

cancer-causing

HPV

linked to cervical cancer

rhinovirus

causes the common cold

zika virus

cause birth defects