Bacteriology Flashcards
obligate aerobe
require oxygen to survive
facultative anaerobe
prefer oxygenated environments, but can survive w/o oxygen if necessary
obligate anaerobe
can not live or grow in the presence of oxygen
describe the characteristics of a gram + cell envelope (inner to outer)
- cytoplasmic membrane of phospholipids with embedded proteins
- THICK peptidoglycan layer (cell wall)
describe the characteristics of a gram - cell envelope (inner to outer)
- cytoplasmic membrane of phospholipids with embedded proteins
- periplasmic space with gel containing proteins and enzymes
- THIN peptidoglycan layer (cell wall)
- outer membrane made of phospholipid layer (inner layer is called lipid A, outer layer contains LPSs)
what color to gram + bacteria stain? gram -?
gram +: violet
gram -: red
define pathogenicity
ability of a pathogen to produce a disease
define virulence
degree of pathogenicity as indicated by case fatality rates and/or the ability of the organism to invade the tissues of the
define lethal dose
the number of organisms required to cause death
define infective dose
the number of organisms required to cause infection
define antigenic switching
the altering of a microorganism’s surface antigens through genetic rearrangement, to elude detection by the host
describe the differences between streptococcus and staphlococcus when looking under a microscope
steptococcus: form strips of cocci
staphlococcus: forms cluster of cocci
what are the clinical applications of knowing if an infection is from G+ vs a G- bacteria colony?
antibiotics that attempt to damage the peptidoglycan cell wall will not be able to penetrate the outer membrane in G- bacteria and therefore will not be effective at treating infections caused G- bacteria. (example: penicillin or lysozyme)
what portion of the G- bacteria is considered pathogenic? what does this mean?
the LPS layer, it can be used to ID the type of bacterium
define exotoxin
proteins released by both G+ and G- that cause disease
define endotoxin
LPS is synonymous with endotoxin. LPS makes up the outer layer of the cell wall in G- bacteria. this layer provides virulence. endotoxin simply means that the bacteria is not secreting anything toxic, but rather is toxic by the nature of its structure.
define virulence factors
characters of a bacterium that increase its pathogenicity
indicate three bacteria that use endotoxins as a virulence factor
- Vibrio cholerae
- Escherichia coli
- Neisseria gonorrhoeae
discuss the features of an acid-fast bacterium
unique cell walls that contain “waxy” lipid called mycolic acid. stain red using acid-fast stain.
give two examples of typical acid-fast bacteria
- Mycobacterium tuberculosis (TB)
2. Mycobacterium leprae (leprosy)
give three examples of G- rods
- Escherichia coli
- Vibrio cholerae
- Yersinia pestis
give two examples of G-cocci
- Neisseria gonorrhoeae
2. Neisseria meningitidis
give three examples of G+ rods
- Listeria monocytogenes
- Clostridium botulinium
- Clostridium difficile
give two examples of G+ cocci
- Staphlococcus aureaus
2. Strephtococcus pneumonia
give two examples of spirochetes
- Treponema pallidum (syphilis)
2. Leptospira interrogans
give three example of an obligate intracellular parasites
- Rickettsia rickettsii
- Listeria monocytogenes
- Treponema pallidum
what is an example of a group of bacteria without a cell wall?
Mycoplasma
give two examples of spore-forming bacteria
- Clostridium (G+, anaerobic)
2. Bacillus (G+, aerobic)
what are spores?
metabolically dormant forms of bacteria, resistant to heat, cold, drying, and chemical agents
name three diseases that are caused by endotoxins
- septic shock
- septicemia (infiltration of blood by N. meningitidis)
- meningitis (movement of N. meningitidis into meninges
discuss and define transmissibility
method of entry for infection of a host (e.g. cut, respiratory tract, GI, urogenital)
discuss bacterial adherence to host cells
ability of bacteria to attach to the host via pili, fimbriae, other adhesion molecules
define toxigenicity
ability of bacteria to generate disease in the host via exo or endotoxins
discuss a key way that bacteria can evade a host’s immune system
via antigenic switching: changing surface antigens by turning on/off genes
Escherichia coli morphology
GN, rod, facultative anaerobe
E. coli S/S
Main: UTI and diarrhea
Other: meningitis in infants, sepsis
E. coli pathogenicity
pili, fimbrae, enterotoxin (exotoxin)
add three important human diseases that can be caused by endotoxins
- septic shock
- septicemia
- meningitis
E. coli diagnostic work up
culture
E. coli Tx
antibiotics, send for sensitivities
Vibrio cholerae morphology
GN rod, comma shaped
Vibrio cholerae S/S
Main: massive diarrhea
Vibrio cholerae pathogenicity
enterotoxin (type of EXOtoxin)
Vibrio cholerae diagnostic work up
culture, oxidase+
oxydase test
assists in differentiating groups of GN bacteria
Vibrio cholerae Tx
water, doxycycline, electrolytes
Neisseria gonorrhoeae morphology
GN, diplococci, kidney bean shaped, aerobic
Neisseria gonorrhoeae S/S
Main: gonorrhea- purulent discharge, urethritis, dysuria
Other: blindness, septic arthritis
Neisseria gonorrhoeae pathogenicity
pili, unencapsulated
Neisseria gonorrhoeae diagnostic work up
culture, oxidase+
Neisseria gonorrhoeae Tx
ceftriaxone
Yersinia pestis morphology
GN, rod
Yersinia pestis S/S
Main: plague
Yersinia pestis transmission
transmitted by fleas w/i an animal resevoir
Yersinia pestis pathogenicity
multiplies in phagocytes
Yersinia pestis diagnostic work up
culture of aspirate
Yersinia Y. pestis Tx
Streptomycin
Clostridium botulinum morphology
GP, rod, obligate anareobe
Clostridium botulinum S/S
Main: flacid paralysis
Clostridium botulinum pathogenicity
form endospores, neurotoxin, inhibits release of AcH
Clostridium botulinum diagnostic work up
clinical presentation, anaerobic culture
Clostridium botulinum Tx
antitoxin horse serum administration
Treponema pallidum morphology
GN, spirochete
chancre
herald patch of syphilis
Treponema pallidum S/S
Main: syphilis
Treponema pallidum pathogenicity
parasite, exotoxin, highly motile
Treponema pallidum diagnostic work up
blood serum test, does NOT show up on a gram stain
Treponema pallidum Tx
penicillin
Mycobacterium tuberculosis morphology
mycobacterium (acid-fast)
Mycobacterium tuberculosis S/S
Main: tuberculosis
Mycobacterium tuberculosis pathogenicity
survives and grows in host macrophages
Mycobacterium tuberculosis diagnostic workup
acid-fast stain, nucleic acid probes
Mycobacterium tuberculosis Tx
multiple drug therapy, long course of combined antibiotic Tx
Rickettsia rickettsii morphology
GN, stains poorly, short rod, obligate intracellular parasite
Rickettsia rickettsii S/S
Main: Rocky Mountain Spotted fever, fever, malaise, rash, begins on extremities, then goes all over
Rickettsia rickettsii diagnostic work up
parasitizes host endothelial cells throughout circulatory system, serology, grows only inside living host cells
Rickettsia rickettsii Tx
doxycycline
catalase test
important to differentiate between different types of GP bacteria
Staphlococcus aureus morphology
GP, cocci, clusters
Staphlococcus aureus S/S
Main: TSS (fever, hypotension, rash)
Other: skin infections, UTI, osteomyelitis, endocarditis, arthritis
Staphlococcus aureus pathogenesis
cell wall enzymes, coagulase and catalase+, exotxins
Staphlococcus aureus diagnostic work ups
gram stain, coagulase, catalase
Staphlococcus aureus Tx
antibiotic and I&D
Streptococcus pneumonia morphology
GP, cocci, strips/chains, can be diplococci
Streptococcus pneumonia S/S
Main: pneumonia
Other: bacterial meningitis, sinusitis, otitis media, mastoiditis, sepsis
Streptococcus pneumonia pathogenicity
alpha hemolytic, capsule, pili, choline binding, protiein A
Streptococcus pneumonia diagnostic work up
culture, light microscope
Steptococcus pneumonia Tx
antibiotics
Listeria monocytogenes morphology
GP, rods, diplococci or short chains, aerobic
Listeria monocytogenes S/S
Main: food poisoning
Other: meningitis, sepsis, spontaneous abortions
Listeria monocytogenes pathogenesis
enters cell by phagocytosis, obligate intracellular parasite, membrane degrading phospholipase (listerialysis)
Listeria monocytogenes diagnostic work up
blood and CSF cultures, catalase+, beta hemolytic, positive motility
Listeria monocytogenes Tx
ampicillin and bactrim
normal flora of the skin
staph aureus
normal flora of the mouth
streptococci, lactobacilli, staphlococci, corynebacteria (great number of anaerobic bacteria)
normal flora of the nares
mostly coagulase - staph and corynebactera, staph aureus
normal flora of the nasopharynx
mostly strep and neisseria species, also strep penumoniae, s. pyrogenes, haemophilus, influenzae and neisseria meningitidis
normal flora of the GI tract and retum
enterobacteria (many types)
normal flora of the genitalia
corynebacteria, staphlococci, streptococci, E. coli, lactobacilli (contributes to low pH and inhibits colonization by other bacilli)
normal flora of the eye/conjunctiva
mostly coagulase- staph; corynebacteria, occasional s. aureus, strep, haemophilus, neisseria
normal flora of the urinary bladder and anterior urethra
coagulase- staph, enterococcus, viridans, strep. GI bacteria and corynebacteria
