Intro to infectious disease Flashcards
Gram positive (structure)
cell wall Rigid, thick
Made up of mostly of peptidoglycan (50-60%)
A series of cross-linking (transpeptidases) help to create the building blocks of the cell wall.
Gram negative (structure)
multiple layered structure
Cell Wall Thin layer-one or two glycan chains
Cell wall protected by lipoprotein outer layer-which functions as penetration barrier.
lipopolysaccharide (LPS)
Matrix protein (porin)-important for regulating influx of molecules
phospholipids
Walls of mycobacteria (acid fast bacteria)
Contains peptidoglycan w/polysaccharide and glycolipids
Associated w/staining characteristics
Cytoplasmic membrane
Osmotic barrier
Energy production (electron transport-energy gradient-ATPases)
Biosynthesis transport (nutrient uptake, enzyme secretion)
Protein and lipid—lacks sterols
Minimum Inhibitory Concentration (MIC)
lowest concentration of antibiotic that inhibits visible growth of the bacteria. value used to indicate susceptible, intermediate and resistant
List of Gram Positive Cocci (Aerobic)
Staphylococcus aureus (coag+): Methicillin-sensitive (MSSA), Hospital or Community aquired MRSA
Staphylococcus epidemidis (coag -)
Staphylococcus saprophyticus (coag -)
Enterococcus faecalis
Enterococcus faecium
Enterococcus durans
β hemolytic: Streptococcus pyogenes (Grp A), Streptococcus agalactiae (Grp B,) Streptococcus bovis (nonenterococci, Grp D)
Viridans streptococci – α hemolytic: Streptococcus sangius, Streptococcus salivarius, Streptococcus mitis, Streptococcus mutans
Streptococcus pneumoniae (pneumococcus)
Staphylococci: colonization and infections caused
Colonization: Skin, Nose
Infections Caused: Cellulitis, wounds, trauma
Bacteremia/Endocarditis, Pneumonia,Osteomyelitis
UTI
Major players in post-surgical infections
Adhere to foreign material and catheters
Staphylococcal resistance
Penicillin Resistance: Beta-lactamase production, > 90% of all staphylococcus are resistant to penicillin
Methicillin Resistance: MecA gene codes for novel PBP2a, ~50% of S. aureus are resistant, ~70% of CoNS are resistant
Methicillin-susceptible isolates are also susceptible to cephalosporins and carbapenems
Streptococcus: Colonization
Skin: Group A- S. pyogenes
Mouth: Viridans Streptococcus, Anaerobes (e.g., peptostreptococcus)
Nasopharynx: Group A- S. pyogenes
Lower GI: Group D- S. bovis, Viridans, Streptococcus, Anaerobes
Female Genital Tract: Group B- S. agalactiae
Streptococcus: infections caused
Cellulitis: Group A- S. pyogenes, may result in Nec fasciitis
Dental carries: Viridans Streptococcus
Pharyngitis (Strep throat): Group A- S. pyogenes
Bacteremia/Endocarditis: Viridans Streptococcus
Neonatal meningitis: Group B- S. agalactiae
When establishing MIC, what is the difference between susceptible, intermediate, or resistant?
Susceptible- isolates may be appropriately treated with the recommended doses
Intermediate- isolates may be appropriately treated in body sites where the drug is physiologically concentrated or when a high dosage of drug can be used
Resistant- isolates are not inhibited by the achievable concentrations of a normal dose
WBC with differential: parameters
Neutrophils 50-70% Lymphocytes 25-35% Monocytes 2-6% Eosinophils 0-6% Basophils0-3%
granulocytes (B.E.N)
neutrophils, eosinophils, basophils
Neutrophils
Prevent microorganism invasion, kill invading organisms
Attracted to site of infection by chemotactic factors
Phagocytize microorganisms- eat up invading organism
Release toxic substances from granules within cell into vacuole containing organism
Absolute Neutrophil Count (ANC)
WBC # x (% segs (mature neutrophils)+ %bands (immature neutrophils)
The lower ANC= the higher risk for infection
Neutropenia defined based on ANC-
Mild = ANC 1000-1500/mm3
Moderate= ANC 500-1000/mm3
Severe= ANC < 500/mm3
Lymphocytes
Effector cells of immune system, recognize invaders, tag them for removal and kill them.
Make antibodies
T cells- 80%
B cells- 20%
Monocytes
precursors to macrophages
Serve to replenish tissues with macrophages prior to and during immune response
Eosinophils
Responsible for immune processes against helminths and parasites (also involved in allergic reaction)