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Pathology
The study and functional changes in cells, tissues, and organs underlying
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Pathophysiology
Changes in the physiological factors that underlie states
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Cell Envelope
- Cytoplasmic membrane
- cell wall
- S-Layer
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Processes
Virulence, Etiology, Pathogenesis, Morphological changes, Clinical significance
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Cell Wall
- External to cyto membrane
- = murein+ outer membrane + Brausn lipoprotein
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Cell Membrane
- = cytoplasmic membrane
- Bacterial membranes have hopanoids, not sterols
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Peptidoglycan
- Gives cell rigidity
- Consists of alternating units of two modified sugars (NAM & NAG)
- Chains are cross-linked btw NAM units
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gram POSITIVE
- Single thick layer - Peptidoglycan
- Teichoic acids
- Lipoteichoic acids
- NO OUTER MEMBRANE
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Gram NEGATIVE
- Multi-layered, complex
- Thin layer peptid- btw 2 lipid bilayers
- No teichoic acids
- Outer membranes (Phospholipid bilayer, LPS, Proteins)
- LPS (Lipid A, Antigen O, Polysaccharide structure)
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S-Layer (Crystalline surface layer)
- Arrangement (Ext to Peptid- or OM, Archea only layer ext)
- Consist of protein subunits (protein/glyco-, tetrahedral/hexagonal)
- Functions (Adhesion, Maintains cell morpholgy, Phage receptor)
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Reasons to care about bacterial cell structure
- Point of attack for most abundant drugs
- Imparts virulence factors
- Mechanisms of identification for bacteria
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Proteins of Bacterial Cytoskeleton
FtsZ, MreB, CreS
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Glycocalyx
- Extracellular polymeric material
- Capsule, slime layer
- Functions - Attachment to substrate, host, other cells; Protection of cell from host, desiccation, viruses, toxins
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Capsule
- well-organized, not easily removed, exludes particles
- Streptococcus, Bacillus, N. Meningitdus, Klebsiella
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Slime Layer
- Diffuse
- Easily removed
- Pseudomonas
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Flagella
- Long thin proties on appendages
- 20nm wide
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Flagella Types
- Monotrichous - 1 hair
- Amph - both/either
- Lopho - tuft
- Hairy - Salmonella, E. coli
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Fimbriae & Pili
- Shorter than flagella
- Similar structure
- Few/cells (1-10)
- Functions (Vertical transfer)
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Types of Vertical Transfer
Conjugation, Transduction, Transformation
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Endospore Structure
- Exporoium (thin) [outer, inner, undercoat]
- Spore coat (thick protein)
- Cortex (peptide-, dipicolonic acid, Ca++)
- Core
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Endospore structure (Cortex)
- Situated btw outer and inner forespore membranes
- Membranes often continuous with core on electron micrograph
- Peptidoglycan, dipicolinic acid, Ca++
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Endospores
- Dehydrated layered structure allowing suspended animation of bacteria
- Formed inside some gram-positive bacteria
- Resistant to heat, radiation, acids, desiccation, UV
- Contains copy of chromosomes
- Position of spore in cell used for identification
- Produced by Bacillus and Clostridium
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Endospore Core
- DNA in A form & bound to small acid-soluble proteins (SASP)
- Core cytoplasm only 10 - 25% water, gel-like
- Ca-diplocolinate but no PG
- pH ~ 5.5 - 6.0
- Also has ribosomes
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Stages of Endospore
- Vegetative cell - Stage 0 (DNA becomes dense)
- Stage II - Asymmetric cell division
- Stage III - Mother engulfs forespore
- Stage IV - Cortex Forms
- Stage V - Protein coat surrounds forespore
- Stage VI - Completion of coat (Dipicolinate)
- Stage VII - Lysis of mother cell to release dormant spores (Different sigma factors and 100+ genes reqd)
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Colonization
- Microbes able to multiply at site
- no interference with normal function
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Infection
= Successful attachment of microbe that may cause damage to the body
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Disease
Process in which host-microbe interaction leads to alteration of structure of function, causing signs and symptoms
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Symbiotic Relationships
- Commensalism
- Mutualism
- Parasitism
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Commensalism
- One benefits, others indifferent
- Corynebacterium spp
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Mutualsim
Both partners benefit, E. coli
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Parasitism
- One organism benefits at the expense of another
- Vibrio spp (Necrotizing Fascitis)
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Est of Normal Flora
- Fetus in utero lives in sterile environment
- Upon vaginal delivery, exposure
- Colonization 24-48 hr post-natal
- Colonization means established growth on/within host
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Importance of Normal Flora
- Prevent attachment of invaders
- Deplete essential nutrients
- Produce antimicrobial substances (Bacteriocins, Produce toxic metabolites)
- Stimulate
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Skin Flora
Staph epi, Prop acnes,Clos perf, Acinto Cac, Staph a, Carynem spp, Kocuria spp, Fungi (Candida, Malassezia)
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Propionibacterium acnes
- Gram +, pleomorphic branching
- may appear diptheroid
- Most common anaerobic rod found in clinical specimens
- Catalase (+) Positive
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Acinetobacter spp
- Gram (-), bacilli, pleomorphic - coccobacilli
- may grow in pairs, do not ferment cabs, Do not reduce to nitrates
- Facultative intracellular organisms
- Oxidase (-) Negative
- Some Citrate (+) Positive
- Contaminate resp. therapy equipment, pillows, catheters
- Resistant to many antibiotics (Aminoglycosides + imipenem)
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Species of Acinetobacter on the skin
- A. baumannii
- A. calcoaceticus
- A. lwoffi
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Normal Flora of Mouth and Pharynx
- Streptococcus mutans, Srtreptococcus Sanguis, Viridans group
- Plaque = biofilm on teeth
- Progression: Strep -> Actinomyces isralli -> Veillonella -> Neissaria, Fusobacteria
- Tooth surface microbes differ from saliva and mucosa due to redox potential
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Normal Oral Flora
- Nasopharynx - Haemophilus spAnaerobes predominate in oral cavity
- Peptostreptococcus, Bacteroides, Prevotella, Fusobacterium, Treponema, Capnocytophaga, Eikenella
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Normal flora in EYE and EAR
- S. epidermisDebate on whether eye has indigenous microbiota or just transients
- Eye may have nasopharynx flora (Viridians, Haemophilus, Neisseria)
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Respiratory Tract Normal Flora
- Normally sterile
- Sterility impeded by trauma, iatrogenic methods
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Stomach Normal Flora
Lactobacillus, Streptococcus, Heliobacter pylori
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Small Intestine Normal Flora
- Anaerobes
- Peptostreptococcus, Prevotella, Candida, Enterococci
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Large Intestine Normal Flora
bacteroides, Fusobacterium, Peptostreptococcus, Enterococcus, E coli
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Bacteroides
- Gram (-) anaerobe, non-pigmented, non-motile, capsulated
- Most common anaerobe in GI tract
- Usually not seen in infections above waist
- B. vulgatisB. fragilis
- Most anaerobe in bactericemia, Most common anaerobe in intrabdominal disease, grows in 20% bile
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GU Tract Normal Flora
- Usually sterile in both sexes
- Only urethra and vagina colonized
- Lactobacilli
- Staph Epi (catalase pos, coagulasse neg)
- Viridans group
- Fusobacterium - anaerobes
- Candida albicans
- Ureaplasma
- Other Gram (+) anaerobic cocci
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Innate
- Nonspecific internal defenses
- First line of defense
- Consist of phys barriers, complement, cytokines, inflammations, receptor proteins
- NOT specifically directed to invading agent
- Responses not affected by prior exposure
- Operates constantly
- no memory
- Usually recognizes HOST
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Types of Nonspecific/Innate Immunity
- Skin, epithelium
- Physical action
- Fever
- Inflammation
- Phagocytosis Antimicrobial activity
- Changes in Fe+ availability
- Complement
- Toll-like receptors
- Phagosome, Phagolysosome
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Natural Killer Cells
- Large granular lymphocytes
- No T cells receptors (TCR), immunoglobulin (Ig) molecules, or CD3 on surface
- Destroy tumor cells and cells infected by some viruses
- Sees every cell as target unless it detects a signal from that cell
- Express CD16 receptor
- NK cells look for MHC Class I molecule
- Destroys these cells = Antibody Dependent Cell-mediated Cytotoxicity
- No memory, Thus part of the innate
- NK cells also involve interaction of FasL of NK cell with Fas protein (CD95) on target cell
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Toll-Like Receptors
- Part of Innate System
- Drosophilia
- Recognize PAMPs
- PAMPs bind CD36 or CD14
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Types of TLRs
- LPS - TLR 4
- Flagellin 0 5
- dsRNA - 3
- ssRNA - 8,7
- CpG DNA 9
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Signal Transduction
- Pamps bind to TLR
- Leads to signals sent to activate transcription factors
- Stimulates production of NF-kB (Cytokine Production) and IRF-3 (Stimulates Type 1 IFN)
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Complement
- 26 proteins; Cascade activation
- Alternate, Classical, Lectin
- Opsonization, Lysis of cell membranes
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Activation of Complement:
Alternate
Classical
Lectin
- Activation on microbial surfaces
- Fc portion of antibody (Ab) binds microbe surface
- Plasmas protein binds mannose on microbe surface glycoproteins
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Adaptive
- Antigen specific
- Memory response
- Involved in two lymphocyte types
- Humoral B-ly secrete Ab; Cell-mediated T-ly activate macrophages
- Includes lymphoctyes and antibodies
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Th1
Cells produce cytokines that support inflammation and cell-mediated responses
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Th2
- Cells stimulate eosinophils activation
- Assist B ly
- Promote production of IgM & IgG
- support allergic reactions
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B cells
Antibody response
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Signal Transduction
- TCR (T cell Receptor) interacts with MHC-peptide-Ag-Complex
- PIP2 -> DAG (Protein Kinases)
- Activation of PKC
- Phosphorylation of several proteins
- Activation of various transcription factors including NF-kB
- Genes activated in nucleus
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Cytokines
- regulate cellular responses through binging
- Innate adn Adaptive
- Greater then or less then 30 kDa
- Interferon - Isaac and Lindemann
- Purified - Pestka
- 1st Described - Nagano & Kojima
- Stimulate production of C-reactive protein
- CRP forms pentamer, and binds complement C3 to convert it to C3b
- Inflammation triggers increased CRP
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4 families of Cytokines
- Hematopoietin
- interferon
- Chemokine
- tumor Necrosis
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Types of Cytokines
- IL - 1, 2, 4, 6, 10, 12, 23
- TGF - Beta
- TNF - Alpha
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Phagocyte
- MEN
- Macorphage
- Eosinophil
- Neutrophil
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Phagocyte Response
- Attachment
- Ingestion
- Fusion to form phagolysosome
- Killing in Phagolysosome
- Digestion
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Inflammatory Process
- Microbe penetrates barrier
- Capillary Dilation (C3a and C5a)
- Cytokine release
- increased Heat and Blood flow
- Edema and Pain
- Diapedesis of leukocytes to injury site
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Diapedesis
- Rolling adhesion
- tight binding
- diapedesis (squeeze btw endothelial cells)
- Migration
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Antibodies
- (2) Heavy chain, Light Chain(Kappa Lambda)
- Variable and constant region
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5 types of antibody Heavy CHains
Mu, Delta, Gamma, Epsilon, and Alpha
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Major Histocompatibility Complex (MHC)
- membrane-bound glycoproteins
- Process and present Ag by T-ly
- Self and non-self
- Highly polymorphic gene loci
- Located on chrom 6
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Class I MHC
Found on all human cells except RBCs
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Class II MHC
- Found on macrophages, dendritic cells
- Present Ag to Naive T cells, B cell
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Responses to Viral Infections
- cell-mediated (Th1 -> IFN-y, IL-2, TNF)
- IL-2 & IFN activate NK and CD16 receptor
- Cytotoxic T ly then specifically kill infected cells
- Abs neutralize Viruses
- slgA prevents viral attachment (stimulate complement)
- Innate responds to interferons
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Interferon Innate Response (Signal Transduction)
- dsRNA detected by Toll-like cell receptors
- Induce IFN-alpha and beta
- Activates 2' - 5' Oligoadenylate synthase
- Causes activation of RNAase L
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Mechanisms towards bacteria
- Ab neutralizes toxins
- C' lyses bacteria
- Ab + C' split C3b - Causing opsonization
- C3a & C5a causes mast cells to degranulate
- macrophage & neutrophil chemotaxis - proteins (toxins0
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Mechanisms towards Helminths
- Humoral Component (IgE, IgG)
- Cell-mediated component (ADCC) (Cytokines - IL-4,5,3)
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Mechanisms vs Fungi
- Innate Immunity (Phagocytosis) (Alt & Lectin pathways of C')
- Cell mediated (T cells)
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Active Immunization
- Stimulation of immune response t challenge with immunogen
- Natural through disease
- Admin by health care worker (Artificial)
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Type of Passive Immunization
- Transfer of performed Ab to recipient
- Given for post-exposure prophylaxis
- Poisonous snake and insect bites
- Risk of type 3 hypersensitivity
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Transfer of performed Ab to recipient
- Includes IgG fraction from plasma of donors
- Natural across placenta
- Injection of purified Ab or serum
- Rapid temporary protection
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Post-exposure prophylaxis
- Botulism
- Tetanus
- Diptheria
- Hepatitis A &B
- Measles
- Rabies
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Type 1 Hypersensitivity
- Immediate Hypersensitivity
- Systemic Anaphylaxis
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Type 2 Hypersensitivity
- Ab-mediated disease
- ADCC
- Cytotoxic cells with Fc receptors to Ab on target
- Transfusions (Hemolytic disease of the newborn) (Drug induced hemolytic anemia)
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Type III Hypersensitivity
- Immune mediated
- Ags in excess
- Results in large and small Ag-Ab complexes
- Small IgG aggregates from immune responses dont fix C'
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Type IV Hypersensitivity
- T cell mediated Ag must be present in context of a MHC class II molecule
- Activated T cells are CD4+TH1 subtype
- T(DTH) is a subset of TH1
- MACs are recruited
- Granulomas
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Granulomas Diseases
- Tuberculosis - mycobacterim tubercolsis
- Leprosy - mycobacterium lepra
- Schistosmiasis
- Sarcoidosis
- Crohn Disease
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Attenuated Vaccine
- Live but not pathogenic
- Trigger cell mediated response
- Gives herd immunity
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Inactivated Vaccines
- Whole Agent
- Subunit Both require booster doses
- no Herd immunity
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Type of Live Vaccines
MMR, Oral Sabin polio, VZV, Tellow Fever, BCG, Francisella
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Live Vaccines Characteristics
- Result in undetectable diseases
- Long-lasting immunity
- Cannot cause disease
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Inactivated (Killed) Vaccines
- Not life long
- Humoral, not cell mediated
- No local IgA response
- Requires booster shots
- Large doses
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Types of inactivated vaccines
- Toxoid
- Killed
- Capsule protein subunit usually given with adjuvant
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Types of adjuvants
- Alum
- Cell wall components
- Fruends Complete
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Types of Killed Vaccines
- Killed
- subunit
- Peptide/polysaccharide
- Toxoid
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Killed Vaccines
Anthrax, Cholera, Salk polio, Pertussis, Rabies, Influenza
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Peptide/polysaccharide Vaccine
- HiB,
- Pneumococcus
- Meninggococcus
- HPV
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Gardasil
- Women 9-26 y/o before sexual activity
- HPV serotypes 6, 11, 16, 18
- Protein subunits produced from gen-engineered microbe
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NO vaccine available
HIV, Herpes, Syphilus, Malaria, Cold Viruses, Hep C, Strep pyro, Flu
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Sites of Antibiotic Activity
- Cell wall synthesis (PEP-, Mycolic acid)
- 30s and 50s ribosomes
- Involves metabolites not seen in eukaryotes
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Beta-Lactamases - Places of drug action
- Inhibit Penicillin-binding proteins
- PBPs can no longer catalyze transpeptidase reaction
- Weakened cell wall
- Vanco- binds terminal D-ala-D-ala of pentapeptides
- Cross link btw NAM
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Cepha- vs Pen
- Differ by R groups attached to Beta-lactam Ring
- Pen - 1 R group
- Ceph - 2R groups
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Aminoglycosides
Block the initiation of translocation and causes the misreading of mRNA
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Tertracycline
Blocs attachment of tRNA to the ribosome
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Streptogramins
Each interferes with a distinct step of protein synthesis
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Macrolides
Prevent the continuation of protein synthesis
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Chloramphenicol
Prevents peptide bonds from being formed
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Lincosamides
Prevents the continuation of protein synthesis
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Oxazolidinones
Interfere with the initiation of protein synthesis
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Resistance - Mechanisms
- Decrease uptake (Alter membrane Perm)
- Drug-activating enzymes (Penicillinase)
- modify drug targets
- Increase export (Efflux pumps)
- Horizontal s Vertical Evolution (qnrA and qnrB)
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Sulfonamides
Competitive inhibitor of para-aminobenzoate
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Trimethoprim
Inhibits dihydrofolate reductase
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Minimum inhibitory Concentration (MIC)
Lowest conc of drugs that prevents growth of organism in vitro
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Minimum Bactericidal Concentration (MBC)
Lowest concentration that kills 99.9% bacteria
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Tigecycline
- Recently approved in US, Europe, UK
- Potent vs Tet-R bacteria
- Broad spectrum, Bacteriostatic, IV use
- More resitant vs ribosomal protection and active efflux
- use vs intra-abdominal and soft tissue infections
- use for MRSA, Pen-R Pneumococcus, VRE
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Pleuromutilins
Interact at 50 ribo subunit in PTC at A and P sites
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Daptomycin (Cubicin)
- Lipopeptide (Sim to Glycopep- such as vanc-)
- Use vs Gm+ cocci (Enodcarditis-right of heart, MRSA)
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Carbepenems
Doripenems (Phase III) - Pseudomonas
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Cephalosporins
Ceftobiprole (PhaseIII) - PBP2a in MRSA
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Glycopeptides
Three Agents for treating complicated skin / skin structure infections (cSSSI)
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Dihydrofolate reductase inhibitor
iclapri (Phase III) - csSSSI
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