Exam 1 lecture 2 Flashcards
What is the use of gram staining? How to stain gram positive and gram negative organisms? What is an Atypical bacteria?
Gram- Stain is a process to differentiate bacteria
Gram Positive- retain crystal violet and iodine complex (appear purple under microscope)
Gram Negative bacteria counterstain with Safranin dye. Appear Red/Pink/
Atypical bacteria do not stain using gram stain.
What are the two different morphologies of Gram positive bacteria?
Cocci and Bacilli (Cocci is most important)
What are the types of Cocci Gram positive bacteria
Anaerobic and Aerobic
Examples of anaerobic cocci gram positive bacteria
Peptococcus/Peptostreptococcus
examples of aerobic cocci gram positive bacteria
Clusters
Pairs/chains
What are the two types of clusters for aerobic gram poitive bacteria
Coagulase + and coagulase -
What are types of coagulase + clusters for aerobic gram positive bacteria? Coagulase -?
Coagulase +- Staphylococcus aureus
Coagulase - - CoNs (Staphylococcus eidermis)
What are the different types of Pair/Chain aerobic gram positive bacterias
Alpha- hemolysis
Beta- Hemolysis
Gamma Hemolysis (Non hemolytic)
What are the different types of alpha hemolysis? Beta hemolysis? Gamma Hemolysis?
Alpha- Streptococcus Pneumoniae, Viridians Streptococci
Beta- Streptococcus Pyogenes (group A), Streptococcus Agalactiae (group B)
Gamma- Enterococcus Faecium, Enterococcus Faecalis
What are the two types of Gram Positive Bacilli
Anaerobic and aerobic
What are the two types of anaerobic Bacilli gram positive bacteria> The two types of aerobic gram positive Bacilli?
Spore forming and Non spore forming
WhatAre the types of spore forming anerobic Gram positive Bacilli? Non spore forming?
Spore forming- Clostridium spp. Clostridiodes difficile
Non spore forming- Cutibacterium Actinomyces
What are the types of spore forming aerobic Gram positive Bacilli? Non spore forming?
Spore forming- Bacillus spp
Non spore- Listeria, corynebacterium, monocytogenes
Most medically important pathogens are cocci or bacilli
Cocci
How do staphylococcus cluster? Streptococci? Enterococci?
Staphylococci form clusters
Streptococci and enterococci appear in pairs or chains
For gram negative bacteria, which ones are going to be the most clinically important
Bacilli
What are the three types of gram negative bacteria
Cocci, Coccibacilli, Bacilli
Name aerobic cocci gram negatuve bacteria? Coccobacili?
Cocci- Neisseri spp, Moraxella Catarrhalis
Coccobacilli- Haemophilus spp
Name anerobic cooci gram negative bacteria?
Veillonella spp
Name Anaerobic bacilli gram negative bacteria
Bacteroides spp
Fusobacteriu spp
Prevotella spp
What are the types of aerobic bacilli
Enterobacterales, non enterobacterales, Lactose fermenters (oxidase positive), Non-lactose fermenters, Fastidious
What are the two types of enterobacterales for aerobic bacilli
Lactose fermenters (oxidase negative)
Non lactose fermenters
Name lactose fermenters (oxidase negative) Enterobacterales
Citrobacter spp
Enterobacter spp
E. COli
Kiebsiella spp
Name non lactose fermenters for entero bacterales aerobic bacilli
Morganella Morganil
Proteus spp
Providencia spp
salmonella spp
Serratia marscens
Shigella Spp
What are the different types of bacteria for lactose fermenters (oxidase positive) for aerobic bacilli gram negative bacteria
Aeromonas hydrophilia
Pasteurella multicida
Vibrio cholerae
What are the different types of non lactose fermenters aerobic bacilli gram negative bateria
Pseudomonas spp
Acinetobacter spp
Alcaligenes spp
Burkholderia cepacia
Stenotrophomonas maltophilia
What are the different types of fastidious aerobic bacilli gram negative bacteria
Campylobacter
helicobacter
Bartonella
HACEK organisms
What are some atypical bacteria
Chlamydia Pneumoniae
Chlamydis Trachomatis
Legionella Oneumophilia
Mycoplasma Oneumoniae
What are some spirochetes
Treponema pallidium
Borrelia burgdorferi
Use of lactose fermentation in gram negative bacteria
Helps identify enterobacterales (enteric gram negative rods or lactose fermienting gram negative rods.) from non fermenting gram negative rods (pseudomonas)
Which of the following is non enteric and non lactose fermenter
a) Pseudomonas aeruginosa
b) CItrobacter freundii
c) Morganella Morganii
D) Aeromonas Hydrophilia
Oseudomonas aeruginosa
Morganella is non lactose but is enteric
What are PBPs? Importance?
Penicillin binding proteins.
They are enzymes vital for cell wall synthesis, cell shape and structural integrity
Betalactams (largest class of antibiotics) bind here
transpeptidase most important PBP
Name betalactams
Penicillins, cephalosporins etc..
Define intrinsic vs acquired resistance? Mechanism of each?
intrinsic- Always resistant to antibiotic
Acquired- initially susceptible but develop resistance due to some mechanism
intrinic mechanism- absence of target site.
Extrinsic mechanism- mutation in bacterial DNA, acquisition of new DNA
define plasmids, transposons, phages, conjugation, transduction and transformation in acquired resistance
Plasmid- Self replocating extrachromosomal DNA transferable between organisms. One plasmid can encode resistance to multiple antibiotics
Transposons- Genetic elements capable of translocating from one location to another. Move from plasmid to chromosome or vice versa. SIngle transposon may encode multiple resistance determinants
Phages- Viruses that can transfer DNA from organsim to organism
Conjugation- DNA shared via direct contact or mating via sex pilli. Most common.
Transduction- Transfer of genes between bacteria by bacteriophages
Transformation- Transfer of DNA from environment
name the 4 mechanisms of antibiotic resistance
efflux pumps
Altered cell wall protein/decreased porin production- Do not let drug in
Efflux pumps- Pumps drug out
Drug- inactivating enzyme
Target site modification
How do B lactamase perform inactivation of B lactams
They are Enzymes that hydrolyze beta-lactam rings by splitting amide bonds. B lactams are broadest class and safest class of antibiotics.
Two classifications of B lactamase
Ambler class- classified according to amino acid structure (Class A-D)
Bush Jacoby medeiros: Classified according to functional characteristics
What are the two types of B lactamases
Serine Beta lactamases- Serine residue at active site
Metallo beta lactamases- Zinc residue at active site
What are the three types of Ambler class A B lactamase
Narrow spectrum B lactamases
Extended spectrum B lactamases (ESBL)
Serine Carbapenemases
What are the characteristics of narrow spectrum B lactamases? Extended spectrum B lactamases? Serine Carbapenemases? Give an example of each
Narrow spectrum B lactamases- Hydrolyze penicillin produced by enterobacterales
example- Staphylococcal penicillinase: TEM-1; SHV-1
Extended spectrum B lactamase (ESBL)- Hydrolyze narrow and extended spectrum B lactam antibiotics
example- CTX-M-15, SHV-2, TEM-3
Serine Carbapenemases- Hydrolyze Carbapenems
Example- KPC-1, KPC-2, KPC-3, IMI-1, SME-1
Type of Ambler class B B-lactamases? Characteristics? Example?
Type- Metallo-B-lactamases
characteristics- Hydrolyze Carbapenems
Enzyme example- NDM-1, VIM-1, IMP-1
Name a type of AMBLER class C B lactamase? Characteristics? Example?
Type- Cephalosporinases
Characteristics- Inductible
Enzyme example- AMP-C
Name a type of AMBLER class D B lactamase? Characteristics? Enzyme example?
Type- OXA type
Characteristics- Hydrolyze Oxacillin, Oxymino B lactams and carbapenems
Enzyme example- OXA-48
What antibiotics do ESBLs usually hydrolyze? What cant they inactivate?
Plasmid mediated enzymes that hydrolyze penicillins, cephalosporins and monobactams
Do not inactivate non beta lactam agents (ciprofloxacin, Doxycycline, gentamycin), however, organisms with ESBL genes often harbor additional resistance gene
What is the most common example of ESBLs in the united states
CTX-M
What bacteria is CTX-M (ESBL) most prevalent in?
E coli, Klebsiella pneumoniae/oxytoca and proteus mirabillis
Treatment of choice for ESBL bacterimia
Carbapenems (meropenem, imipenem, doripenem, ertapenem)
Piperacillin/tazobactam an option for urinary source only
Most frequent cause of carbapenem resistant enterobacterales (CRE)? WHat does it cause resistance to>
Carbapenemase.
Causes resistance to whole beta lactam class
What is the most common resistance mechanism in the US to get a CRE
KPC
What organisms in KPC found in? Treatment options for CRE
K. Pneumoniae, K. Oxytoca, E. cloacae, E. aerogenes, P. Mirabillis
Treatment options for CRE
B lactam with a very strong B lactamase inhibitor
Ceftazidim/avibactam, Meropenem/varobactam, Imipenem/cilastin/relebactam
We can also use non B lactam- Plazomicin, eravacycline, omadacycline
What antibiotics does metallo- B- lactamase confer resistance to?
Confers resistance to all B-lactams except monobactams (aztreonam).
Harbor additional antibiotic resistance genes to other antimicrobial classes
Examples of Metallo B actamases? What organisms is it present in?
NDM (New delhi MBL)
P. Aeruginosa, acinetobacter spp and enterobacterales
Treatment options for metalo B lactamases (NDM)
Limited treatment options
Not inhibited by any current B lactamase inhibitor
Cefiderocol, azteonam + Ceftazidime/avibactam
What are Ambler class D usually found in?
Ther are large heterogenous groups often accompanied by other B lactamase classes (co expression of ESBLs and AmpC)
also called OXA-type
What bacteria are ambler class D usually found in?
Acinetobacter baumannii, psuedomonas aeruginosa and some enterobacterales such as klebsiella pneumonia
Treatment options for ambler class D
Extremely limited.
Cefiderocol
Sulbactam/duriobactam
Does carbapenem resistant enterobacterales (CRE) mean that carbapenemases are present?
No.
You can be a CRE either through enzymatic ways or non enzymatic way (efflux pumps etc..)
So what we want to know is is the CRE enzyme medited or non enzyme mediated as that dictates our treatment options.
What are the 3 different mechanisms for AMB C production
1) Inducible via chromosomally encoded AMPC gene (main one)
2) Non-inducible chromosomal resistance via mutations (rare)
3) Plasmid- mediated resistance
What is Ambler class C (AMP C) inhibited by? WHat is it not inhibited by? What is it found in?
Not inhibited by older B lactamase inhibitors (clavulanic acid, tazobactam, sulbactam)
Inhibited by newer B lactamase inhibitors: avibactam, vadorbactam, relebactam
FOund in Hafnia alvei, enterobacter cloacae, Citrobacter freundil, klebsiella aerogenes, Yersinia Enterocolitica (HECK-YES)
What is the AmpC induction mechanism
Transient elevation in enzyme production in the presence of certain beta lactam agents
Initially, gene for beta lactamase production is repressed-> inducer-> gene depressed-> increased beta-lactamase production
If we remove inducer-> gene repressed-> beta lactamase production back to low level
Genetic mulation-> gene derepressed-> Stable derepression-> High level beta lactamase production continiously
What is a treatment of stable derepressed mutant
Carbapenems and cefepime
cefepime is drug of choice since it is narrow
What could cause a patient to be hypotensive and sudden decompensation? What antibiotic change to recommend
E. cloacae harbors an AmpC gene and this was induced with ceftriaxone treatment. Switch to Cefepime
What is the most common method of aminoglycoside resistance?
Enzymatic inactivation mechanism called Aminoglycoside modifying agent (AME)
Name aminoglycoside drugs
Gentamycin
Tobramycin
3 mechanisms for aminoglycoside resistance
Acetylation
Nucleotidylation
Phosphorylation
What methods of resistance are common on Gram negative bacteria? Gram positive bacteria?
Enzymatic inactivation common mode of resistance in negative
Target site modification/cell wall changes in B lactam class more common in gram positive
What is the method of enterococci species resistance
Cell wall precursor (alteration of target site)
In Enterococcus, target site modification is mediated by
VanA or VanB (both cause vancomycin reesistance)
Treatment of vamcomycin resistance
Daptomycin or linezolid
What do alterations in PBPs lead to (penicillin bincing proteins)
B lactam resistance
Why does PBP alteration lead to resistance
Due to decreased affinity of PBP for antibiotic or change in amount of PBP produced by bacteria
Where do we most commonly see PBPs
Methicilln resistant staphylcoccum aureua (MRSA)
What gene mediates resisience of PBPs and MRSA
mecA gene
What are different ways to denote if MRSA is present
mecA present= PBP2A= MRSA
What are the 2 exceptions in B lactams that are not resistant in mecA gene
Ceftaroline
Ceftobiprole
What does alteration in ribosomal target site lead to? what gene is used?
Macrolide resistance in S pneumoniae via ermB gene.
efflux pumps MOA and name of bacteria is causes resistance in
Efflux pumps actively transport antibiotics out of periplasmic space.
Important resistance mechanism for P. aerughinosa agaist carbapenems and s. pneumoniae against macrolide antibiotics
How are porin channels involved in antibiotic resistance
Porin channels are hydrophillic diffusion channels where mutations may result in loss of specific porins and lead to antibiotic resistance.
What bacteria is porin channel mutation usually seen in?
Enterobacterales and carbapenem resistant P aeruginhosa
What bacteria is Van A? ErmB? KPC? mecA?
Van A- enterococcus
Macrolide is ermB
KPC is gram negatives
mecA is staph aureua
Define PK, PD, bactericidal, bacteristatic, Cmax, AEC, MIC, PAE, concentration dependent, time dependent
PK- process by which drug enters and leaves the body based on ADME
PD-describes biochemical and physiologic response of drug and its MOA
Bactericidal- Killing of the organism
Bacteristatic- Inhibit bacteria replication without killing organism
Cmax- Hughest drug concentration
AUC- overall drug exposure
MIC- minimum inhibitory concentration
PAE- post antibiotic effect, continued growth inhibition for a variable period after concentration at the site of infection
Concentration dependent- maximize concentration at binding site
Time dependent- Optimize duration of exposure at binding site
compare concentration dependent vs time depepndent
Concentration dependent exerts effect when concentration is well above organisms MIC
Increased Cmax/MIC= greater killing-> correlates with increased AUC
Important in fluoroquinolone and aminoglycosides
TIme dependent is the time that free drug concentration remains above MIC.
All B lactam antibiotics (penicillin, cephalosporin, carbapenem, monobactam
What is the dosing optimization of carbapenems, penicillin, cephalosporin and gram positive bacteria
Carbapenems- >40%
Penicillin> or = 50%
Cephalosporin> or = 60%
Gram positive > 40-50%
What are the bactericidal patterns, Predictive PK/PD parameter and cidal/static status of
1) AMinoglycosids
2) B- lactams
C) Daptomycin
4) FLuoroquinolones
5) Vancomycin
Aminoglycosides
Bactericidal pattern- Concentration dependent, Peak/MIC: AUC/MIC, cidal
B lactams
Time dependent, T/MIC, Cidal
Daptomycin
Concentration dependent, AUC/MIC; Peak/MIC, CIdal
FLuoroquinolones
COncentratuon dependent, AUC (o-24)/MIC, Cidal
Vancomycin
Time dependent, AUC/MIC, Cidal (slowly)
