Cephalosporin resistance in E.coli
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Transcript of Cephalosporin resistance in E.coli
Cephalosporin Resistant Escherichia coli
Dr.T.V.Rao MD
Dr.T.V.Rao MD 1
Beta-lactam antibioticsPenicillins
Ampicillin
Amoxicillin
Piperacillin
Cephalosporins (generations)
1st gen: cephalothin
2nd gen (Cephamycins): cefoxitin, cefotetan
3rd gen: ceftazidime, cefotaxime, ceftriaxone
4th gen: cefepimeDr.T.V.Rao MD 2
Dr.T.V.Rao MD3
Definition of beta lactamases
Beta lactamases are enzymes produced by some gram-positive and gram-negative bacteria that hydrolyze beta lactam antibiotics
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BETA LACTAM RING
PENICILLIN
BETA LACTAM RING
CEPHALOSPORIN
BETA LACTAMASES enzymes that inactivate the beta-lactam ring
Dr.T.V.Rao MD
The β-lactam family of antibiotics
Ceftriaxone 3rdTicarcillin
Ceftazidime 3rdMezlocillin
Cefotaxime 3rdCarbenicillin
ErtapenemCefmetazoleCefuroxime 2ndAmpicillin
Meropenem
CefotetanCefamandole 2ndMethicillin
AztreonamImipenemCefoxitinCephalothin 1stBenzyl-penicillin
MonobactamsCarbapenemsCephamycinsCephalosporinsPenicillin's
Cefepime 4th
Dr.T.V.Rao MD 5
Other Beta-lactam antibiotics
Monobactam: aztreonam
Carbapenems:
Imipenem
Meropenem
Ertapenem
Inhibitors
Sulbactam (ampicillin/sulbactam: Unasyn)
Tazobactam (piperacillin/tazobactam: Zosyn)
Clavulanate (amoxicillin/clavulanate: Augmentin)Dr.T.V.Rao MD 6
What are 3rd Generation Cephalosporins
Third-generation cephalosporins are broad-spectrum drugs with high intrinsic activity against gram-negative species. The rising resistance to these drugs is worrisome because it could be a proxy for the emergence and spread of Enterobacteriaceae strains producing extended-spectrum β-lactamase
Dr.T.V.Rao MD 7
-Lactamase Activity
C C
C N
H H
R-CONH
S
COOH
CH3
CH3
O
Enzyme-Ser-OH
-lactam
Dr.T.V.Rao MD 8
-Lactamase Activity
C C
C N
H H
R-CONH
S
COOH
CH3
CH3
O
HO
Ser
Enzyme
HOH
Dr.T.V.Rao MD 9
L
L
L
LL
L
L
L Lb-lactamaseproduction
Dr.T.V.Rao MD 10
MODE OF ACTION OF BETA LACTAMS IN GRAM NEGATIVES
SUSCEPTIBLE RESISTANT
-Lactam Antibiotic
Diffusion through Porin Blocks Entry
Outer Membrane Efflux Pump
Diffusion through Beta-Lactamase
Peptidoglycan Hydolyzes Beta-Lactam
Penicillin Binding Proteins Changes in PBP results in Failure to Bind to -Lactam Cell Death
Dr.T.V.Rao MD 11
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Some beta-lactamases only inactivate a small number of antibiotics e.g.
penicillin
Others have extended spectrum to all the penicillin's and cephalosporins e.g. cefuroxime, ceftriaxone (ESBLs)
In addition may also carry resistance to other antibiotics e.g. ciprofloxacin.Dr.T.V.Rao MD
What it means as ESBLs Extended-spectrum beta-lactamases
(ESBLs) are mutant enzymes with a broader range of activity than their parent molecules
They:
Hydrolyze 3rd and 4th gen cephalosporins and aztreonam
Do not affect Cephamycins (2nd gen ceph) or Carbapenems
Remain susceptible to beta-lactamase inhibitorsDr.T.V.Rao MD 13
Classical ESBLs Primarily found in E. coli and Klebsiella spp.
Differ from their parent TEM or SHV enzymes by only 1-4 amino acids
>100 TEM- or SHV-derived beta-lactamases have been described – most are ESBLs
Dr.T.V.Rao MD 14
Non-classical ESBLs
Many described, but less common than classical ESBLs
CTX-MFound in multiple genera of EnterobacteriaceaePreferentially hydrolyze cefotaximeU.S., Europe, South America, Japan, Canada
OXAMainly in P. aeruginosaPrimarily hydrolyze ceftazidimeFrance, Turkey
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ESBLs
Extended-spectrum β-lactamases
www.lahey.org/studies/webt.htm
>180 enzymes described (119 TEM, 45 SHV)
All mutations of older TEM and SHV plasmid-mediated β -lactamases
TEM-3, TEM-4, etc.
SHV-2, SHV-3, etc.
CTX-M-1,2, etc. and Toho-type
OXA-type
PER-1 and 2Resistance conferred to extended-spectrum penicillins, 3rd
and 4th generation cephalosporins and aztreonam (not imipenem or cephamycins)
Dr.T.V.Rao MD
Extended-Spectrum β-Lactamases
β-lactamases capable of conferring bacterial resistance to
the penicillin's
first-, second-, and third-generation cephalosporins
aztreonam
(but not the Cephamycins or Carbapenems)
These enzymes are derived from group 2b β-lactamases (TEM-1, TEM-2, and SHV-1)
differ from their progenitors by as few as one AA
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Plasmid-Mediated AmpCs
B-lactamases derived from chromosomally encoded clavulanate-resistant AmpC cephalosporinases of Citrobacter, Enterobacter & Morganella spp.
Genes are typically encoded on large plasmids and carry additional resistance genes
Dr.T.V.Rao MD
Some premises
• Growing resistance to 3-gen cephalosporins
• Mostly ESBLs in E. coli & Klebsiella; AmpC in Enterobacter, Citrobacter, Serratia… but not always
• Identification of mechanism aids
– Epidemiological investigation / control– Treatment choice– Recognition of the exceptional e.g. MBLs
Dr.T.V.Rao MD 19
Resistance in E.coli a global concern
IN 2009, E coli resistance levels to third-generation cephalosporins in the United States compared favourably with those of the rest of the developed world with rates about equal to those in Scandinavian countries (Iceland, Estonia, Norway), and a lower reported resistance than the Netherland
Dr.T.V.Rao MD 20
ESBLs characterization
TEM ESBLs
- More than 30 described
- TEM-6, TEM-10, TEM-12, and TEM-26
SHV ESBLs
- More than 10
CTX-M ESBLs
AmpC
Derived from chromosomal AmpC genes of gram- negative organisms, such as Citrobacter freundii, Enterobacter cloacae, and Aeromonas spp.
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Detecting ESBL producers
steps:• Screen for resistance with an indicator
cephalosporin
• Do confirmatory test on those found resistant
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Choice of indicator cephalosporin
Sensitivity Specificity
Cefotaxime & ceftazidime
Good Good
Cefpodoxime Good Moderate
Cefuroxime Poor Poor
Cephalexin or cephradine
Moderate Poor
Cefpirome or Cefepime
Poor Good
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Detection of ESBLs: step 2
Seek ceph/clav synergy in ceph R isolates
Double discCombination discEtest
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Combination discs
Disc with cephalosporin
alone
Disc with cephalosporin + clavulanic
acid
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Dr.T.V.Rao MD 26
Etest for ESBLs
Cefotaxime
Cefotaxime+
clavulanateDr.T.V.Rao MD 27
ESBL – leading cause of Treatment of Failure
ESBLs are bacterial enzymes that confer resistance to many highly effective antibiotic classes that can go undetected if conventional testing methods are used in the lab, ultimately leading to treatment failure.
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Resistance in Gram-negative bacteria: Enterobacteriaceae.
The emergence and spread of resistance in Enterobacteriaceae are complicating the treatment of serious nosocomial infections and threatening to create species resistant to all currently available agents. Approximately 20% of Klebsiella pneumoniae infections and 31% of Enterobacter spp infections in intensive care units in the United States now involve strains not susceptible to third-generation cephalosporins
Dr.T.V.Rao MD 29
The AmpC of E. coliChromosomal, but not
inducible
Normally expressed at low levels
Regulated by a growth rate-dependent attenuation mechanism
Can become highly expressed with mutations
Amp: S
Amox/clav: S
Piperacillin: S
Pip/tazo: S
Cefoxitin: S
Ceftazidime: S
Ceftriaxone: S
Cefepime: S
Aztreonam: S
Imipenem/meropenem: SDr.T.V.Rao MD 30
ESBLs vs AmpCs
ESBLs AmpCs
Inhibitors (pip/tazo, amp/sulbactam, amox/clav) S R
Cefoxitin, cefotetan S R
Ceftazidime, ceftriaxone R R
Cefepime S/R SDr.T.V.Rao MD 31
CTX-M-type ESBLs Until 2000, most ESBL producers were hospital
Klebsiella spp. with TEM and SHV mutant β-lactamases
Now, the dominant ESBLs across most of Europe and Asia are CTX-M enzymes, which originated as genetic escapes from Kluyvera spp
Currently recognized as the most widespread and threatening mechanism of antibiotic resistance, both in clinical and community settings
80% of ESBL-positive E. coli from bacteraemias in the UK and Ireland are resistant to fluoroquinolones 40% are resistant to gentamicin
Livermore, DM J. Antimicrob. Chemother 2009 Dr.T.V.Rao MD 32
Clinical Significance ESBL genes are often carried on plasmids that
also encode resistance to multiple classes of antimicrobials
Aminoglycosides, Fluoroquinolones
Trimethoprim /Sulphmethoxazole
Treatment experience is largely based on classical ESBL producers
Carbapenemsß-lactam/inhibitor combinations
Dr.T.V.Rao MD 33
ESBL – K pneumonia Resistance in K pneumoniae to third-
generation cephalosporins is typically caused by the acquisition of plasmids containing genes that encode for extended-spectrum beta-lactamases (ESBLs), and these plasmids often carry other resistance genes as well. ESBL-producing K pneumoniae and Escherichia coli are now relatively common in healthcare settings and often exhibit multidrug resistance
Dr.T.V.Rao MD 34
ESBLs: evolution in detection and reporting
Until 2009: Search for ESBL production by
specific phenotypic testing
- All confirmed ESBL-producers to be reported as RESISTANT to all PENICILLINS, CEPHALOSPORINS and AZTREONAM regardless of MICs
Dr.T.V.Rao MD 35
Enterobacteriaceae: Breakpoints revised
AgentCLSI 2009 CLSI 2010
S I R S I R
Cefazolin ≤8 16 ≥32 ≤1 2 ≥4
Cefotaxime ≤8 16-32 ≥64 ≤1 2 ≥4
Ceftriaxone ≤8 16-32 ≥64 ≤1 2 ≥4
Ceftazidime ≤8 16 ≥32 ≤4 8 ≥16
Aztreonam ≤8 16 ≥32 ≤4 8 ≥16
Cefipime ≤8 16 ≥32 ≤8 16 ≥32
Dr.T.V.Rao MD 36
ESBLs: Evolution in detection and reportingMIC (mg/L)
Antibiotic CLSI 2012
CLSI 2012 EUCAST 2012 EUCAST 2012
Cefotaxime Ceftriaxone
S≤ 1
R> 2
S≤1
R> 2
Ceftazidime 4 8 1 4
Cefepime 8 16 1 4
Aztreonam 4 8 1 4Dr.T.V.Rao MD 37
Escherichia coli ESBL+ (CTX-M-1), CLSI 2012MIC (mg/L)
Dr.T.V.Rao MD 38
Ampicillin >128 RAmoxi/Clav 32 RPip/Tazo 8 SCephalotin 32 RCefotaxime 32 RCeftazidime 1 SCefepime 8 SErtapenem 0.12 SMeropenem 0.12 SESBL positive
Amikacin 2 SGentamicin 16 RCiprofloxacin >32 RLevofloxacin >32 R
Bacteria not to test for ESBLs
Acinetobacters–Often S to clavulanate alone
S. maltophilia–+ve result by inhibition of L-2
chromosomal b-lactamase, ubiquitous in the species
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Other beta-lactamases capable of hydrolyzing expanded-spectrum cephalosporins:
Some OXA-type variants (e. g. OXA-14/17)
• AmpC beta-lactamases (e. g. CMY, DHA)
• Serine carbapenemases (e. g. KPC)
• Metallo-beta-lactamases (e. g. IMP, VIM, NDM
Dr.T.V.Rao MD 40
Who are At Risk with ESBL+E.coli
Travellers 5.2 times more likely to be colonised by ESBL+ E. coli
Highest rates of ESBL carriage associated with travels to Africa and Indian subcontinent
All ESBL+ E. coli had CTX-M enzymes (71% CTX-M-15, 26% CTX-M-14)
Dr.T.V.Rao MD 41
Larger Inoculum Effect
More vulnerable to hydrolysis of β-lactamase
ESBL-KP + 3rd or 4th generation cephalosporin
How about Cephamycins? Little information
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Role of the Microbiology Lab
“ Each laboratory should have a staff member with the time, interest, and expertise to provide leadership in antibiotic testing and resistance. This person would read relevant publications, network with other laboratories, and evaluate potentially useful tests to detect new forms of resistance before new CLSI-recommended tests become available”
- Ken Thomson, Emerging Infect. Dis., 2001Dr.T.V.Rao MD
ESBL Epidemiology ESBL producers especially prevalent in ICUs and
long term care facilities
Becoming more widespread in the community also
Have been associated with outbreaks
Typically arise in ICUPlasmid transfer between GNRs
Organism transfer between patients
Control of outbreaksInfection control practice – isolation
Restriction of 3rd and 4th generation cephalosporins
Antimicrobial cyclingDr.T.V.Rao MD 44
ESBL are Emerging Challenges in Patient Care for Clinicians and Microbiologists
ESBLs: complex evolution since the 1980s (multiple enzymes, High-Risk clones)
Now a very major resistance issue in enterics: globally disseminated, ubiquitous (hospital, LTCFs, community), high rates
Challenge of intestinal carriage (intra/inter institutional dissemination, cross-border transmission) and of extra-human reservoirs
Detection and reporting issues
Treatment issuesDr.T.V.Rao MD 45
Programme Created by Dr.T.V.Rao MD for Microbiologists and Health Care
Workers email
Dr.T.V.Rao MD 46