Post on 25-Dec-2015
transcript
COL Helen Viscount, PhD, D(ABMM)LTC Steven Mahlen, PhD, D(ABMM)
The Beta-Lactamase Family: Classification, Detection, and
Interpretive Criteria
Transplant patient Extremely resistant
Klebsiella pneumoniae recoveredSensitive only to colistin
and gentamicin Patient put in isolation Isolate transmitted to 10
other patients Outcomes:
4/5 with bacteremia died1 other died2 with renal failureOnly 4/11 discharged
without renal failure
Ampicillin: R Pip/tazo: R Ceftazidime: R Ceftriaxone: R Cefepime: R Imipenem: R Meropenem: R Aztreonam: R Amikacin: R Tobramycin: R Trimeth/sulfa: R Fluoroquinolones: R Gentamicin: S Colistin: S
Nursing home resident83 years oldPneumonia
Admitted to ICUStarted on ceftriaxone
and levofloxacinBlood cultures +
K. pneumoniaeBased on sensi’s:
No more levoKept on ceftriaxone
Patient got worseHad to be ventilated
Ampicillin: RPip/tazo: SCefazolin: RCeftazidime: ICeftriaxone: SCefepime: S Imipenem: SAztreonam: STobramycin: STrimeth/sulfa: RLevofloxacin: ICiprofloxacin: IGentamicin: S
ObjectivesAt the end of this
workshop the attendee should be able to distinguish ESBL positive from carbapenemase-producing bacteria
At the end of this workshop the attendee should be able to describe a method to screen for ESBLs
At the end of this workshop the attendee should be able to interpret the results of the modified Hodge Test
Beta-lactam antibioticsPenicillins
AmpicillinAmoxicillinPiperacillin
Cephalosporins (generations)1st gen: cephalothin2nd gen (cephamycins): cefoxitin, cefotetan3rd gen: ceftazidime, cefotaxime, ceftriaxone4th gen: cefepime
Beta-lactam antibioticsMonobactam: aztreonamCarbapenems:
ImipenemMeropenemErtapenem
InhibitorsSulbactam (ampicillin/sulbactam: Unasyn)Tazobactam (piperacillin/tazobactam: Zosyn)Clavulanate (amoxicillin/clavulanate:
Augmentin)
Mechanisms of ResistanceAltered target (Gram negative/positive)Altered permeability (Gram negative)Production of inactivating enzymes (Gram
negative/positive)
Gram-negative cell Gram-positive cell
Outer membrane
PeptidoglycanPeptidoglycan
PenicillinBinding proteins(PBPs)
Inner (cytoplasmic) membrane
Alteration of TargetResistance to -lactams via altered
penicillin-binding proteins (PBPs)MRSA
Vancomycin resistance in enterococciFluoroquinolone resistance
Altered PermeabilityPassive diffusion of Gram-negative cell wallMutate outer membrane proteinsActive efflux
Production of Inactivating EnzymesChloramphenicol acetyltransferaseAminoglycoside-modifying enzymes-Lactamases
-LactamasesWell over 340 different enzymesExtended spectrum -lactamases (ESBLs)AmpC -lactamases
ChromosomalPlasmid-mediated
Carbapenemases
-LactamasesFirst -lactamase identified: AmpC beta-
lactamase1940, Escherichia coli1940, penicillinase, Staphylococcus aureus
First plasmid-mediated -lactamase: TEM-11965, Escherichia coli, Greece
ESBLsExtended-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
aztreonamDo not affect cephamycins (2nd gen ceph) or
carbapenemsRemain susceptible to beta-lactamase
inhibitors
ESBLsThe most common plasmid-mediated ß-
lactamases in Enterobacteriaceae are TEM-1, TEM-2, and SHV-1TEM: Escherichia coli
Named after first patient with a urinary tract infection that was not treatable with ampicillin
Her name: TemorinaSHV: Klebsiella pneumoniae
“Sulfhydryl variant”; amino acids in the enzyme that cross-link with other molecules
“Classical” ESBLs are derived from TEM and SHV enzymes
“Non-classical” ESBLs are derived from enzymes other than TEM or SHV
Classical ESBLsPrimarily 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
Non-classical ESBLsMany described, but less common than
classical ESBLsCTX-M
Found in multiple genera of EnterobacteriaceaePreferentially hydrolyze cefotaximeU.S., Europe, South America, Japan, Canada
OXAMainly in P. aeruginosaPrimarily hydrolyze ceftazidimeFrance, Turkey
ESBL EpidemiologyESBLs first appeared in Europe in the mid-
1980sWorldwide, but prevalence varies widely
geographically and between institutionsU.S. national average for ESBLs in
Enterobacteriaceae ~3%
ESBL EpidemiologyESBL producers especially prevalent in
ICUs and long term care facilitiesBecoming more widespread in the community
alsoHave been associated with outbreaks
Typically arise in ICUPlasmid transfer between GNRsOrganism transfer between patients
Control of outbreaksInfection control practice – isolationRestriction of 3rd and 4th generation cephalosporinsAntimicrobial cycling
Clinical Significance
Despite appearing susceptible to one or more penicillins, cephalosporins, or aztreonam in vitro, the use of these agents to treat infections due to ESBL-producers has been associated with poor clinical outcome
Clinical SignificanceESBL genes are often carried on
plasmids that also encode resistance to multiple classes of antimicrobialsAminoglycosides, FluoroquinolonesTrimethoprim/Sulfamethoxazole
Treatment experience is largely based on classical ESBL producersCarbapenemsß-lactam/inhibitor combinations
Typical ESBL Susceptibility ProfileAmp: RPiperacillin: RPip/tazo: SCefazolin: RCefoxitin: SCeftazidime: SCeftriaxone: RCefepime: RAztreonam: SImipenem/
meropenem: S
Amp: RPiperacillin: RPip/tazo: SCefazolin: RCefoxitin: SCeftazidime: RCeftriaxone: RCefepime: RAztreonam: RImipenem/
meropenem: S
AmpC: GeneralChromosomal
Escherichia coliCitrobacter freundiiEnterobacter aerogenes, E. cloacaeSerratia marcescensMorganella morganiiHafnia alveiProvidencia rettgeri, P. stuartiiPseudomonas aeruginosaAeromonas sp.
AmpC: GeneralAre not inhibited by -lactamase inhibitorsNormally are repressed, so produced at low
levelsChromosomal: inducible
In all except E. coliIn the presence of certain -lactam
antibioticsNormally, produced at low levels
Plasmid-mediated also
The AmpC of E. coliChromosomal, but
not inducibleNormally expressed
at low levelsRegulated by a
growth rate-dependent attenuation mechanism
Can become highly expressed with mutations
Amp: SAmox/clav: SPiperacillin: SPip/tazo: SCefoxitin: SCeftazidime: SCeftriaxone: SCefepime: SAztreonam: SImipenem/
meropenem: S
AmpC Induction and DerepressionIs induction clinically relevant?True danger—mutation in induction
pathway“Derepressed mutant”150-1000 fold more enzyme produced than
normal
Chromosomal AmpC profileNormal
Amp: RAmox/clav: RPiperacillin: SPip/tazo: SCefoxitin: RCeftazidime: SCeftriaxone: SCefepime: SAztreonam: SImipenem/
meropenem: S
Derepressed profileAmp: RAmox/clav: RPiperacillin: RPip/tazo: RCefoxitin: RCeftazidime: RCeftriaxone: RCefepime: SAztreonam: RImipenem/
meropenem: S
Plasmid-Mediated AmpCs (pAmpC)First true proof of AmpC on plasmid: 1988
MIR-1, found in Klebsiella pneumoniae90% identical to E. cloacae ampC
Some are also inducible (DHA-1)Most frequently found in K. pneumoniaeAlso commonly found in:
K. oxytocaSalmonella sp.P. mirabilis
E. coli, E. aerogenes also
pAmpCs: DistributionWorld-wide distribution
Africa, Asia, Europe, Middle East, North America, South America, Central America
CMY-2 is most prevalent globallyAlgeria, France, Germany, Greece, India,
Pakistan, Taiwan, Turkey, UK, US
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 S
CarbapenemasesCarbapenem resistance:
High level production of chromosomal AmpC with decreased outer membrane permeability (porins)E. cloacae, E. aerogenesC. freundiiE. coliS. marcescensK. pneumoniae (porins)
CarbapenemasesCarbapenem resistance:
Changes in affinity of PBPs for carbapenemsCarbapenemases
Frequently, bugs that produce a carbapenemase produce other -lactamases
CarbapenemasesKPC (plasmid, K. pneumoniae)
“Klebsiella pneumoniae carbapenemase”IMI-1 (plasmid, E. cloacae)Nmc-A (plasmid, E. cloacae)Sme-1 (plasmid S. marcescens)IMP-1 (plasmid, S. marcescens, P.
aeruginosa)L-1 (chromosomal, Stenotrophomonas
maltophilia)
Carbapenemases: ProfileR to carbapenems, penicillins,
cephalosporinsS or R to aztreonam, depending on enzymeSo the key:
Look for intermediate or R to imipenem or meropenem!
KPCInfection control emergency!!!
May test sensitive to carbapenems though!Extensive multidrug resistance (XDR)Very rapid spreadEmpiric therapy: colistin + tigecyclineKPC 1-8
Further readingYang, 2007. Ann. Pharmocother. 41:1427-
1435Jacoby, 2009. Clin. Microbiol. Rev. 22:161-
182Black et al, 2005. J. Clin. Microbiol.
43:3110-3113Livermore et al, 2001. J. Antimicrob.
Chemother. 48 Suppl 1: 87-102Pfaller and Segreti, 2006. Clin. Infect. Dis.
42: S153-163.