Lecture 5 Enzymatic destruction (ESBL) Enzymatic modification (erm )

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Lecture 5Enzymatic destruction
(ESBL)Enzymatic modification (erm )
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Mechanisms of resistance

• Modifying enzymes
• erm
• Degrading enzymes
• ESBL
• Target Change
• Efflux pumps

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ESBL

• Extendened Spectrum ß-lactamases

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Resistance in Gram negative bacteria

• ß-lactamases the most important mechanism of
  resistance to ß-lactam Ab (in Gr-).
• ESBLs (Extended spectrum ß-lactamases)
• Carbapenemase

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V. cholerae
C. jejuni
Helicobacter pylori
Acinetobacter spp.
Gram Negative Rods/Bacilli (GNR)
Stenotrophomonas maltophilia
Many other (H. influenza, etc..)
Pseudomonas aeruginosa
Enterobacteriaceae
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Enterobactericea(E. coli, Klebsiela,
Enterobacter)

• Gram negative rods
• Colonize GI tract
• Clinical manifestations
• Urinary tract infections
• Nosocomial pneumoniae
• Bacteremia / Sepsis
• Other

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Mechanism of resistance

• Enzymes that inactivate ß -lactams by
  hydrolyzing the amide bond of the ß -lactam ring.

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ß-lactamase inhibitors

• Clavulonic acid derived from Streptomyces
  clavuligerus
• Little antibiotic effect in itself
• Given in combination with a ß -lactam Ab
• Function by binding the ß -lactamase enzyme more
  efficiently than the actual ß -lactam
• Thus protect the ß -lactam Ab from hydrolysis
• Not efficient against cephalosporinases

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History of GNR resistance
1965 Broad spectrum ß lactamases (TEM-1 in E.
coli)
ESBL outbreaks in France
1940 Penicillinase detected in E. coli
1983 Extended spectrum ß-lactamases
TEM-1 widespread
Carbapenemases
1964 Cefalotin use
1941 Penicillin use
Early 1980s 3rd generation ceph.
1959 ß -lactamase resistant penicillins
Methicillin
1985 Carbapenem (Imipenem)
1960s Broad spectrum/ extended spectrum
penicillins
1976 ß lactamases inhibitors
2005 Tigecycline
1928 Fleming
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ß-lactamases classification

• Molecular class
• A
• TEM
• SHV
• other
• B
• Metalloenzymes (carbapenemases)
• C
• Prototype chromosomal ampC
• D
• OXA (oxacillin hydrolyzing enzymes)

• Enzyme type (by substrate profile)
• Penicillinase
• Broad-spectrum
• Extended Spectrum
• Carbapenemase
• Genetic classification
• plasmids mediated
• Chromosomal

http//www.lahey.org/studies/webt.asp
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Types of ß-lactamases

• ESBLs
• TEM related
• SHV related
• OXA related
• CTX-M
• Other
• ampC ß-lactamases
• Resistant to ß-lactamase inhibitors
• chromosomal
• Carbapenemases
• Metallo- ß-lactamases
• Serine carbapenemases

• ß-lactamases
• Penicillinase gene blaZ , inducible, on
  transposon (can move between chromosome and
  plasmid).
• Broad spectrum ß-lactamases
• (plasmid encoded)
• TEM
• SHV
• OXA (mainly in pseudomonas)

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Genetic Mechanism
Penicillinase blaZ
Transformation
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ESBL

• Confer resistance to 1st , 2nd, 3rd cef.
• Most are susceptible to ß-lactamase inhibitors
• Most are susceptible to 4th cef.
• All are susceptible to carbapenems
• Diversity of ESBL
• SHV (widespread)
• TEM (gt100 types)
• OXA
• Predominantly in Pseudomonas
• less susceptible to ß-lactamase inhibitors
• CTX-M
• Probably independent evolution
• Highly resistant to 3rd generation
  cephalosporines
• initially in South America, Far East Eastern
  Europe
• Probably most frequent worldwide
• Clonal spread has been documented

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CarbapenemasesPan-resistance

• Carbapenem the magic bullet very broad
  spectrum
• Metallo-ß-lactamases (class B)
• Not susceptible to clavulonate
• Serine-carbapenemases (class A D)
• KPC (Klebsiela pneumonia carbapenemase)- plasmid
  associated

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AmpC ß-lactamase

• Chromosomal
• Inducible
• Fully resistant to ß-lactamase inhibitors

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Further complicating matters

• More than one gene of ß-lactamase / ESBL / ampC /
  carbapenemase can be carried on the same plasmid.
• Genes of ESBL are carried on plasmids that
  usually carry additional resistant genes
  frequently MDR
• Laboratory diagnosis confusing
• susceptibility profiles sometimes
• misleading hidden resistance -gt
• CLSI guidelines are changing.
• CTX-M clones appearing in the
• community (Canada, Greece, Spain,
• Italy).

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Treatment of Gram negative infections

• Penicillins
• Cephalosporines (1st, 2nd)
• Extended spectrum Cephalosporines (3rd, 4th)
• Quinolones
• ß-lactam-ß-lactamase inhibitors
• Carbapenems
• ColistinTigecycline

• ß-lactamase (penicillinase)
• Broad spectrum ß -lactamase
• ESBL
• Quinolone resistance
• ESBL (OXA)
• ampC
• Carbapenemases

• We are running out of treatment options!

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The evolution of ESBL

• In a single patient
• SHV-1-gt 3rd Cef Rx. -gt SHV-8
• ESBL TEM-24 from
• Enterobacter aerogenes -gt E. coli -gt proteus
  mirabilis -gt Pseudomonas aeruginosa
• Mutations efficient horizontal transmission
• K. pneumoniae the major ESBL producer

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Klebsiela resistant to 3rd generation
cephalosporines (CDC)
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MDR (qnl, aminoglycoside 3rd ceph.) in
Klebsiella pneumoniae in Europe (EARSS) 2005
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Risk factors

• Critically ill patients
• Long hospitalization (median 11-67 d)
• Invasive medical devices
• Heavy Ab treatment
• 3rd generation cephalosporines
• Also other quinolones, TMP-SMX, aminoglycosides,
  metronidazole

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Control of ESBL outbreaks

• Monoclonal
• Indicates transmission from patient to patient.
• Probably induced by lack of IC measures
• Infection Control

• Polyclonal
• Indicates multiple events of evolving resistance.
• Probably induced by selective Ab pressure
• Antibiotic control

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Enzymatic modification

• The case of macrolides

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Enzymatic modification

• Aminoglycosides
• Acetyltransferases
• Phosphotransferases
• nucleotidyltransferases
• MLS (macrolides, lincosamides, streptogramin B)
• erm (erythromycin resistance methylase) (most
  common)
• Other hydrolases, esterases, glycosylases,
  phosphotransferases, nucleotidyl-transferases and
  acetyltransferases

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Macrolide resistance

• Macrolides are used to treat Gram bacteria and
  atypical bacteria (mycoplasma, legionella,
  chlamidia).
• Bacteriostatic
• Macrolides act by inhibiting protein synthesis,
  by binding to 50S subunit of the ribosome of the
  bacteria.

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Macrolide resistance

• Phenotypes of macrolide resistance
• MLSB
• M
• Genotypes of macrolide resistance
• erm (erythromycin ribosomal methylase)
• mef (specific macrolide effulx pump )

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erm Erythromycin ribosomal methylase

• The predominant macrolide resistance mechanism.
• 34 different classes of Erm proteins.
• Each functions by methylating a single adenine
  residue of the 23S rRNA.
• Methylation results in MLSB pheontype
  (resistance to most macrolides).
• Can be either inducible or constitutive.

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Macrolide resistance in S. pneumoniae

• ermB
• predominant in most of the world
• High level resistance (MICgt64)
• mefA
• most common in some areas (USA)
• low level resistance (MIC 4-8)
• Increasing level of resistance
• Changing epidemiology
• Strains containing both mefA ermB emerging
  (from 10 to 18 in last 4 y)
• mefA ermB usually clonally related to MDR (19A
  non-vaccine type)
• Correlation between increasing consumption of mac
  and Mac R in SP

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Macrolide resistance in S. pneumoniae (2001-2005)
/ Flemingham et al. J. Infection
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2000-2004
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PROTEKT US 2008 (2000-2004)
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Mac-R in S. pneumoniae in Finland / Bergman et
al. 2006 AAC
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Macrolide resistance in GAS

• Uncommon USlt5
• Single outbreak in Pittsburg (up to 48 Mac-R,
  single clone)
• Mechanisms
• ermA (ErmA subclass TR)
• ermB
• mefA
• All associated with mobile genetic elements

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Mac-R is GAS in Finland / Bergman et al. CID 2004
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Macrolide R in S. aureus

• Clindamycin resistance an important treatment
  issue.
• Mechanism of resistance
• Target modification (MLSBi) (ermA, ermC)
• Efflux pumps (MS phenotype
• not clinda R) (msrA)
• Inactivation