ESBLs Flashcards

Questions and Answers

Which antibiotic classes are Beta-lactam agents?

2-3rd gen cephalosporins (correct)

Penicillins (correct)

1st gen cephalosporins (correct)

Carbapenems (correct)

Monobactam (correct)

In gram negative organisms, Beta-lactamase is located in _______________ ready to act on incoming antibiotics.

Periplasmic Space

In Gram positive organisms, Beta-lactamase is _ as . Therefore they are less protected.

Secreted, Exoenzymes

What are the two methods that Beta-lactamase production is passed to organisms?

Plasmid mediated and Chromosomal and Constitutive Signup and view all the answers

Plasmid mediated Beta-lactamase production is susceptible to?

Beta-lactamase inhibitors such as clavulanic acid Signup and view all the answers

What are the three beta-lactamase inhibitors?

Clavulanic acid, Tazobactam, and Sulbactam Signup and view all the answers

What is the mechanism of Beta-lactamase inhibitors?

They are structural analogues of Beta-lactams and compete for binding. Signup and view all the answers

What type of organisms are capable of bacterial resistance to penicillins, 1-3rd generation cephalosporins, and aztreonam?

Extended spectrum Beta-lactamase producers Signup and view all the answers

ESBLs have no detectable activity to _ and _ and therefore are susceptible.

Cephamycins and Carbapenems Signup and view all the answers

Which ESBLs are the most significant?

E. coli, K. pneumoniae, K. oxytoca, and Proteus mirabilis Signup and view all the answers

Most ESBLs are derivatives of this enzyme type:

TEM Beta-lactamase Signup and view all the answers

This ESBL enzyme type, which contains the Enterobacteriaceae family, is inhibited by B-lactamase inhibitors.

TEM Beta-lactamase Signup and view all the answers

This ESBL enzyme type is sulfhydryl variable.

SHV Signup and view all the answers

SHV, found in GN bacteria, confers resistance to __________.

Oxyimino cephalosporins Signup and view all the answers

SHV is the most common of the chromosomal B-lactamases in this organism.

K. pneumoniae Signup and view all the answers

This ESBL enzyme type is named for their greater activity against CEFOTAXIME.

CTX-M Signup and view all the answers

What are the two classification schemes for ESBLs?

Ambler and Bush-Jacoby Signup and view all the answers

This ESBL classification scheme is the most useful for infection control purposes.

Ambler Signup and view all the answers

This ESBL scheme is based on substrate and inhibitor activity.

Bush-Jacoby Signup and view all the answers

This Ambler class ESBL is considered one of the most clinically important.

Class A: Broad Spectrum Signup and view all the answers

Class A: Broad spectrum is inhibited by ____________.

Clavulanic Acid Signup and view all the answers

Class A Broad Spectrum is _____________ expressed.

Constitutively Signup and view all the answers

This Ambler class is resistant to all penicillins, cephalosporins, and aztreonam, making it of infection control concern.

Class A: Extended spectrum Signup and view all the answers

What are the organisms (of infection control concern) that are found in Class A?

E. coli, K. pneumoniae, K. oxytoca Signup and view all the answers

What are the indicator drugs for Class A ESBLs?

Cefpodoxime, Ceftazidime, Cefotaxime, and Ceftriaxone Signup and view all the answers

In Class A ESBLs, after the indicator drugs have been identified, what comes next?

Confirmation testing with Beta-lactamase inhibitor combinations to phenotype Signup and view all the answers

If activity with the combination drug is restored, then resistance is proven to be the result of ESBLs. This is known as ____________.

Potentiation Signup and view all the answers

What is the treatment of choice for Class A ESBLs?

Carbapenems Signup and view all the answers

You test susceptibility of a Class A ESBL with Cefoxitin and Cefotetan and it shows susceptibility, would you recommend this to the physician?

False Signup and view all the answers

This Ambler class is Metallo Dependant on Zinc ions.

Class B Signup and view all the answers

Class B is ______________ by clavulanic acid.

Not inhibited Signup and view all the answers

This Ambler class is serine based and not inhibited by Clavulanic Acid.

Class C Signup and view all the answers

What gene gives Class C activity?

ampC Signup and view all the answers

Who are the members of the S.P.I.C.E group?

Serratia, Providencia, Morganella Morganii, Indole positive Proteus, Citrobacter, Enterobacter, Hafnia, P. aeruginosa, and Aeromonas Signup and view all the answers

The SPICE group has this type of Beta-Lactamase production.

Inducible chromosomal ampC Signup and view all the answers

Are SPICE members of infection control concern?

False Signup and view all the answers

How do you report an ESBL?

Reported as resistant to all cephalosporins, penicillins, and aztreonam Signup and view all the answers

What are the two classes of Carbapenemase resistant Enterobacteriaceae?

Class A KPC and Class B MBL Signup and view all the answers

What test is recommended to be performed in testing CRE?

Modified Hodge Test Signup and view all the answers

The Beta-Lactamase test is not recommended for which organisms?

Enterobacteriaceae, Pseudomonas, and other aerobic GNB Signup and view all the answers

Hydrolysis of this has been found to be highly effective in detecting beta-lactamase producing isolates.

Nitrocefin Signup and view all the answers

Nitrocefin hydrolysis test is also known as _________.

Cefinase Signup and view all the answers

In the Cefinase test, Beta-lactamase producing organisms hydrolyze Nitrocefin to produce this color.

Pink Signup and view all the answers

This test checks beta-lactamase production in MSSA organisms.

Penicillin Edge test Signup and view all the answers

What edge would be seen in a Staphylococcus aureus organism that is also a beta-lactamase producer?

A sharp cliff Signup and view all the answers

What edge would be seen in a Staphylococcus aureus organism that is not a beta-lactamase producer?

A fuzzy edge (beach) Signup and view all the answers

What is the zone of inhibition for both a positive and negative in the Penicillin Zone Edge test?

Greater than 29mm Signup and view all the answers

What are the specimen types that are used in the surveillance of ESBLs?

Rectal swab or stool Signup and view all the answers

During surveillance of ESBLs, what agar plate is used?

MacConkey with 2ug/mL of cefpodoxime Signup and view all the answers

Why must one use indicator drugs in the identification of ESBLs?

Some isolates may appear susceptible to 3rd generation cephalosporins in vitro, but clinical treatment will fail. Signup and view all the answers

What is potentiation?

An enhancement to the zone of inhibition through the addition of a Beta-Lactamase inhibitor. Signup and view all the answers

What are the four drugs used in the phenotypic confirmation test for ESBLs?

Ceftazidime, Ceftazidime + Clavulanic, Cefotaxime, and Cefotaxime + Clavulanic acid Signup and view all the answers

During a phenotypic confirmation test, an increase of 5mm of inhibition is seen in which ESBL type?

Class A Signup and view all the answers

During a phenotypic confirmation test, this class shows resistance to any one of the four drugs and potentiation is NOT seen.

Class C Signup and view all the answers

In the Modified Hodge Test (MHT), what organism is used for confluent growth?

E. coli Signup and view all the answers

In MHT, what drug is placed in the center?

Meropenem Signup and view all the answers

In the MHT, the test isolate that was streaked to E. coli gives a clover-like appearance in the zone of inhibition. This test isolate is therefore ________.

A carbapenemase producer Signup and view all the answers

Study Notes

Beta-lactam Agents

Common classes include penicillins, first-generation cephalosporins, second and third-generation cephalosporins, monobactams, and carbapenems.

Beta-lactamase Location

In gram-negative bacteria, beta-lactamase is found in the periplasmic space, allowing it to effectively neutralize antibiotics.

Gram-positive Organisms

Beta-lactamase is secreted as exoenzymes in gram-positive organisms, leading to reduced protection against antibiotics.

Mechanisms of Beta-lactamase Transmission

Production can occur via plasmid-mediated transfer or chromosomal and constitutive expression.

Susceptibility to Beta-lactamase Inhibitors

Plasmid-mediated beta-lactamase production can be targeted by inhibitors like clavulanic acid.

Common Beta-lactamase Inhibitors

Clavulanic acid, tazobactam, and sulbactam are commonly used inhibitors to counteract beta-lactamases.

Mechanism of Action of Inhibitors

Beta-lactamase inhibitors act as structural analogues of beta-lactams, competing for binding sites and reducing activity.

Extended Spectrum Beta-lactamase (ESBL) Producers

These organisms demonstrate resistance to penicillins, first to third-generation cephalosporins, and aztreonam.

ESBL Susceptibility Profile

ESBLs show no activity against cephamycins and carbapenems, making them susceptible to these drugs.

Significant ESBLs

Major ESBL producers include E.coli, Klebsiella pneumoniae, Klebsiella oxytoca, and Proteus mirabilis.

Common ESBL Enzyme Type

Most ESBLs are derived from TEM beta-lactamase.

Beta-lactamase Inhibition

TEM beta-lactamase expressed by Enterobacteriaceae can be inhibited by beta-lactamase inhibitors.

SHV Beta-lactamase Traits

SHV type is sulfhydryl variable and confers resistance specifically to oxyimino cephalosporins.

Classifications of ESBLs

Two classification systems exist: Ambler (most useful for infection control) and Bush-Jacoby (based on substrate and inhibitor activity).

Ambler Class A

Class A beta-lactamase is broad-spectrum and susceptible to clavulanic acid; it is constitutively expressed.

Infection Control Concern from Class A

Organisms like E.coli, K.pneumoniae, and K.oxytoca are of significant infection control concern due to their Class A status.

Indicator Drugs for Class A

Common indicator drugs include cefpodoxime, ceftazidime, cefotaxime, and ceftriaxone.

Confirmation Testing Protocol

Following identification, confirmation testing involves beta-lactamase inhibitor combinations to determine resistance phenotype.

Potentiation Concept

If the activity with a combination drug is restored, resistance is identified as due to ESBLs, termed potentiation.

Treatment for Class A ESBLs

Carbapenems are the preferred treatment for Class A ESBL infections.

Caution with Cephamycins

Demonstrating susceptibility to cephamycins may not indicate true clinical efficacy, leading to potential therapy failure.

Class B Resistance

Class B ESBLs are metallo-dependent on zinc ions and are not inhibited by clavulanic acid.

Class C Characteristics

Class C ESBLs are serine-based and also resistant to clavulanic acid, conferred by the ampC gene.

SPICE Organisms

Includes Serratia, Providencia, Morganella, indole-positive Proteus, Citrobacter, Enterobacter, Hafnia, Pseudomonas aeruginosa, and Aeromonas, with inducible chromosomal ampC resistance.

Reporting ESBLs

Resistance should be reported for all cephalosporins, penicillins, and aztreonam.

Carbapenemase Resistant Enterobacteriaceae

Divided into Class A (KPC) and Class B (MBL) resistance mechanisms.

Testing for CRE

The modified Hodge test (MHT) is recommended for testing Carbapenemase Resistant Enterobacteriaceae.

Nitrocefin Hydrolysis Test

Effective in detecting beta-lactamase production; also known as Cefinase.

Cefinase Test Reaction

Beta-lactamase positive organisms will hydrolyze nitrocefin, producing a pink color.

Penicillin Edge Test

Evaluates beta-lactamase production in MSSA; a sharp cliff indicates positive beta-lactamase production.

Zone of Inhibition Interpretation

A 29mm or greater zone indicates susceptibility for both positive and negative beta-lactamase tests.

Specimen Types for ESBL Surveillance

Rectal swabs or stool specimens are typically used for ESBL detection.

MacConkey Agar for Surveillance

MacConkey agar with 2ug/mL of cefpodoxime is utilized during surveillance.

Clinical Importance of Indicator Drugs

Indicator drugs help identify ESBLs, as some isolates may seem susceptible in vitro but fail in clinical treatment.

Definition of Potentiation

Refers to enhancement of the inhibition zone when a beta-lactamase inhibitor is added.

Phenotypic Confirmation Test Drugs

Ceftazidime, Ceftazidime + clavulanic acid, cefotaxime, and cefotaxime + clavulanic acid are used in confirmation tests.

Class A Resistance Characteristics

An increase of 5mm in inhibition indicates Class A ESBLs during confirmation tests.

Class C Resistance Traits

Class C shows resistance to one of the tested drugs without potentiation during confirmation tests.

Modified Hodge Test Procedure

E. coli is used for confluent growth, with meropenem placed in the center.

Clover-like Appearance in MHT

Suggests that the test isolate is a carbapenemase producer.

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Description

Test your knowledge on Extended-Spectrum Beta-Lactamases (ESBLs) with this flashcard quiz. The cards cover various antibiotic classes, their mechanisms, and characteristics in both Gram-negative and Gram-positive organisms. Perfect for students in microbiology or healthcare fields.