Podcast
Questions and Answers
Which antibiotic classes are Beta-lactam agents?
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.
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.
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?
What are the two methods that Beta-lactamase production is passed to organisms?
Plasmid mediated Beta-lactamase production is susceptible to?
Plasmid mediated Beta-lactamase production is susceptible to?
What are the three beta-lactamase inhibitors?
What are the three beta-lactamase inhibitors?
What is the mechanism of Beta-lactamase inhibitors?
What is the mechanism of Beta-lactamase inhibitors?
What type of organisms are capable of bacterial resistance to penicillins, 1-3rd generation cephalosporins, and aztreonam?
What type of organisms are capable of bacterial resistance to penicillins, 1-3rd generation cephalosporins, and aztreonam?
ESBLs have no detectable activity to _______ and _______ and therefore are susceptible.
ESBLs have no detectable activity to _______ and _______ and therefore are susceptible.
Which ESBLs are the most significant?
Which ESBLs are the most significant?
Most ESBLs are derivatives of this enzyme type:
Most ESBLs are derivatives of this enzyme type:
This ESBL enzyme type, which contains the Enterobacteriaceae family, is inhibited by B-lactamase inhibitors.
This ESBL enzyme type, which contains the Enterobacteriaceae family, is inhibited by B-lactamase inhibitors.
This ESBL enzyme type is sulfhydryl variable.
This ESBL enzyme type is sulfhydryl variable.
SHV, found in GN bacteria, confers resistance to __________.
SHV, found in GN bacteria, confers resistance to __________.
SHV is the most common of the chromosomal B-lactamases in this organism.
SHV is the most common of the chromosomal B-lactamases in this organism.
This ESBL enzyme type is named for their greater activity against CEFOTAXIME.
This ESBL enzyme type is named for their greater activity against CEFOTAXIME.
What are the two classification schemes for ESBLs?
What are the two classification schemes for ESBLs?
This ESBL classification scheme is the most useful for infection control purposes.
This ESBL classification scheme is the most useful for infection control purposes.
This ESBL scheme is based on substrate and inhibitor activity.
This ESBL scheme is based on substrate and inhibitor activity.
This Ambler class ESBL is considered one of the most clinically important.
This Ambler class ESBL is considered one of the most clinically important.
Class A: Broad spectrum is inhibited by ____________.
Class A: Broad spectrum is inhibited by ____________.
Class A Broad Spectrum is _____________ expressed.
Class A Broad Spectrum is _____________ expressed.
This Ambler class is resistant to all penicillins, cephalosporins, and aztreonam, making it of infection control concern.
This Ambler class is resistant to all penicillins, cephalosporins, and aztreonam, making it of infection control concern.
What are the organisms (of infection control concern) that are found in Class A?
What are the organisms (of infection control concern) that are found in Class A?
What are the indicator drugs for Class A ESBLs?
What are the indicator drugs for Class A ESBLs?
In Class A ESBLs, after the indicator drugs have been identified, what comes next?
In Class A ESBLs, after the indicator drugs have been identified, what comes next?
If activity with the combination drug is restored, then resistance is proven to be the result of ESBLs. This is known as ____________.
If activity with the combination drug is restored, then resistance is proven to be the result of ESBLs. This is known as ____________.
What is the treatment of choice for Class A ESBLs?
What is the treatment of choice for Class A ESBLs?
You test susceptibility of a Class A ESBL with Cefoxitin and Cefotetan and it shows susceptibility, would you recommend this to the physician?
You test susceptibility of a Class A ESBL with Cefoxitin and Cefotetan and it shows susceptibility, would you recommend this to the physician?
This Ambler class is Metallo Dependant on Zinc ions.
This Ambler class is Metallo Dependant on Zinc ions.
Class B is ______________ by clavulanic acid.
Class B is ______________ by clavulanic acid.
This Ambler class is serine based and not inhibited by Clavulanic Acid.
This Ambler class is serine based and not inhibited by Clavulanic Acid.
What gene gives Class C activity?
What gene gives Class C activity?
Who are the members of the S.P.I.C.E group?
Who are the members of the S.P.I.C.E group?
The SPICE group has this type of Beta-Lactamase production.
The SPICE group has this type of Beta-Lactamase production.
Are SPICE members of infection control concern?
Are SPICE members of infection control concern?
How do you report an ESBL?
How do you report an ESBL?
What are the two classes of Carbapenemase resistant Enterobacteriaceae?
What are the two classes of Carbapenemase resistant Enterobacteriaceae?
What test is recommended to be performed in testing CRE?
What test is recommended to be performed in testing CRE?
The Beta-Lactamase test is not recommended for which organisms?
The Beta-Lactamase test is not recommended for which organisms?
Hydrolysis of this has been found to be highly effective in detecting beta-lactamase producing isolates.
Hydrolysis of this has been found to be highly effective in detecting beta-lactamase producing isolates.
Nitrocefin hydrolysis test is also known as _________.
Nitrocefin hydrolysis test is also known as _________.
In the Cefinase test, Beta-lactamase producing organisms hydrolyze Nitrocefin to produce this color.
In the Cefinase test, Beta-lactamase producing organisms hydrolyze Nitrocefin to produce this color.
This test checks beta-lactamase production in MSSA organisms.
This test checks beta-lactamase production in MSSA organisms.
What edge would be seen in a Staphylococcus aureus organism that is also a beta-lactamase producer?
What edge would be seen in a Staphylococcus aureus organism that is also a beta-lactamase producer?
What edge would be seen in a Staphylococcus aureus organism that is not a beta-lactamase producer?
What edge would be seen in a Staphylococcus aureus organism that is not a beta-lactamase producer?
What is the zone of inhibition for both a positive and negative in the Penicillin Zone Edge test?
What is the zone of inhibition for both a positive and negative in the Penicillin Zone Edge test?
What are the specimen types that are used in the surveillance of ESBLs?
What are the specimen types that are used in the surveillance of ESBLs?
During surveillance of ESBLs, what agar plate is used?
During surveillance of ESBLs, what agar plate is used?
Why must one use indicator drugs in the identification of ESBLs?
Why must one use indicator drugs in the identification of ESBLs?
What is potentiation?
What is potentiation?
What are the four drugs used in the phenotypic confirmation test for ESBLs?
What are the four drugs used in the phenotypic confirmation test for ESBLs?
During a phenotypic confirmation test, an increase of 5mm of inhibition is seen in which ESBL type?
During a phenotypic confirmation test, an increase of 5mm of inhibition is seen in which ESBL type?
During a phenotypic confirmation test, this class shows resistance to any one of the four drugs and potentiation is NOT seen.
During a phenotypic confirmation test, this class shows resistance to any one of the four drugs and potentiation is NOT seen.
In the Modified Hodge Test (MHT), what organism is used for confluent growth?
In the Modified Hodge Test (MHT), what organism is used for confluent growth?
In MHT, what drug is placed in the center?
In MHT, what drug is placed in the center?
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 ________.
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 ________.
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.
