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