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Clinical Bacteriology (Laboratory) > Phenotypic Detection of Bacterial Drug Resistance (M) > Flashcards

Phenotypic Detection of Bacterial Drug Resistance (M) Flashcards

1
Q

What is the meaning of AMR?

A

Antimicrobial resistance

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2
Q

What is AMR?

A

It is a global health and development threat

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3
Q

What does AMR requires?

A

It requires urgent multisectoral action in order to achieve the Sustainable Development Goals (SDGs)

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4
Q

True or False

AMR is one of the top 10 global public health threats facing humanity

A

True, it is declared by WHO

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5
Q

What are the main drivers (or causes) of the development of drug-resistant pathogens?

A

1) Misuse and 2) overuse of antimicrobials

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6
Q

What are the factors that promotes the spread of microbes (whereas some of w/c can be resistant to antimicrobial treatment)?

A

1) Lack of clean H2O and sanitation

2) Inadequate prevention and control

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7
Q

Is the cost of AMR to the economy significant? Why or why not?

A

Yes, because in addition to death and disability, prolonged illness results in longer hospital stays, the need for more expensive medicines and financial challenges for those impacted

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8
Q

What is the cause of increased risk of the success of modern medicine in treating infections, including during major surgery and cancer chemotherapy?

A

W/out effective antimicrobials

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9
Q

Is phenotypic detection vital in the microbio lab? How?

A

Yes, because it helps clinicians prescribe appropriate antibiotics for pts especially those w/ life-threatening infections

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10
Q

A failure to address the problem of antibiotic resistance could result in what?

A

1) 10M deaths by 2050

2) Costing £66 trillion

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11
Q

When are penicillins discovered?

A

1928

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12
Q

When is resistance against penicillins identified?

A

1940

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13
Q

When are tetracyclines discovered?

A

1948

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14
Q

When is resistance against tetracyclines identified?

A

1953

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15
Q

When are macrolides discovered?

A

1948

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16
Q

When is resistance against macrolides discovered?

A

1985

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17
Q

When are fluoroquinolones discovered?

18
Q

When is resistance against fluoroquinolones identified?

19
Q

When are carbapenems discovered?

20
Q

When is resistance against carbapenems identified?

21
Q

What are the methods of phenotypic detection of bacterial drug resistance?

A

1) Testing for Beta-Lactamase Production (Nitrocefin-based test)
2) Screening and confirmatory test for ESBL
3) Inductible Clindamycin resistance and mecA gene detection
4) Detection of Metallo-Betalactamase production

22
Q

What are beta-lactamases?

A

These are specialized bacterial enzymes that degrade beta-lactam antibiotics

23
Q

What is the procedure (or steps) of testing for Beta-lactamase production (Nitrocefin-based test)?

A

1) Remove growth from plate
2) Rub on Cefinase disk
3) If beta lactamase (+), a red color will develop within 30 secs

24
Q

What is the principle of action (steps) of testing for Beta-lactamase production (Nitrocefin-based test)?

A

Chromogenic cephalosporin reagent Cefinase (via the action of beta lactamase) -> hydrolysis of beta lactam ring -> colored products released

25
Q

What are the reactions (or results) on testing for beta-lactamase production (Nitrocefin-based test)?

A

1) (+) rxn: yellow to pink / red color change on the area where the culture is applied
2) (-) rxn: no color change on the disc

26
Q

What are the limitations of Beta-lactamase test?

A

1) Nitrocef Disk method cannot be used to test members of Enterobacteriaceae, Pseudomonas spp., or other aerobic, gram (-) bacilli because the results may not be predictive of susceptibility to the beta-lactams most often used for therapy
2) The Nitrocef Disk cannot be used for organisms where penicillin resistance is not due to beta-lactamase production, such as Streptococcus pneumoiae and Viridans streptococci
3) Detection of beta-lactamase act in staphylococci may take up to one hr. Induction of the enzyme may also be required, this can be done by testing growth from the zone margin around an oxacillin disk
4) A (-) result does not rule out resistance due to other mechanisms

27
Q

Can Nitrocef Disk method be used to test members of Enterobacteriaceae, Pseudomonas spp., or other aerobic, gram (-) bacilli? Why or why not?

A

No, because the results may not be predictive of susceptibility to the beta-lactams most often used for therapy

28
Q

Can the Nitrocef Disk method be used for organisms where penicillin resistance is not due to beta-lactamase production? If yes, why? If no, what are the bacteria where Nitrocef Disk method for penicillin resistance can’t be used?

A

No, the bacteria where Nitrocef Disk method where penicillin resistance is not due to beta-lactamase production can’t be used are Streptococcus pneumoniae and Viridans streptococci

29
Q

What is the time duration of detection of beta-lactamase act in staphylococci?

A

It may take up to 1 hr

30
Q

What is the meaning of ESBL?

A

Extended Spectrum Beta-Lactamase

31
Q

What are ESBL (what is the principle)?

A

These are bacteria that produces enzymes called extended-spectrum beta-lactamases (ESBLs) are resistant to many penicillin and cephalosporin antibiotics and often to other types of antibiotic

32
Q

What are the expected (+) results for screening test for ESBL?

A

1) Ceftazidime: < or equal to 22 mm
2) Aztreonam: < or equal to 27 mm
3) Cefotaxime: < or equal to 27 mm
4) Ceftriaxone: < or equal to 27 mm
* if these zones sizes are noted, confirmatory for ESBL production is done

33
Q

What is the meaning of PCDDT?

A

Phenotypic Confirmatory Disc Diffusion Test (PCDDT) or Disc Potention Assay

34
Q

What are the (+) results of PCDDT?

A

If > or equal to 5 mm increase is observed in the ZOI for either antimicrobial agent tested combination w/ clavulanic acid vs. the zone diameter of the tested alone confirms ESBL

Zone diameter 22 mm, > or equal to 5 mm than zone diameter of cefotaxime alone

35
Q

What is the bacteria that is (+) for ESBL?

A

E. coli (ESBL positive E. coli)

36
Q

The ESBL positive E. coli is confirmed by what test?

37
Q

What is the other term for inducible Clindamycin resistance?

38
Q

What are the (+) results of D-testing?

A

Flattened edge zone of inhibition (D-shape) of clindamycin adjacent to erythromycin
* Clindamycin must be reported as resistant

39
Q

What is the principle of mecA gene detection?

A

Resistant result to cefoxitin indicates resistant to oxacillin
* Resistance to oxacillin indicates methicillin resistance

40
Q

What is the interpretation for the (+) result for detection of metallo-betalactamase production?

A

Key hole formation of phantom zone bet imipenem and EDTA discs indicates MBL production

Clinical Bacteriology (Laboratory) (24 decks)

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