Phenotypic Detection of Bacterial Drug Resistance (M)

Question 1

What is the meaning of AMR?

Answer 1

Antimicrobial resistance

Question 2

What is AMR?

Answer 2

It is a global health and development threat

Question 3

What does AMR requires?

Answer 3

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

Question 4

True or False

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

Answer 4

True, it is declared by WHO

Question 5

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

Answer 5

1) Misuse and 2) overuse of antimicrobials

Question 6

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

Answer 6

1) Lack of clean H2O and sanitation

2) Inadequate prevention and control

Question 7

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

Answer 7

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

Question 8

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

Answer 8

W/out effective antimicrobials

Question 9

Is phenotypic detection vital in the microbio lab? How?

Answer 9

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

Question 10

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

Answer 10

1) 10M deaths by 2050

2) Costing £66 trillion

Question 11

When are penicillins discovered?

Answer 11

1928

Question 12

When is resistance against penicillins identified?

Answer 12

1940

Question 13

When are tetracyclines discovered?

Answer 13

1948

Question 14

When is resistance against tetracyclines identified?

Answer 14

1953

Question 15

When are macrolides discovered?

Answer 15

1948

Question 16

When is resistance against macrolides discovered?

Answer 16

1985

Question 17

When are fluoroquinolones discovered?

Answer 17

1985

Question 18

When is resistance against fluoroquinolones identified?

Answer 18

1985

Question 19

When are carbapenems discovered?

Answer 19

1985

Question 20

When is resistance against carbapenems identified?

Answer 20

1993

Question 21

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

Answer 21

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

Question 22

What are beta-lactamases?

Answer 22

These are specialized bacterial enzymes that degrade beta-lactam antibiotics

Question 23

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

Answer 23

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

Question 24

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

Answer 24

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

Question 25

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

Answer 25

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

Question 26

What are the limitations of Beta-lactamase test?

Answer 26

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

Question 27

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

Answer 27

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

Question 28

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?

Answer 28

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

Question 29

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

Answer 29

It may take up to 1 hr

Question 30

What is the meaning of ESBL?

Answer 30

Extended Spectrum Beta-Lactamase

Question 31

What are ESBL (what is the principle)?

Answer 31

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

Question 32

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

Answer 32

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

Question 33

What is the meaning of PCDDT?

Answer 33

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

Question 34

What are the (+) results of PCDDT?

Answer 34

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

Question 35

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

Answer 35

E. coli (ESBL positive E. coli)

Question 36

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

Answer 36

PCDDT

Question 37

What is the other term for inducible Clindamycin resistance?

Answer 37

D-testing

Question 38

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

Answer 38

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

Question 39

What is the principle of mecA gene detection?

Answer 39

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

Question 40

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

Answer 40

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