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BS131: Health & the Community > Lecture 11. Introduction to Superbug > Flashcards

Lecture 11. Introduction to Superbug Flashcards

1
Q

What is a superbug?

A

Any strain of bacteria that has become resistant to the antibiotics that are used to treat it - Multi-Drug Resistant (MDR)

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2
Q

What are examples of superbugs?

A

Staphylococcus aureus (MRSA)
Escherichia coli
Acinetobacter spp.
Klebsiella pneumoniae
Pseudomonas aeruginosa
Mycobacterium tuberculosis

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3
Q

When was penicillin discovered?

A

1928

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4
Q

When was the first reported instance of penicillin-resistant S. aureus?

A

1944

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5
Q

When was Methicillin introduced to treat penicillin-resistant S. aureus?

A

1959

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6
Q

When was the first case of MRSA?

A

1961

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7
Q

What are the mechanisms of resistance?

A

Exposure to antibiotics selects for bacteria with mutated key genes and/or their control systems and with horizontally acquired antibiotic resistance determinants

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8
Q

Where is MDR Klebsiella pneumoniae spreading?

A

Around Eastern Europe

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9
Q

What are anthropogenic drivers of antibiotic resistance?

A

Overprescription of antibiotics and farming practices involving antibiotics

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10
Q

What does the Gram stain detect?

A

Peptidoglycan

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11
Q

What colour are Gram positive bacilli?

A

Purple

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12
Q

What colour are Gram negative bacilli?

A

Pink

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13
Q

What is the key problem with Gram staining?

A

Poor species resolution

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14
Q

What is biotyping?

A

Traditionally, strain discrimination by examining growth profiles on different substrates. Metabolic activities, colony morphology and environmental tolerances are compared. Strains are referred to as “biotypes”

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15
Q

What are the advantages of biotyping?

A

Most strains are typeable. Reproducible, relatively easy to perform and interpret

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16
Q

What are the disadvantages of biotyping?

A

Poor discriminatory power (variation in gene expression and point mutation alter metabolic activities)

17
Q

What is antibiotyping (antibiogram typing)?

A

Strain discrimination on the basis of antibiotic resistance. Comparison of susceptibility of different isolates to a set of antibiotics. Isolates differing in their susceptibilities are considered as different strains

18
Q

What does antibiotyping do?

A

The identification of new or unusual pattern of antibiotic resistance among isolates cultured from patients is often the first indication of an outbreak

19
Q

What are the advantages of antibiotyping?

A

Almost all strains are typeable. Reproducible. Easy to perform and interpret

20
Q

What are the disadvantages of antibiotyping?

A

Acquisition of antibiotic determinants, point mutations and gene expression changes can alter patterns of antibiotic resistance quickly, reducing discriminatory power

21
Q

What is phage-typing?

A

Strain discrimination on the basis of resistance to various bacteriophage

22
Q

What are the advantages of phage-typing?

A

Fairly reproducible, good discriminatory power and easy to interpret

23
Q

What are the disadvantages of phage-typing?

A

This technique requires maintenance of biologically active ‘phages and hence is available only at reference centres. Even for experienced workers, the technique is time-consuming. Many strains are non-typeable

24
Q

What are bacteriophages?

A

Viruses that infect bacteria

25
Q

What can phage-typing be used for?

A

Type isolates of Staphylococcus aureus and Salmonella sps. Such stains are referred as ‘phage types’

26
Q

What is serotyping?

A

Strain discrimination on the basis of binding of antibodies of known specificity to their cell surface antigens. Target structures are lipopolysaccharides, membrane proteins, capsular polysaccharides, flagellae and fimbriae that exhibit antigenic variation. Strains differentiated by antigenic differences are known as ‘serotypes’.

27
Q

What are the advantages of serotyping?

A

Most strains are typeable

28
Q

What are the disadvantages of serotyping?

A

Some autoagglutinable (rough) strains are untypeable
Some methods of serotyping are technically demanding
Serotyping sometimes has poor discriminatory power (large number of serotypes, cross-reaction of antibodies with surface antigens)

BS131: Health & the Community (23 decks)

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