MRSA

Question 1

List the 5 main major mechanisms of Bacterial Resistance to antimicrobials.

Answer 1

1. Altered cellular target
2. Decreased cellular permeability
3. Efflux pump
4. Metabolic bypass (i.e. TMP/SMX)
5. Drug-modifying enzymes (i.e. aminoglycosides and beta-lactams)

Question 2

Describe the major mechanism of resistance in MRSA.

Answer 2

MecA gene alters PBP with decreased affinity for beta-lactams

Question 3

Provide some examples of where MRSA outbreaks occurred in the community.

Answer 3

1. Contact sports (i.e. football)
2. Prisons
3. Military recruits (barracks)
4. Daycare

Question 4

Briefly describe the clinical features and carriage of community-acquired MRSA.

Answer 4

Cx: skin and soft tissue infection (abscesses), necrotizing pneumonia;
Carriage is less common in the nose than expected

Question 5

Define the treatments of CA-MRSA in skin and soft tissue infections.

Answer 5

1. Incision and drainage of abscesses
2. Antibiotics (oral)
3. Education to prevent recurrences (i.e. clearing the nose and skin for decolonization)

Question 6

How are MRSA-isolated patients still at risk within the hospital setting?

Answer 6

Inanimate environment can facilitate transmission and contaminated surfaces by family and hospital staff can increase cross-transmission

Question 7

Describe the prevalence of S. aureus in nasal colonization in the US and amongst populations.

Answer 7

1. Almost 1/3 of people in US carry S. aureus in the nose
2. Highest rates in young (6-11 y.o.a.)
3. S aureus nasal carriers: 100% in the nose, 90% in the hands

Question 8

Name at least 3 approaches to decolonization of Staph aureus.

Answer 8

1. Nasal ointment - apply in both nostrils (2x/day, 5x/week)
2. Mupirocin - topical AB, bacteriostatic by binding tRNA synthetase to disrupt protein synthesis (unfortunately is not as effective with MRSA anymore).
3. CHG bathing

Question 9

Describe some unfunded legislative mandates for hospitals.

Answer 9

1. Reporting of hospital-acquired infections.
2. All hospitals start with screening in patient-care areas where surveillance is performed.
3. Policies for repeat screening on a periodic basis.

Question 10

Briefly describe the 3 methods that can be employed to screen MRSA.

Answer 10

1. Traditional culture and susceptibility - 48-72 hours
2. CHROMagar MRSA - changes color once ID’d
3. Molecular detection - use of PCR cassette to test culture that’s detected after <2 hours.

Question 11

Briefly explain how the Dutch were so successful in controlling MRSA populations.

Answer 11

Nationwide infection control in 1988 with a “search and destroy” strategy. Private rooms for those with MRSA, use of caps, masks and gloves, screening, restricted use of broad-spectrum ABs. Their MRSA prevalence remains at <1%.

Question 12

Although resistance with MRSA is slowing down, what nosocomial Gram-positive rod bacteria is on the rise in acquiring antimicrobial resistance?

Answer 12

Clostridium difficile which is an anaerobic bacillus that is acquired in patients with frequent use of broad-spectrum antibiotics.

Question 13

What patient population is most at risk of acquiring C. difficile infections?

Answer 13

The elderly and pregnant women

Question 14

Compare and contrast the horizontal program from the vertical to reduce hospital infections.

Answer 14

Horizontal - reduces all infections at a specific anatomical site;
Vertical program - targets single organism at infected site

Question 15

Define CHG bathing in terms of disease control for antibiotic resistant bacteria.

Answer 15

Chlorhexidine Gluconate Baths break the chain of transmission within families. These are specialized cloths that can reduce the spread of hospital acquired infections in patients who maintain good hygiene.