Chapter 8: Infectious Disease

SEPSIS

Sepsis is a systemic disorder characterized by an inflammatory and immune-mediated response to infection. Aggressive and early fluid resuscitation, early antibiotic therapy, and source control are the cornerstones of sepsis management. See also Chapter 1, Resuscitation.

SELECTED BACTERIA

Methicillin-Resistant Staphylococcus Aureus

Methicillin-resistant Staphylococcus aureus (MRSA) was first recognized in the early 1960s shortly after the introduction of semisynthetic penicillins, such as methicillin. The mecA gene confers resistance to all β-lactam antibiotics such as methicillin, dicloxacillin, and many cephalosporins. MRSA infections are classified as either health care–associated MRSA (HA-MRSA) or community-associated MRSA (CA-MRSA). CA-MRSA strains have an additional Panton-Valentine leukocidin (PVL) toxin gene that allows production of necrotizing cytokines, increasing its invasiveness and virulence.

• HA-MRSA:

  • Hospital prevalence rates are as high as 60%.

  • Most common mode of transmission is patient-to-patient spread by health care workers with contaminated hands/gloves.

  • Risks for HA-MRSA include hospitalization, indwelling catheter, recent antibiotic therapy, and residence in a long-term care facility.

• CA-MRSA:

  • Occurs primarily in the absence of health care exposure and often in otherwise healthy individuals.

  • Most common mode of transmission is skin-to-skin contact.

  • High-risk populations include day care attendees, athletes participating in contact sports, those living in close quarters (eg, military, prisoners), injection drug users and men having sex with men.

SYMPTOMS/EXAMINATION

• HA-MRSA: Most commonly presents as bacteremia or a device-associated infection.

• CA-MRSA: Most common presentation is purulent (pus forming) skin/soft tissue infection.

• Other presentations include necrotizing pneumonia, endocarditis, osteomyelitis (Figure 8.1).

DIAGNOSIS

• Suspect (and initiate treatment) based on risk factors and clinical presentation.

• Gold standard is culture.

• Polymerase chain reaction (PCR) is most accurate.

TREATMENT

• HA-MRSA:

  • Treat empirically with vancomycin; consider linezolid/daptomycin.

• CA-MRSA:

  • Abscess: Incision and drainage (I&D) is the mainstay of therapy. Consider antibiotics for:

    • Abscess > 5 cm per or multiple lesions

    • Evidence of surrounding cellulitis

    • Associated comorbidities or immunosuppression such as diabetes or transplant patients

    • Systemic signs of infection

    • Lack of response to initial I&D

  • Trimethoprim-sulfamethoxazole, clindamycin, and doxycycline are typically safe in adults though each has its own side-effect profile.

  • Antibiotic choice should be guided whenever possible by a regional antibiogram.

  • Eradication of colonization:

    • Consider for recurrent MRSA infections or recurrent close contact transmission despite appropriate cleaning and hygiene.

    • Done with mupirocin 2% ointment 0.5 g in each nostril twice a day ...