- Mutated and selected, more virulent and resistant to beta-lactam antibiotics
- Includes resistance to methicillin, penicillin, and cephalosporins
- Susceptible hosts are both immunocompetent and immune compromised
- Invades intact skin or can enter through local injury
- Colonizes conjunctiva and lid margin
- Colonizes and infects obstructed lacrimal system
- Can invade orbit via conjunctiva (Arch Ophthalmol 2009; 127:941)
- Can infect lacrimal gland directly or hematogenously
- Genotype USA300 is the major community associated strain in most of the US (Ophthalmology 2006; 113:1455).
- Healthcare-associated MRSA strain is USA100.
- Community-acquired MRSA (CAMRSA) differs from healthcare-associated MRSA.
- CAMRSA is more easily transmitted through close contact.
- CAMRSA is less likely to be multiply drug resistant to non-beta lactam antibiotics.
- CAMRSA has a higher prevalence of genes for exotoxins (i.e., Panton-Valentine leukocidin) that promote abscess formation.
- Study from Kaiser Healthcare of 137 culture-positive ophthalmic MRSA patients age 0–18 years 2002–2008 (J Am Acad Ped Ophthalmol Strab 2013; 17:243)
- 58% community acquired
- Conjunctivitis 40%, chalazion 25%, orbital cellulitis 19%, dacryocystitis 11%, brow abscess 3%
- Study of 112 Veterans Affairs Medical Centers 2007–2010, MRSA admission prevalence was 11.4% (Clin Infect Dis 2014; 58:32)
- Among residents of long-term care facilities in Hawaii the prevalence of MRSA was 35% in 2000, increased to 58% in 2005 (Hawaii Med J 2010; 69:126).
- Fingertips of 523 healthcare workers exposed to patients with MRSA were culture positive in 5% (J Hosp Inf 2010; 75:107).
- Fingers were culture-positive even if exposure was to patient environment, not direct contact.
- Slightly reduced, but still present, in those who used alcohol hand rub (3%), or washed with soap (3%)
- Decolonization study in Switzerland 2007–2009 of every patient with newly detected MRSA: colonization or infection (Infection 2013; 41:33)
- Regimen was nasal mupirocin ointment for 5 days, chlorhexidine mouth rinse, and whole-body wash with didecyldimonium chloride.
- Success rate was only 65% at 13‑month follow-up.
- Recurrence often due to respiratory tract nidus
- In most US cities MRSA is the most common pathogen cultured from patients with skin and soft-tissue infections (Exp Opin Pharmacother 2010; 11:3009).
- Skin and soft tissue infections represent 1% of patients presenting to an emergency department, 20% have abscesses requiring drainage.
- Skin lesions, often incorrectly attributed to insect bites
- Pain, tenderness
- No specific time course indicative of MRSA
- In addition to cellulitis and abscess, MRSA can cause necrotizing fasciitis.
- Fluctuance can indicate abscess (Figure 1).
- Deep abscess can be obscured by overlying cellulitis.
- Ultrasound can identify deep anechoic space.
- Needle aspiration can identify deep purulence.
- Absence of purulence on needle aspiration might be due to location or high viscosity and does not rule out abscess (NEJM 2014; 370:11).
- Acute bacterial dacryoadenitis a unique clinical presentation of MRSA (BJO 2013; 97:735)
- Among 15 cases of MRSA orbital cellulitis, 5 had lacrimal gland abscess or dacryoadenitis (Ophthalmology 2012; 119:1238).
- In addition to eyelid swelling, redness, ptosis, frequently diplopia, limitation of eye movement
- CT evidence of lacrimal gland swelling
- Indentation of the globe by an edematous lacrimal gland is common.
- In 11 cases, average time to resolution was 9 days (BJO 2013; 97:735).
- Intravenous antibiotics often needed (Arch Ophthalmol 2014; 132:993)
Figure 1. Abscess. Courtesy Scott M. Goldstein, MD.
Figure 2. MRSA infection. Courtesy Richard C. Allen, MD, PhD, FACS.
Figure 3. MRSA infection. Courtesy Richard C. Allen, MD, PhD, FACS.
Figure 4. MRSA infection. Courtesy Rona Z. Silkiss, MD, FACS.
- Culture and sensitivities to confirm diagnosis (Ophthalmology 2006; 113:1455)
- Routine culture of soft tissue infection was less critical prior to the emergence of CAMRSA.
- No staging