Infectious Diseases Case of the Month #13

A 2 y.o. hispanic male was admitted to the hospital for apparent failure of outpatient therapy for an orolabial/peri-oral sore.

Several days prior to admission he had developed a sore at the left corner of his mouth (oral commissure) for which he had been brought for medical attention two days prior to admission. According to his mother he also may have had some sore throat and slight cough at the onset of his illness. At the time of his outpatient evaluation he was described as having a small scab at the oral commissure with a 1 cm area of adjacent induration without vesiculation. He was placed on oral TMP/SMX. When there was apparent progression despite the antibiotic, he was admitted to the hospital two days later. At the time of admission there was obvious discomfort associated with the lesion, but the child otherwise appeared well, was able to eat, and was afebrile. Admission labs included WBC 14.8, Hgb 12.3, Plts 382.

He was born in Traverse City, MI of Mexican-born parents whose primary language remained Spanish. He had not traveled to Mexico since birth, had been in good health, and had received normal childhood immunizations. Several months prior to admission he had had a 3 x 3 cm carbuncle on this buttock that resolved with incision and drainage and oral cephalexin.

The patient had specimens obtained for culture and was placed on IV antibiotics.

       
What micro-organism most most likely caused this patient's orolabial/peri-oral abnormality?
   
     
Diagnosis: Methicillin Resistant Staphylococcus aureus
   

This patient had angular cheilitis and adjacent peri-oral cellulitis secondary to Methicillin Resistant Staphylococcus Aureus (MRSA). The case illustrates one of the myriad ways in which this pathogen can cause skin and soft tissue disease and its new-found potential as a cause of community-acquired disease.

Cultures of the chin lesion from the child in the preceding vignette grew MRSA. Cultures for Herpes simplex virus were negative. He was treated initially with IV Vancomycin followed by p.o. TMP/SMX at hospital discharge. His skin infection resolved. In retrospect his father also related history of having had recent carbuncular disease treated with antibiotic therapy.

Staphylococcus aureus is the most common cause of skin and soft tissue infection in the United States, as well as of invasive infection acquired in hospitals. Methicillin resistant Staphylococcus aureus infections have become increasingly endemic in U.S. hospitals over the past forty years (since the appearance of MRSA in the 1960's). In recent years community acquired MRSA (CA-MRSA) infections have been increasingly identified in persons without known health care exposure.

Surveillance data from three participating sites (Baltimore, Atlanta, 12 Minnesota hospitals) in the Emerging Infections Program found that community-acquired MRSA infections accounted for eight to twenty percent of all MRSA isolates for the period 2001-2002 in those locations. Disease was more common amongst those less than two years old than those older, 6% of cases were invasive, and 77% involved skin and soft tissue. Skin involvement tends to be suppurative in nature (furuncles, carbuncles). Unlike hospital-associated strains of MRSA, many CA-MRSA strains carry a gene encoding the Panton-Valentine leukocidin toxin which causes necrosis. As a consequence deep CA-MRSA infections (pneumonia, necrotizing fasciitis, sepsis) can be severe.

Herpes simplex virus is a common cause of orolabial disease but this organism was not cultured in this case, and the appearance of the lesion was not classic. Tuberculosis occurs more commonly in Hispanic populations in the United States than in the general population, but the skin lesion in this case vignette would be unusual for Mycobacterium tuberculosis. Mycobacterium scrofulaceum is an unusual cause of cervical lymphadenitis in children (not a feature of this case). Candida albicans can be a cause of angular cheilitis but would not typically cause disease as aggressive as occurred here.

Ref: Fridkin, SK, et al, Methicillin-resistant Staphylococcus aureus disease in three communities, NEJM 352:14, pgs 1436-1444, 2005.


 

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