It's Not a Spider Bite, It's Community-Acquired Methicillin-Resistant Staphylococcus Aureus

Tamara J. Dominguez, MD

Disclosures

J Am Board Fam Med. 2004;17(3) 

In This Article

Case Review

Skin and soft tissue infections caused by hospital-acquired methicillin-resistant Staphylococcus aureus, or HA-MRSA, have been a problem in hospital and nursing home settings for several years.[1] In recent years, infections caused by a new isolate termed community-acquired MRSA (CA-MRSA) have been increasing in incidence,[2,3,4] and outbreaks of CA-MRSA have been identified in other settings, including athletic teams and prisons.[5,6,7] Community-acquired MRSA differs from HA-MRSA in that CA-MRSA is not multidrug-resistant and can usually be treated with clindamycin, trimethoprim/ sulfamethoxazole, or linezolid.[8,9] Both organisms carry the staphylococcal cassette chromosome mecA (SCCmecA) gene that encodes resistance to the β-lactams[10,11]—the class of antibiotics most commonly used in treating skin and soft tissue infections. At this time, it is not known whether CAMRSA is the result of HA-MRSA that escaped the hospital setting and mutated to its present form or is community-generated in origin.[12] Several studies are currently being conducted in molecular genetics to identify the source of CA-MRSA and effectively treat it.[13] This article presents a case review of several CA-MRSA infections identified in a community clinic setting, identifies clues that might lead the clinician to suspect a CA-MRSA infection, recommends questions to consider in making this diagnosis, and discusses options for treatment. It may be that contact with prisons or prisoners needs to be placed on the list of known risk factors associated with CA-MRSA.

From July 2002 to September 2003, 10 patients were identified as having CA-MRSA skin and soft tissue infections at an indigent health care clinic in San Antonio, Texas. These infections were classified as community-acquired MRSA based on several factors: (1) none of the patients had risk factors for nosocomially acquired MRSA (ie, recent hospitalization or surgery [1] ) or those risk factors previously associated with acquisition of MRSA outside a short-term care setting: residence in a long-term care facility, current intravenous drug abuse, or underlying illnesses such as cardiovascular or pulmonary disease, diabetes mellitus, malignancy, or chronic skin disease such as eczema, [14] and (2) antimicrobial resistance patterns were consistent with CA-MRSA—ie, they showed susceptibility to several classes of antimicrobial agents other than β-lactams.

Patients were identified through a positive wound culture using an aerobic/anaerobic Culturette. Many had been diagnosed and treated for other causes of their infection, including spider bites, impetigo, and varicella zoster. Four of the patients had been incarcerated and reported they had been treated for recurring skin infections several times while in prison. One of these 4 patients had a positive nasal culture for CA-MRSA. The other 6 patients had contact with either a prison facility or someone recently released from prison. One patient also played on his high school football team. Several patients were treated by other providers for what were thought to be spider bites. All CA-MRSA infections treated at the community clinic responded well to clindamycin, mupirocin, and drainage of the abscess, if present. The sensitivity pattern was similar in the positive MRSA cultures in that all were sensitive to clindamycin, rifampin, trimethoprim/sulfamethoxazole, and vancomycin Table1 . All the isolates were resistant to amoxicillin/clavulanic acid, cefazolin, erythromycin, oxacillin, and penicillin. A brief detail of the patients' histories is outlined below ( Table 2 ):

Case A

A 10-year-old girl was brought to the clinic by her mother for a lesion to her left lower extremity that the family thought was caused by a spider bite. She had been treated for impetigo at her pediatrician's office 2 weeks before, but her condition did not improve after treatment with amoxicillin/clavulanic acid. The patient was then seen at this community clinic, and her wound culture was positive for CAMRSA. Both the patient and her mother had recently visited the patient's father in prison. Her mother had been treated 2 weeks earlier for a similar infection and was told by the emergency department physician that her infection was the result of a spider bite. The patient's infection cleared after treatment with oral clindamycin and topical mupirocin applied to the wound.

Case B

A 24-year-old man presented to the clinic with a 4-day history of painful raised pustules to his left hip that the patient attributed to spider bites. A culture of these lesions proved positive for CAMRSA. The lesions cleared after treatment with oral clindamycin and topical mupirocin. His girlfriend had been treated at our clinic for a similar infection 4 months earlier but a culture was not done at that time. His girlfriend's sister had been hospitalized for an abscess on her abdomen caused by a "spider bite" during that same period. His girlfriend's other roommate was released from prison and had moved in with the patient's girlfriend and her sister 2 weeks before their infections began.

Case C

A 43-year-old man recently released from prison was treated at the clinic for multiple pustules over his legs, arms, and inguinal area. An aerobic/anaerobic wound culture was taken and was positive for CA-MRSA. This patient had been treated several times while in prison for similar lesions and was told they were the result of spider bites. His last intravenous drug use was 4 years before. This infection resolved after treatment with oral clindamycin and topical mupirocin.

Case D

A 25-year-old woman was first treated in the emergency department for varicella zoster then at the clinic for impetigo that did not respond to amoxicillin/clavulanic acid or gatifloxacin. The patient developed an abscess on her right gluteal area with a central eschar. An aerobic/anaerobic culture was positive for CA-MRSA. The patient's boyfriend had recently been released from prison. The patient responded well to drainage of the abscess and was treated with oral clindamycin and topical mupirocin.

Case E

Case D's 45-year-old mother presented at the clinic 1 week after her daughter's treatment for a left gluteal abscess. The wound culture proved positive for CA-MRSA. This infection cleared with incision and drainage of the abscess and antimicrobial treatment with clindamycin and mupirocin.

Case F

A 41-year-old man recently released from prison presented to the clinic with a history of recurring skin infections thought to be impetigo. He had been treated several times while in prison for similar lesions. The wound culture and nasal swab done at clinic were positive for CA-MRSA. The patient's lesions cleared after treatment with oral clindamycin. Mupirocin was applied intranasally and topically to his wounds.

Case G

A 50-year-old man presented to the clinic with multiple furuncles on his legs and arms. He had been recently released from prison and had a history of recurring "staph" infections while in prison. This patient failed treatment with ciprofloxacin for what was thought to be impetigo. His wound culture done at clinic was positive for CA-MRSA. The lesions resolved after treatment with clindamycin and mupirocin.

Case H

A 36-year-old woman was treated at the clinic for multiple furuncles to the left knee, nape of the neck, and scalp. This patient also had an abscess on her left gluteus that was incised and drained. Wound cultures done on all areas proved positive for CA-MRSA. The patient had been visiting her pregnant daughter in prison for several weeks before her outbreak. This infection cleared after drainage of her abscess and treatment with clindamycin and mupirocin.

Case I

A 16-year-old boy presented to the clinic with a 4-day history of a "boil" to his right axilla. The patient stated he had a similar infection on his neck a year before and was told it was from a "spider bite" when he sought medical attention. Cultures taken from his axilla grew CA-MRSA and a Gram stain showed many Gram-positive cocci. It is notable that the patient's father had been recently released from prison and returned home 1 week before the patient's most recent infection. The father reported being treated twice while incarcerated for similar lesions. The patient participated in high school football and was not aware that anyone else on the team had experienced a similar infection.

Case J

A 42-year-old man presented to the clinic with a 3-day history of a "spider bite" to his left inguinal area. (Figures 1-3). He had been treated several times over an 8-year period for similar lesions and was told each time it was the result of a spider bite. His first episode occurred when he was incarcerated in the county jail. The patient stated that his sister and niece were both treated for similar "spider bites." The patient's wound culture was positive for MRSA and responded well to treatment with clindamycin.

Figure 1.

CA-MRSA lesion of patient J. Location: left groin.

Figure 2.

Lesion of patient J.

Figure 3.

CA-MRSA lesion of patient J. Location: left groin.

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