BRIEF REPORTS
It’s Not a Spider Bite, It’s Community-Acquired
Methicillin-Resistant Staphylococcus aureus
Tamara J. Dominguez, MD
Skin and soft tissue infections caused by hospital- Case Review
acquired methicillin-resistant Staphylococcus aureus, From July 2002 to September 2003, 10 patients
or HA-MRSA, have been a problem in hospital and were identified as having CA-MRSA skin and soft
nursing home settings for several years.1 In recent tissue infections at an indigent health care clinic in
years, infections caused by a new isolate termed San Antonio, Texas. These infections were classi-
community-acquired MRSA (CA-MRSA) have fied as community-acquired MRSA based on sev-
been increasing in incidence,2– 4 and outbreaks of eral factors: (1) none of the patients had risk factors
CA-MRSA have been identified in other settings, for nosocomially acquired MRSA (ie, recent hospi-
including athletic teams and prisons.5–7 Com- talization or surgery1) or those risk factors previ-
munity-acquired MRSA differs from HA-MRSA in ously associated with acquisition of MRSA outside
that CA-MRSA is not multidrug-resistant and can a short-term care setting: residence in a long-term
usually be treated with clindamycin, trimethoprim/ care facility, current intravenous drug abuse, or
sulfamethoxazole, or linezolid.8,9 Both organisms underlying illnesses such as cardiovascular or pul-
carry the staphylococcal cassette chromosome mecA monary disease, diabetes mellitus, malignancy, or
(SCCmecA) gene that encodes resistance to the chronic skin disease such as eczema,14 and (2) an-
-lactams10,11—the class of antibiotics most com- timicrobial resistance patterns were consistent with
monly used in treating skin and soft tissue infec- CA-MRSA—ie, they showed susceptibility to sev-
tions. At this time, it is not known whether CA- eral classes of antimicrobial agents other than
MRSA is the result of HA-MRSA that escaped the -lactams.
hospital setting and mutated to its present form or Patients were identified through a positive
is community-generated in origin.12 Several studies wound culture using an aerobic/anaerobic Cul-
turette. Many had been diagnosed and treated for
are currently being conducted in molecular genet-
other causes of their infection, including spider
ics to identify the source of CA-MRSA and effec-
bites, impetigo, and varicella zoster. Four of the
tively treat it.13 This article presents a case review
patients had been incarcerated and reported they
of several CA-MRSA infections identified in a com-
had been treated for recurring skin infections sev-
munity clinic setting, identifies clues that might
eral times while in prison. One of these 4 patients
lead the clinician to suspect a CA-MRSA infection,
had a positive nasal culture for CA-MRSA. The
recommends questions to consider in making this
other 6 patients had contact with either a prison
diagnosis, and discusses options for treatment. It
facility or someone recently released from prison.
may be that contact with prisons or prisoners needs
One patient also played on his high school football
to be placed on the list of known risk factors asso-
team. Several patients were treated by other pro-
ciated with CA-MRSA. viders for what were thought to be spider bites. All
CA-MRSA infections treated at the community
clinic responded well to clindamycin, mupirocin,
Submitted, revised, 20 October 2003. and drainage of the abscess, if present. The sensi-
From the Bishop Ernest T. Dixon Clinic, Methodist tivity pattern was similar in the positive MRSA
Healthcare Ministries of South Texas, Inc., San Antonio.
Address correspondence to Tamara J. Dominguez, MD, cultures in that all were sensitive to clindamycin,
Bishop Ernest T. Dixon Jr. Clinic, 1954 East Houston rifampin, trimethoprim/sulfamethoxazole, and van-
Street #201, San Antonio, TX 78202.
This work was supported by Methodist Healthcare Min- comycin (Table 1). All the isolates were resistant to
istries of South Texas, Inc., which operates the Dixon Clinic. amoxicillin/clavulanic acid, cefazolin, erythromy-
220 JABFP May–June 2004 Vol. 17 No. 3
Table 1. Sensitivity Patterns for Patients Diagnosed with CA-MRSA
Cases
Antimicrobial Agent MIC* A B C D E F G H I J
Amoxicillin/clavulanate 8/4 R R R R R R R R R R
Ampicillin/sulbactam 32 R R – R R R – R R R
Cefazolin 32 R R – R R R R R R R
Ciprofloxacin 0.5/ 4 S S – S S S S R R R
Clindamycin 8 S S S S S S S S S S
Erythromycin 8 R R R R R R R R R R
Gentamycin 2 – – – – – S – – – S
Levofloxacin 1/ 4 S S – S S S – I I I
Nitrofurantoin 32 S S – S S S – – S –
Oxacillin 8 R R R R R R R R R R
Penicillin 16 R R R R R R R R R R
Rifampin 1 S S – S S S – S S S
Tetracycline 1 S S – S S S – S S –
Trimethoprim/sulfa 10 S S – S S S S S S S
Vancomycin 0.5 S S S S S S S S S S
* MIC, minimal inhibitory concentration; R, resistant; S, sensitive; I, intermediate; –, not reported.
cin, oxacillin, and penicillin. A brief detail of the done at that time. His girlfriend’s sister had been
patients’ histories is outlined below (Table 2): hospitalized for an abscess on her abdomen caused
by a “spider bite” during that same period. His
Case A girlfriend’s other roommate was released from
A 10-year-old girl was brought to the clinic by her prison and had moved in with the patient’s girl-
mother for a lesion to her left lower extremity that friend and her sister 2 weeks before their infections
the family thought was caused by a spider bite. She began.
had been treated for impetigo at her pediatrician’s
office 2 weeks before, but her condition did not Case C
improve after treatment with amoxicillin/clavulanic A 43-year-old man recently released from prison
acid. The patient was then seen at this community was treated at the clinic for multiple pustules over
clinic, and her wound culture was positive for CA- his legs, arms, and inguinal area. An aerobic/anaer-
MRSA. Both the patient and her mother had re- obic wound culture was taken and was positive for
cently visited the patient’s father in prison. Her CA-MRSA. This patient had been treated several
mother had been treated 2 weeks earlier for a sim- times while in prison for similar lesions and was
ilar infection and was told by the emergency de- told they were the result of spider bites. His last
partment physician that her infection was the result intravenous drug use was 4 years before. This in-
of a spider bite. The patient’s infection cleared after fection resolved after treatment with oral clinda-
treatment with oral clindamycin and topical mupi- mycin and topical mupirocin.
rocin applied to the wound.
Case D
Case B A 25-year-old woman was first treated in the emer-
A 24-year-old man presented to the clinic with a gency department for varicella zoster then at the
4-day history of painful raised pustules to his left clinic for impetigo that did not respond to amoxi-
hip that the patient attributed to spider bites. A cillin/clavulanic acid or gatifloxacin. The patient
culture of these lesions proved positive for CA- developed an abscess on her right gluteal area with
MRSA. The lesions cleared after treatment with a central eschar. An aerobic/anaerobic culture was
oral clindamycin and topical mupirocin. His girl- positive for CA-MRSA. The patient’s boyfriend
friend had been treated at our clinic for a similar had recently been released from prison. The pa-
infection 4 months earlier but a culture was not tient responded well to drainage of the abscess and
Misdiagnosis of Methicillin-Resistant S aureus 221
Table 2. Presenting Patients Diagnosed with CA-MRSA
Patient Patient’s History Association with Prison
A 10-year-old girl treated for spider bite to left Had visited her father in prison and her mother had
lower extremity. been treated for spider bite on her left elbow 2
weeks prior.
B 24-year-old man presented to clinic with complaint Girlfriend and girlfriend’s sister both treated for spider
of single spider bite lesion to left hip. bites, girlfriend’s other roommate recently released
from prison.
C 43-year-old man with multiple pustules to legs, Recently released from prison. While in prison, he was
arms, and inguinal area. treated several times for similar infections.
D 25-year-old woman diagnosed with varicella zoster Boyfriend recently released from prison.
and then impetigo. Developed abscess with
central eschar on right gluteus.
E 45-year-old woman, mother of case D. Treated for See above.
left gluteal abscess 1 week after her daughter,
F 41-year-old man with recurring skin infections Recently released from prison. Treated several times
thought to be impetigo. while in prison for similar lesions.
G 50-year-old man with multiple furuncles on his Recently released from prison. While in prison, he had
legs and arms. Failed treatment with a history of recurring staph infections.
ciprofloxacin for what was thought to be
impetigo.
H 36-year-old woman with multiple furuncles to Visited her pregnant daughter in prison for several
knee, posterior neck, and scalp. Abscess to left weeks before her outbreak.
gluteus.
I 16-year-old man with single boil to right axilla. Father released from prison and returned home 1 week
Was treated for a spider bite on his neck 1 prior. Father reported being treated twice for spider
year before. bites while incarcerated.
J 42-year-old man with single spider bite to his left Incarcerated 8 years prior. Sister and niece also treated
groin. Had been treated for recurring skin for spider bites during previous year.
infections several times since release from prison
8 years ago. Was treated for his first skin lesion
while in prison.
was treated with oral clindamycin and topical Case G
mupirocin. 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 his-
Case E tory of recurring “staph” infections while in prison.
Case D’s 45-year-old mother presented at the This patient failed treatment with ciprofloxacin for
clinic 1 week after her daughter’s treatment for a what was thought to be impetigo. His wound cul-
left gluteal abscess. The wound culture proved pos- ture done at clinic was positive for CA-MRSA. The
itive for CA-MRSA. This infection cleared with lesions resolved after treatment with clindamycin
incision and drainage of the abscess and antimicro- and mupirocin.
bial treatment with clindamycin and mupirocin.
Case H
Case F A 36-year-old woman was treated at the clinic for
A 41-year-old man recently released from prison multiple furuncles to the left knee, nape of the
presented to the clinic with a history of recurring neck, and scalp. This patient also had an abscess on
skin infections thought to be impetigo. He had her left gluteus that was incised and drained.
been treated several times while in prison for sim- Wound cultures done on all areas proved positive
ilar lesions. The wound culture and nasal swab for CA-MRSA. The patient had been visiting her
done at clinic were positive for CA-MRSA. The pregnant daughter in prison for several weeks be-
patient’s lesions cleared after treatment with oral fore her outbreak. This infection cleared after
clindamycin. Mupirocin was applied intranasally drainage of her abscess and treatment with clinda-
and topically to his wounds. mycin and mupirocin.
222 JABFP May–June 2004 Vol. 17 No. 3
Figure 2. Lesion of patient J.
Figure 1. CA-MRSA lesion of patient J. Location: left
groin. sis of spider bites has been noted in other
investigations of CA-MRSA outbreaks.5 It is not
known why CA-MRSA infections are commonly
Case I misdiagnosed as spider bites. In several of the above
A 16-year-old boy presented to the clinic with a cases, a spider bite was a common diagnosis for
4-day history of a “boil” to his right axilla. The those CA-MRSA infections that presented as soli-
patient stated he had a similar infection on his neck tary lesions. One of the patients at the clinic (case
a year before and was told it was from a “spider D) developed an abscess with a central eschar, sim-
bite” when he sought medical attention. Cultures ilar in appearance to the bite of a brown recluse
taken from his axilla grew CA-MRSA and a Gram spider (Loxosceles reclusa). Both the patient and her
stain showed many Gram-positive cocci. It is nota- physician (the author) had at first attributed her
ble that the patient’s father had been recently re- infection to a brown recluse spider bite, based
leased from prison and returned home 1 week be- solely on the appearance of her lesion. This was not
fore the patient’s most recent infection. The father the first time this misdiagnosis has been made as
reported being treated twice while incarcerated for other skin lesions have been wrongly attributed to
similar lesions. The patient participated in high the brown recluse spider in other disease processes
school football and was not aware that anyone else such as Lyme disease,15 at times in areas outside the
on the team had experienced a similar infection. endemic range of the brown recluse.16 It was not
until the patient’s wound culture showed CA-
Case J MRSA that the correct diagnosis was made.
A 42-year-old man presented to the clinic with a During the interviewing process several other
3-day history of a “spider bite” to his left inguinal points were noted. First, those patients who were
area. (Figures 1–3). He had been treated several incarcerated (cases C, F, G, J) and former prisoners
times over an 8-year period for similar lesions and who had contact with the case study patients (cases
was told each time it was the result of a spider bite. A, B, D, E, H, I) had been incarcerated at different
His first episode occurred when he was incarcer- correctional facilities. This leads us to question the
ated in the county jail. The patient stated that his prevalence of CA-MRSA infections in prisons. Skin
sister and niece were both treated for similar “spi- and soft tissue infections have been recognized
der bites.” The patient’s wound culture was posi- problems in correctional facilities6; until recently,
tive for MRSA and responded well to treatment however, CA-MRSA outbreaks have been reported
with clindamycin. in only 2 prisons— one in Los Angeles County,
California,5 and the other in Mississippi.6 Second,
Discussion all patients who had been incarcerated reported
These cases demonstrate the ease with which pa- that their first outbreak of skin infections started
tients and clinicians can confuse CA-MRSA infec- after being sent to prison. Finally, some patients at
tions with other soft tissue infections. The diagno- the clinic reported or were noted to have large, firm
Misdiagnosis of Methicillin-Resistant S aureus 223
Figure 3. CA-MRSA lesion of patient J. Location: left groin.
pustules with a central hard white core, similar to have contributed to their deaths. At this time, it is
furunculosis. Several patients stated that self- unclear how common CA-MRSA infections occur
removal of this core resulted in clearing of their within the adult or pediatric community, although
infection. they are being reported in increasing numbers.3
Obtaining the proper diagnosis of a CA-MRSA The CDC is currently conducting surveillance for
infection is important because misdiagnosis and CA-MRSA in selected regions of the country to
delay of proper treatment can have serious conse- determine the incidence and risk factors for MRSA
quences for both the patient and the medical com- in the community.4 In this case review, 2 patients
munity. An improperly treated CA-MRSA infec- were of pediatric age (cases A and I), and neither
tion results in increased medical costs for the had any of the known risk factors associated with
patient and community resulting from multiple of- MRSA infections. Both patients had prior contact
fice and emergency department visits and possibil- with a prisoner, prison facility, or athletic facility.
ity of hospitalization. In addition, the risk of Antimicrobial sensitivity patterns are helpful
transferring the infection increases as the number when treating CA-MRSA infections because they
of contacts, especially familial, increases. Commu- can help the clinician choose the correct antibiotic.
nity-acquired MRSA infections with secondary fa- In the cases described above, 3 (30%) showed re-
milial transmission have been described in other sistance or intermediate resistance to the macro-
reports.17 Although skin and soft tissues is the most lides, whereas 6 (60%) were sensitive (one was not
common reported site of infection, CA-MRSA has recorded by the laboratory). The clinician needs to
been noted in invasive diseases such as bacteremia, know that treatment of some clindamycin-suscep-
endocarditis, osteomyelitis, and pneumonia.5,9 In tible CA-MRSA strains carrying the erm (erythro-
1999, 4 pediatric deaths in Minnesota and North mycin ribosome methylase) gene can be induced to
Dakota were attributed to CA-MRSA.18 None of become clindamycin-resistant during clindamycin
the 4 children had established risk factors for treatment.15 The possibility for clindamycin resis-
MRSA infection (ie, prolonged hospitalization, in- tance developing in a clindamycin-susceptible,
vasive or surgical procedures, indwelling catheters, erythromycin-resistant organism can be checked by
endotracheal tubes, and prolonged or recurrent the D test. This laboratory test is done by a double-
exposure to antibiotics).2 All 4 pediatric cases de- disk diffusion method in which the clindamycin
scribed above were initially treated with a cephalo- zone becomes “D” shaped when a nearby erythro-
sporin antibiotic to which the organism was resis- mycin disk is used to induce the erm gene effect. In
tant. The delayed use of the correct antibiotic may the United States, the prevalence of this inducible
224 JABFP May–June 2004 Vol. 17 No. 3
clindamycin-resistant strain seems to vary by geo- (southeastern Nebraska through Texas, east to
graphic location. In Chicago and Minnesota, 94% Georgia and southernmost Ohio).16
and 84% of CA-MRSA isolates, respectively, tested Because transmission of CA-MRSA is primarily
positive for inducible clindamycin resistance by the a problem with hygiene, it is important to instruct
D test. In Houston, only 8% of all CA-MRSA the patient and family on methods to prevent its
isolates had a positive D test and thus were less spread. Patients should keep cuts and abrasions
likely to become clindamycin resistant.9 clean by washing with soap and water and to limit
What then would lead the clinician to suspect a contact with common objects (eg, athletic equip-
CA-MRSA infection? In this case review, several ment, towels, benches) and personal items (linen,
factors seemed common. First, the propensity for pillows, clothing).5 Health care providers should
this infection to be misdiagnosed as either a spider use standard precautions to prevent transmission of
bite or some type of skin or soft tissue infection MRSA infections in health care settings.20
(impetigo or furunculosis) based on appearance;
second, the connection of CA-MRSA infections to
correctional facilities—whether as a prisoner, a vis- Conclusion
itor, or someone having close contact with a former In summary, it is probable that CA-MRSA infec-
prisoner; third, the link to sports facilities; and tions are more common in the medical community
fourth, the recurring nature of the infection. Thus, and correctional facilities than clinicians are cur-
some clues to consider when dealing with a possible rently aware. At this time, the Centers for Disease
CA-MRSA skin or soft tissue infection are summa- Control and Prevention (CDC) are performing
rized below: surveillance in several areas across the country to
determine the prevalence and risk factors associ-
●
ated with this organism. A careful, thorough his-
Has the patient had any form of contact with a
tory will help identify those patients who may have
prisoner or prison facility?
●
had contact with CA-MRSA. Questions to ask the
Has the patient or a close contact been treated
patient should include:
for a “spider bite?”
● Has the patient experienced recurring skin infec-
tions such as “impetigo” or “furunculosis?” ● Has the patient had contact with a correctional
● Does the patient play contact sports or have some facility, prisoner or former prisoner?
other form of contact with a sports facility? ● Have they or any of their close contacts been
recently treated or told they had an infection
If a CA-MRSA infection is suspected, any ab- from a spider bite?
scess should be incised and drained and a microbi- ● Have they been treated for recurring skin infec-
ologic culture of wounds performed to determine tions such as impetigo or furunculosis?
appropriate antimicrobial agents.5 Swab specimens ● Do they play any type of contact sports or work
of the anterior nares could be obtained to check for or work out at a gym or other sports facility?
carrier status6 if a patient has a history of recurring
infections. If the patient is found to be a carrier of
CA-MRSA, intranasal mupirocin may be consid- These questions should help the clinician to
ered, although the use of intranasal mupirocin is quickly identify and properly treat infections
not advocated for use with every CA-MRSA infec- caused by CA-MRSA. Ongoing studies by the
tion because of the concern for future resistance.19 CDC should provide more information on the rec-
If a dermonecrotic lesion is identified, it is impor- ognition and treatment of this growing problem in
tant to think not only of CA-MRSA but other health care.21
infections as well— cutaneous anthrax, Lyme dis-
ease, cancerous lesions, and necrotizing fasciitis. A
diagnosis of a brown recluse spider bite should be Many thanks to Michael Parchman, MD, and Abraham Vergh-
ese, MD, for their time, advice, and help writing this article.
made after careful consideration is given to other
Thanks also to Joe Babb and Methodist Health Care Ministries
possible diagnoses, especially if the patient is not for their support of this article and for allowing time for research
within the region endemic to the brown recluse and writing.
Misdiagnosis of Methicillin-Resistant S aureus 225
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