Retropharyngeal abscess is a deep neck infection of the area between the posterior pharynx and the prevertebral fascia that has been reported to occur most frequently in children 1–5 years of age.1,2 The microbiology of retropharyngeal abscesses is not clearly defined. However, the location and likely pathophysiology together with published surgical culture data suggest that streptococcal species, particularly Streptococcus pyogenes [group A streptococci (GAS)], predominate, followed by Staphylococcus aureus (S. aureus), anaerobes, and Gram negative oral flora. Infections are often polymicrobial.1–7
Prior case reports of methicillin-resistant Staphylococcus aureus (MRSA) retropharyngeal abscess8–11 have been documented in the literature. We present 2 cases of extensive MRSA retropharyngeal abscess in immunocompetent infants (1 in the context of a reactive jugular venous thrombosis) and suggest that the microbiology and clinical characteristics of this retropharyngeal infection may be changing in accordance with increasing MRSA prevalence.
CASE REPORT 1
A previously healthy 3-month-old female was admitted with fever, irritability, and left-sided neck swelling that began 1 day before admission. The neck was erythematous and tender. The patient had not had recent sick contacts, pet exposure, or travel, and her birth history was unremarkable. On admission, body temperature was 39.6°C. The patient was generally well-appearing, but irritable. Physical examination revealed a full but soft anterior fontanelle. There was no rhinorrhea or excessive drooling, but her oropharynx was mildly erythematous. Her neck was edematous, erythematous, and tender to palpation from the left angle of the mandible to the anterior border of the left sternocleidomastoid. The remainder of the physical examination was unremarkable.
The following laboratory data were obtained: white blood cell count 20,400/mm3 with 62% neutrophils; rapid strep test and throat culture negative; C-reactive protein 6.4 mg/dL; blood culture showed no growth. Computerized tomography of the neck and chest revealed prevertebral/retropharyngeal low attenuation extending from the first cervical vertebral body inferiorly to the mediastinum surrounding the great vessels. Ultrasound examination of the neck showed left internal jugular vein thrombosis from the central internal jugular vein to the base of the skull. Incision and drainage of the abscess was performed, and culture of the purulent material grew MRSA, which was susceptible to clindamycin (by disc diffusion and d-test). The patient was treated parenterally with clindamycin.
During the ensuing 15 days, the fever subsided, the patient's neck swelling decreased in size, and she was sent home to receive oral clindamycin and subcutaneous enoxaparin. Immunologic and hypercoagulability evaluations revealed no abnormalities. Two weeks after discharge, the patient's neck swelling and other symptoms had resolved.
CASE REPORT 2
A previously healthy 4-month-old male was admitted for increased sleepiness, poor oral intake, and cough during the 2 days before admission, preceded by 7 days of rhinorrhea and irritability. The patient had not had recent sick contacts, pet exposure, or travel, and his birth history was unremarkable. On admission, his body temperature was 36.8°C. Physical examination revealed an open and flat anterior fontanelle. Thick rhinorrhea was present. Neck examination on admission was notable only for 1 small, mobile, nontender, occipital lymph node. The remainder of the physical examination was unremarkable. The following laboratory data were obtained on admission: white blood cell count 18,500/mm3 with 62% neutrophils; urinanalysis did not show signs of inflammation; urine culture grew Escherichia coli >100,000 cfu and Klebsiella spp. >50,000 cfu, both susceptible to ciprofloxacin; blood culture was sterile.
The patient had persistent lethargy and had increasing right neck swelling. Computerized tomography of the neck revealed extensive right retropharyngeal abscess extending from the palatine tonsils and adenoids to the level of the carotids inferiorly. Incision and drainage of the abscess was performed and culture of the purulent material had large growth of MRSA susceptible to clindamycin (by disc diffusion and d-test) and ciprofloxacin, as well as moderate growth of Pseudomonas aeruginosa, light growth of Klebsiella pneumonia, and peptostreptococcus. The patient was treated with parenteral clindamycin and parenteral ciprofloxacin.
In the next 5 days, the patient's neck swelling decreased, and he was sent home to receive oral ciprofloxacin therapy. An immunologic evaluation was unrevealing. At re-evaluation 2 weeks after hospital discharge, the patient's neck swelling and other symptoms had resolved.
We report 2 cases of MRSA-associated retropharyngeal abscesses that occurred in young infants and which were more severe than has previously been described: 1 infant had an abscess that extended into the mediastinum and was complicated by venous thrombosis.
A retropharyngeal abscess typically arises secondary to an infection of the nasopharynx, paranasal sinuses, or middle ear that drains to the retropharyngeal lymph nodes. Retropharyngeal nodes regress at about 5 years of age, and the median age for presentation is 36 months.1 Prior retrospective studies have shown that only 15% of cases of retropharyngeal abscess occur in children less than 12 months of age.1,5,8,9 Two studies specifically evaluated infants less than 1 year old with deep neck abscesses and noted a higher prevalence of S. aureus deep neck infections in young children, as we observed in our patients.8,9 This is hypothesized to be a reflection of an alternate location of the abscesses (anterior and posterior triangles in infants as opposed to retropharyngeal or parapharyngeal in older children).
To date, there have been only rare reports of MRSA as a cause of retropharyngeal abscess10–13; a recent series that included data collected through 1999 found that 43 of 46 cases of S. aureus retropharyngeal abscess were the result of methicillin-susceptible S. aureus (MSSA).9 We hypothesize that as community-acquired MRSA becomes increasingly prevalent,14 particularly in infants and children,15,16 MRSA will become a more common cause of retropharyngeal abscess. We believe that community-acquired MRSA may cause more extensive pathology than typically develops in patients with retropharyngeal abscesses caused by GAS or MSSA. MRSA bacteremia and surgical site infections are associated with greater morbidity and mortality than MSSA infections, suggesting that this pathogen may be a more virulent organism.17–19
The overall incidence of retropharyngeal abscess seems to be increasing1,5,8,20 and has been attributed to improved radiologic detection methods, decreased initial use of antibiotics for oropharyngeal infections,5 and increased virulence of GAS, the significance of which remains to be fully elucidated.5,20,21 The incidence of retropharyngeal abscess may be expected to increase further with an increasing prevalence and virulence of MRSA infections, particularly in infants. In addition to the increased frequency and more extensive pathology, we postulate that, as with our patients, retropharyngeal abscesses associated with MRSA may target a younger than expected age group already prone to S. aureus deep neck infections.8,9 MRSA skin and soft tissue infections increased in prevalence in neonates, concordant with an increase in maternal skin infections.15
Retropharyngeal abscess with concomitant internal jugular venous thrombosis is rare but has been well-described in the context of Lemierre syndrome when associated with septic emboli and Fusobacterium necrophorum bacteremia.22,23 Our first patient did not have classic Lemierre syndrome, and venous thrombosis was likely because of severe infection-related inflammation. We hypothesize that the likelihood of thrombosis might be increased in the setting of MRSA retropharyngeal infections, as the presence of MRSA Panton-Valentine leukocidin virulence factor has been recently associated with increased incidence of lower extremity infections complicated by deep venous thrombosis.24
The treatment of retropharyngeal abscess consists of empiric antibiotic treatment and surgical drainage, although clinicians debate the need for and timing of surgical drainage in some cases.1,5 Historically, empiric antibiotic treatment has been clindamycin or ampicillin/sulbactam.1,5 However, clindamycin may now be the most appropriate choice of therapy for patients who present with deep neck abscesses in regions with a high prevalence of MRSA. In addition, although the isolates reported here were susceptible to clindamycin, clindamycin-resistant S. aureus is prevalent in some regions and should be considered along with the possibility of a Gram-negative infection in a patient not responding to clindamycin therapy.
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