Microbiology Culture Results and Antibiotic Prescribing in Pediatric Patients With Lymphadenitis Free

We conducted a single-center retrospective study including patients <18 years of age admitted with an International Classification of Diseases, Ninth or Tenth Edition diagnosis of acute cervical bacterial lymphadenitis (A18.2, A31.8, I88.1, I88.8, I88.9, L04.0, L04.4, L04.8, L04.9, 017.20, 031.8, 289.1, 289.3, 683) from January 1, 2010 to December 31, 2019. Patients were excluded if they did not have lymph node cultures collected, had a diagnosis of brachial plexus or retropharyngeal abscess, were medically complex (eg, cystic fibrosis, oncologic or rheumatologic process, transplant recipient, chronic diagnosis with functional limitation), presented with inguinal lymphadenitis, were transferred to another facility for insurance purposes, or were admitted for radiology services only.

At our center, lymph node cultures are routinely plated on aerobic and anaerobic media and inoculated into blood culture bottles. Mycobacterial or fungal cultures were only performed on request. Common commensals that were identified in polymicrobial cultures and mycobacteria were analyzed separately.

Three trained reviewers extracted retrospective data from the electronic medical record. Demographic data were collected, including patient age, sex, weight, diagnosis code, primary inpatient service, and consulting teams. Antibiotic data collected included antibiotics administered before admission, inpatient IV and oral antibiotics, duration of each antibiotic, and discharge antibiotics. Blood and lymph node culture results were recorded.

The analysis included the use of descriptive statistics, such as proportions, means, and medians, as appropriate. Data were recorded and stored in a secure Research Electronic Data Capture database.⁹  This study was determined to be exempt by our institutional review board.

A total of 2845 patients were evaluated at our institution with an International Classification of Diseases, Ninth or Tenth Edition code consistent with lymphadenitis over the 10-year study period. Of those patients, 131 were admitted to an inpatient ward and had lymph node cultures collected during their admission (Fig 1). Most patients were admitted to the Hospital Medicine service (84/131; 64.1%) followed by otolaryngology (46/131; 35.1%). On admission, 109 (109/131; 83.2%) patients were started on antimicrobial therapy and 104 of those patients received IV antibiotics (104/109; 95.4%). The most frequently initiated antibiotic regimen was ampicillin-sulbactam (63/131; 48%; Table 1). Of the 131 patients included, 26 did not receive any antimicrobial therapy in the inpatient or outpatient setting before obtaining lymph node cultures (26/131; 19.8%).

There were 95 (95/131; 72.5%) patients with a positive culture result from lymph node aspirate. Of these, 13 were common commensals (coagulase-negative staphylococci, α-hemolytic streptococci, Cutibacterium acnes). Nineteen (19/95; 20%) specimens demonstrated mycobacteria, 18 with Mycobacterium avium complex (18/95; 18.9%); 1 in culture with methicillin-susceptible S. aureus [MSSA]) and 1 with acid-fast bacilli on pathology that only grew coagulase-negative staphylococci (1/95; 1%), some of which were in a polymicrobial culture with common commensals.

All common commensals were clinically considered contaminants and excluded from further analyses. Specimens with mycobacteria were also excluded from further analyses because these pathogens do not typically have the same clinical presentation or treatment course as patients with acute bacterial lymphadenitis.

Focusing on the 72 nonmycobacterial (and noncommensal) isolates, S. aureus was the most common pathogen (56/72; 77.8%), followed by S. pyogenes (10/72; 13.9%) and S. anginosus (5/72; 6.9%; Tables 2 and 3). When looking at susceptibility patterns for these 72 isolates, 80.6%, 86.1%, and 84% were susceptible to cefazolin/cephalexin, ampicillin-sulbactam/amoxicillin-clavulanate, and clindamycin, respectively.

Seventy patients received discharge prescriptions for antibiotics (70/72; 97.2%), including amoxicillin-clavulanate (30/72; 41.7%), followed by clindamycin (18/72; 25%), and cephalexin (13/72; 18.1%).

The etiology of acute bacterial lymphadenitis as described in the literature is varied, and concerns over the role of anaerobic bacteria have made β-lactam/β-lactamase inhibitors the empirical antibiotic choice at many centers. Our aim with this study was to describe the bacteria recovered from cultures of children with bacterial lymphadenitis and determine the proportion of pathogens at our institution that would be adequately covered by more narrow-spectrum antibiotics.

These findings support that the most common bacteria recovered from patients who present with lymphadenitis are MSSA and GAS, whereas anaerobes are not commonly identified. However, when narrow-spectrum empirical antibiotic therapy is employed, a patient’s lack of clinical improvement or the recovery of a pathogen not covered should prompt a reassessment of the clinical diagnosis and antibiotic coverage.^10–12 

Published literature consistently recommends that the treatment of acute bacterial cervical lymphadenitis should target both S. aureus and S. pyogenes, but there is a disagreement over the need for extended anaerobic coverage with a β-lactam/β-lactamase inhibitor.^1,2,7  At other institutions, β-lactams with a β-lactamase inhibitor are recommended to cover S. aureus, S. pyogenes, as well as common anaerobes that colonize the oropharynx, whereas others suggest that cloxacillin, cephalexin, or clindamycin are sufficient.^7,10,13  The results of this retrospective study revealed that, possibly, broad-spectrum antimicrobial agents such as a β-lactam/β-lactamase inhibitor, may only modestly improve coverage of implicated pathogens, but do have higher incidences of causing antibiotic adverse events.¹⁴ 

The results of a similar retrospective study were published from a regional tertiary children’s hospital in 2013.¹⁵  These authors found that, in pediatric patients who were admitted for lymphadenitis and had intraoperative lymph node cultures collected, the most commonly identified pathogens were S. aureus and S. pyogenes, consistent with our findings. Sixty percent of patients were started on IV clindamycin, followed by 22% who received IV clindamycin with ceftriaxone.¹⁵  Antibiotic choices differed from most patients in our study, who received a β-lactam/β-lactamase inhibitor.

The limitations of our study are largely related to the small sample size and a single-center, retrospective design. Because of the small size, less-common pathogens were not observed. As a single center, the pathogens recovered and susceptibilities may not be generalizable to other centers. Additionally, many patients did receive antibiotics in the inpatient or outpatient setting before obtaining lymph node cultures, which could have contributed to the relatively low number of positive culture results and the infrequent identification of anaerobes from cultures. At our center, anaerobic cultures are routinely done on lymph node tissue, but these cultures were not high-yield, and we recognize pretreatment may have influenced results.

As a next step, if an institutional guideline is developed and implemented, it will be important to evaluate the impact of the guideline on patient outcomes. Patients in this study were healthy overall, and these findings may not be generalizable to children with chronic health conditions. In addition, there were a large number of patients who did not meet inclusion criteria but were managed as outpatients for acute bacterial lymphadenitis. Describing current prescribing practices and implementing a guideline in that setting is another opportunity for improving antibiotic stewardship at our institution.

At our institution, the microbiology of patients presenting with acute bacterial lymphadenitis is predominately MSSA or GAS, thus, empirical treatment with more narrow-spectrum antimicrobial agents may be warranted for some patients. Considering a narrower antibiotic regimen for the treatment of bacterial lymphadenitis is worthwhile as a step toward combating antimicrobial resistance and adverse drug events, but more robust clinical data are necessary to determine the safety and efficacy of using more narrow agents in acute bacterial lymphadenitis.