AT ASM MICROBE 2016
BOSTON (FRONTLINE MEDICAL NEWS) – An underappreciated cause of bacterial pharyngitis had a similar clinical presentation to group A Streptococcus (GAS), although prevalence was low in the population of 300 pediatric patients in a single-site study.
The 10 patients (3.3%) who had positive cultures for Fusobacterium necrophorum were about as likely as those with GAS to have fever, sore throat, exudate, and absence of cough. GAS cultures were positive in 57 (19%) of the patients.
F. necrophorum is a common cause of serious bacterial pharyngitis, especially in adolescents and young adults. The gram-negative species, an obligate anaerobe, is a cause of Lemierre’s syndrome, and “has recently been identified to be an important pathogen of bacterial pharyngitis with higher prevalence than group A Streptococcus (GAS) in adolescents and young adults,” wrote Tam Van, Ph.D., and her colleagues in a poster presented at the annual meeting of the American Society for Microbiology.
To examine the prevalence and disease characteristics of F. necrophorum in the emergency department patient population at Children’s Hospital of Los Angeles, Dr Van, a medical microbiology fellow at the hospital, and her colleagues enrolled 300 patients with pharyngitis aged 1-20 years (mean, 7.8 years).
All patients’ throats were swabbed, and investigators conducted a rapid antigen detection test (RADT) for group A beta-hemolytic Streptococcus and cultured samples for Streptococcus on a blood agar plate, according to usual care; samples also were cultured anaerobically and tested via polymerase chain reaction (PCR) for F. necrophorum.
A total of 67 patients had positive culture or PCR results for both species. Fifteen of the RADT tests were positive, while 57 cultures returned positive for GAS growth. Nine of the 10 positive F. necrophorum PCR tests correlated with positive culture results for that species.
Luckily, said Dr. Van, penicillin is an effective treatment for F. necrophorum, although it’s a gram-negative bacterium, so if a patient is coinfected with F. necrophorum and GAS, or treated for GAS empirically, then standard of care treatment should be effective, she said. However, since the species is associated with serious complications such as Lemierre’s disease, close follow-up and a low threshold for aggressive treatment are warranted if F. necrophorum is suspected or identified.
The relatively low positive culture rate of 3.3% for F. necrophorum in the study population was a bit surprising, Dr. Van said in an interview but was perhaps accounted for by the relatively young age of the Children’s Hospital Los Angeles patients. “Previous reports looked at adolescents and young adults,” wrote Dr. Van and her colleagues, while two-thirds of the patients in their study were under the age of 10 years. “This may contribute to the difference in prevalence.”
“Although rare, recovery of F. necrophorum correlated with true signs and symptoms of bacterial pharyngitis,” wrote Dr. Van and her colleagues. Serious pharyngitis with a negative rapid test and culture for group A Streptococcus should prompt clinical suspicion for F. necrophorum, especially in older adolescents and young adults, said Dr. Tam.
Dr. Tam and her coauthors reported no outside sources of funding and reported no relevant financial disclosures.
On Twitter @karioakes
