P2.N261: Urinary tract infection caused by Gardnerella vaginalis in a 6 week old infant

Introduction: Gardnerella vaginalis is a frequent cause of bacterial vaginosis (BV) in adults. However, G. vaginalis infection is infrequent in infants. Only a few cases of G. vaginalis UTI have been reported so far in infants and none in the United States.

Case Description: A 6-week-old female, ex full-term at 39 3/7 weeks via vaginal delivery with no significant postnatal medical history, presented with a 2-day history of fever, mild cough, and congestion.

In the emergency department, the patient was febrile to 38.1°C, pulse 139 beats/minute, respiratory rate 34 breaths/minute, and SpO2 98% on room air. She was active and alert. Physical examination was normal except for congestion. Laboratory data was significant for mild leukopenia of 3500/μL and normal CRP of 2.5 mg/L. The nasopharyngeal swab came back positive for SARS-CoV-2. The catheterized urine showed 21-50 WBC/hpf and +3 leukocyte esterase. The working diagnosis was upper respiratory infection by SARS-CoV-2 with a suspected UTI. The patient was started empirically on ceftriaxone 50 mg/kg/dose every 24 hours. She became afebrile on day 2 and her urine culture grew >100,000 CFU/ml G. vaginalis. Blood culture remained negative. Renal and bladder ultrasound (RBUS) revealed bilateral grade 2 hydronephrosis. There was no history of hydronephrosis on prenatal ultrasound. Antimicrobial susceptibility for G. vaginalis couldn’t be obtained and antibiotic was switched to oral metronidazole (10 mg/kg/dose every 8 hours) for a total of 7 days followed by prophylactic amoxicillin (15 mg/kg daily). The voiding cystourethrography (VCUG) done one month after discharge showed mild grade 2 vesicoureteral reflux (VUR) on the left side, hence antibiotic prophylaxis was stopped.

Discussion: To the best of our knowledge, our patient was the youngest among the few reported cases of G. vaginalis UTI in children. Our patient had >100,000 CFU/ml G. vaginalis with abnormal RBUS and grade 2 VUR, all pointing to a true infection of G. vaginalis rather than a contamination from the vulva. Furthermore, there was no concern of sexual abuse, and her vulva exam was normal. The mother denied any maternal history of BV during pregnancy.

Although we treated our patient successfully with metronidazole, previously reported cases have all been treated with penicillin derivatives. Since getting antibiotic susceptibilities for G. vaginalis is a challenge, it is important to know the antibiotic choices available.

A previous study showed that the rate of UTI in infants < 90 days with positive SARS-CoV-2 was 5.4%, which is significant. Our case report would reiterate the need to perform urinalysis in all febrile infants with positive SARS-CoV-2 who otherwise could be potentially excluded based on the AAP febrile infant guidelines based on the provider’s decision-making, especially infants >28 days old.

Conclusion: Gardnerella vaginalis could cause UTI in infants.