Neonatal Bacteremia Caused by Herbaspirillum huttiense in a Neonatal Intensive Care Unit: A Case Series

Herbaspirillum huttiense is a rare environmental Gram-negative bacillus increasingly recognized as an emerging opportunistic pathogen in humans. Due to its phenotypic similarities with other non-fermenting Gram-negative bacteria, it is frequently misidentified, and data on its clinical characteristics and management remain limited.

This was a retrospective case series study conducted over one month (March 2023) in the Microbiology Department of Mohammed VI University Hospital, Marrakesh, Morocco. The study included neonates hospitalized in the Neonatal Intensive Care Unit (NICU) with at least one positive blood culture for Herbaspirillum spp. Patients with negative blood cultures or with bloodstream infections caused by pathogens other than Herbaspirillum spp. were excluded. Clinical and biological characteristics, including signs of sepsis, were collected retrospectively from medical records for descriptive analysis. Identification was performed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS, BD, Franklin Lakes, NJ). Antimicrobial susceptibility testing was performed using the automated Phoenix M50 system (BD Diagnostics, Sparks, MD) in accordance with EUCAST guidelines. Only descriptive statistics were used.

Six neonates were included in the study, with an equal sex distribution (three males and three females). The majority were preterm infants (83.3%), with a mean gestational age of 34.2 weeks (range: 30.4-37.4 weeks) and a mean birth weight of 2.3 kg (range: 1.48-3.20 kg). Most deliveries were vaginal (83.3%). The main reasons for admission were neonatal respiratory distress (66.7%), followed by neonatal seizures and hypoglycemia (16.7% each). Comorbidities included severe perinatal asphyxia, persistent pulmonary hypertension of the newborn, and omphalocele. During hospitalization, the neonates developed clinical signs of sepsis after a mean delay of seven days (range: days four and nine), presenting with fever, tachycardia, and skin mottling. Biologically, patients developed leukopenia (mean leukocyte count: 9,500/mm³), elevated C-reactive protein (CRP) levels (mean: 89 mg/L), and thrombocytopenia (mean platelet count: 77,833/mm³). Blood cultures became positive after incubation, yielding Gram-negative, oxidase-positive bacilli identified as H. huttiense. The isolates were susceptible to carbapenems, cefepime, and amikacin, but resistant to colistin. All patients had a favorable outcome, with a 100% survival rate and a mean hospital stay of 16 days.

H. huttiense is an emerging opportunistic pathogen in neonatal infections, often associated with diagnostic challenges due to misidentification. Advanced diagnostic tools such as MALDI-TOF significantly improve detection. Although no standardized treatment guidelines exist, most isolates appear susceptible to broad-spectrum antibiotics, with favorable clinical outcomes under appropriate therapy.