Hao and Wang BMC Pediatrics(2024) 24:527
https://doi.org/10.1186/s12887-024-05004-6

BMC Pediatrics

CASE REPORTOpen Access

Successful treatment of Enterococcus
gallinarum infection in a neonate
with vancomycin: a case report
Liangjie Hao1 and Han Wang2*
Abstract
Background Enterococcus gallinarum (EG) is typically found in the gastrointestinal tracts of birds and mammals.
Although its strains are rarely isolated from clinical specimens, EG can lead to septicemia in immunocompromised
individuals. EG infections are uncommon in household settings, but their incidence has been rising due to increased
antibiotic usage and invasive treatments, particularly in Neonatal Intensive Care Units (NICUs). EG inherently exhibits
resistance to vancomycin but is highly sensitive to linezolid. Despite showing in vitro resistance, vancomycin has
shown clinical efficacy in treating EG meningitis.
Case presentation A neonate born at 30 + 2 weeks gestation was admitted to the Neonatal Intensive Care Unit(NICU) after EG was detected in blood and cerebrospinal fluid cultures. Susceptibility testing indicated that thebacterial strain was resistant to vancomycin and sensitive to linezolid. Initially, vancomycin was selected for treatment.
However, due to persistent EG cultures in the blood and cerebrospinal fluid, the treatment was adjusted to linezolid.
This led to a rapid decrease in platelet (PLT) count, suspected to be an adverse reaction. Concurrently, the patient
experienced recurrent fever and elevated inflammatory marker levels, prompting the discontinuation of linezolid anda return to vancomycin. Subsequent administration of vancomycin stabilized the patient’s condition, as evidenced
by improved C-reactive protein (CRP), procalcitonin (PCT), and cerebrospinal fluid parameters, ultimately leading todischarge after an eight-week treatment period.
Conclusion This retrospective analysis highlights the efficacy of vancomycin in treating EG infections, suggestingthat specific genetic phenotypes may influence treatment sensitivity. Monitoring vancomycin blood levels is crucialfor determining treatment effectiveness.
Keywords Neonate, Enterococcus gallinarum (EG), Linezolid, Vancomycin, Adverse reaction*Correspondence:
Han Wang
shoes724@163.com
1Department of Pharmacy, Linfen Maternal and Child Health HospitalChildren’s Hospital, Linfen 041000, China
2Department of Pharmacy, Chengdu Women’s and Children’s Central
Hospital, School of Medicine, University of Electronic Science andTechnology of China, Chengdu 611731, China© The Author(s) 2024. Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0
International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you
give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified thelicensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images orother third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to thematerial. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation
or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.

Hao and Wang BMC Pediatrics(2024) 24:527

Background
Enterococcus gallinarum (EG) is a predominant component of the normal flora in the intestinal tracts of avian
species. Although its strains are seldom isolated fromclinical specimens, EG, a facultative anaerobe, catalasenegative, chain-forming gram-positive D-group coccus,
is occasionally found in human foods such as fish, meat,and cheese. In immunocompromised hosts, EG can leadto septicaemia. Despite some reports, the clinical epidemiology of EG remains poorly understood. Colonizationand infection by species of the E. gallinarum group areless frequent than those of other well-known enterococcal species, such as E. faecalis and E. faecium. However, according to existing trends, their frequency may
increase worldwide [1]. Although the isolation of EG
from cerebrospinal fluid is infrequent, its occurrence has
been rising due to increased antibiotic use and invasive
therapeutic interventions, particularly in NICUs [2]. EG
inherently exhibits resistance to vancomycin but showshigh sensitivity to linezolid [3]. Despite in vitro resistance, vancomycin has demonstrated clinical efficacy intreating EG meningitis.
Case presentation
A male neonate, born at 30 + 2 weeks gestation andweighing 1.79 kg, was admitted to a local hospital due
to progressive leukopenia over three days. Initially, theinfant received noninvasive ventilation and ceftazidime
for infection control. However, day 1 of admission at thelocal hospital, a decrease in leukocytes prompted a switch
to cefepime/tazobactam. Day 2 of admission, frequentepisodes of respiratory arrest necessitated invasive ventilatory support, and further leukocyte reduction led to theinitiation of meropenem. Day 3 of admission, blood culture revealed the presence of EG, and cerebrospinal fluid
examination indicated purulent meningitis with a whiteblood cell (CSF-WBC) count of 10,050 × 106/L and a protein concentration of 3120 mg/L. In response, vancomycin was initiated for infection control, and the patient
was transferred to our hospital for further management.
Upon admission, the infant exhibited a temperature of
36.5 °C, a pulse rate of 140 beats/min, a respiratory rateof 53 breaths/min, a blood pressure of 57/34 mmHg, andan oxygen saturation of 98% (under normobaric oxygensupply). The infant did not display seizure activity but
showed poor responsiveness without irritability or agitation. Blood tests revealed a white blood cell (WBC)count of 9.23 × 109/L, a neutrophil percentage (NE%) of
58.5%, a platelet (PLT) count of 71 × 109/L, a C-reactive
protein (CRP) level of 101 mg/L, and a procalcitonin(PCT) level of 12.28 ng/mL. Cranial ultrasonography
revealed no significant abnormalities. On the first day
after admission, the infant received intravenous meropenem (0.71 g, 40 mg/kg) and vancomycin (0.027 g, 15 mg/Page 2 of 4kg) every 8 h. By the fifth day, the blood concentrationof vancomycin reached 38.4 µg/mL, leading to a dose
reduction to 10 mg/kg every 12 h. On the sixth day, blood
tests revealed a WBC of 12.13 × 109/L, an NE percentage of 46.9%, a PLT of 288 × 109/L, a CRP concentrationof 9 mg/L, and a PCT concentration of 0.58 ng/mL. Cultures from cerebrospinal fluid and blood confirmed thepresence of EG (identified using bile esculin agar (BEA)and biochemical reactions). Drug sensitivity tests (usingthe broth method and MIC method) demonstrated resistance to vancomycin (minimum inhibitory concentration (MIC) of 1 mg/L), penicillin (MIC ≥ 64 mg/L) andampicillin (MIC ≥ 32 mg/L), but sensitivity to tetracycline(MIC ≤ 8 mg/L) and linezolid (MIC of 2 mg/L). CSF analysis revealed a CSF-WBC of 518 × 106/L, a protein concentration of 3549 mg/L, a glucose concentration of 1.15mmol/L, and a chloride concentration of 134.2 mmol/L.
The laboratory indicators and antimicrobial agents used
are detailed in Table 1.
Despite a decrease in inflammatory markers and cerebrospinal fluid leukocyte count, the patient continued
receiving combined therapy with meropenem and vancomycin, while the patient’s condition was continuously
monitored. On the 11th day, the vancomycin concentration was 9.02 µg/mL. By the 14th day of treatment, withno significant reduction in cerebrospinal fluid protein(CSF-WBC 266 × 106/L, protein 3453 mg/L), vancomycin
was changed to linezolid (0.02 g, 10 mg/kg) administeredintravenously every 8 h, based on drug sensitivity results
and treatment experience. On the 18th day after admission, the patient developed a fever of 37.7 °C. Blood tests
revealed a WBC of 9.63 × 109/L, an NE% of 29.9%, a PLTof 55 × 109/L, a CRP of 54 mg/L, and a PCT of 1.98 ng/
mL. Cerebrospinal fluid re-examination revealed a CSFWBC of 131 × 106/L and a protein level of 3141 mg/L.
Despite a decrease in CSF-WBC following linezolid
treatment, recurrent fluctuations in blood inflammatory
markers and an insignificant reduction in cerebrospinal
fluid protein were observed, along with a rapid decline in
PLT count.
Given the child’s improvement during previous vancomycin treatment and previous literature indicating that
vancomycin had a gene phenotype of low-level resistance to EG, linezolid was discontinued for infection
control. Treatment was adjusted to meropenem (0.09 g,40 mg/kg) and vancomycin (0.02 g, 10 mg/kg) administered intravenously every 8 h, with the goal of maintaining vancomycin blood concentrations between 10 and15 µg/mL. On the 19th day after admission, blood tests
revealed a WBC of 8.44 × 109/L, an NE% of 33.7%, and a
PLT of 115 × 109/L, with a CRP level of 19 mg/L, indicating a recovery in PLT count. On the 21st day after admission, the vancomycin blood concentration was 10 µg/mL. CSF examination revealed a CSF-WBC of 74 × 106/L,

Hao and Wang BMC Pediatrics(2024) 24:527

Page 3 of 4

Table 1 Laboratory indicators and the use of antimicrobial agents

D1D6D14D17D18
D19
D21
D24
D29
D37
D47
D56

Culture results

Antimicrobial therapy

WBC (109/L)

PLT (109/L)

CRP (mg/L)

PCT (ug/L)

CSF-Protein (mg/L)

EG

Meropenem + vancomycin

9.23
12.13
6.84

71
288
396

101
9
7

12.28
0.58

3120
3549
3453

CSF-WBC(109/L)
10,050
518
266

9.63
8.44

55
155

54
19

1.98

3141

131

7338

1

6.29
7.96

329
579

12566
2280
2030
1768
1559
1365

74
97
57
43
26
14

Linezolid
Meropenem + vancomycinNO

EG = Enterococcus gallinarum
WBC = White blood cell count
PLT = Platelet count
CRP = C-reactive protein
PCT = Procalcitonin
CSF = Cerebrospinal fluid
NO = No growth

a protein level of 2566 mg/L, and a glucose level of 1.38mmol/L. Subsequent cultures from cerebrospinal fluidand blood showed no bacterial growth, confirming treatment efficacy. The treatment lasted for eight weeks until
the patient’s inflammation indices returned to normal.
At discharge, blood tests revealed a WBC of 7.96 × 109/L,
an NE% of 18.7%, a PLT of 579 × 109/L, and a CRP levelof 19 mg/L. Cerebrospinal fluid examination revealed aCSF-WBC of 14 × 106/L and a protein level of 1365 mg/L.
During the course of medication, the patient experienced
mild, tolerable gastrointestinal reactions without severe
adverse effects. Multiple head ultrasound and MRI scans
during the hospital stays indicated good brain development. The patient displayed excellent development in
subsequent follow-ups with no residual neurologicalsymptoms.

Discussion and conclusions
EG infections are typically observed in immunocompromised individuals and post-trauma surgical patients [3].
In this particular case, the patient was a premature infantborn at 30 weeks gestation. EG infection was confirmed
through blood and cerebrospinal fluid cultures uponadmission to the local hospital. Sensitivity testing indicated the susceptibility of EG to linezolid. For such cases,
the recommended pediatric dosage for linezolid is 10 mg/kg every 8 h for children aged 12 years or younger. Common adverse effects include diarrhea and decreased PLT
count [4]. After three days of linezolid treatment, blood
tests revealed a PLT count of 55 × 109/L. Furthermore,
the absence of routine monitoring of linezolid blood concentrations has hindered tailored dosage adjustment forpatients, potentially contributing to this adverse reaction[5, 6]. Thus, linezolid therapy was discontinued.
EG is naturally resistant to vancomycin. Enterococcus
strains can be classified into VanA, VanB, and VanC phenotypes based on glycopeptide resistance. EG strains carrying the VanC gene typically exhibit low-level inherent
resistance to vancomycin, displaying either in vitro sensitivity or low-level resistance [1, 7]. The low resistance ofEG to vancomycin might explain its mode of action.
After the initial treatment, adjusting the frequency ofvancomycin to q12h due to higher blood concentrations
resulted in decreased therapeutic effectiveness. A randomized study showed that a dosage of 15 mg/kg q12h
in premature infants was insufficient for adequate plasma
exposure, while 12 mg/kg q8h improved both efficacy andsafety [8]. Newborns under 29 weeks and those between
29 and 35 weeks of gestation required higher final doses
to achieve therapeutic levels, necessitating approximately
2x and 1.5x the empirical dosing, respectively [9]. Thechange in vancomycin frequency from q8h to q12h earlyin treatment led to slight improvements in cerebrospinal
fluid protein levels. However, the compromised antimicrobial effect may be attributed to lower blood concentrations and reduced dosing frequency. For neonatal andpediatric patients, vancomycin concentrations between 5and 15 mg/L are recommended [10]. However, there aresubstantial interindividual differences in the vancomycin dosages required to achieve therapeutic concentrations in critically ill children. Many dosing regimens failto meet these targets, highlighting the need for optimized
dosing to prevent inadequate treatment. A concentration
range of 10–20 mg/L is considered effective and safe [11].

Hao and Wang BMC Pediatrics(2024) 24:527

Therefore, in neonatal treatment, the dosage and frequency of vancomycin administration must be carefully
adjusted according to the patient’s specific conditions toensure both therapeutic efficacy and safety.
Although vancomycin is not the first-line treatment for
EG infections, different genetic phenotypes of EG can
exhibit varying sensitivities to vancomycin in clinical scenarios. In our case, vancomycin trough concentrationsin premature infants were continuously monitored andmaintained within an effective range of 10–15 µg/mL,
successfully treating EG meningitis.
A retrospective analysis highlighted the efficacy of vancomycin in treating EG infections, with sensitivity potentially influenced by specific genetic phenotypes of thebacterium. Monitoring vancomycin blood levels proved
crucial for ensuring treatment effectiveness. Attention
was also given to the impact of linezolid on PLT countsin premature infants. Future expectations include moreclinical data to assist NICU physicians in selecting optimal antimicrobial strategies against EG, minimizing
adverse reactions, and improving clinical cure rates.
This case demonstrates the importance of personalized treatment and emphasizes the necessity for flexible
treatment regimen adjustment based on the individual
responses and clinical needs of pediatric patients, especially in the absence of direct evidence.
Abbreviations
EG	Enterococcus gallinarum
NICUs	Neonatal Intensive Care UnitsNICU	Neonatal Intensive Care Unit
PLT	Platelet
CRP	C-reactive protein
PCT	Procalcitonin
CSF	Cerebrospinal fluidWBC	White blood cell countNE%	Neutrophil percentage
MIC	Minimum inhibitory concentration
BEA	Bile esculin agar
MRI	Magnetic Resonance Imaging
Acknowledgements
Thanks for the help from various departments during my clinical pharmacist
training in Chengdu Women’s and Children’s Central Hospital.
Author contributions
LH drafted the initial manuscript, and reviewed and revised the manuscript.
HW reviewed and revised the manuscript. All authors read and approved thefinal manuscript.
FundingNone.
Data availability
Data related to the case are presented in this article.

Page 4 of 4

Declarations
Ethics approval and consent to participate
As this is a case report, ethics approval is not reruired as per our institution’spolicy.
Consent for publication
Written informed consent was obtained from the baby’s parents to publish
the clinical details.
Competing interests
The authors declare no competing interests.
Received: 5 May 2024 / Accepted: 9 August 2024

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