Antimicrobial Susceptibility Profile of Eggerthella lenta Isolated From Bloodstream and Abdominal Fluid Infections
Funding: This work was supported by Chongqing Technology Innovation and Application Development Special General Project, Grant/Award Number: 2023TIAD-GPX0126; Chongqing Medical Scientific Research Project (Joint Project of Chongqing Health Commission and Science and Technology Bureau), Grant/Award Number: 2025MSXM004; Key Project of Science and Technology Research by Chongqing Municipal Education Commission, Grant/Award Numbers: KJZD-K202400102 and KJZD-K202400103; Medical Research Project of Chongqing Municipal Health Commission, Grant/Award Number: 2024WSJK007.
Yuan Gao and Longfeng Qu contributed equally to this work and shared co-first authorship.
ABSTRACT
Background
Eggerthella lenta is an anaerobic gram-positive bacillus associated with severe bloodstream infections and high mortality rates. However, limited antimicrobial susceptibility data in China hinder effective clinical treatment. We aimed to address this by analyzing the antimicrobial susceptibility profiles of E. lenta strains isolated from bloodstream and abdominal fluid infections to provide evidence-based guidance for empirical treatment in clinical practice.
Methods
This study reviewed 36 cases of E. lenta isolated and cultured from bloodstream and abdominal fluids between 2018 and 2024. The isolates were identified using various methods, including the VITEK 2 ANC card, MALDI-TOF mass spectrometry, and a 16S rRNA gene sequencing assay. Antimicrobial drug susceptibility testing of the 36 E. lenta isolates was conducted using the agar dilution method. A minimum inhibitory concentration (MIC) fold analysis was performed with reference to the CLSI and EUCAST guidelines.
Results
The identification of E. lenta was performed using VITEK-2, MALDI-TOF MS, and 16S rRNA sequencing. All methods showed high consistency, with 16S rRNA sequencing confirming the species classification of the isolates. Eggerthella lenta exhibited varying degrees of resistance to penicillin, ampicillin, ceftriaxone, levofloxacin, clindamycin, ceftazidime, imipenem, piperacillin-tazobactam, and amikacin. Conversely, the bacterium was sensitive to amoxicillin-clavulanic acid, moxifloxacin, chloramphenicol, metronidazole, and vancomycin.
Conclusions
These findings indicate that metronidazole, amoxicillin-clavulanic acid, moxifloxacin, and vancomycin are the preferred empirical treatments for E. lenta. Furthermore, there is an urgent need to optimize anti-E. lenta treatment guidelines and the MIC threshold values for piperacillin-tazobactam to ensure a close correlation with clinical data and to accurately guide the effective management of invasive E. lenta infections.
Abbreviations
-
- AST
-
- antimicrobial susceptibility testing
-
- CLSI
-
- American Clinical and Laboratory Standards Institute
-
- EUCAST
-
- European Committee on Antimicrobial Susceptibility Testing
-
- MALDI-TOF MS
-
- matrix-assisted laser desorption/ionization time-of-flight mass spectrometry
-
- MIC
-
- minimum inhibitory concentration
1 Introduction
Eggerthella lenta, a non-budding, exclusively anaerobic, gram-positive bacillus, has garnered significant attention in the medical community since its initial report in 1935 [1]. This bacterium primarily colonizes the human gastrointestinal tract, female genital tract, oral cavity, and prostate gland, which constitute the normal flora of the body (gastrointestinal tract, lumen, and mucous membranes) [2-6]. It can also induce pathological conditions, such as appendicitis, endometritis, and liver abscesses [7-9], and has the potential to precipitate bloodstream infections, such as bacteremia [10-12]. In cases of bacteremia, particularly chronic bacteremia, symptoms may not be as pronounced as in acute bacteremia; however, patients may still exhibit persistent nonspecific symptoms, such as low-grade fever, malaise, and anorexia [12]. Accumulating evidence indicates that E. lenta can cause infections at multiple anatomical sites as well as bloodstream infections, with the overall mortality rate associated with infection ranging from 22% to 43% [4, 13, 14].
Blood bacterial culture is a critical step in the diagnosis of bacteremia and facilitates the identification of infection. However, owing to the slow growth of E. lenta, which necessitates an extended period for culture and identification, treatment of patients is often delayed, potentially leading to serious consequences. Therefore, early empirical treatment is of particular importance. Nevertheless, the variability in the antimicrobial susceptibility profiles reported in the literature complicates clinical guidance [15-17]. This indicates that E. lenta is highly susceptible to metronidazole, amoxicillin-clavulanic acid, vancomycin, clindamycin, and carbapenems, but frequently demonstrates resistance to penicillin, ceftriaxone, and cefotaxime [18, 19]. Notably, the empirical use of piperacillin-tazobactam for the treatment of E. lenta bloodstream infections has been identified as an independent risk factor for increased mortality [13]. However, piperacillin-tazobactam continues to be widely used clinically for the treatment of E. lenta bloodstream infections, necessitating careful consideration of the clinical application of this antimicrobial agent. Given the high mortality rate associated with E. lenta bloodstream infections, the absence of a clinical consensus on treatment, and increasing anaerobic resistance, there is an urgent need to elucidate the antimicrobial susceptibility profile of E. lenta.
In this study, we conducted a retrospective analysis of 36 strains of E. lenta isolated from the bloodstream and abdominal fluid culture specimens of clinical patients in Chongqing University Jiangjin Hospital from October 2018 to September 2024. We examined their clinical microbiological characteristics and compared the results of various identification methods and antimicrobial drug sensitivities. The objective of our study was to analyze the antimicrobial susceptibility profiles of E. lenta isolated from bloodstream and abdominal fluid infections, and then apply our findings to update current guidance on the empirical treatment of E. lenta infections in clinical practice.
2 Materials and Methods
2.1 Clinical Data Collection
This study was conducted at Chongqing University Jiangjin Hospital in Chongqing, China. Cases were identified by searching our microbiology database for data from October 2018 to September 2024 for all blood cultures positive for E. lenta. Clinical data were collected from medical records. As this was a retrospective study using existing medical records with minimal risk to patients, and obtaining individual consent was impracticable without compromising the scientific validity of the research, the requirement for written informed consent was waived by the Medical Ethics Committee of Chongqing University Jiangjin Hospital. The Medical Ethics Committee of Chongqing University Jiangjin Hospital approved patient-related data obtained from medical records, including age, sex, comorbidities, surgical history, blood culture results, type of antimicrobials used for treatment, and 30-day mortality, as presented in Table 1.
| Patient clinical characteristics | Values (n = 36) |
|---|---|
| Age (years) (median, range) | 72 (48–89) |
| Gender, n (%) | |
| Male | 21 (58.3) |
| Body temperature (°C) (mean, range) | 39.3 (36.5–39.7) |
| Laboratory data (mean, range) | |
| WBC count (×109/mm3) | 14.45 (2.44–19.16) |
| Pct (ng/mL) | 4.62 (0.34–18.93) |
| CRP (mg/L) | 169.8 (60.0–> 200.0) |
| Microbiological characteristics | |
| Mean time to blood culture positive (hours) (mean, range) | 72 (56.9–120.0) |
| Polymicrobial bacteremia, n (%) | 12 (33.3) |
| Comorbidities, n (%) | |
| Cancers | 11 (30.6) |
| Liver cirrhosis | 4 (11.1) |
| Diabetes mellitus | 8 (22.2) |
| Chronic kidney disease | 6 (16.7) |
| Gastrointestinal bleeding | 4 (11.1) |
| Cardiovascular diseases | 7 (19.4) |
| Postoperative gallbladder stones | 1 (2.8) |
| Initial treatment, n (%) | |
| Piperacillin-tazobactam | 18 (50.0) |
| Cefotiam | 6 (16.7) |
| Levofloxacin | 18 (50.0) |
| Outcome, n (%) | |
| 30-day mortality | 8 (22.2) |
- Abbreviations: CRP, C-reactive protein; Pct, procalcitonin; WBC, white blood cell.
2.2 Antibiotics
Penicillin (N1127A), ampicillin (F0216), ceftriaxone (J0126E), levofloxacin (D1222C), clindamycin (D1206C), amoxicillin-clavulanic acid (M0506D), moxifloxacin (S0916D), metronidazole (A0809C), ceftazidime (F0210D), imipenem (D1212D), amikacin (M0327D), and vancomycin (M0512C) were obtained from Dalian Meilun Biological Company, Dalian, China. Piperacillin (G2215567), tazobactam (C13174419), and chloramphenicol (C13814819) were obtained from MACKLIN, Shanghai, China. All 36 isolates were tested for β-lactamase production using a nitrocefin-based β-lactamase detection assay (Chongqing Pang Tong Medical Devices Co. Ltd., Chongqing, China). The assay was performed according to the manufacturer's instructions, and the results were recorded as positive or negative based on a color change.
2.3 Bacterial Isolation and Culture
Thirty-six strains of E. lenta were isolated from clinical specimens, including bloodstream and abdominal fluids. These specimens were obtained from patients with suspected invasive infections. Of the 36 isolates, 30 were derived from blood cultures and 6 were obtained from abdominal fluids. The 30 isolates from blood cultures were recovered using BacT/Alert anaerobic blood culture bottles and the BacT/Alert 3D automated microbial detection system (BacT/ALERT3D; bioMérieux, Marcy l’Etoile, France). These strains were then cultured under anaerobic conditions at 37°C for 48 h on Columbia blood agar plates (Antobio Company, Zhengzhou, China). The specimens from abdominal fluids were directly inoculated onto Columbia blood agar plates, inhibitor-free chocolate agar plates, and MacConkey agar plates, followed by incubation in anaerobic bags at 37°C. The resulting colonies appeared grayish-white, semi-transparent, smooth, and slightly raised with a diameter of 0.1–0.3 mm, and no hemolytic rings were observed (Figure S1). After isolation and identification, the 36 strains were preserved in brain–heart infusion broth supplemented with 15% glycerol and stored at −80°C for long-term use.
2.4 Isolate Identification
Available isolates were retrieved from storage and purity plated on Columbia blood agar plates. After 48 h of incubation, cultured cells were identified via multiple methods. Phenotypic identification was performed based on Gram staining, colony morphology, and VITEK-2 Compact ANC card (bioMérieux) results [20]. Time-of-flight mass spectrometry identification was performed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) (Zybio Inc., Chongqing, China) as previously described [21, 22]. Each isolate was anaerobically grown on a Columbia blood plate for 48 h. The extended direct transfer method was used, whereby a single colony was touched and applied as a thin film directly onto a spot on a MALDI target plate, overlaid with 1 μL of 70% formic acid, and allowed to dry at room temperature. A 1 μL volume of HCCA matrix solution (Sigma-Aldrich, St. Louis, Missouri, USA) was added to each spot and allowed to dry. Escherichia coli (ATCC 25922) was used as a calibration standard. Spectrometric measurements were performed using a MALDI-TOF mass spectrometer (Zybio Inc., Chongqing, China) and analyzed using EX-Accuspec v3 software (Zybio Inc., Chongqing, China). According to the manufacturer's instructions, a log score value of ≥ 2.0 met the criteria for species identification. A score of 1.7–1.9 allowed correct identification to the genus level, while a score of < 1.7 was interpreted as not allowing for identification.
Bacterial DNA was extracted, amplified, and sequenced using a MicroSEQ 16S rDNA bacterial identification kit (PerkinElmer Applied Biosystems Inc., Foster City, CA, USA). The 36 collected strains underwent 16S rRNA sequencing, utilizing the forward primer (5′-AGAGTTTGATCMTGGCTCAG-3′) and reverse primer (5′-GGTTACCTTGTTACGACTT-3′). The resulting 16S rRNA gene sequences were then analyzed with MicroSeq 500 software (version 2.2.1). The resulting sequences were compared against the database of the National Center for Biotechnology Information using BLAST. If the sequences were 99.0% compatible with the database, the identity was acceptable to the species level.
2.5 Antimicrobial Susceptibility Testing (AST)
The AST of the 36 isolated strains of E. lenta was conducted using the agar dilution method, following the M100-ED34 guidelines of the American Clinical and Laboratory Standards Institute (CLSI). The procedure utilized Brucella agar supplemented with 5 μg/mL hemoglobin, 1 μg/mL vitamin K, and 5% (v/v) sheep blood, with a final volume of 20 mL per plate (17 mL agar + 3 mL antibiotics). Eggerthella lenta suspensions and the standard strain ATCC43055 were inoculated onto the prepared Brucella agar plates using the “direct colony suspension” method at a concentration of 105 CFU/spot and incubated anaerobically for 48 h [23]. Interpretive criteria were based on the CLSI document (M100-ED34, http://www.clsi.org/) and the European Committee on Antimicrobial Susceptibility Testing (EUCAST 2023, http://www.eucast.org/) with results classified as sensitive, intermediate, or resistant.
2.6 Statistical Analysis
Categorical data are presented as total numbers and percentages. Continuous variables were presented as mean ± standard deviation, with median (interquartile range) provided when the data distribution warranted nonparametric characterization.
3 Results
3.1 Clinical Data
The clinical characteristics of the 36 patients with E. lenta infection are summarized in Table 1. The median age was 72 years (range, 48–89 years), and 21 patients (58.3%) were men. The median length of hospitalization was 16 days. All patients presented with comorbidities, and 33.3% exhibited polymicrobial bacteremia with the isolation of multiple intestinal microorganisms. The mean time to report positive blood cultures was 72 h (range 57–120 h). The most prevalent prodromal symptom was fever, with a mean temperature of 39.3°C (36.5°C–39.7°C), and the majority of patients exhibited elevated leukocyte levels, with a mean count of 14.45 × 109/L (range, 2.44–19.16 × 109/L). C-reactive protein levels were elevated in all 36 patients. Procalcitonin levels were elevated (> 2 ng/mL) in 83.3% of the patients, with a mean of 4.62 ng/mL (0.34–18.93 ng/mL). Of the 36 patients, 11 had malignancies and 4 had liver cirrhosis. The remaining patients suffered from other comorbidities, including diabetes mellitus (8 patients), cardiovascular disease (7 patients), chronic kidney disease (6 patients), gastrointestinal bleeding (4 patients), and postoperative gallbladder stones (1 patient). During hospitalization, all patients received various antibiotics, with piperacillin-tazobactam and levofloxacin being the most frequently administered. The 30-day mortality rate of all patients was 22.2%.
3.2 Isolate Identification
A total of 36 isolates were identified as E. lenta using the VITEK-2 Compact ANC card (bioMérieux), with a confidence value of 99.9%. MALDI-TOF MS identified all of the isolates as E. lenta, and the scores of all 36 strains exceeded 2.0 (≥ 2.0, indicating possible species-level identification). Concurrently, the 36 collected strains were subjected to 16S rRNA sequencing, and the sequencing results were compared with the National Center for Biotechnology Information database using BLAST for sequence alignment. Of these, 35 strains were identified as E. lenta and 1 strain was identified as Eggerthella sinensis, with sequence similarity exceeding 98%. However, mass spectrometry identified this strain as E. lenta, and this result was chosen as the final identification due to its consistency with the strain's phenotypic characteristics and clinical context, as well as the higher discriminatory power of mass spectrometry for closely related species. Additionally, 12 strains were co-isolated with other intestinal microorganisms, including Enterococcus faecalis, E. coli, Bacteroides fragilis, Parabacteroides distasonis, Fusobacterium varium, Fusobacterium necrophorum, Klebsiella pneumoniae, Clostridium ramosum, and Clostridium innocuum. These findings suggest that E. lenta tends to co-infect with other bacteria commonly associated with gastrointestinal or abdominal infections, particularly in patients with underlying gastrointestinal diseases or immunosuppression.
3.3 AST
The AST results of the 36 E. lenta strains are presented in Tables 2 and 3. The European Union standards for drug sensitivity testing provided by the European Commission (EUCAST version 2023, http://www.eucast.org/) and the American Society for Clinical Laboratory Standardization (CLSI version 2024, http://www.clsi.org/) documents (CLSI M100-ED34) were used as references. The results indicated that 36 strains exhibited varying degrees of resistance to penicillin, ampicillin, levofloxacin, and clindamycin; sensitivity to amoxicillin-clavulanic acid, moxifloxacin, chloramphenicol, and metronidazole; resistance with a minimum inhibitory concentration (MIC) value of > 128 μg/mL to ceftazidime and ceftriaxone; and no breakpoint was established for amikacin, vancomycin, or piperacillin-tazobactam, for which median MIC values of 12, 2, and 24, respectively, were determined. All 36 isolates of E. lenta tested negative for β-lactamase production, indicating the absence of β-lactamase-mediated resistance mechanisms. As the CLSI has not provided a breakpoint for vancomycin, the value for other gram-positive anaerobes from EUCAST was used; imipenem was determined to be 100% susceptible according to the CLSI guidelines and 50% resistant according to EUCAST version 2021, with no breakpoint specified in version 2023. Detailed information about the 36 isolates, including isolate names, isolation sources, patient ages, MIC values for each antimicrobial, and their interpretations, is provided in Table S1.
| Antibiotics | Median MIC values (μg/mL) | MIC breakpoints in CLSI | Intermediate-resistant (%) | ||
|---|---|---|---|---|---|
| S | I | R | |||
| Penicillin | 2 | ≤ 0.5 | 1 | ≥ 2 | 83.3 |
| Ampicillin | 1 | ≤ 0.5 | 1 | ≥ 2 | 83.3 |
| Amoxicillin-clavulanate | 1 | ≤ 4/2 | 8/4 | 16/8 | 0 |
| Piperacillin-tazobactam | 24 | ≤ 16/4 | 32/4–64/4 | ≥ 128/4 | 100.0 |
| Ceftazidime | 128 | ND | ND | ND | 100.0 |
| Ceftriaxone | 96 | ≤ 16 | 32 | ≥ 64 | 83.3 |
| Imipenem | 3 | ≤ 4 | 8 | ≥ 16 | 0 |
| Levofloxacin | 4 | ND | ND | ND | 66.7 |
| Moxifloxacin | 0.12 | ≤ 2 | 4 | ≥ 8 | 0 |
| Chloramphenicol | 0.38 | ≤ 8 | 16 | ≥ 32 | 0 |
| Clindamycin | 0.5 | ≤ 2 | 4 | ≥ 8 | 33.3 |
| Amikacin | 12 | ND | ND | ND | ND |
| Vancomycin | 2 | ND | ND | ND | ND |
| Metronidazole | 1 | ≤ 8 | 16 | ≥ 32 | 0 |
- Note: Median MIC values (in μg/mL) for each antibiotic tested against the 36 E. lenta isolates.
- Abbreviations: I, intermediate; intermediate-resistant (%), the rate of intermediate and resistant strains; ND, no breakpoint determined; R, resistant; S, sensitivity.
| Antibiotics | Median MIC values (μg/mL) | EUCAST | Resistant (%) | |
|---|---|---|---|---|
| S ≤ | R > | |||
| Penicillina | 2 | 0.5 | 0.5 | 83.3 |
| Ampicillin | 1 | ND | ND | ND |
| Amoxicillin-clavulanate | 1 | ND | ND | ND |
| Piperacillin-tazobactama | 24 | 0.5 | 0.5 | 100 |
| Ceftazidime | 128 | ND | ND | ND |
| Ceftriaxone | 96 | ND | ND | ND |
| Imipenem | 3 | ND | ND | ND |
| Levofloxacin | 4 | ND | ND | ND |
| Moxifloxacin | 0.12 | ND | ND | ND |
| Chloramphenicol | 0.38 | ND | ND | ND |
| Clindamycina | 0.5 | 0.25 | 0.25 | 50 |
| Amikacin | 12 | ND | ND | ND |
| Vancomycina | 2 | 2 | 2 | 16.7 |
| Metronidazolea | 1 | 4 | 4 | 0 |
- Note: Median column represents the median MIC values (in μg/mL) for each antibiotic tested against the 36 E. lenta isolates.
- Abbreviations: I, intermediate; ND, no breakpoint determined; R, resistant; resistant (%), the rate of resistant strains; S, sensitivity.
- a Due to the absence of MIC breakpoints for E. lenta in EUCAST, we have referenced the MIC breakpoints for penicillin, piperacillin-tazobactam, clindamycin, vancomycin, and metronidazole from those established for other Gram-positive anaerobes in EUCAST.
4 Discussion
Previous research demonstrated that E. lenta bacteremia infections originated from abdominal disease in 44% of patients and from skin or soft tissue disease in 40% of patients, with the most prevalent being infection associated with decubitus ulcers [14]. Our findings indicate that E. lenta is associated with a spectrum of conditions, ranging from asymptomatic bacteremia (typically observed in transient gastrointestinal disease) to polymicrobial bacteremia of abdominal origin (e.g., visceral perforation) in post-treatment oncology patients, as well as severe monomicrobial-transmitted disease. This suggests that when E. lenta is identified in blood cultures, it should not be dismissed as a contaminant but rather warrants a more comprehensive evaluation of the patient. The 30-day mortality rate of 22.2% among patients, although higher than that in some reports, may be attributed to the patient's underlying comorbidities, including systemic tumor metastases, postoperative infections, and immunocompromised status.
Eggerthella lenta is characterized by a slow growth rate and stringent growth conditions, features that extend the time required for positive blood culture results compared with common Enterobacteriaceae, potentially reducing the effectiveness of empirical antibiotic therapy. The results of our AST are consistent with those of previous reports [12, 13, 24]. However, owing to limited data related to anaerobes, the CLSI and EUCAST have established breakpoints for only a subset of drugs, with discrepancies in breakpoint determination for certain drugs. For example, regarding penicillin and ampicillin, 83.3% of the strains exhibited non-susceptibility (including both intermediate and resistant strains) according to CLSI criteria, whereas if EUCAST breakpoints for other anaerobes were applied (because of the absence of E. lenta-specific breakpoints), all strains would be classified as resistant. Similarly, for clindamycin, 33.3% of strains were categorized as non-susceptible under the CLSI criteria, whereas under the EUCAST criteria, 50% of strains were categorized as resistant. Notably, all 36 strains of E. lenta tested negative for β-lactamase. Despite the lack of direct evaluation of the clinical efficacy of penicillin and ampicillin, this finding suggests that CLSI breakpoints should be referenced when assessing the resistance of these two drugs against E. lenta. Additionally, high MIC values for piperacillin-tazobactam have been demonstrated in drug sensitivity tests, and elevated MIC values have been associated with a significant increase in mortality when piperacillin-tazobactam is used as monotherapy for E. lenta infections [13, 24]. However, the high mortality rate cannot be solely attributed to the MIC value of piperacillin-tazobactam. This study found that even with MIC values of 32 and 64, the mortality rate of patients treated with the drug alone was not 100%, suggesting other factors may contribute to patient outcomes. In fact, previous cases of successful treatment suggest that piperacillin-tazobactam may exhibit some activity against E. lenta [12], which is also corroborated by the case study in this paper. Therefore, greater consideration should be given to individual patient factors such as underlying disease, immune status, comorbidities, and their severity, which may be the primary determinants of mortality. The decision to remove certain drug breakpoints in the 2023 edition of EUCAST further emphasizes that breakpoint determination for drugs such as piperacillin-tazobactam requires optimization in the context of clinical practice to ensure accurate guidance for the effective management of invasive E. lenta infections. Additionally, all 36 strains of E. lenta demonstrated complete sensitivity to imipenem (resistance rate of 0%), further supporting imipenem as a potentially effective option for the treatment of E. lenta infections.
EUCAST does not provide specific MIC breakpoints for vancomycin against E. lenta, and we therefore referred to the MIC breakpoints established for other gram-positive anaerobes. This approach is justified by vancomycin's broad-spectrum activity against gram-positive anaerobes and its clinical relevance in treating invasive infections [25]. For other antibiotics, specific breakpoints for E. lenta or anaerobic bacteria were available in the CLSI or EUCAST guidelines, which we used for interpretation. By contrast, amikacin is generally not suitable for the treatment of certain anaerobic bacteria, and there are no other reports on the MIC range for amikacin against E. lenta. Consequently, we conducted an MIC range test and found relatively high MIC values, with distributions in both the sensitive and intermediate ranges. It is crucial to carefully consider the actual MIC values and the patient's renal function when selecting this drug. This highlights the need for more comprehensive guidelines and data on the use of amikacin for treating E. lenta infections, ensuring that clinicians can make informed decisions based on both susceptibility patterns and patient-specific factors.
5 Conclusions
Eggerthella lenta is a significant pathogen, and careful consideration should be given to its underlying diseases and comorbidities when isolated from bloodstream and abdominal fluid cultures. The VITEK-2 Compact ANC card and MALDI-TOF MS can rapidly identify E. lenta at the species level. The close phylogenetic relationship between E. lenta and E. sinensis can lead to challenges in species differentiation using 16S rRNA sequencing, as their sequence similarity often exceeds 98%. In this study, one strain was initially identified as E. sinensis based on 16S rRNA sequencing; however, mass spectrometry (MALDI-TOF MS) provided a more definitive identification of E. lenta, which was consistent with the strain's phenotypic characteristics and clinical context. This highlights the importance of using complementary identification methods, particularly for closely related bacterial species. Amoxicillin-clavulanic acid, moxifloxacin, and metronidazole were identified as the most effective antibiotics. Although no resistance to chloramphenicol has been identified, its adverse effects, such as myelosuppression, limit its clinical use. Currently, the efficacy and resistance patterns of piperacillin-tazobactam remain unclear, necessitating further investigation. It is advisable that the selection of antimicrobial agents be guided by the results of the patient's AST prior to administration, particularly in cases of severe infection.
Author Contributions
Yuan Gao: data curation (lead), writing – original draft (lead). Longfeng Qu: writing – original draft (equal). Shu Zhang: data curation (equal). Cheng Cheng: supervision (equal), writing – review and editing (equal). Bin Tang: conceptualization (lead), data curation (equal), formal analysis (equal), funding acquisition (lead), project administration (lead), supervision (lead), writing – review and editing (equal).
Acknowledgments
The authors have nothing to report.
Ethics Statement
This study was conducted in accordance with the guidelines of the Declaration of Helsinki and approved by the Institutional Ethics Committee of Chongqing University Jiangjin Hospital (approval number: KY20240929-001), which complies with international ethical standards.
Consent
As this was a retrospective study using existing medical records with minimal risk to patients, and obtaining individual consent was impracticable without compromising the scientific validity of the research, the requirement for written informed consent was waived by the Medical Ethics Committee of Chongqing University Jiangjin Hospital.
Conflicts of Interest
This article belongs to a special issue (SI)-Clinical Microbiology and Immunology. As the SI's Guest Editor, Professor Bin Tang was excluded from all the editorial decisions related to the publication of this article. The other authors declare no conflicts of interest.
Open Research
Data Availability Statement
The datasets used or analyzed in this study can be obtained by contacting the corresponding author upon reasonable request.
