Hepatitis E virus and Klebsiella pneumoniae co-infection detected by metagenomics next-generation sequencing in a patient with central nervous system and bloodstream Infection: a case report

The Hepatitis E virus (HEV) stands as the leading cause of acute viral hepatitis worldwide, notably in developing nations [1, 2]. According to the World Health Organization (WHO), every year there are an estimated 20 million HEV infections worldwide, leading to an estimated 3.3 million symptomatic cases of hepatitis E (https://​www.​who.​int/​en/​news-room/​fact-sheets/​detail/​hepatitis-e). Most cases of acute HEV infection resolve spontaneously and do not require treatment, life-threatening acute liver failure may occur in some cases, especially pregnant women and immunocompromised patients.

HEV infection not only triggers hepatitis but also associates with neurological issues like Guillain − Barré syndrome (GBS), neuralgic amyotrophy, and encephalitis/myelitis [3]. However, the exact mechanisms behind these neurological symptoms remain unclear. Earlier case reports have shown that HEV can be found in the cerebrospinal fluid (CSF) of patients displaying neurological symptoms [4‐7]. Laboratory investigations revealed that HEV has the capacity to harm tight junction proteins like Claudin5, Occludin, and ZO-1 (zonula occludens-1), disrupting the blood–brain barrier and allowing entry into the cerebrospinal fluid. Additionally, HEV can replicate and proliferate within nerve cells, resulting in central nervous system infections [8‐10].

Klebsiella pneumoniae, a Gram-negative bacterium, frequently exists in the environment. Humans, being the primary host, commonly harbor K. pneumoniae in the nasopharynx and gastrointestinal tract. In healthcare facilities, the risk of colonization and consequent infection is elevated, potentially leading to hospital-based outbreaks [11]. Individuals with compromised immune systems are particularly susceptible to various infections, with respiratory, urinary tract, and bloodstream infections being most prevalent [12]. In the context of central nervous system infections, K. pneumoniae is the primary causative agent of bacterial meningitis. Among Chinese patients diagnosed with bacterial meningitis, K. pneumoniae prevalence reached a notable 11.3% [13]. The substantial occurrence and fatality rate of K. pneumoniae-induced meningitis warrant serious attention.

To date, instances of concurrent HEV and K. pneumoniae infections have not been reported. Therefore, we present a case involving a combined infection affecting the central nervous system and bloodstream caused by both HEV and K. pneumoniae, which was successfully treated. In this case, CSF and blood samples underwent analysis through mNGS. This approach enabled the swift identification of pathogens, thus facilitating early treatment and improving the patient's prognosis.

A 68-year-old man suddenly experienced fever and headache, with a slightly stiff neck. He had a history of bronchiectasis for over 40 years and had frequently used ciprofloxacin and amoxicillin to treat bronchiectasis-related infections. A chest CT scan displayed bronchiectasis in the lower left lobe (Fig. 1).

On April 5, 2023, he underwent testing at the hospital. Biochemical assessments indicated heightened alanine aminotransferase (ALT: 1780 U/L), signifying severe liver damage. Magnetic resonance imaging (MRI) showcased age-related brain changes and bilateral sphenoid sinusitis. On April 7, he was transferred to the Third People’s Hospital of Changzhou. Following admission, he exhibited a peak body temperature of 40 °C, noticeable headaches, and had four instances of watery yellow diarrhea. Inflammatory markers were significantly elevated (WBC 10.03E + 09/L, CRP 100.69 mg/L, PCT 2.64 ng/ml, IL-6 114.9 pg/mL). By April 8, the cerebrospinal fluid (CSF) had a light-yellow appearance, and CSF testing revealed increased WBC count (2.126E + 09/L), predominant multinucleated cells (86.3%), heightened protein (2.86 g/L), and decreased glucose (2.00 mmol/L) and chloride (113.3 mmol/L). Further test outcomes are presented in Table 1. Based on these findings, the diagnosis pointed to a central nervous system infection, with a strong likelihood of suppurative meningitis. The patient also exhibited irregular liver function and notably elevated liver enzymes. While tests for hepatitis A, B, C, and D antibodies returned negative, the hepatitis E IgM level was 8.086 S/co, suggesting a potential HEV infection.

Considering the seriousness of central nervous system infection, traditional detection and mNGS were applied for blood and CSF samples. On April 9, mNGS analysis of both CSF and peripheral blood unveiled an infection involving K. pneumoniae and HEV, as illustrated in Fig. 2. Quantitative real-time PCR assessment of HEV in peripheral blood (HEV-RNA) indicated a viral load of 1.8E + 04 copies/ml, and in feces (HEV-RNA), a viral load of 8.4E + 03 copies/ml. On April 19, the peripheral blood culture results from the previous hospital were obtained and confirmed K. pneumoniae infection (which was only resistant to ampicillin and was sensitive to amoxicillin, clavulanate, tobramycin, gentamicin, amikacin, chloramphenicol, cefazolin, cefathiamidine, cefuroxime, cetohexazine, piperacillin tazobactam, aztreonam, meropenem, ciprofloxacin, levofloxacin, moxifloxacin, tetracycline, trimethoprim and sulfamethoxazole.).

Following treatment, the patient's fever subsided, and the headache improved. Re-examinations indicated a reduction in inflammation markers and improved liver function. A CSF test performed on April 18 showed clear and colorless fluid with a pressure of 95 mmH₂O. On April 19, PCR testing did not detect HEV-RNA in the patient's serum and blood. All indicators were found to be within the normal range, as depicted in Table 2.

We present an unusual case involving simultaneous infections with hepatitis E virus and Klebsiella pneumoniae in both the central nervous system and bloodstream. The presence of positive Anti-HEV IgM test results and the detection of nucleic acid in peripheral blood, feces, and cerebrospinal fluid affirmed the diagnosis of acute hepatitis. Concurrently, there were significantly elevated levels of inflammatory markers upon admission. The cerebrospinal fluid displayed turbidity, and tests indicated acute suppurative meningitis. mNGS confirmed the presence of both HEV and K. pneumoniae in both cerebrospinal fluid and blood samples, establishing infections in both the central nervous system and bloodstream.

The transmission of Hepatitis E virus typically occurs via the gastrointestinal tract. Prior to the onset of symptoms, the patient attended a large banquet, which could potentially be the source of infection. Hepatitis E virus frequently manifests as acute liver inflammation accompanied by gastrointestinal symptoms such as fever, nausea, abdominal distension, and diarrhea. These symptoms correspond to the initial ones observed in the patient.

Upon entering the human body through the gastrointestinal tract, recent research suggests that HEV initially replicates in intestinal cells. Subsequently, it infects hepatocytes, and then spreads into the bloodstream, where it targets extrahepatic cells, including nerve cells. Upon release from the apical side, HEV is excreted through feces and urine [14]. By the 8th day of the disease's progression, varying levels of HEV were detected in the feces and peripheral blood. However, on the 18th day, no HEV was detectable, aligning with findings from previous studies [15].

Although HEV is primarily regarded as a virus that targets the liver, it can also lead to infections in the central nervous system by crossing the blood–brain barrier. In this instance, HEV was additionally identified in the cerebrospinal fluid, signifying an infection within the central nervous system.

Klebsiella pneumoniae holds significance within the Klebsiella genus of the Enterobacteriaceae family, commonly found in both the upper respiratory tract and the intestinal tract of humans. This bacterium assumes the role of an opportunistic pathogen, often linked to hospital-acquired infections [16, 17]. It primarily impacts individuals in hospital settings or those with compromised immune systems, particularly patients with pre-existing conditions like liver disease and diabetes [18].

The patient's counts of CD3 + total T cells, CD4 + helper T cells, and CD19 + B lymphocytes have all seen notable reductions, suggesting a deficiency in cellular immunity. This deficiency could heighten the risk of co-infection involving the HEV and K. pneumoniae. While the sequence of infections remains uncertain, it is posited that the patient might have initially contracted the Hepatitis E virus. This, in turn, could have caused diarrhea and significant liver dysfunction, thus permitting K. pneumoniae to breach the intestinal mucosal barrier, enter the bloodstream, and subsequently traverse the blood–brain barrier, resulting in an infection within the central nervous system.

Infections of the nervous system are potential life-threatening and prompt recognition and treatment of a central nervous system(CNS) infection is crucial for patient survival, as these infections have a high morbidity and mortality. Because of notable advantages in terms of timeliness and sensitivity, mNGS has a great diagnostic value in CNS infections and had an overall superior detection rate to culture [19‐21]. In this case, mNGS successfully detected K. pneumoniae and HEV in CSF, while the culture results were negative. This case suggests that mNGS may be a useful diagnostic tool for CNS infection.