Abstract

Hafnia alvei is a rarely seen pathogen in humans. In this article, we present a 58-year-old male case of Hafnia alvei with respiratory impairment due to a severe lower respiratory tract infection. Chest X-ray and computed tomography showed consolidation and significant infiltration in the right lung. Cultures of sputum were positive for Gram-negative rods, which were identified as Hafnia alvei. The patient was prescribed meropenem therapy for the eradication of the infection. This report presents a unique case of respiratory tract infection caused by Hafnia alvei.

Hafnia alvei (H. alvei) i s a G ram-negative, facultative anaerobic, rod-shaped bacterium of the Enterobacteriaceae family.[1] It is typically defined as a gastrointestinal organism[1] and is infrequently considered as a pathogen.[2] It only expresses one virulence factor found in enteropathogenic Escherichia.[3] In 1991, this organism was first described as an gastrointestinal pathogen.[3]

Although, H. alvei is typically considered as a commensal organism of the enteric tract, recent reports have suggested that it has the potential to be a serious human pathogen.[2] Herein, we report a 58-year-old male case with respiratory impairment due to a severe lower respiratory tract infection caused by H. alvei.

Case Presentation

A 58-year-old man with severe chronic obstructive pulmonary disease (COPD) who had a history of smoking 40 packs/day over the course of several years was admitted to the emergency department due to progressive dyspnea, fever, cough, and increasing sputum for three days. O admission, the patient was pale, dyspneic, febrile, and in a poor condition. Physical examination revealed a body weight of 65 kg, a height of 168 cm, a pulse rate of 104 beats/min, a blood pressure of 108/65 mmHg, a body temperature of 39.4 °C, and a respiration rate of 24 breaths/min. Abdominal examination findings were unremarkable. On auscultation of the lungs, crackles in t he right lung base were heard. H is level of consciousness was alert.

Chest X-ray and computed tomography (CT) showed consolidation and significant infiltration in the right lung (Figure 1a, b).

Figure 1: A chest X-ray and computed tomography scan showing (a) consolidation and (b) significant infiltrations in the right lung.

Laboratory test results were as follows: white blood cell count 23,000/mm³, neutrophils 87%, hemoglobin 15.9 g/dL, platelet count 323,000/mm³, and C-reactive protein 97 mg/dL. Arterial blood gas analysis showed increased carbon dioxide retention (PCO2: 59.6 mmHg) and a reduced ratio of partial pressure of oxygen in arterial blood (PaO₂: 52.1 mmHg). Therapy for progressive respiratory failure consisted of inhaled [beta]- adrenergic agonists, oxygen administration, empirical antibiotherapy, and intensive chest care. Initially, ampicillin/sulbactam 1.5 g q6h and clarithromycin 1000 mg/day were prescribed for the treatment of pneumonia.

The cultures of sputum specimens yielded Gramnegative rods identified as H. alvei u sing t he N uve N120 System^® ( Nuve Laboratory and Sterilization Technology, Ankara, Turkey) (Figures 2, 3). Laboratory contamination was ruled out. Based on the culture findings, as H. alvei w as s usceptible to aminoglycosides, meropenem, trimethoprim/ sulfamethoxazole, and cefixime, antibiotic regimen was replaced with intravenous meropenem 3 g/day. The patient completed his treatment, and repeated sputum culture yielded negative for H. alvei.

Figure 2: Cultures of sputum specimen yielding Gramnegative rods, which were then identified as H. alvei.

Figure 3: Gram-negative rods in the microscopy image.

Discussion

Extraintestinal invasive infections caused by H. alvei usually occur in patients with chronic debilitating diseases.[2] This species is rarely isolated in human specimens and it is very rarely thought to be pathogenic. In humans, however, it can cause a range of infections, including urinary tract infections, bacteremia, pneumonia, and extraintestinal infections.[4,5]

To the best of our knowledge, only three H. alvei cases have been reported as the main cause of pulmonary infections in the literature.[6] In one study, H. alvei was isolated in the respiratory tracts of five individuals, from whom 760 enterobacter isolates were obtained over the course of a three-year study.[7] Three of these individuals presented with chronic respiratory disease. Four of the isolates were derived in sputum specimens, and one was in the trachea. Two isolates were the predominant microorganisms in two individuals with bronchopneumonia. Frick et al.[6] also reported that a bronchoscopic sample obtained from a patient with pneumonia on mechanical ventilation for 12 days was positive for H. alvei.

Although H. alvei is thought to originate from the gastrointestinal tract, little is known about its opportunistic nature.[8] However, several studies have demonstrated that it causes infection by entering the bloodstream through the gastrointestinal tract. On the other hand, it is still unknown whether its weak pathogenicity with respect to extraintestinal infections is due to the level of expression of virulence factors.[9] The intra-abdominal area and urinary tract are common sites of H. alvei infections. In addition, it is important to note that this microorganism is associated with biliary tree infections[2] and subsequent abscess formation.[10]

There are numerous extraintestinal infections caused by H. alvei in patients with chronic underlying diseases, such as immunodeficiency and cancer, in particular, hematological malignancies.[5] Our case had severe underlying disease, COPD, which may have promoted the occurrence of this uncommon infection. In addition, although H. alvei is an unusual etiological factor for pulmonary infections, several cases have been reported. Therefore, patients with respiratory and chronic diseases should be given information on this microorganism.[11] In the literature, most reports on invasive infection have been based on individual patients.[12,13]

Furthermore, this rare organism can occur in patients with surgical wound infections or abscesses, organ transplant patients,[7] and patients with a postoperative indwelling catheter.[10] Standard surgical treatments can be performed in these patients, when necessary. Respiratory isolates can be isolated in patients undergoing thoracic surgery or inpatients due to trauma. The prevalence of so-called rare bacterial infections increases, contributing considerably to morbidity and mortality following thoracic surgery.[14]

In our case, we prescribed the most appropriate treatment based on the results of sensitivity testing. Antibiotic susceptibility to Hafnia alvei was evaluated using a disk diffusion method according to the guidelines published by the National Committee for Clinical Laboratory Standards. Strains were evaluated as susceptible, moderately susceptible, or resistant. Hafnia alvei is typically resistant to the first-generation cephalosporin and amoxicillin and is able to rapidly become resistant to the second- or third-generation cephalosporins.[15] Antimicrobials which are known to be effective against the isolated strain of H. alvei include ciprofloxacin, aminoglycosides, ceftriaxone, cefotaxime, imipenem, ticarcillin, piperacillin, and co-trimoxazole.[13,15] In our case, the results were consistent with those reported in previously published studies (Table 1). However, in our case, no susceptibility to amoxicillin/clavulanic acid or firstgeneration cephalosporin was detected. Considering these results, we treated our patient with meropenem, which eradicate the infection successfully. In conclusion, this report presents a rare causative agent of pneumonia, H. alvei. We believe that further researches would be useful to elucidate the pathogenesis of H. alvei in detail, as this is one of very few studies of this pathogen.

Table 1: Antibiotic susceptibility of Hafnia alvei

Declaration of conflicting interests
The authors declared no conflicts of interest with respect to the authorship and/or publication of this article.

Funding
The authors received no financial support for the research and/or authorship of this article.

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