Ewingella americana Infections in Humans-A Narrative Review.

Ewingella americana is a Gram-negative rod that belongs to the order Enterobacterales and the family Yersiniaceae and was first identified in 1983 from 10 clinical strains in the United States of America. The present study aimed to identify all the published cases of E. americana in the literature, describe the epidemiological, clinical, and microbiological characteristics, and provide data regarding its antimicrobial resistance, treatment, and outcomes. A narrative review was performed based on a PubMed and Scopus databases search. In total, 16 studies provided data on 19 patients with infections by E. americana. The median age of the patients was 55 years, and 47.4% were male. The most common infections were those of the bloodstream, the respiratory tract, and the peritoneal cavity. Antimicrobial resistance to cephalosporins, aminoglycosides, and the combination of trimethoprim with sulfamethoxazole was minimal, and these were the most commonly used antimicrobials for treating these infections. No included study provided information on the genetic or molecular mechanism of this pathogen's antimicrobial resistance. The overall mortality was minimal, with only one patient with bacteremia succumbing to the infection. Further studies are needed to better understand this microorganism, its pathogenic potential in humans, and the genetic and molecular mechanisms underlying its antimicrobial resistance, for which very little evidence exists to date.

Osteolytic Lesions in a Sub-Adult Loggerhead Sea Turtle (Caretta caretta): A Case Report.

Osteolytic lesions in loggerhead sea turtles (Caretta caretta) during rehabilitation are attributed to multiple causes, including gas embolism, hypothermia, and osteomyelitis due to bacterial or fungal infection. This study reports the appearance of osteolytic lesions in a sub-adult loggerhead sea turtle with involvement of the right fore and hind flippers, visible swelling of the elbow and knee joints, and accompanied by lameness after 45 days of rehabilitation. Radiographs and computed tomography revealed multiple lytic bone lesions. This was the fourth rehabilitation admission of the turtle after being accidentally captured by trawler ships (bycatch) in 2019, 2020, 2022, and 2023. Potential causes were dysbaric osteonecrosis due to a past decompression sickness event and hypothermia with osteomyelitis from bacterial infection. Blood cultures and antibiotic susceptibility testing led to the isolation of Ewingella americana responsive to enrofloxacin. This study investigates extensive fore and hind flipper involvement in a sub-adult loggerhead turtle, aiming to determine causes and risk factors. The pathogenesis and significance of these lesions is discussed.

The First Known Documented Case of Ewingella Americana Urinary Tract Infection.

We present a 73-year-old male with a history of end-stage renal disease (ESRD) on dialysis, type 2 diabetes mellitus, coronary artery disease status post stents, prostate carcinoma status post radiation, and prostatectomy, with recurrent bladder neck contracture requiring suprapubic catheter, left urethral stricture with nephrostomy tube placement, penile implant, and recurrent urinary tract infections, who presented to the emergency room complaining of constant bilateral groin pain for one day. Physical exam was significant for suprapubic tenderness and a chronic suprapubic catheter and left-sided nephrostomy tube. An initial examination of the patient's urine revealed turbid, yellow-colored fluid, positive for white blood cells, leukocyte esterase, and bacteria. A urine culture was obtained, which returned positive for E. americana,  with >100,000colony-forming units (CFUs)as well as Enterococcus faecalis (E. faecalis) demonstrating low colony counts. The patient was treated with a seven-day course of meropenem 1 gm twice daily, which improved of his symptoms, and then completed a 10-day course of ertapenem 500 mg daily. The patient received a five-day course of vancomycin 1 gm on dialysis days for additional coverage of E. faecalis, despite low colony counts. This is the first documented case of a urinary tract infection caused by E. americana. The organism is primarily found in immunocompromised individuals, and a debate is still ongoing as to whether it is a true pathogen or exists primarily as an opportunistic infection. We suggest further inquiry and study of this resistant organism are paramount in establishing its role in both immunocompromised as well as immunocompetent individuals. E. americana is a multidrug-resistant organism, which to date has sparse documentation regarding its prevalence and potential for morbidity, especially in compromised individuals. In the era of increasing antibiotic resistance, we suggest that more research is needed to understand the pathogenicity of E. americana.

First Report of Bacterial Brown Rot Disease Caused by Ewingella americana on Cultivated Naematelia aurantialba in China.

Naematelia aurantialba (synonym Tremella aurantialba) is one of the jelly fungi and highly valued edible and medicinal mushrooms. It has been cultivated industrially in recent years and consumed popularly in China. In September 2022, brown rot disease of fruiting bodies was observed at the N. aurantialba factory in Tongzhou district, Beijing with a disease incidence of ~10%. Symptoms initially appeared as color changing from orange to light brown. The infected area expanded gradually until covered fully the fruiting body. Meanwhile, the interior of the fruiting body became rotten and dark brown. Finally, the whole fruiting body became wrinkled and brown, resulting in significantly reduced yield and economic loss. Isolations were made from 12 infected mushroom samples. Infected tissue within the fruiting body was mashed in sterilized 1.5 mL tubes containing 1 mL of sterile distilled water. After standing for 5-10 min, the suspensions were streaked on the Luria-Bertani (LB) medium and cultured at 37°C for 24h. The physiological and biochemical reactions of isolated strains were determined using the API 20E system (Reyes et al. 2004) according to the manufacturer's instructions. All the strains showed the same reaction results. The bacterial colonies were streaked on fresh LB medium at 37°C for 24 h, and a single pure culture was obtained with round, smooth and semitransparent. The bacterial cells were gram-negative, short-rod, (0.3) 0.8-2.0 (2.5) × (0.1) 0.6-1.0 (1.5) µm, and peri-flagellate. The isolates were further confirmed by sequence analysis of the 16S rRNA and gyrB genes with primer 27F/1492R and gyrB-UP1s/gyrB-UP2sr (Liu et al. 2018). Using EzBioCloud data searches, the 16S rRNA sequence of four strains (GenBank accession OP727593, OP727595, OP727596, OP727601) matched the sequence of E. americana type strain ATCC 33852 (accession JMPJ01000013) with identity of 99.65%~99.93 and 100% completeness. The GyrB sequence matched the E. americana in GenBank (MK460250) and showed 98.71% identity and 100% completeness. Finally, the pathogen was identified as E. americana based on morphological, physiological, biochemical, and molecular characteristics. The pathogenicity test was conducted by spreading bacterial suspensions cultured 48h onto 12 healthy cultivated fruiting bodies of N. aurantialba, with sterile distilled water as a control, and then cultured in a chamber at 23°C with 85% relative humidity. Brown symptoms, similar to natural symptoms, were observed on all inoculated fruiting bodies after 48h, whereas the controls remained symptomless. Pathogenic bacteria were isolated from the inoculated fruiting body and confirmed to be E. americana based on morphological and 16S rRNA molecular characteristics, thus fulfilling Koch's postulates. E. americana caused stipe necrosis on Agaricus bisporus in Egypt (Madbouly et al. 2014), the oak tree in Thailand, and pneumonia in Humans (Doonan et al. 2016), and brown blotch on Flammulina velutipes (Liu et al. 2018). To our knowledge, this is the first worldwide report of E. americana infecting jelly fungus N. aurantialba causing brown rot disease. E. americana is an opportunistic cross-kingdom pathogen (Liu et al. 2018). That will provide a critical alert on the prevention, effective monitoring, and control of the disease.

Ewingella americana Peritonitis in a Patient on Peritoneal Dialysis: A Case Report and Review of the Literature.

Most episodes of peritoneal dialysis (PD)-associated peritonitis are caused by skin-dwelling gram-positive bacteria and gram-negative bacteria colonizing gut and urinary tract. Occasionally, however, uncommon bacteria can cause peritonitis in PD patients. We describe a case of Ewingella americana peritonitis, the first such case reported from the United States. A 68-year-old woman with end-stage kidney disease due to hypertension was initiated on PD 2 years prior to the present event. She presented with abdominal pain associated with nausea and vomiting. She was afebrile and hemodynamically stable. Abdomen was diffusely tender with guarding and rebound. No obvious root cause was apparent. Initial PD fluid white count was 502/mm3 with 87% neutrophils. Gram stain was negative. Culture grew gram-negative rods, which were later identified as Ewingella americana, resistant to ampicillin and cefazolin but sensitive to gentamicin, ceftazidime, and cefepime. After empiric intraperitoneal vancomycin and gentamicin, she was continued on intraperitoneal gentamicin for a total period of 21 days. She responded to the treatment rapidly with complete recovery. PD fluid on day four showed 40 nucleated cells with 12% neutrophils. Patient remained on PD without consequences. Ewingella americana is a gram-negative facultative anaerobic bacillus that can survive in water, including domestic water. Inadequate hand hygiene is a potential root cause of infection. Although rare, Ewingella peritonitis can be observed in PD patients and is treatable. Clinicians should be aware of Ewingella as a potential cause of PD peritonitis.

First Case of Ewingella americana Meningitis in a Term Newborn: A Rare but Real Pathogen.

Ewingella americana is a Gram-negative, catalase positive and anaerobic enterobacterium first described in 1983. Infections caused by this pathogen, such as bacteremia and pneumonia, are extremely rare and primarily occur in patients with underlying pathologies or immunosuppression. There is still a debate as to whether Ewingella americana is a real pathogen or if it can be considered an opportunistic infectious agent. We report the first documented case of Ewingella americana meningitis in literature and the first case of this pathogen causing infection in a newborn. Case presentation: A term newborn male was born via spontaneous vaginal delivery to a Gravida 2 Para 0, 28 year old woman with negative prenatal screening tests with a birth weight of 4.70 kilograms and Apgar scores of 9 and 9 at 1 and 5 minutes respectively. Rupture of membranes was 27 hours prior to delivery. Infant was noted to be febrile to 101°F at birth, so infant was admitted in the neonatal intensive care unit and started empirically on ampicillin and gentamycin. Cerebrospinal fluid (CSF) drawn due to irritability on day of life 1 presented normal cell and protein count but grew Gram negative rods after 2 days, identified subsequently as Ewingella americana; repeat CSF analysis done at 6 days of life showed pleocytosis. Brain MRI performed at 2 weeks of life showed leptomeningitis. The infant was treated with ceftazidime for 21 days from the first negative CSF culture. He has since followed up with the neurologist and infectious disease specialist. He had a normal electroencephalogram (EEG) and is meeting all developmental milestones at the 24 months of age follow up visit. Conclusion: Our case highlights that Ewingella americana can cause serious invasive infections such as meningitis in the neonatal period with minimal symptomatology. Antibiotic treatment in the neonatal period can present challenges due to the Ewingella americana's variable sensitivity. The role of these emerging low virulence organisms in causing infections has to be further elucidated, especially in vulnerable patients such as newborns.

Comparative Genomic Analysis Provides Insights into the Phylogeny, Resistome, Virulome, and Host Adaptation in the Genus Ewingella.

Ewingella americana is a cosmopolitan bacterial pathogen that has been isolated from many hosts. Here, we sequenced a high-quality genome of E. americana B6-1 isolated from Flammulina filiformis, an important cultivated mushroom, performed a comparative genomic analysis with four other E. americana strains from various origins, and tested the susceptibility of B6-1 to antibiotics. The genome size, predicted genes, and GC (guanine-cytosine) content of B6-1 was 4.67 Mb, 4301, and 53.80%, respectively. The origin of the strains did not significantly affect the phylogeny, but mobile genetic elements shaped the evolution of the genus Ewingella. The strains encoded a set of common genes for type secretion, virulence effectors, CAZymes, and toxins required for pathogenicity in all hosts. They also had antibiotic resistance, pigments to suppress or evade host defense responses, as well as genes for adaptation to different environmental conditions, including temperature, oxidation, and nutrients. These findings provide a better understanding of the virulence, antibiotic resistance, and host adaptation strategies of Ewingella, and they also contribute to the development of effective control strategies.

What is the role of Ewingella americana in humans? A case report in a healthy 4-year-old girl.

BACKGROUND: Ewingella americana (Ea) is a Gram-negative, lactose-fermenting, oxidase-negative and catalase-positive bacterium that was first described in 1983 as a new genus and species in the family Enterobacteriaceae. It is not known whether Ea is a true pathogen or simply an opportunistic infectious agent, as most of the cases have been described in patients at risk. CASE PRESENTATION: A 4-year-old girl described here was hospitalized due to a productive cough over the previous 3 weeks and a fever > 38 °C associated with tachypnea over the previous 2 days. Her familial and personal medical histories were negative for relevant diseases, including respiratory infections. At admission, she was febrile (axillary temperature 39.2 °C) and had dyspnea with retractions, grunting and nasal flaring. A chest examination revealed fine crackling rales in the left upper field associated with bilateral wheezing. A chest X-ray revealed segmental consolidation of the lingula of the left lung. Laboratory tests revealed leukocytosis (15.,800 white blood cells/mm3 with 50.3% neutrophils), a slight increase in serum C-reactive protein (11.9 mg/L) and normal procalcitonin values (< 0.12 ng/mL). A nasopharyngeal swab culture did not reveal viral or bacterial respiratory pathogens, including atypical bacteria. A blood culture revealed the presence of a Gram-negative, lactose-fermenting rod that was oxidase negative and catalase positive. The isolate was identified by means of the VITEK®2 identification system (bioMérieux, Firenze, Italy) as Ea. This identification was confirmed by sequencing the 16 s ribosomal deoxyribonucleic acid (rDNA). The pathogen was sensitive to aminoglycoside, fluoroquinolones, carbapenems, cefotaxime, and ceftazidime but was intermediate against sulfametoxazole/trimethoprim and resistant to amoxicillin-clavulanic acid, fosfomycin, and oxacillin. The child was immediately treated orally with amoxicillin-clavulanic acid and erythromycin. Based on the results of a blood culture and sensitivity tests, the amoxicillin-clavulanic acid medication was stopped after 3 days. Erythromycin was continued for a total of 10 days, and the child was discharged after 3 days in the hospital. Follow-up visit 1 month later did not reveal any respiratory problems. CONCLUSION: This case shows that Ea infections in healthy subjects are mild even in pediatric age, and the need for antibiotic therapy is debated. Cases occurring in subjects with underlying chronic disease can be significantly more complicated and require appropriate antibiotic therapy.

Occurrence of Internal Stipe Necrosis of Cultivated Mushrooms (Agaricus bisporus) Caused by Ewingella americana in Korea.

The internal stipe necrosis of cultivated mushrooms (Agaricus bisporus) is caused by the bacterium Ewingella americana, a species of the Enterobacteriaceae. Recently, Ewingella americana was isolated from cultivated white button mushrooms in Korea evidencing symptoms of internal stipe browning. Its symptoms are visible only at harvest, and appear as a variable browning reaction in the center of the stipes. From these lesions, we isolated one bacterial strain (designated CH4). Inoculation of the bacterial isolate into mushroom sporocarps yielded the characteristic browning symptoms that were distinguishable from those of the bacterial soft rot that is well known to mushroom growers. The results of Gram stain, flagellal staining, and biochemical tests identified these isolates as E. americana. This was verified by pathogenicity, physiological and biochemical characteristics, and the results of an analysis of the 16S rRNA gene sequences and the fatty acids profile. This is the first report of the isolation of E. americana from cultivated white button mushrooms in Korea.

Occurrence of Internal Stipe Necrosis of Cultivated Mushrooms (Agaricus bisporus) Caused by Ewingella americana in Korea

The internal stipe necrosis of cultivated mushrooms (Agaricus bisporus) is caused by the bacterium Ewingella americana, a species of the Enterobacteriaceae. Recently, Ewingella americana was isolated from cultivated white button mushrooms in Korea evidencing symptoms of internal stipe browning. Its symptoms are visible only at harvest, and appear as a variable browning reaction in the center of the stipes. From these lesions, we isolated one bacterial strain (designated CH4). Inoculation of the bacterial isolate into mushroom sporocarps yielded the characteristic browning symptoms that were distinguishable from those of the bacterial soft rot that is well known to mushroom growers. The results of Gram stain, flagellal staining, and biochemical tests identified these isolates as E. americana. This was verified by pathogenicity, physiological and biochemical characteristics, and the results of an analysis of the 16S rRNA gene sequences and the fatty acids profile. This is the first report of the isolation of E. americana from cultivated white button mushrooms in Korea.

A Case of Pneumonia Caused by Ewingella americana in a Patient with Chronic Renal Failure

Though the pathogenic significance and the reservoir of Ewingella americana have not been clarified, this organism has caused several pathogenic infections, especially in immunocompromised patients. We report a pneumonia in a patient with chronic renal failure, who had chronic rejection of transplanted kidney. E. americana was identified to be the pathogen of pneumonia with clinical symptoms and signs and radiological examination. As soon as he was treated with ceftriaxone and isepamicin, clinical improvement was followed with no further growth of E. americana or other pathogenic isolates from sputum culture. This suggests to be the case of pneumonia caused by E. americana for the first time in the Korean literature.