A Case of Serratia Fonticola Urinary Tract Infection in an Elderly Patient

Introduction

The species Serratia fonticola was first described in 1979 by Gavini et al. [1] as a new member of the Enterobacteriaceae family, isolated from water and soil [1]. Very few cases of Serratia fonticola infection in humans have been reported, including a case of emphysematous pyelonephritis [2], endocarditis [3], skin infection in diabetic foot [4], biliary tract infection [5], infection complicating parotid malignant tumors [6], and cerebellar abscess [7], urinary tract infections [8,9], knee septic arthritis [10], blood stream infections [9,11] and even an infection following a bear bite [12]. We present a case of Serratia fonticola urinary tract infection in an elderly patient.

Case Presentation

A 90-year-old female patient was admitted to our hospital due to electrolyte imbalance and diarrhea. The patient had a history of diabetes mellitus, dyslipidemia, ischemic heart disease and atrial fibrillation, for which she was receiving medication and she was admitted to the Internal Medicine Clinic for further investigation. On admission the patient had: temperature 37.2°C, blood pressure 101/55mmHg, HR 88/min, SO2: 94%, respiratory auscultation: bilateral ronchi, abdominal examination: abdomen soft to touch with no masses, swelling, pain and rigidity, bowel sounds: present. The patient was admitted to the Internal Medicine Clinic for further investigation.

The initial laboratory results were as below:
a. CBC: WBC 7960/μL, (Neutrophils 68.3%, Lymphocytes 18.7%), Hemoglobin 10.5gr/dL, Hematocrit 31.9%,
b. Clinical Chemistry: Glucose: 164mg/dL, Urea: 39mg/dL, Creatinine 1.52mg/dL, Κ 3.0mmol/L, Na 129 mmol/L,CRP 0.17mg/dL, hs-cTnT 8.49 ng/L, 2) Urinalysis: WBC >200hpf, RBC: 15-20 hpf, abundant microorganisms.
c. Urine culture: >105cfu/mL of a Gram (-) rod. The identification and susceptibility testing were performed with the Microscan Autoscan System (Siemens).

The microorganism was identified as Serratia fonticola (Microscan ID: 99.99%) and was resistant ampicillin, ampicillin/sulbactam, cefepime, cefoxitine, ertapenem, levofloxacine and piperacillin and susceptible to piperacillin/tazobactam, amikacin, gentamicin, tobramycin, imipenem, meropenem, nitrofurantoin, fosfomycin and cotrimoxazole, according to the EUCAST criteria. The patient was prescribed fosfomycin and was discharged with instructions for follow up.

Discussion

Serratia fonticola is a Gram negative, motile, peritrichous bacterium which was primarily isolated in aquatic environments, soil and sewage, but it is also reported to be found in several plants, birds, mammals and reptiles [2]. Aljorayid et al. [9] assume that Serratia fonticola may be, albeit sporadically, a member of the gastrointestinal microbiota as a result of consuming contaminated vegetables, causing, given the opportunity, infections [9].

Although Serratia fonticola infections have not been described as particularly challenging as far as antimicrobial resistance goes, this microorganism has been found to harbour resistance genes, such as a chromosome-encoded AmpC β-lactamase SFDC-1 [13], the vanW gene, responsible for resistance to vancomycin, on a transposon of the environmental strain S. fonticola DSM4576, a class A β-lactamase gene blaCTX-M and an inducible FONA-type extended-spectrum β-lactamase gene [9], which has the theoretical, yet undeniable, potential to transmit to other microorganisms. This potential risk renders Serratia fonticola additionally interesting in relation to infectious diseases and antimicrobial resistance surveillance.

Conclusion

The fact that an increasing number of Serratia fonticola infections are reported should raise our attention not only to the role of this microorganism as a human pathogen, but also to its potential in the spread of antimicrobial resistance genes.

Acknowledgement

None.

Conflict of Interest

None.

References

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