A case of multiple splenic abscesses due to Enterococcus hirae

Introduction: Enterococci are prevalent human pathogens that display increasing resistance to antimicrobial agents. Twelve species pathogenic for humans have been described to date, including the most common human isolates, Enterococcus faecalis and Enterococcus faecium. Enterococcus hirae is a known member of the intestinal flora of several domestic animal species but rarely encountered in humans.


Introduction
Splenic abscess is an uncommon infection that manifests as a single or multiple abscesses, detected in 0.14 % to 0.7 % autopsy studies (Chang et al., 2006).However, increasing incidence is reported, possibly because of enhanced diagnosis as a result of developments in imaging studies.The risk factor for splenic abscess is endocarditis, as it typically results from seeding from pre-existing endocarditis or in some instances, seeding from other infected organs (Ooi & Leong, 1997).Earlier, the incidence of splenic abscess as a complication of infective endocarditis was reported in 4.8 % of patients (Robinson et al., 1992).
Clinical features of splenic abscess include recurrent or persistent fever and left upper quadrant pain with or without splenomegaly (Robinson et al., 1992).However, these features are not evident in all patients, and some may present with other non-specific symptoms, such as chills and constitutional symptoms observed in 40 % and 36 % of patients, respectively, by Westh et al. (1990).Splenic abscesses can be diagnosed via computed tomography scan of the abdomen (CT-Abdomen) but are often confused with splenic infarction, which is associated with similar risk factors (Robinson et al., 1992;Westh et al., 1990).Previous reports focusing on the etiology of splenic abscess have described a wide variety of pathogens that differ according to geographical distribution and the timeperiod of the studies conducted (Robinson et al., 1992;Westh et al., 1990).The most commonly reported pathogens include Staphylococci, Streptococci, Escherichia coli, and Salmonella spp.Mycobacterium tuberculosis was reported to be the cause in 0.8 % to 7.8 % of cases, but occurred more frequently in high-prevalence areas (Robinson et al., 1992).Fungi, especially Candida spp., have also been frequently identified as a cause of splenic abscess, especially with the increasing numbers of immunocompromised patient populations (Johnson & Raff, 1984).
The treatment of choice for splenic abscesses involves both surgical and medical options.Medical therapy entails providing targeted antimicrobial therapy tailored to the infective organism (Ooi & Leong, 1997;Chang et al., 2006), while the gold standard surgical management is splenectomy (Johnson & Raff, 1984).Percutaneous aspiration of splenic abscesses has shown moderate success in reported cases, and therefore should not replace splenectomy as the standard measure.The optimal duration of antimicrobial therapy for splenic abscesses is yet to be established, since insufficient trials have been performed to determine the most favourable agents and duration of therapy (Chang et al., 2006).
To our knowledge, only 9 human infections due to E. hirae have been documented to date.The current case, an immunocompetent patient displaying splenic abscesses with sepsis, represents the first case of infection by this organism leading to such clinical syndromes.

Case report
A 48-year-old woman was admitted in November 2012 to the Emergency Department of Farwania Hospital, presenting with 1-month history of mild left upper quadrant (LUQ) abdominal pain, productive cough and fever.The patient did not complain of any changes in bowel habits, haemoptysis, night sweats or weight loss.She had a history of insulin-dependent type 2 diabetes mellitus and had undergone tubal ligation 17 years beforehand.The patient denied any recent contact with animals.On physical examination, temperature was 40 uC, heart rate was 112 bpm and blood pressure was 110/70 mmHg, with oxygen saturation of 94 % in room air.An abdominal examination revealed LUQ tenderness, but no guarding or rigidity.There was no sign of hepatomegaly or splenomegaly.On chest auscultation, breath sounds appeared diminished in the left lower zone without crackles or wheeze.Heart sounds were normal with no murmurs or added sounds.Neurological examination revealed normal results.

Investigations
Laboratory investigations revealed a white blood cell (WBC) count of 20 6 10 9 /L (83 % neutrophils; 13 % lymphocytes) and haemoglobin (6.6 g L 21 ).Liver and renal function tests were normal, but the C-reactive protein (CRP) level was 212 mg L 21 (normal range less than 10 mg/l 21 ).Blood was drawn, and two sets of blood culture vials incubated in BACTEC 9240 blood culture system (BD Diagnostic Systems).Both aerobic and one of the anaerobic vials displayed positive signals after 12, 15, and 16 h, respectively.Gram staining of smears from the blood culture vials revealed gram-positive cocci in chains resembling streptococci.Bacterial growth was facultatively anaerobic, producing small, grey, alpha-haemolytic colonies on 5 % sheep blood agar.The isolate was identified as Enterococcus spp. with a negative catalase test reaction, and positive bile-aesculin and growth in 6.5 % salt broth tests.Moreover, the isolate reacted with Lancefield group D antisera (Streptex).Biochemical identification with VITEK 2 (bioMe ´rieux) indicated E. gallinarum with 98 % probability while the Analytical Profile Index for streptococci (API Strept, bioMe ´rieux) classified the strain as E. durans (81 % probability), leading to inconclusive identification.The strain was finally identified as E. hirae using the BD Phoenix Automated Microbiology System (BD Diagnostic Systems) with the sequence number 427610338643 and 99 % confidence value, and confirmed via 16S rDNA sequencing.DNA isolation and amplification for 16S rDNA sequencing was performed using the MicroSeqH 500 16S rDNA sequencing kit (AB Applied Biosystems), according to the manufacturer's instructions.DNA sequencing was conducted with BigDye Terminator V1.1 Chemistry in a ABI 313061 genetic analyzer (Applied Biosystems).Strain identity was established by querying the 16S rDNA bacterial gene database using MicroSeq ID Analysis software (AB Applied Biosystems).
Abdominal ultrasonography (US) revealed cystic lesions in the spleen suggestive of two splenic abscesses, which were confirmed with a computed tomography (CT) scan (Fig. 1).Transthoracic echocardiography, followed by transoesophageal echocardiography, did not show evidence of infective endocarditis or other cardiac abnormalities.Empirical therapy with piperacillin/tazobactam (PTZ) 4.5 g q8h intravenously (IV), vancomycin 1 g q12h IV, and metronidazole 500 mg q8h IV was initiated, and splenectomy performed on day 2 of hospital stay.Pus from splenic abscess was submitted to the laboratory for microbiologic analysis.Examination of pus using gramstained smear revealed pus cells and few gram-positive cocci in chains, while culture revealed growth of E. hirae similar to the blood culture isolate.Histopathological analysis of the spleen confirmed the presence of abscesses,

Treatment
Following identification the isolate and availability of its antimicrobial susceptibility profile, vancomycin and metronidazole were discontinued and ampicillin 4.0 g q4h IV and linezolid 600 mg q12h IV added to the regimen with PTZ.Blood culture was repeated on day 7 of hospital stay, but no growth was evident after 5 days of incubation.

Outcome and follow-up
The patient improved clinically and became asymptomatic.All antibiotics were discontinued after two weeks of therapy.She received Haemophilus influenzae type b, quadrivalent meningococcal and pneumococcal polysaccharide vaccines before discharge from the hospital.A follow-up appointment at the surgical outpatient clinic a month later revealed good progress.
Phenotypic identification of E. hirae by semi-automated and other biochemical systems is usually difficult, perhaps owing to its common properties with E. durans (Canalejo et al., 2008;Devriese et al., 2002;Gilad et al.,1998;Poyart et al., 2002;Talarmin et al., 2011).Molecular studies have shown that E. hirae and E. durans are genotypically very similar and differentiated based on detection of mur-2 and mur-2 ed , respectively (Arias et al., 2006;Talarmin et al., 2011).Splenic abscess is an uncommon clinical condition, previously documented at a rate of 0.14 % to 0.7 % in autopsy studies (Lee et al., 2011) and reported more frequently in recent literature.Splenic abscesses are generally evident in patients with endocarditis where seeding of the incriminating organism occurs in the spleen, as well as those with obliterated immune systems, such as cases of neoplasia, trauma, and diabetes mellitus.Although our patient was free of cardiac lesions, she was a diabetic on insulin therapy.A recent surge in cases of splenic abscesses may be explained by the increase in the immunocompromised population and improved diagnostic imaging techniques, such as US and CT (Chang et al., 2006;Lee et al., 2011).The causative agents in most series have been identified as Streptococci, Escherichia coli and Treatment modalities entail antimicrobial therapy, percutaneous drainage (PCD) and splenectomy.However, no gold standard treatment for splenic abscess is currently available (Talarmin et al., 2011).Nevertheless, the mortality rate does not appear to differ among the three groups and is usually related to the underlying condition of the patient.Since our patient was diagnosed with multiple abscesses in the spleen, PCD was not an option, and considering her clinical condition, splenectomy was performed and parenteral antibiotics added to the treatment because of systemic infection.There is a paucity of data regarding the antimicrobial susceptibility profile of E. hirae, but ampicillin and high-level resistance to gentamicin have been reported (Canalejo et al., 2008).
In conclusion, E. hirae is a rare human pathogen accounting for ,1 to 3 % of all enterococcal species isolated from clinical samples (Canalejo et al., 2008).The source of infection remains dubious.Since knowledge of the antimicrobial susceptibility profile of E. hirae is limited, it is advisable that treatment is guided by antibiotic susceptibility testing and applied to patients on an individual basis.

Fig. 1 .
Fig. 1.Abdominal CT showing low-density lesions characteristic of splenic abscess in our patient

Table 1 .
Reported cases of human infections due to E. hirae Klebsiella pneumonia.Mycobacterium tuberculosis and Salmonella typhi have also been reported, highlighting geographical and population variations.To our knowledge, this is the first case of splenic abscess caused by E. hirae reported in the literature.