Salmonella-induced ovarian abscess developing in bilateral ovarian endometriomas: A case report

Abstract

Salmonella species are common causes of foodborne illnesses, typically resulting in self-limiting gastroenteritis. In rare cases, however, they can cause extraintestinal infections, including pelvic infections. This report concerns a rare case of Salmonella infection of bilateral ovarian endometriomas. A 29-year-old nulligravid woman with known bilateral ovarian endometriomas presented with persistent fever and lower abdominal pain, following symptoms of diarrhea. Computed tomography on admission showed moderate ascites and increased density of mesenteric fat, suggestive of peritonitis. Her symptoms and inflammatory markers persisted, despite 5 days of empirical antibiotic therapy for pelvic inflammatory disease (intravenous ceftriaxone 1 g/day, clindamycin 2400 mg/day, and oral doxycycline 200 mg/day). Repeat computed tomography showed worsening peritonitis and a new right-sided pleural effusion, prompting surgical intervention. Laparotomy revealed purulent material within both endometriomas and cultures confirmed Salmonella infection. Detailed history-taking indicated that the patient had ingested raw eggs before symptom onset. The patient made a full recovery after surgery and tailored antibiotic therapy adjusted according to the susceptibility. This case highlights the importance of considering Salmonella as a rare cause of tubo-ovarian abscess, especially in patients with a history of dietary exposure and pre-existing endometriomas. Prompt surgical drainage and appropriate antibiotic therapy are key to preventing complications and preserving fertility.

Highlights

• •Salmonella can cause tubo-ovarian abscess in women with pre-existing endometriomas.
• •This report concerns the case of a woman with known endometriomas in whom symptoms of fever and lower abdominal pain persisted despite 5 days of empirical antibiotic therapy.
• •Salmonella enterica was present in the patient's endometriomas and peritoneal fluid.
• •Ceftriaxone monotherapy and surgery led to a full recovery.

1. Introduction

Salmonella is a genus of Gram-negative bacilli that cause foodborne illnesses worldwide. Although most cases are self-limiting gastrointestinal infections, bacteremia and extraintestinal infections may also occur, particularly in immunocompromised hosts. The pelvic cavity is an uncommon site of secondary infection, and ovarian involvement is particularly rare.

Ovarian endometriomas are not typically considered to be susceptible to hematogenous infection; however, when infections do occur, clinical deterioration can be rapid, and delayed diagnosis may lead to further complications and infertility. This report concerns a rare case of bilateral ovarian endometriomas infected with Salmonella enterica serovar Saintpaul, likely acquired through the ingestion of raw eggs. The diagnostic and therapeutic challenges are discussed.

2. Case Presentation

A 29-year-old nulligravid woman with known bilateral ovarian endometriomas under gynecologic surveillance presented with a 2-week history of persistent fever and lower abdominal pain. Although she had experienced self-limiting diarrhea for a few days prior to the onset of fever and lower abdominal pain, this history was not initially revealed.

On presentation, the patient complained of chills and diffuse low-abdominal tenderness. She had a fever of 39.8 °C, a white blood cell count of 6860/μL (within the normal range), and markedly elevated C-reactive protein, at 31.40 mg/dL. Vaginal swab culture showed normal flora, and polymerase chain reaction tests for Neisseria gonorrhea and Chlamydia trachomatis were negative. Blood cultures obtained on admission were also negative.

Transvaginal ultrasound revealed bilateral ovarian cysts measuring 11 × 8 cm on the right and 8 × 7 cm on the left, and magnetic resonance imaging confirmed a diagnosis of bilateral ovarian endometriomas (Fig. 1). Contrast-enhanced computed tomography showed moderate ascites and increased density of mesenteric fat, suggestive of peritonitis (Fig. 2).

Fig. 1.

Magnetic resonance imaging T1-weighted image revealing bilateral ovarian endometriomas, measuring up to 9 cm in diameter on the right and 8 cm on the left.

Fig. 2.

Repeat contrast-enhanced computed tomography, performed on hospital day 6, showed worsening peritonitis (arrow) and a new right-sided pleural effusion (arrowhead) compared with the initial image at admission.

Empirical antibiotic therapy for presumed pelvic inflammatory disease was initiated, with intravenous ceftriaxone 1 g/day, clindamycin 2400 mg/day, and oral doxycycline 200 mg/day. Despite 5 days of treatment, however, there was no clinical or biochemical improvement. Repeat computed tomography showed worsening peritonitis and a new right-sided pleural effusion (Fig. 2).

Because of her lack of response, the patient underwent laparotomy on hospital day 6. Intraoperatively, the peritoneal cavity was filled with dark reddish fluid and the bilateral ovarian endometriomas were adherent to the uterus and rectum (Fig. 3). The Douglas pouch was obliterated. Severe inflammation and adhesions were also observed around the sigmoid colon, ileocecal region, greater omentum, and liver surface.

Fig. 3.

The peritoneal cavity filled with dark reddish fluid. Bilateral endometriomas (right: arrowhead; left: arrow) were adherent to the uterus and rectum. The Douglas pouch was obliterated.

Cultures of the cyst contents and peritoneal fluid were sent for microbiological analysis, and bilateral ovarian cystectomy was performed. Peritoneal lavage was performed with 7000 mL of saline, and drains were placed in the Douglas pouch, Morrison's fossa, and splenic fossa.

The antibiotic regimen was modified after surgery: ceftriaxone was increased to 2 g/day and clindamycin was replaced with metronidazole 2000 mg/day for anaerobic coverage. Salmonella group O4 was identified from the contents of both endometriomas and the peritoneal fluid on postoperative day 1. Further history-taking revealed that the patient had eaten raw eggs the day before the onset of her diarrhea, followed by the development of persistent fever and lower abdominal pain. The organism was sensitive to all tested antibiotics, and ceftriaxone monotherapy 2 g/day was therefore continued. Stool cultures submitted after the diagnosis of Salmonella infection were negative. Her clinical condition and inflammatory markers improved significantly, and all drains were removed on postoperative day 7. A small residual intra-abdominal abscess and right pleural effusion remained on day 10, and intravenous ceftriaxone was therefore continued and switched to oral levofloxacin 500 mg/day on postoperative day 17, at the time of her discharge. Oral antibiotic therapy was continued for about 1.5 months until abdominal ultrasonography confirmed complete resolution of the intra-abdominal abscess. Genetic analysis identified the pathogen as Salmonella enterica serovar Saintpaul. Dienogest was initiated upon resumption of menstruation to prevent the recurrence of endometriosis. At the latest follow-up, the patient remained well with no evidence of recurrence.

3. Discussion

This report presents a rare case of Salmonella infection involving bilateral ovarian endometriomas. Although Salmonella is a common cause of foodborne illnesses, it rarely causes extraintestinal infections, including ovarian abscesses.

There are over 2500 serotypes of Salmonella, broadly classified into typhoidal and nontyphoidal strains [1]. Nontyphoidal Salmonella typically causes self-limiting gastroenteritis; however, bacteremia and hematogenous spread may occur in around 5 % of these cases, particularly in immunocompromised hosts [2]. The most frequently affected extraintestinal sites include the nervous system, bone, lungs, spleen, kidneys, and reproductive organs, but ovarian involvement is rare, with only about 30 reported cases over the past five decades. Among these cases, Salmonella enteritidis and Salmonella typhi are the most commonly isolated strains [2,3]. Salmonella Saintpaul is less frequently implicated in ovarian abscesses, but has sometimes been associated with large-scale foodborne outbreaks [4] and is known for its bacteremia potential. The pathophysiology likely involves bacterial translocation through the intestinal epithelium, residence in mesenteric lymph nodes, and subsequent dissemination to other sites via macrophages [2,5].

In the present case, considering that Salmonella can translocate directly through the intestinal epithelium, the most likely route of infection was transenteric spread to the adjacent organ, i.e., the ovarian endometriomas. Secondary infection by Salmonella was not suspected at the initial presentation, and stool cultures were therefore not performed prior to antibiotic administration. Although the detection rate of Salmonella in stool cultures is generally low [6], it is possible that the organism would have been detected if the culture had been analyzed.

Hematogenous spread represents another potential route of infection. Although blood cultures obtained on admission, before antibiotic administration, were negative, it is possible that transient bacteremia occurred during the episode of Salmonella gastroenteritis, resulting in seeding of the endometriomas. In either case, the patient developed febrile lower abdominal pain attributable to the endometrioma infection, after resolution of the diarrheal symptoms caused by Salmonella enteritis. This temporal sequence may have contributed to the difficulty in isolating the organism in stool or blood cultures.

The white blood cell count at admission remained within the normal range, differing from the typical leukocytosis observed in many bacterial infections. As an intracellular pathogen, Salmonella is capable of surviving within macrophages, thereby evading the host immune response. This intracellular persistence may account for the discrepancy between normal leukocyte counts and markedly elevated C-reactive protein levels, which reflect cytokine-mediated activation of cellular immunity [7].

Based on the initial clinical findings, empirical antibiotic treatment for pelvic inflammatory disease was initiated. Pelvic inflammatory disease is typically caused by infection ascending from the vagina or cervix, usually due to sexually transmitted pathogens, although enteric bacteria, anaerobes, and normal vaginal flora may also be involved. Accordingly, broad-spectrum antibiotic coverage was initially selected. Ceftriaxone was active against the Salmonella strain isolated in this case and was administered from the outset; however, the infection worsened over time, and the lack of response to empirical antibiotic therapy ultimately led to surgical intervention. The delay in proceeding to surgery may have contributed to the need for prolonged postoperative intravenous and oral antibiotic therapy to resolve the infection.

Previous reports of Salmonella-infected ovarian tumors indicate that most cases require surgical drainage, suggesting that infection control is challenging with antimicrobial therapy alone, even when the strains show susceptibility. In addition, the recent increase in the use of broad-spectrum antimicrobials has been associated with the emergence of quinolone-resistant strains, particularly in Asia [8], and such cases can be difficult to manage. The present infection involved bilateral endometriomas and surgery was therefore initially avoided, to preserve the patient's fertility. Previous literature [5,6] and the patient's clinical course, however, suggest that earlier surgical drainage may have been preferable in terms of both infection control and fertility preservation.

This case highlights the importance of detailed history-taking, and secondary infection following a foodborne illness should be considered in patients presenting with symptoms such as nausea or diarrhea. Stool and blood cultures should be obtained prior to antibiotic therapy, and the possible need for early surgical drainage should always be considered.

4. Conclusion

Tubo-ovarian abscesses caused by Salmonella infection should be considered in women with known endometriomas presenting with fever and lower abdominal pain following gastrointestinal symptoms. The current case highlights the importance of thorough history-taking, and the timely collection of stool and blood cultures prior to antibiotic administration. In cases where secondary Salmonella infection is strongly suspected, prompt surgical drainage is essential, while continuing empirical antibiotic therapy. Culture of the abscess contents is also critical for pathogen identification and targeted therapy. Early intervention can lead to favorable outcomes and fertility preservation.

Contributors

Eriko Iito contributed to patient care, date collection, and drafting and editing the manuscript.

Lifa Lee contributed to acquiring and interpreting the data and reviewing the manuscript.

Tomohito Kobiyama and Naho Tokunaga contributed to undertaking the literature review.

Koki Yagi contributed to patient care and acquiring and interpreting the data.

Mao Sekimata, Naoki Abe, Sachino Kira, Sotaro Hayashi, Masamitsu Kurakazu and Satoshi Nishiyama contributed to undertaking the literature review.

Hiroshi Tsujioka contributed to revising the article critically for important intellectual content and supervision.

Patient consent

Written informed consent was obtained from the patient for publication of the case report and accompanying images.

Provenance and peer review

This article was not commissioned and was peer reviewed.

Funding

This work did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Declaration of competing interest

The authors declare that they have no competing interest regarding the publication of this case report.