A Rare Thermophilic Bug in Complicated Diverticular Abscess


Actinomyces are gram-positive, acid fast, anaerobic, filamentous normal bacteria in the human gastrointestinal tract. It was a common disease of human beings and cattle in the 18th century and was reportedly recognized as human disease by Von Langenbeck in 1845, but the very first case report was published by Lebert in 1957.A. meyeri infection in the gastrointestinal tract is a disease of mimicry presenting usually with vague symptoms while a straight diagnosis cannot be made easily.

Case Report

A 56-year-old female with a history significant for HIV infection managed properly with HAART and diverticulosis manifesting with recurrent abdominal abscess formation was readmitted for a 1-week history of recurrent left lower abdominal pain. Abdominal pain was described as constant, colicky, of high intensity, radiating to the left upper abdomen, aggravated by lying on her affected side, and relieved slightly with lying flat and curling and was associated with frequent nausea and vomiting. 


 Her past surgery history included hysterectomy for a 10 × 15 cm uterine myoma and ascending colonic abscess about 7 cm in diameter manifested from diverticulitis requiring surgical decompression of abscess with diverting colostomy for 2 years and fluoroscopy-guided drainage of a 7-cm diverticular abscess 3 months prior to admission.

She was managed with broad-spectrum antibiotics that were tailored to a specific antibiotic according to culture and sensitivity of the abscess until full remission was attained. Regarding her HIV, her viral load had persistently been undetectable. CD4 counts had been sustained between 600 and 1,000/mm3 with Truvada, Prezista, and Norvir combination. She had never been given prophylaxis or got treatment for HIV-associated opportunistic infections or malignancy. Her systemic review was insignificant for fever, night sweat, diarrhea, blood in stool, loss of weight, and poor appetite.

During admission, her vital signs were unremarkable except for low-grade fever of 100.7°F and physical examination was significant for diverting colostomy at the left lower quadrant of the abdomen with tenderness on the left side of the abdomen on palpation and rebound tenderness as well. Bowel sound was normal.

Admission labs including lipase, lactic acid, and liver function test were unrevealing for a source. Blood cultures, urine cultures, and fungal cultures showed no growth. ESR 122 and CRP 99.19 and fluid abscess for AFB showed no growth and cultures of fluid abscess showed gram-positive cocci in pairs and in clusters, E. coliBacteroides fragilis, and rare A. meyeri.

Later, blood cultures and sensitivity showed she is resistant to ampicillin, levofloxacin, Doxycycline, and intermediately susceptible to Unasyn (Ampicillin and sulbactam).

X-ray (abdomen) showed no evidence of small bowel obstruction. Presence of bowel outside of the abdominal cavity lateral to the iliac crests was consistent with parastomal hernia.

CT scan (abdomen and pelvis) on admission  showed status post left lower quadrant colostomy. Large parastomal hernia containing fat and nondilated small bowel loops with long segment mural thickening involving descending and sigmoid colon was seen. Left lower quadrant colostomy and large peristomal hernia containing fat and small bowel lobes were seen.

Moderate inflammatory changes were again seen surrounding the sigmoid colon suggestive of diverticulitis. Interval increase in the size of the fluid collection or abscess formation at or adjacent to the sigmoid colon since the previous exam measured approximately 5.5 × 4.3 cm.

Either extension or additional collection was also seen to the left of the colon measuring 3.6 × 3.2 cm. Mildly enlarged mesenteric lymph nodes were seen at the left lower abdomen.

CT scan (after 6 weeks of completion of antibiotics) showed near complete resolution of diverticular abscess. Persistent left lower quadrant phlegmonous stranding and hazy opacification was noticed. ESR was trending down to 50 and so was CRP (10.01) on recent follow-up.


Initially, she was on Zosyn 3.375G (Pipercillin and Tazobactam) every 6 h. Later, Zosyn was switched to Unasyn 3G and Bactrim DS every 12 h for 6 weeks with PICC line according to cultures and sensitivity. On follow-up, she felt better and had no more abdominal pain after 6 weeks of Unasyn, and repeated CT showed improved inflammation along the distal descending/sigmoid colon before the patient's left lower quadrant. The patient continues to follow in infectious disease for close monitoring of HIV and abdominal actinomyces.


A. israelii is the primary causal agent in actinomycosis in the gastrointestinal tract, but several novel species including A. neuii and A. meyeri are increasingly recognized. Actinomyces is reportedly distributed worldwide and the incidence is mostly found in middle age and is 2–4 times more common in men. With the progression of the disease process, it is presenting with the formation of chronic granulomatous tissue, extensive fibrosis and necrosis, abscesses, draining sinuses, and fistulas.Actinomycosis is usually a localized, single organ disease. Presence of multisystem involvement (e.g., lungs) in patients might favor systemic inflammatory conditions such as TB or Crohn's disease. The common site of infection is the cervicofacial region (50%), intra-abdominal cavity (20%), and thoracic region (15–20%). In abdominal actinomycosis, the common site being involved are the ileocecal areas, especially the appendix. However, lymphadenopathy and hematogenous spread is rare. Predisposing factors are recent abdominal procedures, trauma, neoplasia, or a perforated viscus.The disease usually runs in a chronic, indolent course with vague symptoms such as fever, weight loss, lethargy, and abdominal pain associated with a palpable mass, visible sinus tracts, or fistulas on physical examination. Laboratory abnormalities may only show anemia and leukocytosis.CT scan is the most useful imaging for the location and extent of the disease: an accurate diagnosis is fine-needle aspiration, which is used to detect the radiological response to treatment on follow-ups. CT-guided percutaneous aspiration may identify Actinomyces sulfur granules in pus and is also a good means of collecting material for culture. Combined with antibiotics, this maneuver can preclude unnecessary surgical intervention. During colonoscopy, findings include normal or thickened-appearing mucosa or colitis, ulceration, a nodular lesion, and button-like elevation of an inverted appendiceal orifice.A definitive diagnosis is made by histological finding of sulfur granules and/or cultures of actinomyces. The preferred specimen for culture is pus. Specimen should be sent under anaerobic conditions. Growth is faster in semiselective medium (5–7 days) but identification can often take 2–4 weeks even after growth has initially been observed. Sulfur granules, characterized by a zone of granulation tissue surrounding one or more oval eosinophilic granules, represent colonies of actinomyces.Before established diagnosis, many patients undergo resection. So, empiric treatment with penicillin in patients with suspected diagnosis prior to surgery is beneficial. The recommended dose is penicillin G (10–20 million units per day divided by every 4–6 h) for 4–6 weeks, followed by oral penicillin (2–4 g/day) or amoxicillin for 6–12 months. For penicillin-allergic patients, the alternatives are tetracycline, erythromycin, or clindamycin.Surgery should be usually reserved for complicated cases associated with severe necrosis, extensive lesions, large abscesses, persistent fistulas, or recurrent diseases. With combined medical and surgical treatment, the outcome is favorable in more than 90 percent of the cases. Mortality is rare.In our patient, although she is compliant with HIV medications, previous invasive surgery such as hysterectomy for uterine myoma, surgical decompression with diverting colostomy for complicated diverticulitis, and recent fluoroscopy-guided drainage 3 months prior for diverticular abscess on top with immunocompromised state, predisposes her to rare commensal bug from the GI tract.In conclusion, diverticular actinomycosis is a rare but often overlooked etiology for common conditions such as tuberculosis or carcinoma. Given its nonspecific presentation and nondescriptive symptomatology, physicians should be aware of this as a differential diagnosis. Medical treatment should be considered prior to surgery and other invasive procedures.


Actinomyces meyeri, Diverticular abscess, Gastroenterology

Author : Kyawzaw Lin et.al.,