Isolated gonococcal ascending aorta aneurysm

Abstract

We present a very rare case of an acute septic infection and vegetative mycotic aneurysm caused by Neisseria gonorrhoeae in a 52-year old male. The aortic valve was bicuspid and calcified. He was successfully treated by the resection of the ascending aorta and the aortic valve with a replacement by separate prostheses, followed by 2 weeks of intravenous antibiotic therapy. The patient was followed up 18 months postoperatively with no signs of reinfection.

INTRODUCTION

Since the introduction of penicillin, disseminated infections caused by Neisseria gonorrhoeae are rare, but can occur in 1-3% of patients [1]. A localized infectious aortitis is collectively called a mycotic aneurysm regardless of the microbiological background. The aortic intima is generally highly resistant to bacteria, but if this barrier is disrupted, certain bacteria have a tendency for this location.

CASE REPORT

A 52-year old male was referred to the Helsinki University Hospital with sudden upper abdominal pain. His previous medical history consisted of diet-controlled type 2 diabetes mellitus and chronic gastritis with an associated tendency to anaemia. Six months prior to the hospital admission, he had visited Thailand where he suffered from an open leg wound.

At the hospital admission, he was haemodynamically stable without any signs or symptoms of neurological disorder. A systolic murmur was audible. The left upper quadrant of his abdomen was tender and an enlarged lymph node could be palpated in the neck. The body temperature was 37.5°C and the blood pressure was 150/70 mmHg. The white blood cell count was 23 × 10⁹/l and the c-reactive protein (CRP) value was 161 mg/l.

In the abdominal computed tomography (CT) scan, an enlarged spleen with a local infarction was detected. Transthoracic echocardiography revealed a mild regurgitation in the aortic valve and calcification in the cusps. The mean transvalvular gradient was 12 mmHg. A mobile mass was seen in the ascending aorta. Consequently, an aortic CT scan was performed where, 4 cm above the sinotubular junction (STJ), a saccular aneurysm was visible (Fig. 1). As there was no clear delineation of the aortic wall to the surrounding structures, a localized rupture was suspected.

Figure 1:

(A) A transverse section of CT depicts a local aneurysm at the ascending aorta with no clear delineation to the surrounding structures. (B) Reconstruction images of the aorta demonstrate a good distance between the aneurysm and the innominate artery. The aneurysm was resected with the aortic cross-clamped proximal to the aortic arch.

The patient was admitted to the operating theatre for emergency surgery. In the intraoperative transoesophageal echocardiography (TEE), a bicuspid aortic valve was found with the anterior–posterior orientation where the fused anterior leaflet was thickened and had a restricted motion. In addition, a mild aortic regurgitation was noted. After the induction of anaesthesia (with propofol–etomidate–fentanyl–esmeron), the right femoral artery was exposed, median sternotomy was performed and heparin was given. The ascending aorta was tightly adherent to the pericardium and every effort was made to minimize the manipulation of the aneurysmatic area prior to the cardiac arrest. The cannulation for the heart–lung machine was to the right femoral artery and to the right atrial appendix. After the cardiopulmonary bypass was initiated, the ascending aorta distal to the aneurysm was carefully dissected and cross-clamped proximal to the innominate artery. The aorta was transected above the STJ and the heart was arrested with cold blood cardioplegia administered to both coronary ostia under the direct vision. The aneurysm was dissected from the surrounding tissues and the ascending aorta resected as a whole. The purulent secretion was seen in the lesions of the aortic wall and freely mobile vegetations could be seen within the saccular aneurysm (Fig. 2). In accordance with the TEE findings, the aortic valve was found to be bicuspid with a calcified fused anterior cusp, but no visual evidence of valve endocarditis. The decision to replace the valve was made as, based on the echo findings, macroscopic appearance and bicuspid morphology, the risk of reoperation in the near future was deemed to be high. This was performed with a 25-mm SJM Regent™ (St. Jude Medical Inc., St. Paul, MN, USA) mechanical valve prosthesis. The ascending aorta was reconstructed with 28-mm Wovex™ (C.R. Bard Inc., Murray Hill, NJ, USA) collagen-impregnated woven Dacron graft.

Figure 2:

Intraoperative image of the ascending aorta after opening the aorta. *Aortic clamp, **transected proximal aorta and ***large thrombotic vegetations protruding from the aneurysm towards the aortic lumen.

The patient was weaned from the respirator within 12 h, and with no major complications. He was discharged from the ICU on the first postoperative day. The blood cultures showed the growth of N. gonorrhoeae in all three specimens. Tissue sample cultivations from the aortic wall, aortic valve and pericardial fluid were negative. The antibiotic therapy consisted initially, and prior to obtaining the bacterial sensitivity analysis, of meropenem, ceftazidime and doximycine. Thereafter, this was switched to intravenous ceftriaxone which was continued up to 2 weeks. The patient was in good condition 18 months after the surgery with no evidence of recurrent infection. The white blood cell count and CRP values have remained within a normal limit since 3 weeks after surgery. An aortic CT scan 16 months postoperatively has no signs of infection. He is still denying any possibility of a sexually transmitted disease.

DISCUSSION

Neisseria gonorrhoeae is one of the most prevalent sexually transmitted pathogen, and an increase of ciprofloxacillin-resistant strains is observed. Some gonococcal strains have shown higher virulence and tissue invasiveness and, furthermore, variations in the gonococcal protein and lipooligosaccarides actively suppress host-adaptive immune reactions. These factors added to the increasing rate of the uncomplicated gonococcal disease, and behavioural changes might predict the increasing infection rate [3, 4].

Dissemination of gonococcal infection has been observed in 0.5–3% of patients. Symptoms of disseminated infection can range from minor joint pain, a few skin lesions and no fever to highly febrile and severe polyartritis. Myocarditis and meningitis are also occasionally encountered [1]. While gonococcus accounted for 11–26% of the endocarditis cases in the pre-antibiotic era, it has virtually disappeared since the advent of modern antibiotic treatment [2]. Of note, pulmonic valve involvement in this infection is also observed [5]. Isolated aortitis with associated mycotic aneurysm is, however, a true rarity and is not generally known to be a clinical feature in a systemic gonococcal infection. Prior to the patient presented herein, only one case report after World War II could be found in the literature.

The aortic intima is resistant to bacteremic invasions and it is highly possible that a predisposing disease has been at the site of the mycotic aneurysm. It is nowadays widely accepted that congenital bicuspid aortic valve disease is frequently associated with intrinsic smooth muscle abnormality leading to the aneurysmal degeneration of the ascending aorta. This might have been the predisposing factor for the localized infection and formation of the mycotic aneurysm. On the other hand, the patient had risk factors for atherosclerotic disease such as smoking and obesity which might predispose to intimal discontinuity. Septic emboli to the vasa vasorum have also been proposed as a common pathogenic mechanism, but this is not clinically proven. Gonorrhea has been traditionally diagnosed with Gram stain and culture; however, nucleic acid amplification techniques are becoming more common and have shown a good sensitivity and specificity. In our case, N. gonorrhoeae grew in all preoperative blood cultures but not in intraoperative tissue specimens that were obtained first after the antimicrobial treatment had already been commenced. Unfortunately, no PCR was performed. Histology showed large areas of granulation and abscess-like leukocyte pools, but tissue stainings were negative to bacteria or fungi. The common treatment for a mycotic aneurysm is the combination of the adequate surgical resection and proper antibiotic therapy. Contamination of the field is seldom totally avoided. False aneurysm, rupture, thrombosis or abscess is common results of a persistent infection. The infection might also affect the foreign graft material, which might then lead to persistent infection until the exogenous material is removed. In our case, 2-week antibiotic treatment  proved to be enough to eradicate the infectious agent, when no involvement of the aortic valve was seen.

Conflict of interest: none declared.