A 69-year-old man was admitted in August 2005, following a six hour history of suprapubic pain, fever and rigors. He had a long term catheter for a prostate problem and his past history included a myocardial infarction in 2001, followed by a series of small strokes. As a result of these, he had a mild residual left hemiparesis and had received a stent to his right carotid artery. On examination he was pyrexial (39.2°C) with otherwise normal vital signs and no new findings. Investigations showed a low white cell count (2.5 × 109/litre) and raised inflammatory markers, with an ESR of 84 mm/hr and C-reactive protein of 176 mg/l. Chest X- ray revealed no abnormalities of clinical significance.
Cultures of blood and urine grew E. coli resistant to all cephalosporins and fluoroquinolones but susceptible to meropenem. A diagnosis of septicaemia originating from a urinary tract infection was made. Intravenous meropenem 1 gm three times a day was commenced. However the patient continued to have raised inflammatory markers with intermittent pyrexia and meropenem was stopped after 14 days. Three sets of blood cultures taken 7 days later all grew E. coli with the same antibiogram as found previously. Meropenem was recommenced at the same dose.
A computed tomography (CT) scan was requested to explore the possibility of lymphoma or a deep abscess. This showed a small abdominal aortic aneurysm and a mild dilatation of the left subclavian artery (Figure ). A further scan was performed 2 weeks later to exclude leakage from the abdominal aneurysm. Whilst this possibility was discounted, two new intra-thoracic pseudo-aneurysms and associated haematomas were found; one was arising at the anterior aspect of the origin of the left subclavian artery and the second in the descending thoracic aorta (Figure ).
First scan showing only mild dilation of left subclavian artery.
Second scan showing new mycotic aneurysms and thrombus**.
The patient was transferred to a cardiothoracic surgery centre but intervention was not advised due to his vascular co-morbidities. Instead he was returned to our care for conservative management and continuation of his antibiotics. His fever and inflammatory markers gradually settled to normal. A third scan (Figure ) was performed after 4 weeks of consistent control over the infection. The rationale was to seek any resolution of the mycotic aneurysm as a prelude to withdrawing antibiotics. As can be seen from these final images, considerable resolution of the pseudo-aneurysms and haematomas had occurred. After a further check that blood cultures and inflammatory markers had normalised, intravenous meropenem was stopped after a total of 16 weeks. No further pyrexia occurred, and the patient remained well 3 months later.
Third scan (recuperative phase) showing reduced size of left subclavian artery aneurysm and clearing of thrombus.
An 80-year-old man was admitted in November 2004 with a 3-day history of malaise, anorexia and reduced mobility. His past history included three strokes affecting his left side. He also had a long term urinary catheter for prostatic disease. A routine catheter specimen of urine (CSU) taken three weeks prior to admission grew mixed coliform bacteria susceptible to several agents. This was not considered to be clinically significant.
On admission his vital signs were initially satisfactory and physical examination did not reveal any new abnormality. A chest X-ray showed bilateral hilar lymphadenopathy, with no clear cause. On the second day after admission, he developed transient pyrexia of 38°C. A CSU again grew coliform susceptible only to mecillinam, meropenem and gentamicin. No treatment was given.
On the 19th day pyrexia (38.1°C) recurred and oral trimethoprim 200 mg twice a day was commenced for presumed urinary infection. This was changed to intravenous gentamicin 300 mg once a day after blood cultures yielded E. coli, susceptible only to gentamicin and meropenem. Gentamicin was stopped after a week but pyrexia recurred the following day. A diagnosis of chest infection was made and further blood cultures were taken. E. coli with a similar resistance profile was isolated and the patient was commenced on intravenous meropenem 500 mg, three times daily.
At day 44, he developed a swelling on the right side of his neck. An ultrasound scan showed this to be a pseudoaneurysm of the right common carotid artery. Meropenem was increased to 1 g, three times daily and gentamicin was added. In spite of apparently responding to this regimen, with the CRP falling from 203 to 23 mg/l, the patient died on day 69 after contracting aspiration pneumonia.
The isolates from both cases were sent to the reference laboratory for molecular typing and characterisation of their Β-lactamases. Both belonged to UK epidemic E. coli
strain A, which produces CTX-M-15 ESBL [5
]. They also produced a CIT-type acquired CMY-23 AmpC Β-lactamase.
Multi Locus Sequence Typing (MLST) showed that these two isolates belonged to a genetic lineage ST 131, which has been identified as an important uro-pathogenic strain often with multiple antibiotic resistances (personal communication S.Lau).