Enterococcus faecalis-Related Prostatitis Successfully Treated with Moxifloxacin

LETTER

An Enterococcus sp. is involved in 5 to 10% of prostatitis cases (1). The treatment of enterococcal prostatitis remains a challenge because of the paucity of antibiotics achieving both bactericidal effect and good prostatic diffusion. Indeed, prostatic concentrations of amoxicillin have not been consistently assessed, with concentrations varying from 0.77 to 26 μg/ml (2). Cephalosporins achieve therapeutic levels in the prostatic tissue and fluid but are intrinsically inefficient against Enterococcus sp. Trimethoprim as a lipid-soluble base easily penetrates the prostatic tissue and fluid, whereas sulfamethoxazole does not, jeopardizing the synergy of the combination (3). Furthermore, trimethoprim-sulfamethoxazole appears active against enterococci when tested in vitro on folate-deficient medium but would fail in animal models, because enterococci absorb folate from the environment. Nitrofurantoin does not achieve therapeutic concentrations in the prostatic tissue (3). Most quinolones display moderate activity toward enterococci, with modal MICs of 1 to 2 mg/liter for ofloxacin, ciprofloxacin, levofloxacin, and norfloxacin (4). Despite excellent prostatic diffusion, they do not consistently achieve tissular concentration above the MICs, and Enterococcus faecalis eradication rates after ciprofloxacin or levofloxacin treatment (1 g/day, 28 days) were suboptimal in various studies (50 to 75%) (5). Moxifloxacin displays better activity, with MICs ranging from 0.125 to 0.25 mg/liter. Prostatic concentrations are reported to be twice as high as those in serum and 10-fold above the MIC for E. faecalis (6).

However, data regarding the use of moxifloxacin in enterococcal prostatitis remain limited to a single case report (7). We here report three cases of E. faecalis-related prostatitis successfully treated by moxifloxacin-based regimens. The main clinical features are detailed in Table 1.

TABLE 1.

Main features of the 3 patients with Enterococcus faecalis prostatitis and of the previously published case (7)

Reference	Age (yr)	Significant medical history	MIC of moxifloxacin (mg/liter)	Creatinine clearance (ml/min)	Antibiotic therapy	Clinical cure	Microbiological eradication	Relapse	Adverse effect
Our series	54	Kidney transplantation (polycystic kidney disease)	0.125	42	Amoxicillin, 3 g/day, 2 days; moxifloxacin, 400 mg/day, 19 days	Yes	Yes	No	No
Our series	45	None	0.125	75	Amoxicillin, 3 g/day, 3 days; moxifloxacin, 400 mg/day, 18 days	Yes	Yes	No	No
Our series	59	Diabetes mellitus, hypertension, kidney transplantation (diabetic nephropathy)	0.25	61	Moxifloxacin, 400 mg/day, 7 days; amoxicillin, 3 g/day, 21 days	Yes	Yes	No	Partial Achilles tendon rupture
7	47	Kidney transplantation	0.19		Amoxicillin, 4 g/day, 10 days; moxifloxacin, 400 mg/day, 42 days	Yes	Yes	No	No

All patients received moxifloxacin for ≥7 days, with good clinical (regression of fever, pain, and voiding symptoms) and microbiological (negative urine cultures at days 1 to 3 and at the end of moxifloxacin treatment for case 3) responses. Repeated urine cultures remained negative in all cases, with no recurrence reported during the 2-year follow-up. Two patients received amoxicillin for 2 to 3 days before moxifloxacin. Case 3 received moxifloxacin at 400 mg/day for 7 days but developed a partial Achilles tendon rupture that required a switch to amoxicillin.

Achilles tendinitis is a rare complication of fluoroquinolone treatment, reported in 1/2,000 prescriptions after a mean 8-day interval (8). Incidence is higher with levofloxacin and pefloxacin, in patients >60 years of age (8), and in those exposed to corticosteroids, with 52% of ruptures reported in corticosteroid-treated patients in a retrospective cohort (9). Additional side effects of moxifloxacin include a 3-times-higher risk of tachyarrhythmia and torsade de pointes than with other quinolones (10). It should not be used in patients with prolonged QT interval, hypokalemia, and hypomagnesemia and in those receiving class IA or III antiarrhythmic agents. Severe liver injuries have also been seldom reported (11). Altogether, adverse events requiring discontinuation of moxifloxacin occur in 3.6% of cases (12).

Such precautions, along with ecological considerations about selection of quinolone-resistant gut flora, hamper the use of moxifloxacin as a first-line drug in prostatitis (13). However, its usefulness in selected complex situations should be underlined. Our observations suggest that it could be an interesting tool for the treatment of prostatitis with susceptible E. faecalis.