Antibiotic activity and concentrations in clinical samples from patients with chronic bacterial prostatitis

Objectives: Chronic bacterial prostatitis (CBP) is the most common urological disease in patients younger than 50 years, whose long-standing symptoms could be related to an inappropriate therapeutic regimen. The objective was to analyse the sensitivity of microorganisms isolated from patients with CBP and measure the weekly antibiotic concentrations in serum, semen and urine.

Material and methods: For the antibiotic sensitivity study, 60 clinical isolates were included between January 2013 and December 2014 from semen samples from patients with microbiologically confirmed CBP. Broth microdilution was performed on the samples. For the antibiotic concentration study from January to May 2014, urine, blood and semen samples were collected weekly, over 4 weeks of treatment from 8 patients with positive cultures for CBP. The concentrations were measured using ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS).

Results: The antibiotics fosfomycin and nitrofurantoin had the highest activity (95.2% in both cases). The mean antibiotic concentrations in semen during the 4 weeks studied were as follows: 1.68mg/L, 8.30mg/L, 2.61mg/L, 0.33mg/L and 2.90mg/L, respectively, for patients 1 to 5, who were treated with levofloxacin; 1.625mg/L for patient 6, who was treated with ciprofloxacin; 2.67mg/L for patient 7, who was treated with ampicillin; and 1.05mg/L for patient 8, who was treated with doxycycline. Higher concentrations were obtained in the urine samples than in serum and semen, the latter 2 of which were comparable.

Conclusions: Fosfomycin is proposed as the primary alternative to the empiric treatment of CBP due to its high in vitro activity. The antibiotic concentration in semen was higher than the minimal inhibitory concentration against the aetiological agent, although microbiological negativisation was not always correlated with a favourable clinical outcome.