Preliminary clinical study of the effect of ascorbic acid on colistin-associated nephrotoxicity.

Nephrotoxicity is a dose-limiting factor of colistin, a last-line therapy for multidrug-resistant Gram-negative bacterial infections. An earlier animal study revealed a protective effect of ascorbic acid against colistin-induced nephrotoxicity. The present randomized controlled study was conducted in 28 patients and aimed to investigate the potential nephroprotective effect of intravenous ascorbic acid (2 g every 12 h) against colistin-associated nephrotoxicity in patients requiring intravenous colistin. Thirteen patients received colistin plus ascorbic acid, whereas 15 received colistin alone. Nephrotoxicity was defined by the RIFLE classification system. Additionally, urinary neutrophil gelatinase-associated lipocalin (NGAL) and N-acetyl-beta-d-glucosaminidase (NAG) were measured as markers of renal damage, and plasma colistin concentrations were quantified. The baseline characteristics, clinical features, and concomitant treatments of the patients in the two groups were comparable. The incidences of nephrotoxicity were 53.8% (7/13) and 60.0% (9/15) in the colistin-ascorbic acid group and the colistin group, respectively (P = 0.956; relative risk [RR], 0.9; 95% confidence interval, 0.47 to 1.72). In both groups, the urinary excretion rates of NGAL and NAG on day 3 or 5 of colistin treatment and at the end of colistin treatment were significantly higher than those at the respective baselines (P < 0.05). However, the urinary excretion rates of these biomarkers at the various times during colistin treatment did not differ significantly between the groups (P > 0.05). The plasma colistin concentrations in the two groups were not significantly different (P > 0.28). The clinical and microbiological outcomes and mortality of the patients in the two groups were not significantly different. This preliminary study suggests that ascorbic acid does not offer a nephroprotective effect for patients receiving intravenous colistin. (This study has been registered at ClinicalTrials.gov under registration no. NCT01501968.).

Listeria monocytogenes brain abscess: two cases and review of the literature.

Listeria monocytogenes is a gram-positive bacillus that exhibits predilection to infect the central nervous system in immunocompromised individuals; the most common manifestations are meningitis and rhombencephalitis. Listerial brain abscesses are rare. We report here two brain abscess cases caused by L. monocytogenes in patients receiving immunosuppressive agents. The first patient presented with left hemiparesis mimicking stroke and the second patient presented with neurological symptoms without fever, which was indistinguishable from brain tumor. In both cases, magnetic resonance spectroscopy (MRS) was performed to differentiate infectious processes from other causes. Diagnosis was made with a positive blood culture in both cases. Listerial DNA was detected in the pus aspirated from the abscess in the first case. Both patients were successfully treated with intravenous ampicillin followed by oral amoxicillin. MRS was useful in differentiating infectious processes from non-infectious causes.