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The case of a patient with highly gentamicin-resistant Enterococcus faecalis endocarditis treated with an ampicillin + ceftriaxone combination is described. We have designed a method to evaluate synergism between the antibacterial activity of patient's serum taken during a given antibiotic regimen (ampicillin) to which another antibiotic (ceftriaxone) is added in vitro. In this patient the two-drug combination was able to stop the bacteremia and prevent the infection of the prosthetic valve.

The aim of the study was to assess the microbiological activity and clinical efficacy of colistin and rifampin combination against multidrug-resistant (MDR) Pseudomonas aeruginosa infections. The antimicrobial activity of the colistin/rifampin combination was evaluated using the checkerboard and time-kill curve methods against different MDR P. aeruginosa strains. The combination of rifampin and colistin resulted fully (1 strain) or partially (5 strains) synergistic for 6/7 strains and minimum inhibitory concentrations (MICs) in combination were reduced to easily obtainable therapeutic levels. The time-kill curves showed that the combination was bactericidal against the strains tested. The clinical efficacy of the combination was tested in four patients with difficult-to treat infections (sepsis or pneumonia) caused by MDR P. aeruginosa. All infections were successfully treated. Our microbiological and clinical observations suggest that the addition of rifampin to colistin may result in a synergistic bactericidal combination that may be useful in patients with infections caused by MDR P. aeruginosa which are difficult to cure.

To the Editor: We read with interest the paper by Pallecchi et al. titled Antipneumococcal activity of ulifloxacin compared to levofloxacin and ciprofloxacin, recently published on Journal of Chemo...

(2011). Vancomycin-Resistant Enterococcus faecium (VRE) Bacteremia in Infective Endocarditis Successfully Treated with Combination Daptomycin and Tigecycline. Journal of Chemotherapy: Vol. 23, No. 4, pp. 240-241.

The broad resistance to antibody-mediated neutralization of lentiviruses recently isolated from infected hosts is a poorly understood feature which might contribute to the ability of these viruses to persist and to the failure of experimental vaccines to protect against virulent viruses. We studied the underlying molecular mechanisms by examining the evolution of a neutralization-sensitive, tissue culture-adapted strain of feline immunodeficiency virus upon reinoculation into specific-pathogen-free cats. Reversion to broad neutralization resistance was observed in seven of seven inoculated animals and, in individual hosts, started to develop between less than 4 and more than 15 months from infection. After comparison of the envelope sequences of the inoculum virus, of an additional 4 neutralization-sensitive in vitro variants, and of 14 ex vivo-derived variants (6 neutralization sensitive, 5 resistant, and 3 with intermediate phenotype), a Lys→Asn or →Glu change at position 481 in the V4 region of the surface glycoprotein appeared as a key player in the reversion. This conclusion was confirmed by mutagenesis of molecularly cloned virus. Analysis of viral quasispecies and biological clones showed that the intermediate phenotype was due to transient coexistence of neutralization-sensitive and -resistant variants. Since the amino acid position involved was the same in four of four recent revertants, it is suggested that the number of residues that control reversion to broad neutralization resistance in FIV might be very limited. Amino acid 481 was found to be changed only in one of three putative long-term revertants. These variants shared a Ser→Asn change at position 557 in region V5, which probably collaborated with other mutations in long-term maintenance of neutralization resistance, as suggested by the study of mutagenized virus.

Two methods for genotyping hepatitis C virus (DNA enzyme immunoassay [DEIA] and line probe assay [Inno-LiPA HCV I and II]) were compared on 120 samples and of these 87% were assigned to the same subtype by both assays. There were 15 subtyping discrepancies which involved 5% of type 1 isolates and 90% of type 2 isolates. Amplified products from the core and 5′ untranslated regions (UTR) were sequenced to resolve conflicts. Type 1 discordant samples had a guanosine at position −99 in the 5′ UTR, a characteristic of genotype 1b, and a core region typical of subtype 1a. The eight isolates classified as 2a/2c by LiPA and as subtype 2c by DEIA belonged to type 2.

(2010). Administration Interval and Daptomycin Toxicity: A Case Report of Rhabdomyolysis. Journal of Chemotherapy: Vol. 22, No. 6, pp. 434-435.

The mortality for carbapenem-resistant Klebsiella pneumoniae (KPC-Kp) infection ranges from 18 to 48% depending on the type of therapy. Mortality rates in hematologic patients are even higher, up to 85%. Gut decontamination with oral gentamicin might be an option to avoid a subsequent KPC-Kp infection in colonized patients. We treated 14 hematologic patients with oral gentamicin, 80 mg four times daily, for 7 to 25 days in order to eradicate KPC-Kp from the gut, starting oral gentamicin therapy when possible after the discontinuation of systemic antibiotic therapy. The overall decontamination rate in the entire study population was 71% (10/14). Out of the 4 patients who did not respond to oral gentamicin therapy, 1 KPC-Kp strain was gentamicin resistant and 4 patients received concomitant systemic antibiotic therapy (CSAT). One of these patients died from KPC-Kp sepsis. The decontamination rate was 90% (9/10) in patients receiving oral gentamicin only, versus 25% (1/4) in those also treated with CSAT. No new gentamicin-resistant KPC-Kp strain was isolated during oral gentamicin therapy Oral gentamicin might be useful for gut decontamination and prevention of KPC-Kp infection. This option should be considered in patients colonized by a gentamicin-susceptible KPC-Kp strain and not receiving CSAT.