Comparative activity of a polyhexanide-betaine solution against biofilms produced by multidrug-resistant bacteria belonging to high-risk clones.

The aim of this study was to investigate the effect of polyhexanide (polyhexamethylene biguanide)-betaine (PHMB-B) compared with 2% chlorhexidine against biofilms of high-risk and/or multidrug-resistant bacterial clones. The minimum inhibitory concentrations of both biocides were determined by microdilution. The effect of PHMB-B and chlorhexidine on biofilm was evaluated by spectrophotometry and cell viability assays. At commercial concentrations, PHMB-B reduced 24 h, 48 h and 1-week biofilms of all pathogens tested. PHMB-B was more active than 2% chlorhexidine against Gram-negative bacterial 24 h and 48 h biofilms and Gram-positive bacterial 7-day biofilms. In summary, the activity of PHMB-B was superior to that of 2% chlorhexidine in those biofilms.

Physicochemical and microbiological stability of two news oral liquid formulations of clonidine hydrochloride for pediatric patients.

Pediatric patients present changing physiological features. Because of the lack of land suitable for commercial management, pediatric specialties very often need to prepare extemporaneous formulations to improve the dosage and administration of drugs for children. Oral liquid formulations are the most suitable for pediatric patients. Clonidine is widely used in the pediatric population for opioid withdrawal, hypertensive crisis, attention deficit disorders and hyperactivity syndrome, and as an analgesic in neuropathic cancer pain. The objective was to study the physicochemical and microbiological stability and determine the shelf life of an oral solution containing 20 µg/mL clonidine hydrochloride in different storage conditions (5 ± 3 °C, 25 ± 3 °C, and 40 ± 2 °C). Using raw material with excipients safe for all pediatric age groups, two oral liquid formulations of clonidine hydrochloride were designed (with and without preservatives). Solutions stored at 5 ± 3 °C (with and without preservatives) were physically and microbiologically stable for at least 90 days in closed containers and for 42 days after opening. Two oral solutions of clonidine hydrochloride 20 µg/mL were developed for pediatric use from raw materials that are readily available and easy to process, containing safe excipients that are stable over a long period of time.

Impact of qnrA1, qnrB1 and qnrS1 on the efficacy of ciprofloxacin and levofloxacin in an experimental pneumonia model caused by Escherichia coli with or without the GyrA mutation Ser83Leu.

OBJECTIVES: The aim of this study was to evaluate the impact of qnrA1, qnrB1 and qnrS1 on the in vivo efficacies of ciprofloxacin and levofloxacin in an experimental model of pneumonia caused by Escherichia coli. METHODS: Two isogenic groups of E. coli transformants, based on two ATCC 25922 strains, with or without the GyrA mutation Ser83Leu, and carrying qnrA1, qnrB1 or qnrS1, were used in an experimental pneumonia model. The efficacies of ciprofloxacin (40 mg/kg/day) and levofloxacin (50 and 150 mg/kg/day) were evaluated. RESULTS: For the pneumonia caused by the parental strains lacking qnr genes, both fluoroquinolones significantly (P<0.05) reduced the bacterial lung concentration by >7 log10 cfu/g against E. coli ATCC/pBK and between 5.09 and 6.34 log10 cfu/g against E. coli ATCC-S83L/pBK. The presence of any qnr genes in the strains of both isogenic groups diminished the reduction of bacterial lung concentration with any therapy (P<0.05). Furthermore, all therapeutic schemes reduced the percentage of positive blood cultures in both isogenic groups (P<0.05). Finally, the survival results suggest a higher mortality with the strains expressing qnr genes. CONCLUSIONS: The presence of qnrA1, qnrB1 and qnrS1 in E. coli reduced the efficacy of ciprofloxacin and levofloxacin in a murine pneumonia model.

Inoculum effect on the efficacies of amoxicillin-clavulanate, piperacillin-tazobactam, and imipenem against extended-spectrum ß-lactamase (ESBL)-producing and non-ESBL-producing Escherichia coli in an experimental murine sepsis model.

Escherichia coli is commonly involved in infections with a heavy bacterial burden. Piperacillin-tazobactam and carbapenems are among the recommended empirical treatments for health care-associated complicated intra-abdominal infections. In contrast to amoxicillin-clavulanate, both have reduced in vitro activity in the presence of high concentrations of extended-spectrum ß-lactamase (ESBL)-producing and non-ESBL-producing E. coli bacteria. Our goal was to compare the efficacy of these antimicrobials against different concentrations of two clinical E. coli strains, one an ESBL-producer and the other a non-ESBL-producer, in a murine sepsis model. An experimental sepsis model {~5.5 log10 CFU/g [low inoculum concentration (LI)] or ~7.5 log(10) CFU/g [high inoculum concentration (HI)]} using E. coli strains ATCC 25922 (non-ESBL producer) and Ec1062 (CTX-M-14 producer), which are susceptible to the three antimicrobials, was used. Amoxicillin-clavulanate (50/12.5 mg/kg given intramuscularly [i.m.]), piperacillin-tazobactam (25/3.125 mg/kg given intraperitoneally [i.p.]), and imipenem (30 mg/kg i.m.) were used. Piperacillin-tazobactam and imipenem reduced spleen ATCC 25922 strain concentrations (-2.53 and -2.14 log10 CFU/g [P < 0.05, respectively]) in the HI versus LI groups, while amoxicillin-clavulanate maintained its efficacy (-1.01 log10 CFU/g [no statistically significant difference]). Regarding the Ec1062 strain, the antimicrobials showed lower efficacy in the HI than in the LI groups: -0.73, -1.89, and -1.62 log10 CFU/g (P < 0.05, for piperacillin-tazobactam, imipenem, and amoxicillin-clavulanate, respectively, although imipenem and amoxicillin-clavulanate were more efficacious than piperacillin-tazobactam). An adapted imipenem treatment (based on the time for which the serum drug concentration remained above the MIC obtained with a HI of the ATCC 25922 strain) improved its efficacy to -1.67 log10 CFU/g (P < 0.05). These results suggest that amoxicillin-clavulanate could be an alternative to imipenem treatment of infections caused by ESBL- and non-ESBL-producing E. coli strains in patients with therapeutic failure with piperacillin-tazobactam.

In vitro and in vivo reduced fitness and virulence in ciprofloxacin-resistant Acinetobacter baumannii.

Limited data on relative fitness and virulence of antimicrobial-resistant Acinetobacter baumannii are known. We aimed to study the virulence and fitness cost of ciprofloxacin-resistance in A. baumannii (CipR) compared with the susceptible parental wild-type strain (CipS). Human lung epithelial cells were infected with CipS and CipR for 24 h. Competition fitness was monitored in vitro and in vivo in a murine peritoneal sepsis model. We showed that CipR induced less cell death than CipS and CipR growth was slow when in competition with CipS. Altogether, acquisition of ciprofloxacin resistance confers a biological fitness cost and reduces virulence in A. baumannii.

Efficacy of daptomycin versus vancomycin in an experimental model of foreign-body and systemic infection caused by biofilm producers and methicillin-resistant Staphylococcus epidermidis.

Staphylococcus epidermidis is a frequent cause of device-associated infections. In this study, we compared the efficacy of daptomycin versus vancomycin against biofilm-producing methicillin-resistant S. epidermidis (MRSE) strains in a murine model of foreign-body and systemic infection. Two bacteremic biofilm-producing MRSE strains were used (SE284 and SE385). The MIC of daptomycin was 1 mg/liter for both strains, and the MICs of vancomycin were 4 and 2 mg/liter for SE284 and for SE385, respectively. The in vitro bactericidal activities of daptomycin and vancomycin were evaluated by using time-kill curves. The model of foreign-body and systemic infection of neutropenic female C57BL/6 mice was used to ascertain in vivo efficacy. Animals were randomly allocated into three groups (n = 15): without treatment (controls) or treated with daptomycin at 50 mg/kg/day or vancomycin at 440 mg/kg/day. In vitro, daptomycin showed concentration-dependent bactericidal activity, while vancomycin presented time-dependent activity. In the experimental in vivo model, daptomycin and vancomycin decreased liver and catheter bacterial concentrations (P < 0.05) and increased the survival and the number of sterile blood cultures (P < 0.05) using both strains. Daptomycin produced a reduction in the bacterial liver concentration higher than 2.5 log(10) CFU/g compared to vancomycin using both strains, with this difference being significant (P < 0.05) for infection with SE385. For the catheter bacterial concentrations, daptomycin reduced the concentration of SE284 3.0 log(10) CFU/ml more than did vancomycin (P < 0.05). Daptomycin is more effective than vancomycin for the treatment of experimental foreign-body and systemic infections by biofilm-producing methicillin-resistant S. epidermidis.

In vitro activity of several antimicrobial peptides against colistin-susceptible and colistin-resistant Acinetobacter baumannii.

At present, colistin is among the few antibiotics effective against Acinetobacter baumannii clinical isolates. However, in the last few years, colistin-resistant A. baumannii strains have been isolated. Therefore, antibiotics effective against these usually pan-resistant colistin-resistant A. baumannii strains are required. The main objective of this study was to analyse the activity of 15 peptides against colistin-susceptible and colistin-resistant A. baumannii. The MICs were determined by microdilution. Among these 15 antimicrobial peptides (AMPs), melittin, indolicidin and mastoparan showed good activity against both colistin-susceptible and colistin-resistant A. baumannii. Further studies of mastoparan with time-killing curves showed bactericidal activity at MIC ×8 for both colistin-susceptible and colistin-resistant A. baumannii. In conclusion, mastoparan may be a potential alternative for the treatment of colistin-resistant A. baumannii infections.

Pre-clinical studies of a new quinolone (UB-8902) against Acinetobacter baumannii resistant to ciprofloxacin.

The in vitro activity and in vivo efficacy of a new ciprofloxacin derivative (UB-8902) were evaluated. In vitro time-kill curves were performed for ciprofloxacin (CIP), moxifloxacin (MXF) and UB-8902 against CIP-susceptible (Ab58) and CIP-resistant (Ab661 and Ab33) Acinetobacter baumannii strains. UB-8902 showed similar bactericidal activity to CIP and MXF against these strains. In the in vivo experiments in mice, the toxicity of UB-8902, its 50% protective dose (PD(50)) (peritoneal sepsis model), its pharmacokinetic/pharmacodynamic (PK/PD) parameters and its efficacy in a pneumonia model were studied. The maximum tolerated dose of UB-8902 was 512 mg/kg. PD(50) values were 16, 128 and 32 mg/kg for Ab58, Ab661 and Ab33, respectively. Pharmacokinetic parameters of UB-8902 were similar to MXF and were lower than those for CIP, whilst pharmacodynamic parameters were better than CIP. In the pneumonia model, UB-8902 decreased the bacterial lung concentration [4.62 colony-forming units (CFU)/g and 4.15log(10)CFU/g] and positive blood cultures (60% and 62.5%) for Ab58 and Ab33, respectively, compared with the control. In conclusion, UB-8902 presents bactericidal activity against A. baumannii strains resistant to CIP. Moreover, it is effective at reducing mortality in a model of peritoneal sepsis with a dose lower than the toxic one, and it is efficacious in a murine pneumonia model.

Efficacy of cecropin A-melittin peptides on a sepsis model of infection by pan-resistant Acinetobacter baumannii.

Pan-resistant Acinetobacter baumannii have prompted the search for therapeutic alternatives. We evaluate the efficacy of four cecropin A-melittin hybrid peptides (CA-M) in vivo. Toxicity was determined in mouse erythrocytes and in mice (lethal dose parameters were LD(0), LD(50), LD(100)). Protective dose 50 (PD(50)) was determined by inoculating groups of ten mice with the minimal lethal dose of A. baumannii (BMLD) and treating with doses of each CA-M from 0.5 mg/kg to LD(0). The activity of CA-Ms against A. baumannii was assessed in a peritoneal sepsis model. Mice were sacrificed at 0 and 1, 3, 5, and 7-h post-treatment. Spleen and peritoneal fluid bacterial concentrations were measured. CA(1-8)M(1-18) was the less haemolytic on mouse erythrocytes. LD(0) (mg/kg) was 32 for CA(1-8)M(1-18), CA(1-7)M(2-9), and Oct-CA(1-7)M(2-9), and 16 for CA(1-7)M(5-9). PD(50) was not achieved with non-toxic doses (≤ LD(0)). In the sepsis model, all CA-Ms were bacteriostatic in spleen, and decreased bacterial concentration (p < 0.05) in peritoneal fluid, at 1-h post-treatment; at later times, bacterial regrowth was observed in peritoneal fluid. CA-Ms showed local short-term efficacy in the peritoneal sepsis model caused by pan-resistant Acinetobacter baumannii.

Local imipenem activity against Pseudomonas aeruginosa decreases in vivo in the presence of siliconized latex.

Zinc eluted from siliconized latex (SL) increases resistance of Pseudomonas aeruginosa to imipenem in vitro. A foreign body peritonitis model was used to evaluate the activity of imipenem using SL or silicone (S) implants. No differences were observed in mortality, positive blood cultures and tissue bacterial counts between SL and S implants. Implant-associated counts, however, were significantly higher in the SL group. It is concluded that SL decreases the activity of imipenem against P. aeruginosa.

Efficacy of tigecycline vs. imipenem in the treatment of experimental Acinetobacter baumannii murine pneumonia.

The in vivo activity of tigecycline was evaluated in an experimental pneumonia model (C57BL/6 mice) by Acinetobacter baumannii. Two clinical strains were used: minimum inhibitory concentrations (MICs) of imipenem and tigecycline 1 and 2 microg/mL (imipenem-susceptible, IPM-S), and 8 and 2 microg/mL (imipenem-intermediate, IPM-I), respectively. For imipenem (30 mg/Kg), T/CMI (h) were 1.04 and 0.51 for IPM-S and IPM-I, respectively. For tigecycline (5 mg/Kg), the area under the concentration-time curve (AUC)/MIC(0-24 h) (serum and lung) were 9.24 and 4.37 (for the two strains), respectively. In the efficacy experiments with the IPM-S, imipenem (log CFU/g 3.59 +/- 0.78, p = 0.006) and tigecycline (2.82 +/- 1.2, p = 0.054) decreased the bacterial counts in lungs with respect to its controls; with the IPM-I, both imipenem (1.21 +/- 0.52, p = 0.002) and tigecycline (3.21 +/- 0.28, p = 0.035) decreased the bacterial counts with respect to the controls. In the survival experiments, with the IPM-S, the mortality was the same in the control (67%) and in the tigecycline (77%) groups, and imipenem reduced it (21%, p = 0.025); with the IPM-I, the mortality was the same in the control (87%) and in the tigecycline (85%) groups, and imipenem (0%) reduced it (p < 0.001). In summary, the present study shows that tigecycline is less efficacious than imipenem in the treatment of experimental A. baumannii pneumonia caused by IPM-S and IPM-I strains.