Comparative efficacies of ciprofloxacin, amoxicillin, amoxicillin-clavulanic acid, and cefaclor against experimental Streptococcus pneumoniae respiratory infections in mice

P. mirabilis-derived pore-forming haemolysin, HpmA drives intestinal alpha-synuclein aggregation in a mouse model of neurodegeneration

BACKGROUND

Recent studies suggesting the importance of the gut-microbiome in intestinal aggregated alpha synuclein (α-syn) have led to the exploration of the possible role of the gut-brain axis in central nervous system degeneration. Proteus mirabilis (P. mirabilis), a gram-negative facultative anaerobic bacterium, has been linked to brain neurodegeneration in animal studies. We hypothesised that P. mirabilis-derived virulence factors aggregate intestinal α-synuclein and could prompt the pathogenesis of dopaminergic neurodegeneration in the brain.

METHODS

We used vagotomised- and antibiotic-treated male murine models to determine the pathogenesis of P. mirabilis during brain neurodegeneration. The neurodegenerative factor that is driven by P. mirabilis was determined using genetically mutated P. mirabilis. The pathological functions and interactions of the virulence factors were determined in vitro.

FINDINGS

The results showed that P. mirabilis-induced motor dysfunction and neurodegeneration are regulated by intestinal α-syn aggregation in vagotomised- or antibiotic-treated murine models. We deduced that the specific virulence factor, haemolysin A (HpmA), plays a role in the pathogenesis of P. mirabilis. HpmA is involved in α-synuclein oligomerisation and membrane pore formation, resulting in the activation of mTOR-mediated autophagy signalling in intestinal neuroendocrine cells.

INTERPRETATION

Taken together, the results of the present study suggest that HpmA can interact with α-syn and act as a possible indicator of brain neurodegenerative diseases that are induced by P. mirabilis.

FUNDING

This study was supported by a grant from the National Research Foundation of Korea.

A rapid, simple and sensitive liquid chromatography tandem mass spectrometry assay to determine amoxicillin concentrations in biological matrix of little volume

To assess pharmacokinetics of amoxicillin (AMX) in mice, limitations such as a small sampling volume and low drug concentrations have to be addressed. Similar challenges are faced in a clinical framework, e.g. for therapeutic drug monitoring in neonates or small-scale in vitro investigations. An assay enabling quantification of small sample volumes but still at very low concentrations covering a broad concentration range is thus needed. A simple, rapid and highly sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed and successfully validated for quantification of AMX in mouse serum according to European Medicines Agency guidelines. Sample preparation enabled the use of only 10 μL of serum, which is 5-fold less than comparable assays and allows to reduce the number of mice used in pharmacokinetic studies. After protein precipitation with 40 μL chilled methanol and dilution of the supernatant with water, the sample was injected into the LC system on a Poroshell 120 Phenyl Hexyl column (2.1 × 100 mm, 2.7 μm). Chromatographic separation was achieved using a gradient method consisting of acetonitrile and ultra-pure water, both with 0.1% (V/V) formic acid. Positive electrospray ionisation in multiple reaction monitoring mode was used for detection and quantification of AMX. Application to murine study samples demonstrated the reliability of the developed method being accurate and precise with a quantification range from 0.01 to 10 μg/mL. The assay is easily transferable due to a simple sample preparation and confirmed stability of AMX under various applied conditions.

Amoxicillin is effective against penicillin-resistant Streptococcus pneumoniae strains in a mouse pneumonia model simulating human pharmacokinetics

High-dose oral amoxicillin (3 g/day) is the recommended empirical outpatient treatment of community-acquired pneumonia (CAP) in many European guidelines. To investigate the clinical efficacy of this treatment in CAP caused by Streptococcus pneumoniae strains with MICs of amoxicillin > or =2 microg/ml, we used a lethal bacteremic pneumonia model in leukopenic female Swiss mice with induced renal failure to replicate amoxicillin kinetics in humans given 1 g/8 h orally. Amoxicillin (15 mg/kg of body weight/8 h subcutaneously) was given for 3 days. We used four S. pneumoniae strains with differing amoxicillin susceptibility and tolerance profiles. Rapid bacterial killing occurred with an amoxicillin-susceptible nontolerant strain: after 4 h, blood cultures were negative and lung homogenate counts under the 2 log(10) CFU/ml detection threshold (6.5 log(10) CFU/ml in controls, P < 0.01). With an amoxicillin-intermediate nontolerant strain, significant pulmonary bacterial clearance was observed after 24 h (4.3 versus 7.9 log(10) CFU/ml, P < 0.01), and counts were undetectable 12 h after treatment completion. With an amoxicillin-intermediate tolerant strain, 24-h bacterial clearance was similar (5.4 versus 8.3 log(10) CFU/ml, P < 0.05), but 12 h after treatment completion, lung homogenates contained 3.3 log(10) CFU/ml. Similar results were obtained with an amoxicillin-resistant and -tolerant strain. Day 10 survival rates were usually similar across strains. Amoxicillin with pharmacokinetics simulating 1 g/8 h orally in humans is bactericidal in mice with pneumonia due to S. pneumoniae for which MICs were 2 to 4 microg/ml. The killing rate depends not only on resistance but also on tolerance of the S. pneumoniae strains.

Single-dose intrapulmonary pharmacokinetics of azithromycin, clarithromycin, ciprofloxacin, and cefuroxime in volunteer subjects

The intrapulmonary pharmacokinetics of azithromycin, clarithromycin, ciprofloxacin, and cefuroxime were studied in 68 volunteers who received single, oral doses of azithromycin (0.5 g), clarithormycin (0.5 g), ciprofloxacin (0.5 g), or cefuroxime (0.5 g). In subgroups of four subjects each, the subjects underwent bronchoscopy and bronchoalveolar lavage at timed intervals following drug administration. Drug concentrations, including those of 14-hydroxyclarithromycin (14H), were determined in serum, bronchoalveolar lavage fluid, and alveolar cells (ACs) by high-pressure liquid chromatography. Concentrations in epithelial lining fluid (ELF) were calculated by the urea diffusion method. The maximum observed concentrations (mean +/- standard deviation) of azithromycin, clarithromycin, 14H, ciprofloxacin, and cefuroxime in serum were 0.13 +/- 0.07, 1.0 +/- 0.6, 0.60 +/- 0.41, 0.95 +/- 0.32, and 1.1 +/- 0.3 microgram/ml, respectively (all at 6 h). None of the antibiotics except clarithromycin (39.6 +/- 41.1 micrograms/ml) was detectable in ELF at the 6-h bronchoscopy. The movement into and persistence in cells was different for azithromycin and clarithromycin. In ACs azithromycin was not detectable at 6 h, reached its highest concentration at 120 h, and exhibited the greatest area under the curve (7,403 micrograms.hr ml-1). The peak concentration of clarithromycin (181 +/- 94.1 micrograms/ml) was greater and occurred earlier (6 h), but the area under the curve (2,006 micrograms.hr ml-1) was less than that observed for azithromycin. 14H was detectable in ACs at 6 h (40.3 +/- 5.2 micrograms/ml) and 12 h (32.8 +/- 57.2 micrograms/ml). The peak concentration of ciprofloxacin occurred at 6 h (4.3 +/- 5.2 micrograms/ml), and the area under the curve was 35.0 micrograms.hr ml-1. The data indicate that after the administration of a single dose, azithromycin, clarithromycin, and ciprofloxacin penetrated into ACs in therapeutic concentrations and that only clarithromycin was present in ELF. The correlation of these kinetic observations with clinical efficacy or toxicity was not investigated and is unclear, but the data provide a basis for further kinetic and clinical studies.

Assessment of a fluoroquinolone, three beta-lactams, two aminoglycosides, and a cycline in treatment of murine Yersinia pestis infection

Amoxicillin, cefotaxime, ceftriaxone, gentamicin, doxycycline, and ofloxacin were active in vitro, like the reference drug streptomycin, against the virulent strain Yersinia pestis 6/69M. The comparative efficacies of these drugs in vivo were evaluated in a standardized and reproducible mouse model of systemic infection. Each antibiotic was injected intravenously once, at 24 h postinfection, and then repeatedly during 48 h. In vivo results were measured by counting the viable bacteria recovered from the whole spleens of mice sacrificed at selected times. All the drugs were manifestly successful; ceftriaxone, ofloxacine, and the reference drug were the most effective. Therefore, gentamicin and doxycycline could be used, depending on the clinical forms of the Y. pestis infection. Further investigations on beta-lactams, especially those used in the present study, could be carried out to confirm or not confirm their activities against Y. pestis. Ofloxacin appeared to be as active and to perform as rapidly as streptomycin in the treatment of murine Y. pestis infection, which is in agreement with the previous successes obtained with the use of fluoroquinolones in the treatment of murine infections caused by other pathogenic yersiniae.

Evaluation of the efficacy of ciprofloxacin against Streptococcus pneumoniae by using a mouse protection model

A mouse protection model was used to investigate the association of the pharmacokinetics and pharmacodynamics with the in vivo efficacy of ciprofloxacin compared with that of penicillin G in the treatment of mice infected with Streptococcus pneumoniae ATCC 6303. Mice were inoculated intraperitoneally with 10 times the minimum lethal dose of S. pneumoniae. For determination of the 50% protective dose, subcutaneous antibiotics were begun 1 h after infection and were continued for 24 h. The 50% protective doses of ciprofloxacin and penicillin G were 25.52 +/- 1.95 and 0.307 +/- 0.006 mg/kg of body weight, respectively, an 83-fold difference in efficacy. For 100% protection with penicillin G, the time that the drug concentration needed to remain above the MIC was 51 min, a value easily achieved in most clinical situations. For 100% protection with ciprofloxacin, the peak concentration/MIC ratio must reach a value of 10.6. This ratio is rarely achieved with this drug against S. pneumoniae in clinical practice. These pharmacodynamic differences probably contribute to the reported differences in clinical success between these agents.

Quinolones in the treatment of lower respiratory tract infections in adult patients

The potential role of quinolones is discussed on the basis of data obtained during the past 2 years from epidemiological studies, in vitro investigations, animal experiments and clinical trials. Although the newest compounds exhibit good activity against Streptococcus pneumoniae and intracellular pathogens in animal models, the role of quinolones as first line therapy in community-acquired pneumonia is still debatable and may be modified according to clinical presentation and the rate of resistance of pneumococci to beta-lactams and macrolides. Cost-utility and cost-benefit studies are required to delineate precisely the role of quinolones in the treatment of acute exacerbations of chronic bronchitis. In addition, promising results indicating a possible future for the clinical use of quinolones in the therapy of mycobacterial infections have been obtained.