Maintaining fluoroquinolone class efficacy: review of influencing factors

Continuous evaluation of single-dose moxifloxacin concentrations in brain extracellular fluid, cerebrospinal fluid, and plasma: a novel porcine model

BACKGROUND

Knowledge regarding CNS pharmacokinetics of moxifloxacin is limited, with unknown consequences for patients with meningitis caused by bacteria resistant to beta-lactams or caused by TB.

OBJECTIVE

(i) To develop a novel porcine model for continuous investigation of moxifloxacin concentrations within brain extracellular fluid (ECF), CSF and plasma using microdialysis, and (ii) to compare these findings to the pharmacokinetic/pharmacodynamic (PK/PD) target against TB.

METHODS

Six female pigs received an intravenous single dose of moxifloxacin (6 mg/kg) similar to the current oral treatment against TB. Subsequently, moxifloxacin concentrations were determined by microdialysis within five compartments: brain ECF (cortical and subcortical) and CSF (ventricular, cisternal and lumbar) for the following 8 hours. Data were compared to simultaneously obtained plasma samples. Chemical analysis was performed by high pressure liquid chromatography with mass spectrometry. The applied PK/PD target was defined as a maximum drug concentration (Cmax):MIC ratio >8.

RESULTS

We present a novel porcine model for continuous in vivo CNS pharmacokinetics for moxifloxacin. Cmax and AUC0-8h within brain ECF were significantly lower compared to plasma and lumbar CSF, but insignificantly different compared to ventricular and cisternal CSF. Unbound Cmax:MIC ratio across all investigated compartments ranged from 1.9 to 4.3.

CONCLUSION

A single dose of weight-adjusted moxifloxacin administered intravenously did not achieve adequate target site concentrations within the uninflamed porcine brain ECF and CSF to reach the applied TB CNS target.

Terpene-Functionalized Fluoroquinolones as Potential Antimicrobials: Synthesis and Properties

This study was the first to synthesize terpene-containing conjugates of fluoroquinolones, ciprofloxacin and norfloxacin, and to evaluate their antibacterial activity against gram-positive methicillin sensitive (MSSA) and methicillin resistant (MRSA) S. aureus, gram-negative P. aeruginosa as well as antifungal activity against C. albicans. The ability of obtained fluoroquinolones to inhibit S. aureus growth was found to depend upon the presence of a linker separating the bulky terpene and fluoroquinolone fragments, and this activity diminished with increasing its length. The highest activity against MSSA was demonstrated by ciprofloxacin derivatives with campholenic (MIC 1 μg/mL) and 2-(isobornan-2-yl-sulfanyl)acetyl (MIC 0.5 μg/mL) substituents. The compound with the last fragment showed high activity against MRSA (MIC 8 μg/mL). The terpene-functionalized norfloxacin derivatives generally proved to be less active than those containing ciprofloxacin fragment. Camphor-10-sulfonylamide derivative with the ciprofloxacin fragment was the only one of all compounds that showed high antifungal activity against C. albicans (8 μg/mL). The study presents data on docking fluoroquinolones to S. aureus DNA gyrase to explain the reasons for manifestation or disappearance of antibacterial activity. The cytotoxicity of fluoroquinolones that showed any antimicrobial activity was investigated against bovine primary lung cells, and they were found to be not toxic in most cases.

Prodrug Rewards in Medicinal Chemistry: An Advance and Challenges Approach for Drug Designing

This article emphasizes the importance of prodrugs and their diverse spectrum of effects in the field of developing novel drugs for a variety of biological applications. Prodrugs are chemicals that are supplied inactively, but then go through enzymatic and chemical transformation in vivo to release the active parent medication that can have the desired pharmacological effect. By adding an inactive chemical moiety, prodrugs are improved in a number of ways that contribute to their potency and durability. For the purpose of illustrating the usefulness of the prodrug approach, this review covers examples of prodrugs that have been made available or are now undergoing human trials. Additionally, it included lists of the most common functional groups, carrier linkers, and reactive chemicals that can be used to create prodrugs. The current study also provides a brief introduction, several chemical methods and modifications for creating prodrugs and mutual prodrugs, as well as an explanation of recent advancements and difficulties in the field of prodrug design. The primary chemical carriers employed in the creation of prodrugs, such as esters, amides, imides, NH-acidic carriers, amines, alcohols, carbonyl, carboxylic, and azo-linkages, are also discussed. This review also discusses glycosidic and triglyceride mutually activated prodrugs, which aim to deliver the drugs after bioconversion at the intended site of action. The article also discusses the extensive chemistry and wide variety of applications of recently approved prodrugs, such as antibacterial, anti-inflammatory, cardiovascular, antiplatelet, antihypertensive, atherosclerotic, antiviral, etc. In order to illustrate the prodrug and mutual drug concept's various applications and highlight its many triumphs in overcoming the formulation and delivery of problematic pharmaceuticals, this work represents a thorough guide that includes the synthetic moiety for the reader.

Nano delivery systems to the rescue of ciprofloxacin against resistant bacteria "E. coli; P. aeruginosa; Saureus; and MRSA" and their infections

Ciprofloxacin (CIP) a broad-spectrum antibiotic, is used extensively for the treatment of diverse infections and diseases of bacteria origin, and this includes infections caused by E. coli; P. aeruginosa; S. aureus; and MRSA. This extensive use of CIP has therefore led to an increase in resistance by these infection causing organisms. Nano delivery systems has recently proven to be a possible solution to resistance to these organisms. They have been applied as a strategy to improve the target specificity of CIP against infections and diseases caused by these organisms, thereby maximising the efficacy of CIP to overcome the resistance. Herein, we proffer a brief overview of the mechanisms of resistance; the causes of resistance; and the various approaches employed to overcome this resistance. The review then proceeds to critically evaluate various nano delivery systems including inorganic based nanoparticles; lipid-based nanoparticles; capsules, dendrimers, hydrogels, micelles, and polymeric nanoparticles; and others; that have been applied for the delivery of CIP against E. coli; P. aeruginosa; S. aureus; and MRSA infections. Finally, the review highlights future areas of research, for the optimisation of various nano delivery systems, to maximise the therapeutic efficacy of CIP against these organisms. This review confirms the potential of nano delivery systems, for addressing the challenges of resistance to caused by E. coli; P. aeruginosa; S. aureus; and MRSA to CIP.

The effect of fluoroquinolones and antioxidans on biofilm formation by Proteus mirabilis strains

Background

Fluoroquinolones are a group of antibiotics used in urinary tract infections. Unfortunately, resistance to this group of drugs is currently growing. The combined action of fluoroquinolones and other antibacterial and anti-biofilm substances may extend the use of this therapeutic option by clinicians. The aim of the study was to determine the effect of selected fluoroquinolones and therapeutic concentrations of ascorbic acid and rutoside on biofilm formation by Proteus mirabilis.

Materials and methods

The study included 15 strains of P. mirabilis isolated from urinary tract infections in patients of the University Hospital No. 1 dr A. Jurasz in Bydgoszcz (Poland). The metabolic activity of the biofilm treated with 0.4 mg/ml ascorbic acid, 0.02 µg/ml rutoside and chemotherapeutic agents (ciprofloxacin, norfloxacin) in the concentration range of 0.125–4.0 MIC (minimum inhibitory concentration) was assessed spectrophotometrically.

Results

Both ciprofloxacin and norfloxacin inhibited biofilm formation by the tested strains. The biofilm reduction rate was correlated with the increasing concentration of antibiotic used. No synergism in fluoroquinolones with ascorbic acid, rutoside or both was found. The ascorbic acid and rutoside combination, however, significantly decreased biofilm production.

Conclusions

Our research proves a beneficial impact of ascorbic acid with rutoside supplementation on biofilm of P. mirabilis strains causing urinary tract infections.

Direct-from-specimen microbial growth inhibition spectrums under antibiotic exposure and comparison to conventional antimicrobial susceptibility testing

Increasing global travel and changes in the environment may escalate the frequency of contact with a natural host carrying an infection and, therefore, increase our chances of encountering microorganisms previously unknown to humans. During an emergency, the etiology of infection may be unknown at the time of patient treatment. The existing local or global Antimicrobial Stewardship Programs may not be fully prepared for emerging/re-emerging infectious disease outbreaks, especially if they are caused by an unknown organism, engineered bioterrorist attack, or rapidly evolving superbug. We demonstrate an antimicrobial efficacy profiling method that can be performed in hours directly from clinical urine specimens. The antimicrobial potency was determined by the level of microbial growth inhibition and compared to conventional antimicrobial susceptibility testing results. The oligonucleotide probe pairs on the sensors were designed to target Gram-negative bacteria, specifically Enterobacterales and Pseudomonas aeruginosa. A pilot study of 10 remnant clinical specimens from the Clinical Laboratory Improvement Amendments-certified labs of New York-Presbyterian Queens was conducted, and only one sample was not detected by the probes. The remaining nine samples agreed with reference AST methods (Vitek and broth microdilution), resulting in 100% categorical agreement. In a separate feasibility study, we evaluated a dual-kinetic response approach, in which we inoculated two antibiotic stripwells containing the same antimicrobial concentrations with clinical specimens at the original concentration (1x) and at a 10-fold dilution (0.1x) to cover a broader range of microbiological responses. The combined categorical susceptibility reporting of 12 contrived urine specimens was 100% for ciprofloxacin, gentamicin, and meropenem over a range of microbial loads from 10⁵ to 10⁸ CFU/mL.

Biochemical Characterization of New Gemifloxacin Schiff Base (GMFX-o-phdn) Metal Complexes and Evaluation of Their Antimicrobial Activity against Some Phyto- or Human Pathogens

Four novel ligand-metal complexes were synthesized through the reaction of Fe(III), pleaseCo(II), Zn(II), and Zr(IV) with Schiff base gemifloxacin reacted with ortho-phenylenediamine (GMFX-o-phdn) to investigate their biological activities. Elemental analysis, FT-IR, ¹H NMR, UV-visible, molar conductance, melting points, magnetic susceptibility, and thermal analyses have been carried out for insuring the chelation process. The antimicrobial activity was carried out against Monilinia fructicola, Aspergillus flavus, Penicillium italicum, Botrytis cinerea, Escherichia coli, Bacillus cereus, Pseudomonas fluorescens, and P. aeruginosa. The radical scavenging activity (RSA%) was in vitro evaluated using ABTS method. FT-IR spectra indicated that GMFX-o-phdn chelated with metal ions as a tetradentate through oxygen of carboxylate group and nitrogen of azomethine group. The data of infrared, ¹H NMR, and molar conductivity indicate that GMFX–o-phdn reacted as neutral tetra dentate ligand (N₂O₂) with metal ions through the two oxygen atoms of the carboxylic group (oxygen containing negative charge) and two nitrogen atoms of azomethine group (each nitrogen containing a lone pair of electrons) (the absent of peak corresponding to ν(COOH) at 1715 cm⁻¹, the shift of azomethine group peak from 1633 cm⁻¹ to around 1570 cm⁻¹, the signal at 11 ppm of COOH and the presence of the chloride ions outside the complex sphere). Thermal analyses (TG-DTG/DTA) exhibited that the decaying of the metal complexes exists in three steps with the final residue metal oxide. The obtained data from DTA curves reflect that the degradation processes were exothermic or endothermic. Results showed that some of the studied complexes exhibited promising antifungal activity against most of the tested fungal pathogens, whereas they showed higher antibacterial activity against E. coli and B. cereus and low activity against P. fluorescens and P. aeruginosa. In addition, GMFX-o-phdn and its metal complexes showed strong antioxidant effect. In particular, the parent ligand and Fe(III) complex showed greater antioxidant capacity at low tested concentrations than that of other metal complexes where their IC₅₀ were 169.7 and 164.6 µg/mL, respectively.

Different Nanotechnology Approaches for Ciprofloxacin Delivery Against Multidrug-Resistant Microbes

The percentages of organisms exhibiting antimicrobial resistance, especially resistance to multiple antibiotics, are incessantly increasing. Studies investigated that many bacteria are being resistant to ciprofloxacin. This review addresses the current knowledge on nano-based ciprofloxacin delivery approaches to improve its effectiveness and overcome the resistance issues. Ciprofloxacin delivery can be modified by encapsulating with or incorporating in different polymeric nanoparticles such as chitosan, PLGA, albumin, arginine, and other organic and inorganic nanostructure systems. Most of these nano-approaches are promising as an alternative strategy to improve the therapeutic effectiveness of ciprofloxacin in the future.

Phenotypic and molecular characterization of fluoroquinolone resistant Pseudomonas aeruginosa isolates in Palestine

Fluoroquinolones are important antimicrobial agents for the treatment of Pseudomonas infections. A total of 11 isolates of P. aeruginosa were collected from different clinical samples from different medical centers in the North West Bank-Palestine during 2017. In this study, resistance to fluoroquinolones and secretions of β-lactamases were detected by phenotypic methods, while presence of β-lactamase gene sequences and other virulence factors were detected by PCR technique. PCR product for gyrA, parC and parE genes were sequenced for further analyses. The phylogenetic analyses, population diversity indices and haplotypes determination were conducted using computer programs MEGA version 6, DnaSP 5.1001 and median-joining algorithm in the program Network 5, respectively. Results of this study showed that the MIC for ciprofloxacin and norfloxacin had a range of 32-256 µg/ml. In addition, all isolates carried either exoT or exoT and exoY genes, different β-lactamase genes and 82% of these isolates harbored class 1 integrons. Analyses of the gyrA, parC and parE sequences were found to be polymorphic, had high haplotype diversity (0.945-0.982), low nucleotide diversity (0.01225-0.02001) and number of haplotypes were 9 for each gyrA and parE genes and 10 haplotypes for parC gene. The founder haplotypes being Hap-1 (18%), Hap-2 (27.3%) and Hap-6 (9.1%) for gyrA, parC and parE genes, respectively. Two of ParE haplotypes were detected as indel haplotypes. The Median-joining- (MJ) networks constructed from haplotypes of these genes showed a star-like expansion. The neutrality tests (Tajima's D test and Fu's Fs test) for these genes showed negative values. Palestinian fluoroquinolone resistant P. aeruginosa strains showed high MIC level for fluoroquinolones, β-lactamase producers, carried type III secretion exotoxin-encoding genes, most of them had integrase I gene and had high level of mutations in QRDR regions in gyrA, parC and parE genes. All these factors may play an important role in the invasiveness of these strains and make them difficult to treat. Isolation of these strains from different medical centers, indicate the need for a strict application of infection control measures in Medical centers in the North West Bank-Palestine that aim to reduce expense and damage caused by P. aeruginosa infections. Molecular analyses showed that Palestinian fluoroquinolone resistant P. aeruginosa haplotypes are not genetically differentiated; however, more mutations may exist in these strains.

Real-Time Single-Cell Imaging Reveals Accelerating Lipid Peroxyl Radical Formation in Escherichia coli Triggered by a Fluoroquinolone Antibiotic

The formation of reactive oxygen species (ROS) induced by bactericidal antibiotics has been associated with a common, nonspecific mechanism of cellular death. Herein, we report real-time single-cell fluorescence studies on Escherichia coli stained with a fluorogenic probe for lipid peroxyl radicals showing the generation of this form of ROS when exposed to the minimum inhibitory concentration (MIC) and 10× MIC of the fluoroquinolone antibiotic ciprofloxacin (3 and 30 μM, respectively). Single-cell intensity-time trajectories show an induction period followed by an accelerating phase for cells treated with antibiotic, where initial and maximum intensity achieved following 3.5 h of incubation with antibiotic showed dose-dependent average values. A large fraction of bacteria remains viable after the studies, indicating ROS formation is occurring a priori of cell death. Punctate structures are observed, consistent with membrane blebbing. The addition of a membrane embedding lipid peroxyl radical scavenger, an α-tocopherol analogue, to the media increased the MIC of ciprofloxacin. Lipid peroxyl radical formation precedes E. coli cell death and may be invoked in a cascade event including membrane disruption and consequent cell wall permeabilization. Altogether, our work illustrates that lipid peroxidation is caused by ciprofloxacin in E. coli and suppressed by α-tocopherol analogues. Lipid peroxidation may be invoked in a cascade event including membrane disruption and consequent cell wall permeabilization. Our work provides a methodology to assess antibiotic-induced membrane peroxidation at the single-cell level; this methodology provides opportunities to explore the scope and nature of lipid peroxidation in antibiotic-induced cell lethality.

A review of antibiotic resistance in Group B Streptococcus: the story so far

Group B Streptococcus (GBS) is the leading cause of neonatal disease worldwide, and invasive disease in adults is becoming more prevalent. Currently, some countries adopt an intrapartum antibiotic prophylaxis regime to help prevent the transmission of GBS from mother to neonate during delivery. This precaution has reduced the incidence of GBS-associated early-onset disease; however, rates of late-onset disease and stillbirths associated with GBS infections remain unchanged. GBS is still recognized as being universally susceptible to beta-lactam antibiotics; however, there have been reports of reduced susceptibility to beta-lactams, including penicillin, in some countries. Resistance to second-line antibiotics, such as erythromycin and clindamycin, remains high amongst GBS, with several countries noting increased resistance rates in recent years. Moreover, resistance to other antibiotic classes, such as fluoroquinolones and aminoglycosides, also continues to rise. In instances where patients are allergic to penicillin and second-line antibiotics are ineffective, vancomycin is administered. While vancomycin, a last resort antibiotic, still remains largely effective, there have been two documented cases of vancomycin resistance in GBS. This review provides a comprehensive analysis of the prevalence of antibiotic resistance in GBS and outlines the specific resistance mechanisms identified in GBS isolates to date.

Antibacterial Prodrugs to Overcome Bacterial Resistance

Bacterial resistance to present antibiotics is emerging at a high pace that makes the development of new treatments a must. At the same time, the development of novel antibiotics for resistant bacteria is a slow-paced process. Amid the massive need for new drug treatments to combat resistance, time and effort preserving approaches, like the prodrug approach, are most needed. Prodrugs are pharmacologically inactive entities of active drugs that undergo biotransformation before eliciting their pharmacological effects. A prodrug strategy can be used to revive drugs discarded due to a lack of appropriate pharmacokinetic and drug-like properties, or high host toxicity. A special advantage of the use of the prodrug approach in the era of bacterial resistance is targeting resistant bacteria by developing prodrugs that require bacterium-specific enzymes to release the active drug. In this article, we review the up-to-date implementation of prodrugs to develop medications that are active against drug-resistant bacteria.

A Baker's Dozen of Top Antimicrobial Stewardship Intervention Publications in 2018

With an increasing number of antimicrobial stewardship–related articles published each year, attempting to stay current is challenging. The Southeastern Research Group Endeavor (SERGE-45) identified antimicrobial stewardship–related peer-reviewed literature that detailed an actionable intervention for 2018. The top 13 publications were selected using a modified Delphi technique. These manuscripts were reviewed to highlight the actionable intervention used by antimicrobial stewardship programs to provide key stewardship literature for teaching and training as well as to identify potential intervention opportunities within one’s institution.

A comparative assessment of clinical, pharmacological and antimicrobial profile of novel anti-methicillin-resistant Staphylococcus aureus agent levonadifloxacin: Therapeutic role in nosocomial and community infections

Staphylococcus aureus is of significant clinical concern in both community- and hospital-onset infections. The key to the success of S. aureus as a pathogen is its ability to swiftly develop antimicrobial resistance. Methicillin-resistant S. aureus (MRSA) is not only resistant to nearly all beta-lactams but also demonstrates resistance to several classes of antibiotics. A high prevalence of MRSA is seen across worldwide. For many decades, vancomycin remained as gold standard antibiotic for the treatment of MRSA infections. In the past decades, linezolid, daptomycin, ceftaroline and telavancin received regulatory approval for the treatment of infections caused by resistant Gram-positive pathogens. Although these drugs may offer some advantages over vancomycin, they also have significant limitations. These includes vancomycin's slow bactericidal activity, poor lung penetration and nephrotxicity;linezolid therapy induced myelosuppression and high cost of daptomycin greatly limits their clinical use. Moreover, daptomycin also gets inactivated by lung naturally occurring surfactants. Thus, currently available therapeutic options are unable to provide safe and efficacious treatment for those patients suffering from hospital-acquired pneumonia, bloodstream infections (BSIs), bone and joint infections and diabetic foot infections (DFI). An unmet need also exists for a safe and efficacious oral option for switch-over convenience and community treatment. Herein, the review is intended to describe the supporting role of anti-staphylococcal antibiotics used in the management of S. aureus infections with a special reference to levonadifloxacin. Levonadifloxacin and its prodrug alalevonadifloxacin are novel benzoquinolizine subclass of quinolone with broad-spectrum of anti-MRSA activity. It has been recently approved for the treatment of complicated skin and soft-tissue infection as well as concurrent bacteraemia and DFI in India.

Exploitation of Antibiotic Resistance as a Novel Drug Target: Development of a β-Lactamase-Activated Antibacterial Prodrug

Expression of β-lactamase is the single most prevalent determinant of antibiotic resistance, rendering bacteria resistant to β-lactam antibiotics. In this article, we describe the development of an antibiotic prodrug that combines ciprofloxacin with a β-lactamase-cleavable motif. The prodrug is only bactericidal after activation by β-lactamase. Bactericidal activity comparable to ciprofloxacin is demonstrated against clinically relevant E. coli isolates expressing diverse β-lactamases; bactericidal activity was not observed in strains without β-lactamase. These findings demonstrate that it is possible to exploit antibiotic resistance to selectively target β-lactamase-producing bacteria using our prodrug approach, without adversely affecting bacteria that do not produce β-lactamase. This paves the way for selective targeting of drug-resistant pathogens without disrupting or selecting for resistance within the microbiota, reducing the rate of secondary infections and subsequent antibiotic use.

Improvement of gram-negative susceptibility to fluoroquinolones after implementation of a pre-authorization policy for fluoroquinolone use: A decade-long experience

OBJECTIVE

Due to concerns over increasing fluoroquinolone (FQ) resistance among gram-negative organisms, our stewardship program implemented a preauthorization use policy. The goal of this study was to assess the relationship between hospital FQ use and antibiotic resistance.

DESIGN

Retrospective cohort.

SETTING

Large academic medical center.

METHODS

We performed a retrospective analysis of FQ susceptibility of hospital isolates for 5 common gram-negative bacteria: Acinetobacter spp., Enterobacter cloacae, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa. Primary endpoint was the change of FQ susceptibility. A Poisson regression model was used to calculate the rate of change between the preintervention period (1998-2005) and the postimplementation period (2006-2016).

RESULTS

Large rates of decline of FQ susceptibility began in 1998, particularly among P. aeruginosa, Acinetobacter spp., and E. cloacae. Our FQ restriction policy improved FQ use from 173 days of therapy (DOT) per 1,000 patient days to <60 DOT per 1,000 patient days. Fluoroquinolone susceptibility increased for Acinetobacter spp. (rate ratio [RR], 1.038; 95% confidence interval [CI], 1.005-1.072), E. cloacae (RR, 1.028; 95% CI, 1.013-1.044), and P. aeruginosa (RR, 1.013; 95% CI, 1.006-1.020). No significant change in susceptibility was detected for K. pneumoniae (RR, 1.002; 95% CI, 0.996-1.008), and the susceptibility for E. coli continued to decline, although the decline was not as steep (RR, 0.981; 95% CI, 0.975-0.987).

CONCLUSIONS

A stewardship-driven FQ restriction program stopped overall declining FQ susceptibility rates for all species except E. coli. For 3 species (ie, Acinetobacter spp, E. cloacae, and P. aeruginosa), susceptibility rates improved after implementation, and this improvement has been sustained over a 10-year period.

Ubiquitous Nature of Fluoroquinolones: The Oscillation between Antibacterial and Anticancer Activities

Fluoroquinolones are synthetic antibacterial agents that stabilize the ternary complex of prokaryotic topoisomerase II enzymes (gyrase and Topo IV), leading to extensive DNA fragmentation and bacteria death. Despite the similar structural folds within the critical regions of prokaryotic and eukaryotic topoisomerases, clinically relevant fluoroquinolones display a remarkable selectivity for prokaryotic topoisomerase II, with excellent safety records in humans. Typical agents that target human topoisomerases (such as etoposide, doxorubicin and mitoxantrone) are associated with significant toxicities and secondary malignancies, whereas clinically relevant fluoroquinolones are not known to exhibit such propensities. Although many fluoroquinolones have been shown to display topoisomerase-independent antiproliferative effects against various human cancer cells, those that are significantly active against eukaryotic topoisomerase show the same DNA damaging properties as other topoisomerase poisons. Empirical models also show that fluoroquinolones mediate some unique immunomodulatory activities of suppressing pro-inflammatory cytokines and super-inducing interleukin-2. This article reviews the extended roles of fluoroquinolones and their prospects as lead for the unmet needs of "small and safe" multimodal-targeting drug scaffolds.

Nationwide surveillance of bacterial respiratory pathogens conducted by the surveillance committee of Japanese Society of Chemotherapy, the Japanese Association for Infectious Diseases, and the Japanese Society for Clinical Microbiology in 2012: General view of the pathogens' antibacterial susceptibility

The nationwide surveillance on antimicrobial susceptibility of bacterial respiratory pathogens from the patients in Japan was conducted by Japanese Society of Chemotherapy, Japanese association for infectious diseases and Japanese society for Clinical Microbiology in 2012. The isolates were collected from clinical specimens obtained from well-diagnosed adult patients with respiratory tract infections during the period between January and December in 2012 by three societies. Antimicrobial susceptibility testing was conducted at the central reference laboratory according to the method recommended by Clinical Laboratory Standard Institutes. Susceptibility testing was evaluated in 1236 strains (232 Staphylococcus aureus, 225 Streptococcus pneumoniae, 16 Streptococcus pyogenes, 231 Haemophilus influenzae, 147 Moraxella catarrhalis, 167 Klebsiella pneumoniae and 218 Pseudomonas aeruginosa). Ratio of methicillin-resistant S. aureus was 51.3%, and those of penicillin-intermediate S. pneumoniae was 0.4%. Among H. influenzae, 5.6% of them were found to be β-lactamase-producing ampicillin-resistant strains, and 37.2% to be β-lactamase-non-producing ampicillin-resistant strains. Extended spectrum β-lactamase-producing K. pneumoniae and multi-drug resistant P. aeruginosa with metallo β-lactamase were 4.2% and 3.2%, respectively. Continuous national surveillance is important to determine the actual situation of the resistance shown by bacterial respiratory pathogens to antimicrobial agents.

Impact of Combination Antibiogram and Related Education on Inpatient Fluoroquinolone Prescribing Patterns for Patients With Health Care-Associated Pneumonia

BACKGROUND

Previous studies have shown that development of a unit-specific combination antibiogram improves optimal selection of empiric therapy for Gram-negative infections, yet no published data exist regarding the role of the combination antibiogram as an antimicrobial stewardship program tool for disease-specific prescribing.

OBJECTIVE

To evaluate the utility of a combination antibiogram to guide antibiotic prescribing for patients with health care-associated pneumonia (HCAP).

METHODS

This was a retrospective preprovider and postprovider education intervention study aimed to evaluate fluoroquinolone (FQ) use in patients with HCAP. Data were collected retrospectively to evaluate antibiotic prescribing patterns and patient outcomes.

RESULTS

A total of 87 patients were eligible for study inclusion. The primary end point, FQ days of therapy (DOT) was decreased by 2.3 days (P < 0.001). The secondary end point included FQ DOT per 1000 patient-days in patients with discharge diagnosis-related group of pneumonia and was decreased by 83.5 days (P = 0.08); double coverage reduced by 13% postintervention (P = 0.22); mean days of double coverage decreased by 2.1 days (P < 0.001), and length of stay was shortened by 2.1 days (P = 0.22). Clinical success was achieved more often in the postintervention group (90% vs 98%, P = 0.18) when compared with the preintervention group. No difference was found in microbiological outcomes in the subset of microbiologically evaluable patients (P = 0.57).

CONCLUSION

Facility-specific combination antibiograms may be used to inform antibiotic prescribing in HCAP patients.

Multiple antibiotic resistance indexing of Escherichia coli to identify high-risk sources of faecal contamination of water

We evaluated the antibiogram profile of Escherichia coli (n = 300) isolated from selected rivers in Osun State, Nigeria. The identities of the E. coli isolates were confirmed by polymerase chain reaction (PCR) technique. Susceptibility of the isolates to 20 antibiotics conventionally used in clinical cases was assessed in vitro by the standardized agar disc-diffusion method. All the isolates were susceptible to imipenem, meropenem, amikacin and gatilofloxacin. The isolates were variously susceptible to the other antibiotics as follows: ciprofloxacin (96 %), kanamycin (95 %), neomycin (92 %), streptomycin (84 %), chloramphenicol (73 %), nalidixic acid (66 %), nitrofurantoin (64 %), gentamycin (63 %), doxycycline (58 %), cefepime (57 %), tetracycline (49 %) and cephalothin (42 %). The multiple antibiotic resistance indexing ranged from 0.50 to 0.80 for all the sampling locations and exceeded the threshold value of 0.2, suggesting the origin of the isolates to be of high antimicrobial usage. Our findings signify an increase in the incidence of antimicrobial resistance of E. coli towards conventionally used antibiotics necessitating proper surveillance programmes towards the monitoring of antimicrobial resistance determinants in water bodies.

Repurposing the antihistamine terfenadine for antimicrobial activity against Staphylococcus aureus

Staphylococcus aureus is a rapidly growing health threat in the U.S., with resistance to several commonly prescribed treatments. A high-throughput screen identified the antihistamine terfenadine to possess, previously unreported, antimicrobial activity against S. aureus and other Gram-positive bacteria. In an effort to repurpose this drug, structure-activity relationship studies yielded 84 terfenadine-based analogues with several modifications providing increased activity versus S. aureus and other bacterial pathogens, including Mycobacterium tuberculosis. Mechanism of action studies revealed these compounds to exert their antibacterial effects, at least in part, through inhibition of the bacterial type II topoisomerases. This scaffold suffers from hERG liabilities which were not remedied through this round of optimization; however, given the overall improvement in activity of the set, terfenadine-based analogues provide a novel structural class of antimicrobial compounds with potential for further characterization as part of the continuing process to meet the current need for new antibiotics.

Antiproliferative and cytotoxic properties of moxifloxacin on rat retinal ganglion cells

Abstract Purpose: To evaluate the antiproliferative and cytotoxic properties of moxifloxacin on cultured rat retinal ganglion cells (RGC5).

MATERIALS AND METHODS

Rat retinal ganglion cells were exposed to various concentration of moxifloxacin (5-1500 μg/mL). For antiproliferative properties, the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) test was performed. Cellular cytotoxicity was assessed by using the Live/Dead viability/cytotoxicity assay and analyzed by fluorescence microscopy after 24 and 72 h of incubation, respectively.

RESULTS

Neither cytotoxic nor antiproliferative effect of moxifloxacin was observed below 50 μg/mL on RGC5 cells after 24 and 72 h of incubation. At higher concentrations of moxifloxacin (150 μg/mL, 500 μg/mL, and 1500 μg/mL (p < 0.001)) the number of viable cells and the proliferation rate of RGC5 were significantly reduced.

CONCLUSIONS

These results suggest a dose-dependent cytotoxic and antiproliferative effect of moxifloxacin on RGC5. Therefore, intracameral application of moxifloxacin should be used cautiously in patients with increased risk of retinal ganglion cells damage, particularly in glaucoma patients.

Treatment ofPseudomonas aeruginosainfection in critically ill patients

Critically ill patients are on the increase in the present clinical setting. Aging of our population and increasingly aggressive medical and therapeutic interventions, including implanted foreign bodies, organ transplantation and advances in the chemotherapy of malignant diseases, have created a cohort of particularly vulnerable patients. Pseudomonas aeruginosa is one of the leading gram-negative organisms associated with nosocomial infections. This organism is frequently feared because it causes severe hospital-acquired infections, especially in immunocompromised hosts, and is often antibiotic resistant, complicating the choice of therapy. The epidemiology, microbiology, mechanisms of resistance and currently available and future treatment options for the most relevant infections caused by P. aeruginosa are reviewed.

Levofloxacin: update and perspectives on one of the original ‘respiratory quinolones’

The fluoroquinolone class of antimicrobials has enjoyed enormous clinical and marketing success over the past 20 years. These drugs have proven to be extremely useful in a broad range of clinical indications including both common community-acquired as well as nosocomial bacterial infections. Levofloxacin (Levaquin, Tavanic), like ciprofloxacin (Cipro), has established an enviable record of safe and efficacious use, and in many ways has become the agent against which all of the newer fluoroquinolones are judged. New clinical indications in complicated skin and skin structure infections, nosocomial pneumonia and chronic bacterial prostatitis continue to expand the important role of this already versatile drug. In addition, the use of 'short-course, high-dose' therapies are being studied in indications, such as community-acquired pneumonia, in an effort to optimize the efficacy and convenience of the drug while minimizing the future development of resistance. As the use of levofloxacin continues to expand, future challenges will include the threat of increasing antimicrobial resistance and the availability of newer alternative agents, both newer fluoroquinolones as well as agents of other antibiotic classes.

Future Trends in Antimicrobial Chemotherapy: Expert Opinion on the 43rdICAAC

The current document bestows an expert synopsis of key new information presented at the 43rd Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC) meeting in 2003. Data is presented on the socio-political aspects of and policies on antimicrobial prescribing, novel mechanisms of resistance in Streptococcus pneumoniae, and current epidemiological trends in global resistance. Novel information on new (and existing) antimicrobial agents--new penicillins, cephalosporins, monobactams and oxipenem inhibitors, ketolides, glycopeptides, fluoroquinolones (and hybrids), peptides, daptomycin, aminomethylcyclines, glycylcyclines, and newer formulations of agents such as amoxycillin-clavulanate--provides renewed hope that resistant pathogens can be controlled through use of more potent agents. Improved strategies for the use of existing antimicrobial agents, such as the use of high-dose regimens, short-course therapy, also may delay or reduce the development of resistance and preserve the value of our antibiotic armamentarium.

Monitoring of Antibiotic Resistance in Bacterial Isolates from Bacteremic Patients

The aim of the study was to monitor the prevalence of pathogens and development of resistance in bacteria isolated from bacteremic patients. Five University Clinics and/or Regional Hospitals in the Slovak Republic participated in the study and a total of 421 isolates were collected in the second half of the year 2002. The most prevalent organisms were coagulase-negative staphylococci (CONS) (19%), Staphylococcus aureus (18.3%), among Gram-negative bacteria Escherichia coli (13.3%), Klebsiella pneumoniae (11.4%) and Pseudomonas aeruginosa (7.8%) followed by enterococci, Acinetobacter baumannii and Enterobacter sp. All CONS and S. aureus were susceptible to vancomycin; resistance to oxacillin was observed for 55% of the CONS and only for 4% of S. aureus isolates. A higher prevalence of resistance to erythromycin, clindamycin, gentamicin and ofloxacin was found in CONS in comparison to S. aureus. Enterococcus sp. isolates were fully susceptible to vancomycin and teicoplanin. Gentamicin, amoxicillin/clavulanate, third generation cephalosporins and ciprofloxacin showed good activity against E. coli. Although 17% of K. pneumoniae isolates were resistant to ciprofloxacin, it was the most effective drug against K. pneumoniae; the prevalence of resistance to other antibiotics was rather higher. Gentamicin and ciprofloxacin were the most active against Enterobacter sp. isolates and ceftazidime and meropenem against P. aeruginosa.

Bacteria tracking by in vivo magnetic resonance imaging

Background

Different non-invasive real-time imaging techniques have been developed over the last decades to study bacterial pathogenic mechanisms in mouse models by following infections over a time course. In vivo investigations of bacterial infections previously relied mostly on bioluminescence imaging (BLI), which is able to localize metabolically active bacteria, but provides no data on the status of the involved organs in the infected host organism. In this study we established an in vivo imaging platform by magnetic resonance imaging (MRI) for tracking bacteria in mouse models of infection to study infection biology of clinically relevant bacteria.

Results

We have developed a method to label Gram-positive and Gram-negative bacteria with iron oxide nano particles and detected and pursued these with MRI. The key step for successful labeling was to manipulate the bacterial surface charge by producing electro-competent cells enabling charge interactions between the iron particles and the cell wall. Different particle sizes and coatings were tested for their ability to attach to the cell wall and possible labeling mechanisms were elaborated by comparing Gram-positive and -negative bacterial characteristics. With 5-nm citrate-coated particles an iron load of 0.015 ± 0.002 pg Fe/bacterial cell was achieved for Staphylococcus aureus. In both a subcutaneous and a systemic infection model induced by iron-labeled S. aureus bacteria, high resolution MR images allowed for bacterial tracking and provided information on the morphology of organs and the inflammatory response.

Conclusion

Labeled with iron oxide particles, in vivo detection of small S. aureus colonies in infection models is feasible by MRI and provides a versatile tool to follow bacterial infections in vivo. The established cell labeling strategy can easily be transferred to other bacterial species and thus provides a conceptual advance in the field of molecular MRI.

Levofloxacin for the treatment of respiratory tract infections

INTRODUCTION

Fluoroquinolone use has dramatically increased since the introduction of the first respiratory fluoroquinolone in the late 1990s. Levofloxacin , like other fluoquinolones, is a potent antibiotic, due to high levels of susceptibility among Gram-negative, Gram-positive (including penicillin-resistant strains of Streptococcus pneumonia) and atypical pathogens. Levofloxacin is recommended for the treatment of community-acquired pneumonia (CAP), hospital-acquired pneumonia (HAP) and in the management of acute exacerbations of chronic bronchitis (AECB). Levofloxacin demonstrates good safety, bioavailability and tissue penetration, thus maintaining adequate concentrations at the site of infection. High-dose (750 mg), short-course (5 days) therapy regimens may offer improved treatment, especially in HAP, due to higher drug concentrations, increased adherence and the potential to reduce the development of resistance.

AREAS COVERED

This article covers medical literature published in any language since 1990 until November 2011, on 'levofloxacin', identified using PubMed and MEDLINE. The search terms used were 'levofloxacin' and 'community acquired pneumonia', 'hospital pneumonia' or 'AECB'.

EXPERT OPINION

Levofloxacin is a valuable antimicrobial agent and an optimal treatment option for AECB, CAP (as a monotherapy) and HAP (as combination therapy at a high-dose regimen). Its improved bioavailability and safety profile makes the possibility of shorter hospital stays a reality.

Gram-negative and Gram-positive bacterial infections give rise to a different metabolic response in a mouse model

Metabolomics has become an important tool to study host-pathogen interactions and to discover potential novel therapeutic targets. In an attempt to develop a better understanding of the process of pathogenesis and the associated host response we have used a quantitative ¹H NMR approach to study the metabolic response to different bacterial infections. Here we describe that metabolic changes found in serum of mice that were infected with Staphylococcus aureus, Streptococcus pneumoniae, Escherichia coli and Pseudomonas aeruginosa can distinguish between infections caused by Gram-positive and Gram-negative bacterial strains. By combining the results of the mouse study with those of bacterial footprinting culture experiments, bacterially secreted metabolites could be identified as potential bacterium-specific biomarkers for P. aeruginosa infections but not for the other strains. Multivariate statistical analysis revealed correlations between metabolic, cytokine and physiological responses. In TLR4 and TLR2 knockout mice, host-response pathway correlated metabolites could be identified and allowed us for the first time to distinguish between bacterial- and host-induced metabolic changes. Since Gram-positive and Gram-negative bacteria activate different receptor pathways in the host, our results suggest that it may become possible in the future to use a metabolomics approach to improve on current clinical microbiology diagnostic methods.

Elderly patients with community-acquired pneumonia: optimal treatment strategies

Community-acquired pneumonia (CAP) is a common infectious disease that still causes substantial morbidity and mortality. Elderly people are frequently affected, and several issues related to care of this condition in the elderly have to be considered. This article reviews current recommendations of guidelines with a special focus on aspects of the care of elderly patients with CAP. The most common pathogen in CAP is still Streptococcus pneumoniae, followed by other pathogens such as Haemophilus influenzae, Mycoplasma pneumoniae, Chlamydophila pneumoniae and Legionella species. Antimicrobial resistance is an increasing problem, especially with regard to macrolide-resistant S. pneumoniae and fluoroquinolone-resistant strains. With regard to β-lactam antibacterials, resistance by H. influenzae and Moraxella catarrhalis is important, as is the emergence of multidrug-resistant Staphylococcus aureus. The main management decisions should be guided by the severity of disease, which can be assessed by validated clinical risk scores such as CURB-65, a tool for measuring the severity of pneumonia based on assessment of confusion, serum urea, respiratory rate and blood pressure in patients aged ≥65 years. For the treatment of low-risk pneumonia, an aminopenicillin such as amoxicillin with or without a β-lactamase inhibitor is frequently recommended. Monotherapy with macrolides is also possible, although macrolide resistance is of concern. When predisposing factors for special pathogens are present, a β-lactam antibacterial combined with a β-lactamase inhibitor, or the combination of a β-lactam antibacterial, a β-lactamase inhibitor and a macrolide, may be warranted. If possible, patients who have undergone previous antibacterial therapy should receive drug classes not previously used. For hospitalized patients with non-severe pneumonia, a common recommendation is empirical antibacterial therapy with an aminopenicillin in combination with a β-lactamase inhibitor, or with fluoroquinolone monotherapy. With proven Legionella pneumonia, a combination of β-lactams with a fluoroquinolone or a macrolide is beneficial. In severe pneumonia, ureidopenicillins with β-lactamase inhibitors, broad-spectrum cephalosporins, macrolides and fluoroquinolones are used. A combination of a broad-spectrum β-lactam antibacterial (e.g. cefotaxime or ceftriaxone), piperacillin/tazobactam and a macrolide is mostly recommended. In patients with a predisposition for Pseudomonas aeruginosa, a combination of piperacillin/tazobactam, cefepime, imipenem or meropenem and levofloxacin or ciprofloxacin is frequently used. Treatment duration of more than 7 days is not generally recommended, except for proven infections with P. aeruginosa, for which 15 days of treatment appears to be appropriate. Further care issues in all hospitalized patients are timely administration of antibacterials, oxygen supply in case of hypoxaemia, and fluid management and dose adjustments according to kidney function. The management of elderly patients with CAP is a challenge. Shifts in antimicrobial resistance and the availability of new antibacterials will change future clinical practice. Studies investigating new methods to detect pathogens, determine the optimal antimicrobial regimen and clarify the duration of treatment may assist in further optimizing the management of elderly patients with CAP.

The newer fluoroquinolones

Clinicians have enthusiastically used fluoroquinolones owing to their good safety profile and wide range of indications. This article reviews fluoroquinolone pharmacology, pharmacodynamic principles, and fluoroquinolone resistance mechanisms, highlighting recent trends in the epidemiology of fluoroquinolone resistance among gram-negative organisms and Streptococcus pneumonia. Important fluoroquinolone safety concerns are discussed, along with indications for the most commonly used fluoroquinolones--ciprofloxacin, levofloxacin, and moxifloxacin.

Intravenous moxifloxacin in routine hospital treatment of respiratory tract infections in China: results of a multicenter, noninterventional study

Objective:

To investigate the effectiveness, safety, and tolerability of moxifloxacin (MXF) (intravenous [IV] or sequential therapy [IV followed by oral]) under daily treatment conditions in a large number of patients with respiratory tract infections.

Design:

Patients with a diagnosis of respiratory tract infection should be treated with MXF IV and/or tablets 400 mg once daily for a duration at the physician’s discretion. For each patient, the physician documented data at an initial visit and at the end of therapy (EOT) visit and/or, in the case of sequential therapy, an interim visit when the patient switched to oral treatment.

Results:

A total of 1953 patients treated with MXF were documented and were valid for an effectiveness and safety evaluation. An improvement was observed in 98.1% (n = 1911/1949) of patients treated with MXF. Recovery was documented in 89.9% (n = 1754/1951) of the patients. At the EOT visit, severity of infection was assessed to be “relieved” or at least “improved” in 96.5% (n = 1873/1940) of the patients. Physicians assessed overall effectiveness as “good” or “very good” in 93.3% (n = 1822/1953) of all patients. The physicians’ overall tolerability rating was “very good” or “good” in 93.5% (n = 1827/1953) of all patients. The incidence rates of adverse events (AEs) and adverse drug reactions (ADRs) were 0.72% (n = 14) and 0.67% (n = 13), respectively. One serious AE “falling white blood cell count” occurred (0.05%), which was also defined as a serious ADR and resolved.

Conclusion:

MXF was generally well tolerated and highly effective in the treatment of different respiratory tract infections. The incidence of AEs and ADRs was low. The efficacy, safety, and tolerability information collected in this study confirms the clinical safety profile of MXF and its value as antibiotic treatment for respiratory tract infections.

Fluoroquinolones in the management of community-acquired pneumonia in primary care

A literature search was conducted to evaluate the pharmacokinetic and pharmacodynamic profile of the respiratory fluoroquinolones (gemifloxacin, levofloxacin and moxifloxacin) and their efficacy and safety in the management of community-acquired pneumonia (CAP). Data show that CAP is a common presentation in primary care practice, and is associated with high rates of morbidity and mortality, particularly in the elderly. Although the causative pathogens differ depending on treatment setting and patient factors, Streptococcus pneumoniae is the primary pathogen in all treatment settings. As a class, the respiratory fluoroquinolones have a very favorable pharmacokinetic and pharmacodynamic profile. Pharmacodynamic criteria suggest that moxifloxacin and gemifloxacin are more potent against S. pneumoniae, which may have the added benefit of reducing resistance selection and enhancing bacterial eradication. The respiratory fluoroquinolones are also generally well tolerated, and are first-line options for outpatient treatment of CAP in patients with comorbidities or previous antibiotic use.

Strategies to Address Appropriate Fluoroquinolone Use in the Hospital

Purpose

Strategies to optimally use fluoroquinolones in the hospital setting are reviewed.

Summary

Fluoroquinolones possess broad-spectrum antimicrobial coverage and are widely used to treat a variety of infections including some serious, life-threatening conditions. Overuse and inappropriate use of fluoroquinolones has led to rapid emergence of fluoroquinolone-resistant organisms as well as multidrug-resistant pathogens. Preserving the fluoroquinolone class is important, especially given the lack of new antibiotics currently in clinical development. Maintaining the fluoroquinolone class as a therapeutic option requires the successful implementation of guidelines to promote appropriate, optimal use of these agents. Among many recommendations to control the growing problem of antimicrobial resistance, antimicrobial stewardship programs offer the most comprehensive solution to gain appropriate antimicrobial prescribing. Effective programs include selection of the most effective agents, specific dosages, frequency of administration, routes of administration, and duration of therapy. Additionally, a dual fluoroquinolone formulary, which typically incorporates one respiratory fluoroquinolone and ciprofloxacin, has been employed to increase the diversity of fluoroquinolone treatment and thus reduce the selective antimicrobial pressure. A combination of antimicrobial stewardship programs and a dual formulary option has been demonstrated to be a good approach to optimize the use of fluoroquinolones in the hospital. Two successful experiences in applying such strategies have been reported; in both cases the empiric fluoroquinolone prescribing was reduced.

Conclusion

Implementation of aggressive optimization strategies such as the combined use of antimicrobial stewardship programs and a dual fluoroquinolone formulary may maintain the efficacy of fluoroquinolones and preserve their utility for future patients.

Emergence of fluoroquinolone-resistant Streptococcus pneumoniae in Lebanon: a report of three cases

The global emergence of Streptococcus pneumoniae resistance to fluoroquinolones is alarming and has grown to be a cause for significant concern worldwide. We report the first three cases of levofloxacin resistant S. pneumoniae isolates in a tertiary medical center in Beirut, Lebanon. Judicious use of antimicrobial agents is imperative to limit the spread of such resistant strains.

Doxycycline vs. levofloxacin in the treatment of community-acquired pneumonia

BACKGROUND

Community-acquired pneumonia (CAP) affects 5-10 million adults annually in the United States with approximately 1.1 million hospitalizations. Current guidelines recommend fluoroquinolones as monotherapy for treatment of CAP in general medical wards and doxycycline monotherapy for outpatient therapy only. Fluoroquinolones are expensive and development of bacterial resistance to them has become a concern. Therefore, we studied whether doxycycline is as efficacious as levofloxacin in treatment of CAP in general medical wards.

METHODS

In this prospective double-blinded trial, non-pregnant adults with clinical and radiological evidence of pneumonia requiring hospitalization were enrolled. Patients who were septic, hypoxic requiring intubations, nursing home residents, diagnosed with severe hepatic or renal dysfunction, recently hospitalized or immunocompromised were excluded from the study. Subjects were randomly assigned to either i.v. levofloxacin 500 mg daily or doxycycline 100 mg twice daily. After discharge, patients were followed for 2 months.

RESULTS

There were 30 patients in the levofloxacin group and 35 patients in the doxycycline group. Groups were comparable in both clinical and laboratory profiles. Additionally, efficacy of treatment was not significantly different between the two groups (P = 0.844). Length of stay was 5.7 +/- 2.05 days in the levofloxacin group and 4.0 +/- 1.82 days in the doxycycline group (P < 0.0012). Failure rate was similar in both groups (P = 0.893). Total antibiotic cost was $122.07 +/- 15.84 for levofloxacin and $64.98 +/- 24.4 for doxycycline (P < 0.0001).

CONCLUSIONS

Our study supports doxycycline as an effective and economical alternative therapy for levofloxacin in the empirical treatment of CAP in general medical wards.

Combination of 16S rRNA variable regions provides a detailed analysis of bacterial community dynamics in the lungs of cystic fibrosis patients

Chronic bronchopulmonary bacterial infections remain the most common cause of morbidity and mortality among patients with cystic fibrosis (CF). Recent community sequencing work has now shown that the bacterial community in the CF lung is polymicrobial. Identifying bacteria in the CF lung through sequencing can be costly and is not practical for many laboratories. Molecular techniques such as terminal restriction fragment length polymorphism or amplicon length heterogeneity-polymerase chain reaction (LH-PCR) can provide many laboratories with the ability to study CF bacterial communities without costly sequencing. The aim of this study was to determine if the use of LH-PCR with multiple hypervariable regions of the 16S rRNA gene could be used to identify organisms found in sputum DNA. This work also determined if LH-PCR could be used to observe the dynamics of lung infections over a period of time. Nineteen samples were analysed with the V1 and the V1_V2 region of the 16S rRNA gene. Based on the amplicon size present in the V1_V2 region, Pseudomonas aeruginosa was confirmed to be in all 19 samples obtained from the patients. The V1 region provided a higher power of discrimination between bacterial profiles of patients. Both regions were able to identify trends in the bacterial population over a period of time. LH profiles showed that the CF lung community is dynamic and that changes in the community may in part be driven by the patient's antibiotic treatment. LH-PCR is a tool that is well suited for studying bacterial communities and their dynamics.

The fluoroquinolones: How long will their utility last?

Injudicious use of the fluoroquinolones may result in treatment failure, increased patient morbidity, increased health care cost, and possible patient fatality. Fluoroquinolone-resistant bacteria may also adversely impact the microbiological environment in the hospital, the local community and eventually large geographical regions. Fluoroquinolone resistance develops in a stepwise fashion, and current susceptibility testing methods and recommended MIC susceptible breakpoint values for the United States may fail to identify some bacteria that are resistant due to first step mutations at the fluoroquinolone target site gene sequences. C-8 methoxy- fluoroquinolone compounds are more active against resistant bacteria than the older compounds. Fluoroquinolone resistance relates directly to human and veterinary usage and emerging bacterial resistance poses the single greatest threat to the future survival of the fluoroquinolone drugs as an antibiotic class.

The newer fluoroquinolones

Clinicians have enthusiastically used fluoroquinolones owing to their good safety profile and wide range of indications. This article reviews fluoroquinolone pharmacology, pharmacodynamic principles, and fluoroquinolone resistance mechanisms, highlighting recent trends in the epidemiology of fluoroquinolone resistance among gram-negative organisms and Streptococcus pneumonia. Important fluoroquinolone safety concerns are discussed, along with indications for the most commonly used fluoroquinolones-ciprofloxacin, levofloxacin, and moxifloxacin.