A critical review of the fluoroquinolones: focus on respiratory infections

Efficacy of moxifloxacin monotherapy versusgatifloxacin monotherapy, piperacillin-tazobactam combination therapy, and lindamycin plus gentamicin combination therapy: An experimental study in a rat model of intra-abdominal sepsis induced by fluoroquinolone-resistant Bacteroides fragilis

BACKGROUND

In intra-abdominal infections, the activity of antimicrobial agents against Bacteroides fragilis and phenotypically related organisms, and the increasing resistance of these organisms, are of particular importance and concern to surgeons. In vitro data suggest that moxifloxacin is more active than other quinolones against obligately anaerobic organisms, including Bacteroides spp.

OBJECTIVE

The aim of this study was to compare the efficacy of moxifloxacin monotherapy versus gatifloxacin monotherapy and 2 combination therapies (piperacillin-tazobactam and clindamycin plus gentamicin) in a rat model of intra-abdominal sepsis. The end point was marked by the incidence of mortality and intra-abdominal abscesses at necropsy 7 days after bacterial challenge.

METHODS

Three different strains of B fragilis with different degrees of resistanceto moxifloxacin (minimum inhibitory concentrations [MICs]: 4, 8, and 16 pg/mL) were added to the challenge inoculum in 3 separate experiments. Groups of 20 animals were used in each experiment. Group 1 served as saline-treated controls; group 2 received moxifloxacin 15 mg QD; group 3 received gatifloxacin 25 mg QD; group 4 received piperacillin-tazobactam 93 mg (-83 mg of piperacillin) QD; and group 5 received a combination of clindamycin 15 mg TID plus gentamicin 2 mg TID. All treatments were given intramuscularly. For all antimicrobials, dose was based on peak and trough serum drug concentrations determined by prior testing, with animal doses adjusted based on the ratio of body surface area to body weight, and comparing these doses and levels with studies in humans.

RESULTS

In all 3 experiments, the mortality rate with moxifloxacin was significantlylower or statistically similar compared with antibiotic active comparators (P ≤ 0.024). In addition, there were no significant differences in the incidence of abscess with moxifloxacin versus its comparators or between the 3 moxifloxacin groups across experiments. The best results for moxifloxacin were found in the experiment in which the B fragilis strain with MIC 16 μg/mL was added to the inoculum.

CONCLUSION

The results of this study in an animal model of intra-abdominalsepsis induced by fluoroquinolone-resistant B fragilis suggest that moxifloxacin monotherapy performs as well as combination regimens such as piperacillin-tazobactam and clindamycin plus gentamicin, and is as effective as other fluoroquinolones with antianaerobic activity, such as gatifloxacin.

Tigecycline: a novel glycylcycline antibiotic

Tigecycline, the first-in-class glycylcycline, was developed to recapture the broad spectrum of activity of the tetracycline class and to treat patients with difficult-to-treat bacterial infections. Tigecycline's in vitro spectrum of activity encompasses aerobic, facultative and anaerobic Gram-positive and -negative bacteria, including antimicrobial-resistant bacteria such as methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus faecalis and Enterococcus faecium, and extended-spectrum beta-lactamase-producing Enterobacteriaceae. Clinical trials involving patients with complicated skin and skin-structure infections and complicated intra-abdominal infections, including patients infected with methicillin-resistant S. aureus, demonstrated that tigecycline was bacteriologically and clinically effective with mild-to-moderate gastrointestinal adverse events (i.e., nausea, vomiting and diarrhea) the most commonly reported. Tigecycline is a promising new broad-spectrum parenteral monotherapy for the treatment of patients with Gram-positive and -negative bacterial infections.

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.

Moxifloxacin population pharmacokinetics and model-based comparison of efficacy between moxifloxacin and ofloxacin in African patients

Pharmacokinetic exposure and the MIC of fluoroquinolones are important determinants of their efficacy against Mycobacterium tuberculosis. Population modeling was used to describe the steady-state plasma pharmacokinetics of moxifloxacin in 241 tuberculosis (TB) patients in southern Africa. Monte Carlo simulations were applied to obtain the area under the unbound concentration-time curve from 0 to 24 h (fAUC0-24) after daily doses of 400 mg or 800 mg moxifloxacin and 800 mg ofloxacin. The MIC distributions of ofloxacin and moxifloxacin were determined for 197 drug-resistant clinical isolates of Mycobacterium tuberculosis. For a specific MIC, the probability of target attainment (PTA) was determined for target fAUC0-24/MIC ratios of ≥53 and ≥100. The PTAs were combined with the MIC distributions to calculate the cumulative fraction of response (CFR) for multidrug-resistant (MDR) Mycobacterium tuberculosis strains. Even with the less stringent target ratio of ≥53, moxifloxacin at 400 mg and ofloxacin at 800 mg achieved CFRs of only 84% and 58% for multidrug-resistant isolates with resistance to an injectable drug, while the 800-mg moxifloxacin dose achieved a CFR of 98%. Using a target ratio of ≥100 for multidrug-resistant strains (without resistance to injectable agents or fluoroquinolones), the CFR was 88% for moxifloxacin and only 43% for ofloxacin, and the higher dose of 800 mg moxifloxacin was needed to achieve a CFR target of >90%. Our results indicate that moxifloxacin is more efficacious than ofloxacin in the treatment of MDR-TB. Further studies should determine the optimal pharmacodynamic target for moxifloxacin in a multidrug regimen and clarify safety issues when it is administered at higher doses.

Characterization of plasmid-mediated quinolone resistance (PMQR) genes in extended-spectrum β-lactamase-producing Enterobacteriaceae pediatric clinical isolates in Mexico

This work describes the characterization of plasmid-mediated quinolone-resistance (PMQR) genes from a multicenter study of ESBL-producing Enterobacteriaceae pediatric clinical isolates in Mexico. The PMQR gene-positive isolates were characterized with respect to ESBLs, and mutations in the GyrA and ParC proteins were determined. The phylogenetic relationship was established by PFGE and the transfer of PMQR genes was determined by mating assays. The prevalence of the PMQR genes was 32.1%, and the rate of qnr-positive isolates was 15.1%; 93.3% of the latter were qnrB and 6.4% were qnrA1. The distribution of isolates in terms of bacterial species was as follows: 23.5% (4/17) corresponded to E. cloacae, 13.7% (7/51) to K. pneumoniae, and 13.6% (6/44) to E. coli. In addition, the prevalence of aac(6')-Ib-cr and qepA was 15.1% and 1.7%, respectively. The molecular characteristics of qnr- and qepA-positive isolates pointed to extended-spectrum β-lactamase (ESBL) CTX-M-15 as the most prevalent one (70.5%), and to SHV-12 in the case of aac(6')-Ib-cr-positive isolates. GyrA mutations at codons Ser-83 and Asp-87, and ParC mutations at codons Ser-80 were observed in 41.1% and 35.2% of the qnr-positive isolates, respectively. The analysis of the transconjugants revealed a co-transmission of bla(CTX-M-15) with the qnrB alleles. In general, the prevalence of PMQR genes (qnr and aac(6')-Ib-cr) presented in this work was much lower in the pediatric isolates, in comparison to the adult isolates in Mexico. Also, ESBL CTX-M-15 was the main ESBL identified in the pediatric isolates, whereas in the adult ones, ESBLs corresponded to the CTX-M and the SHV families. In comparison with other studies, among the PMQR-genes identified in this study, the qnrB-alleles and the aac(6')-Ib-cr gene were the most prevalent, whereas the qnrS1, qnrA1 and qnrB-like alleles were the most prevalent in China and Uruguay.

Risk of severe dysglycemia among diabetic patients receiving levofloxacin, ciprofloxacin, or moxifloxacin in Taiwan

BACKGROUND

Observational studies and fatal case reports raise concern about the safety of severe dysglycemia associated with fluoroquinolone use. The objective of this study was to assess the risk of severe dysglycemia among diabetic patients who received different fluoroquinolones.

METHODS

In a population-based inception cohort study of diabetic patients covering the period from January 2006 to November 2007, outpatient new users of levofloxacin, ciprofloxacin, moxifloxacin, cephalosporins, and macrolides orally were identified. Study events were defined as emergency department visits or hospitalization for dysglycemia within 30 days following the initiation of antibiotic therapy. Results were analyzed with adjusted multinomial propensity score.

RESULTS

A total of 78 433 diabetic patients receiving the antibiotics of interest were included in the study. The absolute risk of hyperglycemia per 1000 persons was 6.9 for moxifloxacin and 1.6 for macrolides. In contrast, the risk of hypoglycemia was 10.0 for moxifloxacin and 3.7 for macrolides. The adjusted odds ratios (AORs) and 95% confidence intervals (CIs) of levofloxacin, ciprofloxacin, and moxifloxacin compared with macrolides were 1.75 (1.12-2.73), 1.87 (1.20-2.93), and 2.48 (1.50-4.12), respectively, for hyperglycemia and 1.79 (1.33-2.42), 1.46 (1.07-2.00), and 2.13 (1.44-3.14), respectively, for hypoglycemia. Patients taking moxifloxacin faced a significantly higher risk of hypoglycemia than those receiving ciprofloxacin. A significant increase in the risk of hypoglycemia was also observed among patients receiving moxifloxacin concomitantly with insulin (AOR, 2.28; 95% CI, 1.22-4.24).

CONCLUSIONS

Diabetics using oral fluoroquinolones faced greater risk of severe dysglycemia. The risk of hypoglycemia varied according to the type of fluoroquinolone administered, and was most commonly associated with moxifloxacin.

Photodegradation assessment of ciprofloxacin, moxifloxacin, norfloxacin and ofloxacin in the presence of excipients from tablets by UPLC-MS/MS and DSC

Background

Ciprofloxacin (CIP), moxifloxacin (MOX), norfloxacin (NOR) and ofloxacin (OFL), are the antibacterial synthetic drugs, belonging to the fluoroquinolones group. Fluoroquinolones are compounds susceptible to photodegradation process, which may lead to reduction of their antibacterial activity and to induce phototoxicity as a side effect. This paper describes a simple, sensitive UPLC-MS/MS method for the determination of CIP, MOX, NOR and OFL in the presence of photodegradation products.

Results

Chromatographic separations were carried out using the Acquity UPLC BEH C₁₈ column; (2.1 × 100 mm, 1.7 μm particle size). The column was maintained at 40°C, and the following gradient was used: 0 min, 95% of eluent A and 5% of eluent B; 10 min, 0% of eluent A and 100% of eluent B, at a flow rate of 0.3 mL min^-1. Eluent A: 0.1% (v/v) formic acid in water; eluent B: 0.1% (v/v) formic acid in acetonitrile. The method was validated and all the validation parameters were in the ranges acceptable by the guidelines for analytical method validation. The photodegradation of examined fluoroquinolones in solid phase in the presence of excipients followed kinetic of the first order reaction and depended upon the type of analyzed drugs and coexisting substances. Photodegradation process of analyzed drugs was confirmed by differential scanning calorimetry. In addition, the identification of degradation products was carried out by mass spectrometry.

Conclusion

The developed UPLC-MS/MS method enables the determination of CIP, MOX, NOR and OFL in the presence of photodegradation products and identification of photodegradation products.

Genomic characterization of ciprofloxacin resistance in a laboratory-derived mutant and a clinical isolate of Streptococcus pneumoniae

The broad-spectrum fluoroquinolone ciprofloxacin is a bactericidal antibiotic targeting DNA topoisomerase IV and DNA gyrase encoded by the parC and gyrA genes. Resistance to ciprofloxacin in Streptococcus pneumoniae mainly occurs through the acquisition of mutations in the quinolone resistance-determining region (QRDR) of the ParC and GyrA targets. A role in low-level ciprofloxacin resistance has also been attributed to efflux systems. To look into ciprofloxacin resistance at a genome-wide scale and to discover additional mutations implicated in resistance, we performed whole-genome sequencing of an S. pneumoniae isolate selected for resistance to ciprofloxacin in vitro (128 μg/ml) and of a clinical isolate displaying low-level ciprofloxacin resistance (2 μg/ml). Gene disruption and DNA transformation experiments with PCR fragments harboring the mutations identified in the in vitro S. pneumoniae mutant revealed that resistance is mainly due to QRDR mutations in parC and gyrA and to the overexpression of the ABC transporters PatA and PatB. In contrast, no QRDR mutations were identified in the genome of the S. pneumoniae clinical isolate with low-level resistance to ciprofloxacin. Assays performed in the presence of the efflux pump inhibitor reserpine suggested that resistance is likely mediated by efflux. Interestingly, the genome sequence of this clinical isolate also revealed mutations in the coding region of patA and patB that we implicated in resistance. Finally, a mutation in the NAD(P)H-dependent glycerol-3-phosphate dehydrogenase identified in the S. pneumoniae clinical strain was shown to protect against ciprofloxacin-mediated reactive oxygen species.

Rothia mucilaginosa pneumonia diagnosed by quantitative cultures and intracellular organisms of bronchoalveolar lavage in a lymphoma patient

Rothia mucilaginosa is a gram-positive coccus of the family Micrococcaceae. R. mucilaginosa is considered a part of the normal flora of the human oropharynx and upper respiratory tract and lower respiratory tract infections attributable to R. mucilaginosa are not frequent. We present a case of pneumonia, in which the R. mucilaginosa infection was diagnosed by quantitative cultures of a bronchoalveolar lavage (BAL) specimen. A 46-yr-old woman with B lymphoblastic lymphoma was admitted to the hospital for scheduled chemotherapy. Her chest computed tomography (CT) scan revealed bilateral multifocal nodular and patchy consolidation in both lungs. Investigation of the BAL specimen revealed that 7% of leukocytes had intracellular gram-positive cocci. The quantitative cultures of the BAL specimen grew mucoid, non-hemolytic, and grayish convex colonies on blood agar at a count of approximately 200,000 colony-forming units/mL. The colonies were identified as R. mucilaginosa. The patient was empirically treated with levofloxacin for 7 days, after which findings on the chest radiograph and CT scan improved. She was discharged with improvement on hospital day 46. To our knowledge, this is the first report of R. mucilaginosa pneumonia diagnosed in Korea. Quantitative culture of BAL specimen and examination of intracellular organisms are crucial for assessing the clinical significance of R. mucilaginosa recovered from the lower respiratory tract.

Efficacy and tolerability of moxifloxacin in 2338 patients with acute exacerbation of chronic bronchitis

OBJECTIVE

A post-marketing surveillance (PMS) study was conducted to evaluate the efficacy and tolerability of moxifloxacin 400mg once daily in patients with acute exacerbation of chronic bronchitis (AECB) treated by pulmonologists and pulmonary specialists in community-based practice settings.

PATIENT AND METHODS

2338 patients with AECB (54% male; 46% female) were included in the analysis. PMS studies are prospective, open, uncontrolled and observational in design. All therapeutic decisions were made by the attending physician, based on their clinical practice and experience. This approach was adopted in order to provide valuable information on the safety and efficacy of moxifloxacin therapy in routine clinical practice.

RESULTS

The main symptoms of AECB (cough, expectoration, dyspnoea, chest pain and fever) were either resolved or improved in 80-97% of patients. Most patients (65%) improved within 3 days of starting moxifloxacin therapy and 91.6% by day 5. Mean time to improvement was 3.2±1.6 days. Overall, 96.1% of patients were judged by their physician to be either cured or improved following moxifloxacin therapy. Approximately 57% of patients had previously been treated with an antibiotic for their last episode of AECB. The antibiotics used were mostly macrolides (18.2% of patients), beta-lactams (16.9%), tetracycline/ doxycycline (9.9%) and quinolones (9.5%). The tolerability of moxifloxacin therapy was rated as 'very good' or 'good' in 95.4% of patients. Adverse events were reported in only 1.5% of patients.

CONCLUSION

In conclusion, moxifloxacin 400mg once daily was effective and well tolerated in this group of patients with AECB, combined with a rapid onset of action and a similarly high clinical success rate to that observed in controlled comparative clinical trials.

Effect of total and partial nephrectomy on the elimination of ciprofloxacin in humans

BACKGROUND

Renal cell carcinoma (RCC) is the most common form of kidney cancer. Surgery is a standard procedure to resect the tumor during total (TN) or partial (nephron-sparing) nephrectomy (PN). Ciprofloxacin is most often administered at the usual intravenous dose of 100-400 mg/12 h. The application of such low doses of ciprofloxacin as 200 mg/24 h carries the risk of achieving subtherapeutic concentrations even in patients with limited renal function. The aim of the study was a comparison of concentrations and pharmacokinetics for ciprofloxacin at steady-state in patients after total and partial nephrectomy and evaluation of the effectiveness of the iv dose 200 mg/24 h against the theoretical value of MIC, 0.5 μg/ml.

METHODS

The research was carried out on two groups of patients after nephrectomy: total (group 1, n = 21; mean [SD], age, 62.9 [14.4] years; weight, 76.0 [14.6] kg; creatinine clearance, CL(CR), 90.7 [22.2] ml/min) and partial (group 2, n = 15; 61.7 [9.3] years; 87.8 [16.4] kg; CL(CR), 107.8 [36.4] ml/min). The patients were treated with ciprofloxacin in the dose of 200 mg/24 h (iv). Plasma concentrations of ciprofloxacin at steady state were measured with validated HPLC method with UV detection.

RESULTS

The mean values of plasma concentrations of ciprofloxacin at steady state in group 1 and 2 were: C(ss)(max), 2.012 and 1.345; C(ss)(min), 0.437 and 0.244 μg/ml, respectively. The main pharmacokinetic parameters for ciprofloxacin in group 1 and 2 were as follows: AUC((0-last)), 30.9 [17.9] and 19.5 [8.7] μg h/ml; AUMC((0-last)), 177.91 [11.1] and 91.9 [66.5] μg h(2)/ml; t(1/2β), 13.9 [7.7] and 9.8 [3.3] h; MRT, 16.5 [12.1] and 9.77 [5.4] h; V(d), 115.0 [67.2] and 142.2 [78.7] l; CL, 6.2 [3.3] and 10.8 [5.7] l/h, respectively. With the assumed MIC = 0.5 μg/ml, the values of C(ss)(max)/MIC < 10 and AUC/MIC < 125 were obtained in all the patients.

CONCLUSION

In our patients we observed significant differences in some pharmacokinetic parameters of ciprofloxacin after two types of nephrectomy.

Pharmacokinetics and pharmacodynamics of ciprofloxacin in critically ill patients after the first intravenous administration of 400 mg

PURPOSE

To investigate the pharmacokinetics and pharmacodynamics of ciprofloxacin in critically ill patients after the first intravenous administration of 400 mg.

MATERIAL/METHODS

Plasma concentrations were measured in 20 critically ill patients (mean [SD]; age, 55.5 [16.5] years; weight, 80.3 [16.9] kg; and creatinine clearance, 110.0 [71.5] mL/min). Four blood samples were drawn at the following time points 0, 0.5, 6 , 8 hours after infusion. Ciprofloxacin concentrations were determined by high-performance liquid chromatography.

RESULTS

In the cases where ciprofloxacin was applied in targeted antibiotic therapy the minimum inhibitory concentrations (MIC) were ≤0.5 mg/l. The maximum and minimum plasma concentrations of ciprofloxacin were 1.74 (0.58-7.90) and 0.45 (0.16-2.96) mg/l, respectively. The main pharmacokinetic parameters for ciprofloxacin in the analyzed patients were as follows: k(el), 0.21 h-1; t(1/2kel), 3.37 h; AUC(0-inf), 10.10 mg×h/l; AUMC(0-last), 15.36 mg×h(2)/l; MRT, 1.71 h; V(d), 214.8 l; Cl, 39.70 l/h. Considering the maximum value of MIC (0.5 mg/l) only 30% and 25% of analyzed patients had desired values of the PK/PD indexes AUIC>125 and C(max) /MIC>10, respectively.

CONCLUSIONS

The target plasma concentrations after the first dose of ciprofloxacin were reached only in a few critically ill patients. Considerable inter-subject variability for PK/PD parameters in ICU patients requires systematic monitoring.

Fluoroquinolones in the treatment of bronchopulmonary disease in cystic fibrosis

Fluoroquinolones are commonly used to treat lung infections in patients with cystic fibrosis. These patients are susceptible to lung infection with common bacteria such as Staphylococcus aureus and Haemophilus influenzae, but are also prone to infection by opportunistic bacteria, including Pseudomonas aeruginosa. The good oral bioavailability and broad antimicrobial spectrum of activity, including antipseudomonal properties, make this class of antimicrobial attractive. We review the evidence assessing the use of fluoroquinolones in the context of preventing and eradicating early lung infection and in managing chronic lung infection and pulmonary exacerbations. The safety of fluoroquinolones and the use of newer agents in the class are also discussed.

Moxifloxacin safety: an analysis of 14 years of clinical data

Background

Moxifloxacin, a fluoroquinolone antibiotic, is used for the treatment of respiratory tract, pelvic inflammatory disease, skin, and intra-abdominal infections. Its safety profile is considered favorable in most reviews but has been challenged with respect to rare but potentially fatal toxicities (e.g. hepatic, cardiac, or skin reactions).

Objective

To analyze and compare the safety profile of moxifloxacin versus comparators in the entire clinical database of the manufacturer.

Setting

Data on the valid-for-safety population from phase II–IV actively controlled studies (performed between 1996 and 2010) were analyzed. Studies were either double blind (n = 22 369) or open label (n = 7635) and included patients with indications that have been approved in at least one country [acute bacterial sinusitis, acute exacerbation of chronic bronchitis, community-acquired pneumonia, uncomplicated pelvic inflammatory disease, complicated and uncomplicated skin and skin structure infections, and complicated intra-abdominal infections] (n = 27 824) and patients with other indications (n = 2180), using the recommended daily dose (400 mg) and route of administration (oral, intravenous/oral, intravenous only). The analysis included patients at risk (age ≥65 years, diabetes mellitus, renal impairment, hepatic impairment, cardiac disorders, or body mass index <18 kg/m²). Patients with known contraindications were excluded from enrollment by study protocol design, but any patient having entered a study, even if inappropriately, was included in the analysis.

Main Outcome Measure

Crude incidences and relative risk estimates (Mantel-Haenszel analysis) of patients with any adverse event (AE), adverse drug reaction (ADR), serious AE (SAE), serious ADR (SADR), treatment discontinuation due to an AE or ADR, and fatal outcomes related to an AE or ADR.

Results

Overall incidence rates of AEs were globally similar in the moxifloxacin and comparator groups. By filtering the data for differences in disfavor of moxifloxacin (i) at ≥2.5% for events with an incidence ≥2.5% or at ≥2-fold for events with an incidence <2.5% in one or both groups and (ii) affecting ≥10 patients in either group, we observed slightly more (i) AEs in double-blind intravenous-only and open-label oral studies, (ii) SAEs in double-blind intravenous-only studies, (iii) ADRs and SADRs in open-label oral studies, (iv) SADRs in open-label intravenous/oral studies, and (v) premature discontinuation due to AEs in open-label intravenous-only studies. The actual numbers of SADRs (in all studies) were small, with clinically relevant differences noted only in intravenous/oral studies and mainly driven by ‘gastrointestinal disorders’ (15 versus 7 patients) and ‘changes observed during investigations’ (23 versus 7 patients [asymptomatic QT prolongation: 11 versus 4 patients in double-blind studies]). Analysis by comparator (including another fluoroquinolone) did not reveal medically relevant differences, even in patients at risk. Incidence rates of hepatic disorders, tendon disorders, clinical surrogates of QT prolongation, serious cutaneous reactions, and Clostridium difficile-associated diarrhea were similar with moxifloxacin and comparators.

Conclusion

The safety of moxifloxacin is essentially comparable to that of standard therapies for patients receiving the currently registered dosage and for whom contraindications and precautions of use (as in the product label) are taken into account.

Global fluoroquinolone resistance epidemiology and implictions for clinical use

This paper on the fluoroquinolone resistance epidemiology stratifies the data according to the different prescription patterns by either primary or tertiary caregivers and by indication. Global surveillance studies demonstrate that fluoroquinolone resistance rates increased in the past years in almost all bacterial species except S. pneumoniae and H. influenzae, causing community-acquired respiratory tract infections. However, 10 to 30% of these isolates harbored first-step mutations conferring low level fluoroquinolone resistance. Fluoroquinolone resistance increased in Enterobacteriaceae causing community acquired or healthcare associated urinary tract infections and intraabdominal infections, exceeding 50% in some parts of the world, particularly in Asia. One to two-thirds of Enterobacteriaceae producing extended spectrum β-lactamases were fluoroquinolone resistant too. Furthermore, fluoroquinolones select for methicillin resistance in Staphylococci. Neisseria gonorrhoeae acquired fluoroquinolone resistance rapidly; actual resistance rates are highly variable and can be as high as almost 100%, particularly in Asia, whereas resistance rates in Europe and North America range from <10% in rural areas to >30% in established sexual networks. In general, the continued increase in fluoroquinolone resistance affects patient management and necessitates changes in some guidelines, for example, treatment of urinary tract, intra-abdominal, skin and skin structure infections, and traveller's diarrhea, or even precludes the use in indications like sexually transmitted diseases and enteric fever.

Once-daily moxifloxacin therapy for community-acquired pneumonia in general practice : evidence from a post-marketing surveillance study of 1467 patients

OBJECTIVE

To assess the efficacy, safety and tolerability of oral moxifloxacin in outpatients with respiratory tract infections treated in general practices in Germany with the focus on community-acquired pneumonia (CAP). METHODS, DESIGN AND PATIENTS: This was an open-label, prospective, uncontrolled, post-marketing surveillance study undertaken between October 2001 and June 2002. Symptoms associated with pneumonia were documented at baseline and at follow-up visits. A general assessment was given and the number of days until improvement/cure were recorded by the attending physician at the end of therapy.

RESULTS

A total of 9036 patients were treated with moxifloxacin, of which 1467 had CAP. The recommended dosage of moxifloxacin (400mg once daily) was used in 97.8% of all CAP patients. Between the initial and final follow-up visits, symptoms of CAP were either improved or cured in 90-99% of patients. More than half of the patients showed improvement after 3 days (54.2%); 89.2% of patients were improved after 5 days. The mean time for patients to recover was 8.0 +/- 2.7 days, with 88.7% of patients recovered by day 10 of treatment. Physicians rated moxifloxacin therapy as 'very good' or 'good' in 96.6% of patients and virtually all favoured prescribing moxifloxacin again. Ten patients (0.7%) reported adverse events during moxifloxacin therapy, mostly gastrointestinal disturbances.

CONCLUSIONS

Moxifloxacin is a very effective and safe treatment for patients with CAP and is highly accepted by physicians and patients because of rapid symptom improvement and good tolerability.

Efficacy and tolerability of moxifloxacin in patients with sinusitis treated in general practice : results of a post-marketing surveillance study

OBJECTIVE

To assess the efficacy, safety and tolerability of moxifloxacin, an 8-methoxy fluoroquinolone, in patients with respiratory tract infections (RTIs) treated in general practice in Germany. Different RTIs were analysed separately, and this paper focuses on patients with acute sinusitis. METHODS, DESIGN AND PATIENTS: This was an open-label, prospective, uncontrolled, post-marketing surveillance study undertaken between October 2001 and June 2002. Symptoms of sinusitis (fever, cough, nasal obstruction, nasal secretion and headache) were assessed at baseline and at follow-up visits, and classified as 'absent', 'mild' or 'severe' by the attending physician.

RESULTS

Altogether 9036 patients were treated with moxifloxacin, of whom 2405 adult men and women had sinusitis. Sinusitis symptoms were improved or cured in at least 92% of patients. Moxifloxacin produced significant improvements after only 3 days (71.6% of patients); 96.2% of patients were improved after 5 days. Most patients (89.5%) had recovered by day 8 and 97.3% by day 10. Physicians rated moxifloxacin therapy as 'good' or 'very good' in 96.6% of patients and almost all favoured prescribing moxifloxacin in the future. Very few adverse events were reported with moxifloxacin (<0.4%), and were mostly gastrointestinal disturbances.

CONCLUSIONS

Moxifloxacin is a very effective and safe treatment for patients with acute sinusitis in general practice and is highly regarded by both physicians and patients because of rapid symptom improvement and good tolerability.

Cefepime

Cefepime (Maxipime), Maxcef, Cepimax, Cepimex, Axepim, a parenteral fourth-generation cephalosporin, is active against many organisms causative in pneumonia. Cefepime has in vitro activity against Gram-positive organisms including Staphylococcus aureus and penicillin-sensitive, -intermediate and -resistant Streptococcus pneumoniae similar to that of cefotaxime and ceftriaxone. Cefepime also has good activity against Gram-negative organisms, including Pseudomonas aeruginosa, similar to that of ceftazidime. Importantly, cefepime is stable against many of the common plasmid- and chromosome-mediated beta-lactamases and is a poor inducer of AmpC beta-lactamases. As a result, it retains activity against Enterobacteriaceae that are resistant to third-generation cephalosporins, such as derepressed mutants of Enterobacter spp. Cefepime may be hydrolyzed by the extended-spectrum beta-lactamases produced by some members of the Enterobacteriaceae, but to a lesser extent than the third-generation cephalosporins. Monotherapy with cefepime 1 or 2g, usually administered intravenously twice daily, was as effective for clinical and bacteriological response as ceftazidime, ceftriaxone or cefotaxime monotherapy (1 or 2g two or three times daily) in a number of randomized, clinical trials in hospitalized adult, or less commonly, pediatric, patients with generally moderate to severe community-acquired or nosocomial pneumonia. More limited data indicated that monotherapy with cefepime 2g three times daily was also as effective in treating patients with nosocomial pneumonia as imipenem/cilostatin 0.5g four times daily, and when combined with amikacin, cefepime was as effective as ceftazidime plus amikacin. Patients with pneumonia who failed to respond to previous antibacterial therapy with penicillins or other cephalosporins responded to treatment with cefepime. Cefepime is generally well tolerated, with a tolerability profile similar to those of other parenteral cephalosporins. In clinical trials, the majority of adverse events experienced by cefepime recipients were mild to moderate and reversible. The most common adverse events with a causal relationship to cefepime reported in clinical trials included rash and diarrhea. Other, less common, adverse events included pruritus, urticaria, nausea, vomiting oral candidiasis, colitis, headache, fever, erythema and vaginitis.

CONCLUSION

Cefepime is an established and generally well tolerated parenteral drug with a broad spectrum of antibacterial activity which, when administered twice daily, provides coverage of most of the pathogens that may be causative in pneumonia. In randomized clinical trials in hospitalized patients with generally moderate to severe community-acquired or nosocomial pneumonia, cefepime monotherapy exhibited good clinical and bacteriological efficacy. Cefepime may become a preferred antibacterial agent for infections caused by Enterobacter spp. With prudent use in order to prevent the emergence of resistant organisms, cefepime will continue to be a suitable option for the empiric treatment of pneumonia.

Pseudomonal Infections in Patients with COPD

COPD is a common disease with increasing prevalence. The chronic course of the disease is characterized by acute exacerbations that cause significant worsening of symptoms. Bacterial infections play a dominant role in approximately half of the episodes of acute exacerbations of COPD. The importance of pseudomonal infection in patients with acute exacerbations of COPD stems from its relatively high prevalence in specific subgroups of these patients, and particularly its unique therapeutic ramifications. The colonization rate of Pseudomonas aeruginosa in patients with COPD in a stable condition is low.A review of a large number of clinical series of unselected outpatients with acute exacerbations of COPD revealed that P. aeruginosa was isolated from the patients' sputum at an average rate of 4%. This rate increased significantly in COPD patients with advanced airflow obstruction, in whom the rate of sputum isolates of P. aeruginosa reached 8-13% of all episodes of acute exacerbations of COPD. However, the great majority of bacteria isolated in these patients were not P. aeruginosa, but the three classic bacteria Streptococcus pneumoniae, Hemophilus influenzae, and Moraxella catarrhalis. The subgroup of patients, with acute exacerbations of COPD, with the highest rate of P. aeruginosa infection, which approaches 18% of the episodes, is mechanically ventilated patients. However, even in this subgroup the great majority of bacteria isolated are the above-mentioned three classic pathogens. In light of these epidemiologic data and other important considerations, and in order to achieve optimal antibacterial coverage for the common infectious etiologies, empiric antibacterial therapy should be instituted as follows. Patients with acute exacerbations of COPD with advanced airflow obstruction (FEV(1) <50% of predicted under stable conditions) should receive once daily oral therapy with one of the newer fluoroquinolones, i.e. levofloxacin, moxifloxacin, gatifloxacin, or gemifloxacin for 5-10 days. Patients with severe acute exacerbations of COPD who are receiving mechanical ventilation should receive amikacin in addition to one of the intravenous preparations of the newer fluoroquinolones or monotherapy with cefepime, a carbapenem or piperacillin/tazobactam. In both subgroups it is recommended that sputum cultures be performed before initiation of therapy so that the results can guide further therapy.

Bacterial Infections in the Elderly Patient: Focus on Sitafloxacin

Sitafloxacin (DU-6859a) is a new-generation oral fluoroquinolone with in vitro activity against a broad range of Gram-positive and -negative bacteria, including anaerobic bacteria, as well as against atypical bacterial pathogens. Particularly in Japan this antibiotic was approved in 2008 for treatment of a number of bacterial infections caused by Gram-positive cocci and Gram-negative cocci and rods, including anaerobia atypical bacterial pathogens. As compared to oral levofloxacin sitafloxacin was non-inferior in the treatment of community-acquired pneumonia and non-inferior in the treatment of complicated urinary tract infections, according to the results of randomized, double-blind, multicentre, non-inferiority trials. Non-comparative studies demonstrated the efficacy of oral sitafloxacin in otorhinolaryngological infections, urethritis in men, cervicitis in women and odontogenic infections. Most common adverse reactions were gastrointestinal disorders and laboratory abnormalities in patients receiving oral sitafloxacin; diarrhea and liver enzyme elevations were among the common. In the Japanese population sitafloxacin covers broad spectrum of bacteria as compared to carbapenems, whereas in the Caucasians its use is currently limited due to the potential for ultraviolet A phototoxicity. Sitafloxacin is a promising therapeutic agent which merits further investigation in randomized clinical trials of elderly patients.

Cethromycin versus clarithromycin for community-acquired pneumonia: comparative efficacy and safety outcomes from two double-blinded, randomized, parallel-group, multicenter, multinational noninferiority studies

Community-acquired pneumonia (CAP) continues to be a major health challenge in the United States and globally. Factors such as overprescribing of antibiotics and noncompliance with dosing regimens have added to the growing antibacterial resistance problem. In addition, several agents available for the treatment of CAP have been associated with serious side effects. Cethromycin is a new ketolide antibiotic that may provide prescribing physicians with an additional agent to supplement a continually limited armamentarium. Two global phase III noninferiority studies (CL05-001 and CL06-001) to evaluate cethromycin safety and efficacy were designed and conducted in patients with mild to moderate CAP. Study CL05-001 demonstrated an 83.1% clinical cure rate in the cethromycin group compared with 81.1% in the clarithromycin group (95% confidence interval [CI], -4.8%, +8.9%) in the intent to treat (ITT) population and a 94.0% cethromycin clinical cure rate compared with a 93.8% clarithromycin cure rate (95% CI, -4.5%, +5.1%) in the per protocol clinical (PPc) population. Study CL06-001 achieved an 82.9% cethromycin clinical cure rate in the ITT population compared with an 88.5% clarithromycin cure rate (95% CI, -11.9%, +0.6%), whereas the clinical cure rate in the PPc population was 91.5% in cethromycin group compared with 95.9% in clarithromycin group (95% CI, -9.1%, +0.3%). Both studies met the primary endpoints for clinical cure rate based on predefined, sliding-scale noninferiority design. Therefore, in comparison with clarithromycin, these two noninferiority studies demonstrated the efficacy and safety of cethromycin, with encouraging findings of efficacy in subjects with Streptococcus pneumoniae bacteremia. No clinically significant adverse events were observed during the studies. Cethromycin may be a potential oral therapy for the outpatient treatment of CAP.

Antituberculosis drugs: drug interactions, adverse effects, and use in special situations. Part 2: second line drugs

The main objectives of tuberculosis therapy are to cure the patients and to minimize the possibility of transmission of the bacillus to healthy subjects. Adverse effects of antituberculosis drugs or drug interactions (among antituberculosis drugs or between antituberculosis drugs and other drugs) can make it necessary to modify or discontinue treatment. We describe the general mechanism of action, absorption, metabolization, and excretion of the drugs used to treat multidrug resistant tuberculosis (aminoglycosides, fluoroquinolones, cycloserine/terizidone, ethionamide, capreomycin, and para-aminosalicylic acid). We describe adverse drug reactions and interactions (with other drugs, food, and antacids), as well as the most appropriate approach to special situations, such as pregnancy, breastfeeding, liver failure, and kidney failure.

Review of moxifloxacin hydrochloride ophthalmic solution in the treatment of bacterial eye infections

Moxifloxacin hydrochloride ophthalmic solution 0.5% (Vigamox((R))) is the ocular formulation/adaptation of moxifloxacin. Moxifloxacin is a broad spectrum 8-methoxyfluoroquinolone which terminates bacterial growth by binding to DNA gyrase (topoisomerase II) and topoisomerase IV, essential bacterial enzymes involved in the replication, translation, repair and recombination of deoxyribonucleic acid. Affinity for both enzymes improves potency and reduces the probability of selecting resistant bacterial subpopulations. Vigamox is a bactericidal, concentration dependent, anti-infective. It is preservative free, and well tolerated with minimal ocular side effects. It provides increased penetration into ocular tissues and fluids with improved activity against Streptococci and Staphylococci species and moderate to excellent activity against clinically relevant, gram-negative ocular pathogens.

Clinical practice guidelines for hospital-acquired pneumonia and ventilator-associated pneumonia in adults

Hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP) are important causes of morbidity and mortality, with mortality rates approaching 62%. HAP and VAP are the second most common cause of nosocomial infection overall, but are the most common cause documented in the intensive care unit setting. In addition, HAP and VAP produce the highest mortality associated with nosocomial infection. As a result, evidence-based guidelines were prepared detailing the epidemiology, microbial etiology, risk factors and clinical manifestations of HAP and VAP. Furthermore, an approach based on the available data, expert opinion and current practice for the provision of care within the Canadian health care system was used to determine risk stratification schemas to enable appropriate diagnosis, antimicrobial management and nonantimicrobial management of HAP and VAP. Finally, prevention and risk-reduction strategies to reduce the risk of acquiring these infections were collated. Future initiatives to enhance more rapid diagnosis and to effect better treatment for resistant pathogens are necessary to reduce morbidity and improve survival.

Susceptibility of Streptococcus pneumoniae to fluoroquinolones in Canada

Ciprofloxacin, the first fluoroquinolone to be used to treat lower respiratory tract infections (LRTI), demonstrates poor potency against Streptococcus pneumoniae, and its use has been associated with the emergence of resistance. During the last decade, fluoroquinolones with enhanced in vitro activity against S. pneumoniae have replaced ciprofloxacin for the treatment of LRTI. Here, we analyzed the impact of more active fluoroquinolone usage on pneumococci by examining the fluoroquinolone usage, prevalence of fluoroquinolone resistance, and mutations in the genes that encode the major target sites for the fluoroquinolones (gyrA and parC) in pneumococcal isolates collected in Canada-wide surveillance. A total of 26,081 isolates were collected between 1998 and 2009. During this time period, total per capita outpatient use of fluoroquinolones increased from 64 to 96 prescriptions per 1,000 persons per year. The proportion of prescriptions for respiratory tract infection that were for fluoroquinolones increased from 5.9% to 10.7%, but the distribution changed: the proportion of prescriptions for ciprofloxacin decreased from 5.3% to 0.5%, and those for levofloxacin or moxifloxacin increased from 1.5% in 1999 to 5.9% in 2009. The prevalence of ciprofloxacin resistance (MIC ≥ 4 μg/ml), levofloxacin resistance, and moxifloxacin resistance remained unchanged at <2%. Multivariable analyses showed that prevalence of mutations known to be associated with reduced susceptibility to fluoroquinolones did not change during the surveillance period. If fluoroquinolone therapy is required, the preferential use of fluoroquinolones with enhanced pneumococcal activity to treat pneumococcal infections may slow the emergence of resistance in S. pneumoniae.

Factors affecting drug encapsulation and stability of lipid-polymer hybrid nanoparticles

Lipid-polymer hybrid nanoparticles are polymeric nanoparticles enveloped by lipid layers that combine the highly biocompatible nature of lipids with the structural integrity afforded by polymeric nanoparticles. Recognizing them as attractive drug delivery vehicles, antibiotics are encapsulated in the present work into hybrid nanoparticles intended for lung biofilm infection therapy. Modified emulsification-solvent-evaporation methods using lipid as surfactant are employed to prepare the hybrid nanoparticles. Biodegradable poly (lactic-co-glycolic acid) and phosphatidylcholine are used as the polymer and lipid models, respectively. Three fluoroquinolone antibiotics (i.e. levofloxacin, ciprofloxacin, and ofloxacin), which vary in their ionicity, lipophilicity, and aqueous solubility, are used. The hybrid nanoparticles are examined in terms of their drug encapsulation efficiency, drug loading, stability, and in vitro drug release profile. Compared to polymeric nanoparticles prepared using non-lipid surfactants, hybrid nanoparticles in general are larger and exhibit higher drug loading, except for the ciprofloxacin-encapsulated nanoparticles. Hybrid nanoparticles, however, are unstable in salt solutions, but the stability can be conferred by adding TPGS into the formulation. Drug-lipid ionic interactions and drug lipophilicity play important roles in the hybrid nanoparticle preparation. First, interactions between oppositely charged lipid and antibiotic (i.e. ciprofloxacin) during preparation cause failed nanoparticle formation. Charge reversal of the lipid facilitated by adding counterionic surfactants (e.g. stearylamine) must be performed before drug encapsulation can take place. Second, drug loading and the release profile are strongly influenced by drug lipophilicity, where more lipophilic drug (i.e. levofloxacin) exhibit a higher drug loading and a sustained release profile attributed to the interaction with the lipid coat.

In vitro evaluation of IgE-mediated hypersensitivity reactions to quinolones

BACKGROUND

  Hypersensitivity IgE-mediated reactions to quinolones are not easy to diagnose, with skin testing inducing false positive results. The aim of the study was to evaluate the in vitro-specific IgE response in patients with immediate allergic reactions to quinolones.

METHODS

  We evaluated 38 patients with confirmed immediate allergic reactions to quinolones. Those with anaphylaxis were considered allergic by clinical history, once other possible causes were ruled out, and those with urticaria by drug provocation. Sepharose-radioimmunoassay (RIA) and basophil activation test (BAT) with ciprofloxacin, moxifloxacin and levofloxacin were performed.

RESULTS

  The quinolones involved were moxifloxacin (N = 24), ciprofloxacin (N = 11) and levofloxacin (N = 3). Sepharose-RIA was positive in 12 cases (31.57%) and BAT in 27 (71.05%). With Sepharose-RIA, 8 (21%) were positive to ciprofloxacin, 7 (18.4%) to moxifloxacin and 7 (18.4%) to levofloxacin. With BAT, 23 (60.5%) were positive to ciprofloxacin, 12 (31.6%) to moxifloxacin and 8 (21%) to levofloxacin. The specificity of the Sepharose-RIA was demonstrated by inhibition tests. To confirm that the BAT results observed were IgE mediated, the PI3K inhibitor wortmannin was used, with this compound inhibiting the BAT when stimulated with anti-IgE and the different quinolones, but not when fMLP was used as the basophil stimulator. Sepharose-RIA and BAT were repeated in positive cases 1 year later, detecting a decrease in all cases, with four becoming negative.

CONCLUSION

  Immediate hypersensitivity reactions to quinolones do occur, with moxifloxacin being the drug most frequently involved. The BAT is a useful method for diagnosing patients. Specific IgE was demonstrated by Sepharose-RIA and inhibition assay.

Community-acquired pneumonia in the elderly

BACKGROUND

Community-acquired pneumonia (CAP) is a frequent cause of hospitalization and death among the elderly.

OBJECTIVE

This article reviews information on CAP among the elderly, including age-related changes, predisposing risk factors, causes, treatment strategies, and prevention.

METHODS

Searches of MEDLINE (January 1990-November 2009), International Pharmaceutical Abstracts (January 1990-November 2009), and Google Scholar were conducted using the terms community-acquired pneumonia, pneumonia, treatment guidelines, and elderly. Additional publications were found by searching the reference lists of the identified articles. Studies that reported diagnostic criteria as well as the treatment outcomes achieved in adult patients with CAP were selected for this review.

RESULTS

Three practice guidelines, 5 reviews, and 43 studies on CAP in the elderly were identified in the literature search. Based on those publications, risk factors that predispose the elderly to pneumonia include comorbid conditions, poor functional and nutritional status, consumption of alcohol, and smoking. The clinical presentation of pneumonia in the elderly (>/=65 years of age) may be subtle, lacking the typical acute symptoms (fever, cough, dyspnea, and purulent sputum) observed in younger adults. Pneumonia should be suspected in all elderly patients who have fever, altered mental status, or a sudden decline in functional status, with or without lower respiratory tract symptoms such as cough, purulent sputum, and dyspnea. Treatment of CAP in the elderly should be guided by the latest recommendations of the Infectious Diseases Society of America and the American Thoracic Society (IDSA/ATS), along with consideration of local rates and patterns of antimicrobial resistance, as well as individual patient risk factors for acquiring less common or more resistant pathogens. Recommended empiric antimicrobial regimens generally consist of either a beta-lactam plus a macrolide or a respiratory fluoroquinolone alone. Adherence to the IDSA/ATS guidelines has been found to improve in-hospital mortality (adherence vs nonadherence, 8%; 95% CI, 7%-10% vs 17%; 95% CI, 14%-20%; P< 0.01), length of hospital stay (8 days; interquartile range [IQR], 5-15 vs 10 days; IQR, 6-24 days, respectively; P < 0.01), and time to clinical stability in elderly patients with CAP (percentage of stable patients by day 7, 71%; 95% CI, 68%-74% vs 57%; 95% CI, 53%-61%, respectively; P < 0.01). All elderly patients should be vaccinated against pneumococcal disease and influenza based on recommendations from the Centers for Disease Control and Prevention. Lifestyle modifications and nutritional support are also important elements in the prevention of pneumonia in the elderly.

CONCLUSION

Adherence to established guidelines, along with customization of antimicrobial therapy based on local rates and patterns of resistance and patient-specific risk factors, likely will improve the treatment outcome of elderly patients with CAP.

Impact of different empirical antibiotic treatment regimens for community-acquired pneumonia on the emergence of Clostridium difficile

BACKGROUND

Treatment of community-acquired pneumonia (CAP) with newer fluoroquinolones may contribute to selection for Clostridium difficile. We studied the prevalence of C. difficile carriage and C. difficile infection (CDI) on admission, and nosocomial acquisition rates in patients hospitalized for CAP and compared different empirical treatment strategies.

METHODS

In a prospective study among patients admitted for antibiotic treatment of CAP, consecutive stool and skin samples were collected and cultured for C. difficile. Cultured isolates were typed by PCR ribotyping and characterized for toxinogenicity.

RESULTS

In total, 20 of 107 (18.7%) patients included carried C. difficile. Various ribotypes were found and 14 (70%) isolates were toxinogenic. On admission, prevalence of C. difficile carriage was 9.4% (n=9), of which 22% also carried C. difficile on the skin and one patient had mild CDI with persistent positive cultures. The overall nosocomial acquisition rate of C. difficile carriage was 11.2%. No nosocomially acquired CDI occurred. Acquisition rates of C. difficile were 11.9% (5/45) in moxifloxacin-, 11.1% (5/47) in β-lactam- and 9.0% (1/14) in β-lactam plus macrolide- or fluoroquinolone-treated patients (P=0.84). Risk factors for C. difficile carriage were intravenous antibiotic treatment >7 days [odds ratio (OR) 3.89; 95% confidence interval (CI) 1.30 to 11.79] and hospitalization during the past 3 months (OR 4.08; 95% CI 1.40 to 11.90).

CONCLUSIONS

In a non-outbreak setting with a low endemic rate, the prevalence of C. difficile carriage in patients admitted because of CAP is high and nosocomial acquisition rates for C. difficile colonization are 11%. Fluoroquinolones were not associated with increased acquisition rates for C. difficile as compared with other empirical regimens for CAP.

Comparative study of the disposition of levofloxacin, netilmicin and cefepime in the isolated rat lung

An experimental model of artificially perfused and mechanically ventilated lung has been applied to compare the kinetic behaviour of levofloxacin, cefepime and netilmicin in this body tissue. The study has been performed to explore the usefulness of the isolated lung technique in the pharmacokinetic field, particularly to study the disposition of antibiotics in pulmonary tissue. The lung was perfused with Krebs-Henseleit medium containing 3% bovine albumin at a flow rate of 5 mL min−1. It was ventilated at 60 respirations/min with a 2-mL tidal volume of air previously humidified and warmed to 37°C. The concentrations of the above antibiotics were determined by HPLC techniques and the outflow curves were analysed by stochastic, as well as by model-dependent, methods. The results show pharmacokinetic differences among these antibiotics, which are in accordance with previously reported data, levofloxacin being the drug with the highest distribution coefficient in this tissue (1.25 ± 0.14 vs 0.39 ± 0.07 and 0.41 ± 0.06 mL g−1 for netilmicin and cefepime, respectively). Accordingly, the isolated lung of the rat, under the experimental conditions used here, constitutes an alternative model to be incorporated to pharmacokinetic studies with a great potential use for those drugs that show a pharmacological or toxicological action depending on the kinetic profile in the lung tissue.

Intervention strategies for an influenza pandemic taking into account secondary bacterial infections

Influenza infections often predispose individuals to consecutive bacterial infections. Both during seasonal and pandemic influenza outbreaks, morbidity and mortality due to secondary bacterial infections can be substantial. With the help of a mathematical model, we investigate the potential impact of such bacterial infections during an influenza pandemic, and we analyze how antiviral and antibacterial treatment or prophylaxis affect morbidity and mortality. We consider different scenarios for the spread of bacteria, the emergence of antiviral resistance, and different levels of severity for influenza infections (1918-like and 2009-like). We find that while antibacterial intervention strategies are unlikely to play an important role in reducing the overall number of cases, such interventions can lead to a significant reduction in mortality and in the number of bacterial infections. Antibacterial interventions become even more important if one considers the--very likely--scenario that during a pandemic outbreak, influenza strains resistant to antivirals emerge. Overall, our study suggests that pandemic preparedness plans should consider intervention strategies based on antibacterial treatment or prophylaxis through drugs or vaccines as part of the overall control strategy. A major caveat for our results is the lack of data that would allow precise estimation of many of the model parameters. As our results show, this leads to very large uncertainty in model outcomes. As we discuss, precise assessment of the impact of antibacterial strategies during an influenza pandemic will require the collection of further data to better estimate key parameters, especially those related to the bacterial infections and the impact of antibacterial intervention strategies.

Gemifloxacin use in the treatment of acute bacterial exacerbation of chronic bronchitis

The newest generation of fluoroquinolones have proven efficacy against bacterial organisms associated with acute exacerbation of chronic bronchitis (AECB). Gemifloxacin, as one of the quinolones in this class, exhibits many of the pharmacokinetic and pharmacodynamic characteristics of the class with a few notable differences. Against Streptococccus pneumoniae it has a lower minimal inhibitory concentration (MIC) than the other respiratory fluoroquinolones and it has activity against both bacterial DNA gyrase and topoisomerase IV. The increased activity of gemifloxacin against both enzymes may be associated with decreased rates of resistance. Clinically, gemifloxacin has been shown to have positive effects on length of hospitalization and increased success at long-term follow-up in AECB patients. These associations were observed in noninferiority comparison studies. Although an advantage with the use of gemifloxacin in AECB is suggested, there are no comparison data is available to conclude that gemifloxacin is superior to the other respiratory fluoroquinolones. Gemifloxacin is generally well tolerated, but is associated with a characteristic rash and gastrointestinal upset as its most common observed side effects.

Effect of subinhibitory concentrations of antibiotics on intrachromosomal homologous recombination in Escherichia coli

Subinhibitory concentrations of some antibiotics, such as fluoroquinolones, have been reported to stimulate mutation and, consequently, bacterial adaptation to different stresses, including antibiotic pressure. In Escherichia coli, this stimulation is mediated by alternative DNA polymerases induced via the SOS response. Sublethal concentrations of the fluoroquinolone ciprofloxacin have been shown to stimulate recombination between divergent sequences in E. coli. However, the effect of ciprofloxacin on recombination between homologous sequences and its SOS dependence have not been studied. Moreover, the possible effects of other antibiotics on homologous recombination remain untested. The aim of this work was to study the effects of sublethal concentrations of ciprofloxacin and 10 additional antibiotics, including different molecular families with different molecular targets, on the rate of homologous recombination of DNA in E. coli. The antibiotics tested were ciprofloxacin, ampicillin, ceftazidime, imipenem, chloramphenicol, tetracycline, gentamicin, rifampin (rifampicin), trimethoprim, fosfomycin, and colistin. Our results indicate that only ciprofloxacin consistently stimulates the intrachromosomal recombinogenic capability of homologous sequences in E. coli. The ciprofloxacin-based stimulation occurs at concentrations and times that apparently do not dramatically compromise the viability of the whole population, and it is dependent on RecA and partially dependent on SOS induction. One of the main findings of this work is that, apart from quinolone antibiotics, none of the most used antibiotics, including trimethoprim (a known inducer of the SOS response), has a clear side effect on homologous recombination in E. coli. In addition to the already described effects of some antibiotics on mutagenicity, DNA transfer, and genetic transformability in naturally competent species, the effect of increasing intrachromosomal recombination of homologous DNA sequences can be uniquely ascribed to fluoroquinolones, at least for E. coli.

Side effects of antibiotics on genetic variability

In recent years, there has been accumulating evidence that antibiotics, besides their antimicrobial action, potentially have a number of undesired side effects that can, at least in some cases, promote genetic variability of bacteria. In addition to resistant variants, antibiotics have also been shown to select mutator clones, thus stimulating evolution towards further resistance. Furthermore, mutations, recombination and horizontal gene transfer have been reported to be somehow affected when bacteria are exposed to subinhibitory concentrations of certain antibiotics. These findings may have implications for the use of antibiotics, because they may have undesired side effects, such as enhancing antibiotic resistance evolution. Here we present data supporting (or not) this fearsome possibility and discuss whether this potential threat should be taken into consideration.

Penetration of moxifloxacin into bone evaluated by Monte Carlo simulation

Moxifloxacin is a fluoroquinolone with a broad spectrum of activity and good penetration into many tissues, including bone. Penetration of moxifloxacin into bone has not yet been studied using compartmental modeling techniques. Therefore, we determined the rate and extent of bone penetration by moxifloxacin and evaluated its pharmacodynamic profile in bone via Monte Carlo simulation. Twenty-four patients (10 males, 14 females) undergoing total hip replacement received 400 mg moxifloxacin orally 2 to 7 h prior to surgery. Blood and bone specimens were collected. Bone samples were pulverized under liquid nitrogen by a cryogenic mill, including an internal standard. Drug concentrations were analyzed by high-performance liquid chromatography. We used ADAPT II (results reported), NONMEM, and WinBUGS for pharmacokinetic analysis. Monte Carlo simulation was performed to reverse engineer the necessary area under the free concentration-time curve fAUC(SERUM)/MIC in serum and total AUC(BONE)/MIC in bone for a successful clinical or microbiological outcome. The median (10% to 90% percentile for between-subject variability) of the AUC in bone divided by the AUC in serum (AUC(BONE)/AUC(SERUM)) was 80% (51 to 126%) for cortical bone and 78% (42 to 144%) for cancellous bone. Equilibration between serum and bone was rapid. Moxifloxacin achieved robust (> or = 90%) probabilities of target attainment (PTAs) in serum, cortical bone, and cancellous bone up to MICs of < or = 0.375 mg/liter based on the targets fAUC(SERUM)/MIC > or = 40 and AUC(BONE)/MIC > or = 33. Moxifloxacin showed high bone concentrations and a rapid equilibrium between bone and serum. The favorable PTAs compared to the 90%-inhibitory MIC of Staphylococcus aureus warrant future clinical trials on the effectiveness of moxifloxacin in the treatment of bone infections.

Mechanism of action of and resistance to quinolones

Fluoroquinolones are an important class of wide-spectrum antibacterial agents. The first quinolone described was nalidixic acid, which showed a narrow spectrum of activity. The evolution of quinolones to more potent molecules was based on changes at positions 1, 6, 7 and 8 of the chemical structure of nalidixic acid. Quinolones inhibit DNA gyrase and topoisomerase IV activities, two enzymes essential for bacteria viability. The acquisition of quinolone resistance is frequently related to (i) chromosomal mutations such as those in the genes encoding the A and B subunits of the protein targets (gyrA, gyrB, parC and parE), or mutations causing reduced drug accumulation, either by a decreased uptake or by an increased efflux, and (ii) quinolone resistance genes associated with plasmids have been also described, i.e. the qnr gene that encodes a pentapeptide, which blocks the action of quinolones on the DNA gyrase and topoisomerase IV; the aac(6')-Ib-cr gene that encodes an acetylase that modifies the amino group of the piperazin ring of the fluoroquinolones and efflux pump encoded by the qepA gene that decreases intracellular drug levels. These plasmid-mediated mechanisms of resistance confer low levels of resistance but provide a favourable background in which selection of additional chromosomally encoded quinolone resistance mechanisms can occur.