Susceptibility of twenty penicillin-susceptible and -resistant pneumococci to levofloxacin, ciprofloxacin, ofloxacin, erythromycin, azithromycin, and clarithromycin by MIC and time-kill

Spatial and temporal analysis of invasive pneumococcal disease due to erythromycinresistant serotypes

OBJECTIVES

To study the spatio-temporal distribution of cases of invasive pneumococcal disease (IPD) due to serotypes resistant to erythromycin and its relationship with community consumption of macrolides and childhood vaccination coverage.

METHODS

We selected IPD cases in adults over 59 years old, residents in the Community of Madrid (MC), notified in the period 2007-2016. The variables studied were obtained from the Vaccination Information Systems and the Pharmaceutical Service. The cut-off point (minimum inhibitory erythromycin concentration > 0.5 mg/L) of the EUCAST classification was used to define erythromycin resistant serotypes. We used JointPoint to estimate the incidence trends by erythromycin resistant serotypes included in the 13-valent vaccine (STPCV13) and not included in it (STnoPCV13). The association of these incidences with the community consumption of macrolides and vaccination coverage was made using Poisson models. Statistical scanning was used for the detection of temporal-spaces clusters of cases.

RESULTS

1936 cases were identified, of which 427 erythromycin resistant serotypes were identified. The incidence of all cases due to resistant serotypes was decreasing (AAPC: -5,40%). During the period studied, the incidence of cases due to erythromycin resistant STPCV13 was decreasing with an annual percentage change (APC): -13.8 and was inversely associated with childhood vaccination coverage (IRR 0.641), while that of cases due to erythromycin resistant STnoPCV13 was ascending (APC): 4.5; and was not associated with coverage. 1 cluster was detected by STnoPCV13 and none by STPCV13 after the date of inclusion of the 13-valent in the childhood vaccination calendar.

CONCLUSIONS

The decrease in IPD due to resistant STPCV13 was associated with an increase in childhood vaccination coverage. The presence of clusters due to STnoPCV13 after the date of inclusion of the 13-valent vaccine in the childhood vaccination calendar indicates serotypes replacement. The increase in cases of resistant STnoPCV13 could be related to the replacement of vaccine serotypes in nasopharyngeal colonization, facilitated by the consumption of macrolides still at high levels in MC.

Spatial and temporal analysis of invasive pneumococcal disease due to erythromycinresistant serotypes

OBJECTIVES

To study the spatio-temporal distribution of cases of invasive pneumococcal disease (IPD) due to serotypes resistant to erythromycin and its relationship with community consumption of macrolides and childhood vaccination coverage.

METHODS

We selected IPD cases in adults over 59 years old, residents in the Community of Madrid (MC), notified in the period 2007-2016. The variables studied were obtained from the Vaccination Information Systems and the Pharmaceutical Service. The cut-off point (minimum inhibitory erythromycin concentration > 0.5 mg/L) of the EUCAST classification was used to define erythromycin resistant serotypes. We used JointPoint to estimate the incidence trends by erythromycin resistant serotypes included in the 13-valent vaccine (STPCV13) and not included in it (STnoPCV13). The association of these incidences with the community consumption of macrolides and vaccination coverage was made using Poisson models. Statistical scanning was used for the detection of temporal-spaces clusters of cases.

RESULTS

1936 cases were identified, of which 427 erythromycin resistant serotypes were identified. The incidence of all cases due to resistant serotypes was decreasing (AAPC: -5,40%). During the period studied, the incidence of cases due to erythromycin resistant STPCV13 was decreasing with an annual percentage change (APC): -13.8 and was inversely associated with childhood vaccination coverage (IRR 0.641), while that of cases due to erythromycin resistant STnoPCV13 was ascending (APC): 4.5; and was not associated with coverage. 1 cluster was detected by STnoPCV13 and none by STPCV13 after the date of inclusion of the 13-valent in the childhood vaccination calendar.

CONCLUSIONS

The decrease in IPD due to resistant STPCV13 was associated with an increase in childhood vaccination coverage. The presence of clusters due to STnoPCV13 after the date of inclusion of the 13-valent vaccine in the childhood vaccination calendar indicates serotypes replacement. The increase in cases of resistant STnoPCV13 could be related to the replacement of vaccine serotypes in nasopharyngeal colonization, facilitated by the consumption of macrolides still at high levels in MC.

Chiral separation of quinolones by liquid chromatography and capillary electrophoresis

The quinolones are derivatives of oxoquinolines and mostly known for their antibacterial and antiviral activities. Many quinolones are chiral compounds having asymmetric centers and important due to their enantioselective biological activities. In order to study the biological activities of quinolone enantiomers, to control the manufacturing of homochiral drugs and to prepare necessary quantities of pure enantiomers for preclinical or clinical trials, respective chiral separation methods are urgently needed. In this context, the present review discusses chromatographic and electrophoretic methods for the enantioseparation of chiral quinolones and provides some useful information on their physical and pharmaceutical properties. The drawbacks of currently used techniques are revealed and ways to overcome them are outlined. Moreover, recommendations for an optimal choice of a separation protocol are given.

A new dosing paradigm: High-dose, short-course fluoroquinolone therapy for community-acquired pneumonia

The goals of optimal antimicrobial therapy are to treat infection effectively, to improve the clinical condition of the patient, and to prevent the emergence of resistant bacterial strains. For ideal drug usage the World Health Organization recommends administering the correct drug by the best route, in the right amount, at optimum intervals for the appropriate period, and after an accurate diagnosis. This article discusses the use of high-dose, short-course fluoroquinolone therapy as an effective option for patients with community-acquired pneumonia.

Comparative in vitro activity of penicillin G, levofloxacin, moxifloxacin, telithromycin, pristinamycin, quinupristin-dalfopristin and linezolid against ofloxacin-intermediate and -resistant Streptococcus pneumoniae

Screening by ofloxacin disk was carried out on 1158 strains of Streptococcus pneumoniae in order to investigate the in vitro bacteriostatic activity of penicillin G, levofloxacin, moxifloxacin, telithromycin, linezolid, pristinamycin and quinupristin-dalfopristin against ofloxacin-intermediate and -resistant S. pneumoniae strains. It was concluded that these new antimicrobial agents could be useful for the treatment of pneumococcal infections caused by penicillin-sensitive and -resistant S. pneumoniae, and would represent a valid therapeutic option for patients allergic to beta-lactams, should they prove to be potent in vivo.

Antibiotic resistance

Widespread resistance problems exist today in a global sense because of the incorporation of antibiotics with a high resistance potential into animal feeds and because of the uncontrolled use of antibiotics with a high resistance potential in the clinical setting. The only proven method of controlling nonoutbreak resistance problems in hospitals is to limit the hospital formulary to antibiotics with little or no resistance potential. The control of multiresistant organisms in outbreaks occurring in hospitals is best contained using appropriate infection control containment measures. Physicians treating infections in the community, with all other factors being equal, should preferentially select antibiotics with a low resistance potential. The titles and headings of much of the resistance literature are misleading. Articles should not contain fluoroquinolone resistant in the title when ciprofloxacin-resistant organisms are described. Many articles concerning penicillin-resistant pneumococci are entitled fluoroquinolone-resistant S. pneumoniae. These articles describe ciprofloxacin-resistant S. pneumoniae and not resistance to other fluoroquinolones. The same error is perpetuated in describing third-generation cephalosporins and carbapenems. Virtually all of the resistance problems associated with third-generation cephalosporins and carbapenems are due to ceftazidime or imipenem. More precise titling in the literature would remind physicians that antibiotic resistance is related to a specific agent and not class phenomena.

Levofloxacin

Levofloxacin (DR-3355, Daiichi) is a new fluoroquinolone antibiotic which is the active isomer of ofloxacin (DL-8280, Daiichi). By removing the inactive isomer, the in vitro activity of levofloxacin is 8-128 times higher than that of ofloxacin. This means that bacterial species, which have borderline susceptibility to ofloxacin and other first generation fluoroquinolones (e.g., pneumococci and organisms causing atypical pneumonia), are considerably more sensitive to levofloxacin. The pharmacokinetics of levofloxacin, which is available for both oral and i.v. administration, are characterised by a very high bioavailability, low (30-40%) protein binding, high tissue concentrations and elimination via the kidneys with minimal liver metabolism. As a consequence of the low degree of metabolism, levofloxacin does not interact with other drugs to any major extent. The safety and efficacy of levofloxacin are well documented in lower respiratory tract infections, skin and soft tissue infections, and urinary tract infections. The safety profile seems advantageous and the risks of phototoxicity, CNS toxicity and cardiac reactions (prolongation of QT-time) are low. Serious liver toxicity, leading to the recent withdrawal of trovafloxacin, has not been a problem in levofloxacin studies. Levofloxacin is a valuable addition to the group of fluoroquinolone antibiotics.

Pharmacodynamics of levofloxacin and ciprofloxacin against Streptococcus pneumoniae

An in-vitro pharmacokinetic model was used to compare the pharmacodynamics of levofloxacin and ciprofloxacin against four penicillin-susceptible and four penicillin-resistant Streptococcus pneumoniae. Logarithmic-phase cultures were exposed to the peak concentrations of levofloxacin or ciprofloxacin observed in human serum after 500 mg and 750 mg oral doses, human elimination pharmacokinetics were simulated, and viable bacterial counts were measured at 0, 1, 2, 4, 6, 8, 12, 24 and 36 h. Levofloxacin was rapidly and significantly bactericidal against all eight strains evaluated, with eradication of six strains occurring despite area under the inhibitory curve over 24 h (AUIC24) values of only 32-64 SIT(-1) x h (serum inhibitory titre over time). The pharmacodynamics of ciprofloxacin were more variable and the rate of bacterial killing was consistently slower than observed with levofloxacin. Ciprofloxacin eradicated five strains despite having an AUIC24 of only 44 SIT(-1) x h. These data suggest that the increased potency of levofloxacin and more favourable pharmacokinetics compared with ciprofloxacin provide enhanced pharmacodynamic activity against S. pneumoniae. Furthermore, these data suggest that the minimum AUIC required for clinical efficacy against and eradication of S. pneumoniae with levofloxacin and ciprofloxacin may be well below the 125 SIT(-1) x h identified by other studies.

Antipneumococcal activities of levofloxacin and clarithromycin as determined by agar dilution, microdilution, E-test, and disk diffusion methodologies

The activities of levofloxacin and clarithromycin against 199 penicillin- and macrolide-susceptible and -resistant pneumococci were tested by agar and microdilution methods in air and by disk diffusion and E-test methods in air and CO2. For levofloxacin, >/=99. 0% of strains were susceptible at /=17 mm, regardless of incubation in air or CO2. Although zone sizes were smaller and E-test MICs were higher for clarithromycin in CO2 than those in air, category differences were minor, and susceptibility rates for clarithromycin were similar to those obtained by agar and microdilution in air (range, 76.9 to 80.9% by all methods). For clarithromycin, adjustment of breakpoints based upon distribution of results resulted in susceptibility rates which were similar by all methods (75.8 to 76.9% susceptible, 0 to 1.5% intermediate, 22.6 to 23.1% resistant). Minor discrepancies were obtained with levofloxacin for one strain (0.5%) by microdilution and two strains (1.0%) by disk diffusion in CO2. For clarithromycin, minor discrepancies were found in three strains (1.5%) by microdilution, seven strains (3.5%) by agar dilution, four strains (2.0%) by E-test in air, six strains (3.0%) by disk diffusion in air, and five strains (2.5%) by disk diffusion in CO2. Major discrepancies occurred with levofloxacin in one strain (0.5%) by microdilution but were not found with clarithromycin. Very major discrepancies were not seen with levofloxacin, but occurred with clarithromycin in five strains (2.5%) by microdilution, three strains (1.5%) by agar dilution, two strains (1.0%) by E-test in air, eight strains (4.0%) by disk diffusion in air, and one strain (0.5%) by disk diffusion in CO2.

Levofloxacin. Its use in infections of the respiratory tract, skin, soft tissues and urinary tract

Levofloxacin, the optically pure levorotatory isomer of ofloxacin, is a fluoroquinolone antibacterial agent. Like other fluoroquinolones, it acts on bacterial topoisomerase and has activity against a broad range of Gram-positive and Gram-negative organisms. Levofloxacin also appears to have improved activity against Streptococcus pneumoniae compared with ciprofloxacin or ofloxacin. Levofloxacin distributes well and achieves high levels in excess of plasma concentrations in many tissues (e.g., lung, skin, prostate). High oral bioavailability allows switching from intravenous to oral therapy without dosage adjustment. In patients with mild to severe community-acquired pneumonia receiving treatment for 7 to 14 days, oral levofloxacin was similar in efficacy to amoxicillin/clavulanic acid, and intravenous and/or oral levofloxacin was superior to intravenous ceftriaxone and/or oral cefuroxime axetil. With levofloxacin use, clinical success (clinical cure or improvement) rates were 87 to 96% and bacteriological eradication rates were 87 to 100%. In the 5- to 10-day treatment of acute exacerbations of chronic bronchitis, oral levofloxacin was similar in efficacy to oral cefuroxime axetil or cefaclor. Levofloxacin resulted in clinical success in 78 to 94.6% of patients and bacteriological eradication in 77 to 97%. Oral levofloxacin was also similar in efficacy to amoxicillin/clavulanic acid or oral clarithromycin in patients with acute maxillary sinusitis treated for 7 to 14 days. Equivalence between 7- to 10-day therapy with oral levofloxacin and ciprofloxacin was seen in patients with uncomplicated skin and soft tissue infections. Clinical success was seen in 97.8 and 96.1% of levofloxacin recipients and bacteriological eradication in 97.5 and 93.2%. Complicated urinary tract infections, including pyelonephritis, responded similarly well to oral levofloxacin or ciprofloxacin for 10 days or lomefloxacin for 14 days. Clinical success and bacteriological eradication rates with levofloxacin occurred in 92 to 93.3% and 93.6 to 94.7% of patients.

CONCLUSIONS

Levofloxacin can be administered in a once-daily regimen as an alternative to other fluoroquinolones in the treatment of infections of the urinary tract, skin and soft tissues. Its more interesting use is as an alternative to established treatments of respiratory tract infections. S. pneumoniae appears to be more susceptible to levofloxacin than to ciprofloxacin or ofloxacin. Other newer fluoroquinolone agents that also have enhanced in vitro antipneumococcal activity may not share the well established tolerability profile of levofloxacin, which also appears to improve on that of some older fluoroquinolones.