Short-Course Therapy of Gemifloxacin Effective Against Pneumococcal Pneumonia in Mice

Duration and cessation of antimicrobial treatment

Shortening the duration of antimicrobial therapy is an important strategy for optimizing patient care and reducing the spread of antimicrobial resistance. It is best used in the context of an overall approach to infection management that includes a focus on selecting the right initial drug and dosing regimen for empiric therapy, and de-escalation to a more narrowly focused drug regimen (or termination) based on subsequent culture results and clinical data. In addition to reducing resistance, other potential benefits of shorter antimicrobial courses include lowered antimicrobial costs, reduced risk of superinfections (including Clostridium difficile-associated diarrhea), reduced risk of antimicrobial-related organ toxicity, and improved drug compliance. There have been relatively few randomized clinical trials that study the optimal treatment durations for such serious infections as pneumonia (community- and healthcare/hospital-acquired), complicated intra-abdominal infection, and catheter-related bloodstream infection (CRBSI). Nonetheless, a growing number of studies have explored the possibilities of reducing the duration of antimicrobial therapy for at least certain patients with these infections, under certain circumstances. Professional organizations have compiled these data and used them to develop clinical practice guidelines to aid clinicians in choosing optimal treatment durations for individual patients. Many patients with hospital-acquired pneumonia, ventilator-associated pneumonia, or healthcare-associated pneumonia can be treated for 7-8 days, while 4-7 days and 14-day treatment durations may suffice for many patients with complicated intra-abdominal infections and uncomplicated CRBSI, respectively. This article first provides a general background on the rationale and data supporting shortened courses of antimicrobial therapy, before using 3 case studies to explore the practical implications of current knowledge and treatment guidelines when making decisions about treatment duration for individual patients with healthcare-associated pneumonia, complicated intra-abdominal infection, and CRBSI.

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.

Synergy between gemifloxacin and trimethoprim/sulfamethoxazole against community-associated methicillin-resistant Staphylococcus aureus

OBJECTIVES

The rapid emergence of methicillin-resistant Staphylococcus aureus from the community (CA-MRSA) presents difficulties in making treatment choices. We evaluated whether combining another orally available agent commonly used to treat CA-MRSA with gemifloxacin would enhance gemifloxacin activity against CA-MRSA.

METHODS

Fifty strains of SCCmec IV, agr group 1, Panton-Valentine leucocidin-positive CA-MRSA were evaluated for susceptibilities to gemifloxacin, trimethoprim/sulfamethoxazole, doxycycline, levofloxacin, rifampicin, clindamycin and erythromycin. Twenty of these strains were evaluated for the potential for synergy between gemifloxacin and trimethoprim/sulfamethoxazole, clindamycin and rifampicin by time-kill analysis. Two strains were further evaluated in an in vitro pharmacokinetic/pharmacodynamic (PK/PD) model.

RESULTS

In time-kill analyses, gemifloxacin combined with trimethoprim/sulfamethoxazole produced additivity (6/20) or synergy (11/20) in 85% of the isolates tested. The addition of clindamycin to gemifloxacin showed additivity (3/20) or synergy (2/20) in 25% of the isolates. All isolates displayed indifference to the combination of gemifloxacin and rifampicin. In the PK/PD model, combining gemifloxacin and trimethoprim/sulfamethoxazole provided potent and sustained bactericidal activity to detection limits of 2 log(10) cfu/mL by 48 h; gemifloxacin combined with clindamycin or with rifampicin killed to detection limits by 56 h or later. One isolate developed efflux-mediated resistance to gemifloxacin at 96 h with gemifloxacin monotherapy. All combinations prevented the emergence of this resistance.

CONCLUSIONS

Synergy or additivity was demonstrated by time-kill analysis between gemifloxacin and trimethoprim/sulfamethoxazole in most isolates tested. In the PK/PD model, the addition of trimethoprim/sulfamethoxazole, clindamycin and rifampicin enhanced the activity of gemifloxacin against CA-MRSA and suppressed the emergence of resistance to gemifloxacin.

Role of gemifloxacin in the management of community-acquired lower respiratory tract infections

Respiratory tract infections (RTIs) form a substantial clinical and financial burden, with the increasing complication of antimicrobial resistance. This resistance may compromise the use of many empirically prescribed antimicrobials. The new respiratory fluoroquinolones have been developed to overcome this burgeoning resistance. This group includes gemifloxacin, an enhanced-affinity fluoroquinolone that has been approved for clinical use in several countries and is characterised as a potent dual-acting agent with excellent in vitro activity against Streptococcus pneumoniae (minimum inhibitory concentration for 90% of strains (MIC90)=0.03-0.06 microg/mL). Gemifloxacin given once daily for 5-7 days has been shown to be non-inferior to, or in some instances superior to, comparator agents for the treatment of common lower RTIs. Moreover, it is generally well tolerated and is as safe as many frequently empirically prescribed antimicrobials. In addition, studies have shown gemifloxacin to be a cost-effective agent for some lower RTIs.