|GLOBAL Surveillance Data-|
Updating the European S. pneumoniae Resistance Profile
In order to maintain the optimal efficacy of antibacterial agents, it is extremely important that they are prescribed judiciously, thereby reducing the likelihood of resistance developing. A major feature of such evidence-based prescribing includes using knowledge about regional and international resistance patterns, as well as that relating to specific patient locations. Therefore, ongoing surveillance studies provide pivotal data on which the clinicians can base their therapeutic decision-making. Dr. Daniel F. Sahm, USA, outlined the current European situation in regard to antibacterial activity against the common respiratory pathogen S. pneumoniae, using data from the GLOBAL surveillance program.
When assessing the susceptibility profiles of pathogens, it is crucial to differentiate not only between results obtained from different nations, but also between specific sites. For example, it is important to know before prescribing an empiric agent whether the patient has presented from the community or is an outpatient or a hospitalized inpatient. In addition, sites within the hospital need to be further categorized into general medical wards, intensive care units (ICU) or long-term care facilities, as pathogens taken from these different areas can have marked differences in susceptibility profiles. This is because resistant organisms are much more likely to be found among hospitalized patients, in particular, those from specialist units such as intensive care. Dr. Daniel F. Sahm presented the latest European results investigating the activity of agents against the respiratory pathogen S. pneumoniae from a variety of different patient populations.
Figure 1. Rate of PEN-R and MDR rates among patient populations
In regard to the fluoroquinolone activity against S. pneumoniae, Dr. Sahm reported that the MIC90s for levofloxacin remained stable at 1 mg/L regardless of the patient location or resistance phenotypes. In fact, the overall susceptibility of S. pneumoniae to levofloxacin remained at 98.8%, compared with the overall lower susceptibility rate for ciprofloxacin of 90.7% (Table).
Table. Antimicrobial susceptibility of all agents against all S. Pneumoniae isolates
Susceptibility to specific antibacterial agents including ceftazidime, azithromycin, penicillin and trimethoprim-sulfamethoxazole was significantly influenced by the patient location. In fact, the MICs of β-lactams (penicillin, cefuroxime, ceftriaxone and amoxicillin-clavulanate) taken from ICU and inpatient isolates were at least 2- to 4-fold higher than those from outpatients and long-term care patients. In addition, the susceptibility of pathogens to azithromycin and trimethoprim-sulfamethoxazole was lowest among isolates from the ICU and inpatient populations. Further analysis of the results confirmed that more than 30% of S. pneumoniae isolates from these two locations had azithromycin MICs greater than 4 mg/L and over 16% had trimethoprim-sulfamethoxazole MICs greater than 4 mg/L.
Figure 2. Percentage susceptibility of all agents tested against S. pneumoniae by patient location
Investigating the activity of levofloxacin and another fluoroquinolone, ciprofloxacin, in more detail, revealed clear differences. While levofloxacin was active against 99.6% of S. pneumoniae from ICU, ciprofloxacin was only active against 89.1% of isolates from this site. In addition, levofloxacin was active against 98.4% of inpatient isolates compared with 90.9% for ciprofloxacin; levofloxacin was active against 98.9% of outpatient isolates compared with 92.0% for ciprofloxacin and, even more marked, levofloxacin was active against 99.4% of S. pneumoniae isolates from long-term care patients while ciprofloxacin was only active against 87.5% of these isolates.
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