Question 9

What is the current situation in regard to macrolide resistance among S. pneumoniae?

Macrolide-resistance among S. pneumoniae is gaining prominence, becoming more of a problem than PRSP. In Spain there is a 30-35% macrolide resistance rate among pneumococci. Unfortunately, this resistance rate has not shown the same decrease that the penicillin resistance rate has. Moreover, it seems to be similar to that we had in pre-vaccination isolates (10).

Latest results from the PROTEKT study have shown that world-wide macrolide resistance has increased significantly in the 2005-2006 year period (11). It is now 35.3%, a sharp increase from approximately 30%, which it had been stable at for the past 3 years (p < 0.0001). This study measures rates in the US and incorporates data from almost 7,000 isolates from 119 centers. This increase in macrolide resistant pneumococci was seen across all US regions, and for patients of all ages and was described as the first significant increase since 2000. This is of great concern, as it is now known that macrolide-resistant pneumococcal infection is a risk factor for failure of macrolide therapy in community RTIs (11).

In Asia, there are very high rates of macrolide resistant S. pneumoniae and these rates have unfortunately continued to climb. Latest data from China investigating the correlation between macrolide use and resistance among S. pneumoniae found that the resistance rate had increased from 88% in 2002 to 96% in 2005, a tragedy as it means that macrolides are no longer of clinical value in these regions (12).

However, epidemiological data such as the latest PROTEKT results have confirmed that more than 98% of macrolide-resistant S. pneumoniae remain susceptible to levofloxacin (11). These results should be considered when selecting antimicrobial agents and guidelines implementation.