Question 13

What have been the trends in fluoroquinolone resistance over the past decade?

A few years ago there was concern that fluoroquinolone resistance among S.pneumoniae would continue to increase similar to that shown by Enterobacteriaceae. However, this has not happened, and the resistance rates have remained relatively stable around the world. For example levofloxacin non-susceptibility (MICs≥4 μg/ml) among S. pneumoniae was 0 to 1.3% in Europe over the 2001-2003 period, 2% in Japan in 2002, and 2.2% in Canada in 2002. However, while this rate was 13.3% in Hong Kong in 2000, the most recent reports have shown that levofloxacin-resistant S. pneumoniaeprevalence rates have now decreased in Hong Kong (15).

Around the rest of the world long-term surveillance data has confirmed that the low rates of fluoroquinolone-resistant S. pneumoniae have not changed significantly. Resistance trends documented over the 2001-2004 period reveal that levofloxacin has maintained exceptional pneumococcal activity and the latest PROTEKT results covering the 2005-2006 years confirm that this has continued (Table 3) (11,16).

These results are confirmed by data from The Tracking Resistance in the United States Today (TRUST) study which has reported high resistance rates among S. pneumoniae to penicillin and azithromycin (15-44% depending on the age group), while at the same time resistance to levofloxacin was minimal (0-1.3%) (17).

In addition, the Global Landscape On the Bactericidal Activity of Levofloxacin (GLOBAL) surveillance study has collected 9,323 S. pneumoniae isolates, 5,828 H. influenzae isolates, and 1,878 M. catarrhalisisolates from 15 countries worldwide. Results revealed that penicillin susceptibility among S. pneumoniae ranged from 41.5% in Asia to 75.3% in Europe, while erythromycin susceptibility ranged from 23.7% in Asia to 87% in Central and South America. Results from this international program confirmed that susceptibility to levofloxacin was ≥98% in all regions, while susceptibility to ciprofloxacin was 81%. Susceptibility of H. influenzae to levofloxacin was greater than 99% in all countries (18).

Table 3. In vitro activity of a range of levofloxacin against Streptococcus pneumoniae isolates collected during Years 3-5 (2001-2004) of the PROTEKT study