Tracking Susceptibility and Reducing Resistance - Fluoroquinolones at the Forefront in the Fight Against Bacterial Pathogens

29 March, 2018

Question 8

There are now two sides to antimicrobial treatment- a dose regimen that effectively treats a patient but also one that is more likely to avoid the development of resistance. In this regard monitoring of resistance is an integral aspect to maintaining antibacterial efficacy. You have been involved in important surveillance studies looking at S. pneumoniae isolates. Could you comment on the prevalence of penicillin resistant S. pneumoniae (PRSP)?

We continue to gain data on the susceptibility of this important pathogen, with data from different worldwide surveillance studies tracking trends over a long period. We know that there was an increase in both penicillin and macrolide resistance among the pneumococci during the nineties and at the very beginning of current century. However, it is now clear that PRSP rates are decreasing in most parts of the world. Our own data from Spain, which previously had some of the highest rates of penicillin-resistant pneumococci, confirms this decrease. A number of hypotheses have been put forward for this drop including the introduction of the heptavalent pneumococcal vaccine, better treatment guidelines and use of more effective antibiotics. The impact of vaccination is being debated but seems to be stronger in children and while a factor involved in reducing pneumococcal penicillin resistance it is not the sole reason.

It is not clear whether the use of fluoroquinolones has also played a part in decreasing prevalence of penicillin resistance. In Spain, the pneumococcal resistance rate to penicillin is now 25-30%, including both high and low level resistance. However these rates are higher in some other parts of Europe and globally the rates of penicillin resistance are very high in Asia at 50-60%. In the 2003-2004 data from the Prospective Resistant Organism Tracking and Epidemiology for the Ketolide Telithromycin (PROTEKT) surveillance study 35.7% of S. pneumoniae were not susceptible to penicillin but levofloxacin was effective in more than 99% of these isolates, making it one of the most active agents tested in this setting (Figure 2) (9). In addition, levofloxacin possessed excellent activity against multidrug resistant S. pneumoniae isolates (9).

Figure 2. Antibacterial susceptibility of MDRSP isolates by infection

Abbreviations: MDRSP = multidrug resistant Streptococcus pneumoniae, AECB = acute exacerbations of chronic bronchitis, CAP = community-acquired pneumonia.
Adapted from reference (9).