Eleven-year surveillance of antibiotic resistance in Streptococcus pneumoniae in Casablanca (Morocco).

Objective: To analyze trends of antibiotic resistance rates in Streptococcus pneumoniae from 1998 to 2008 in Casablanca (Morocco).

Methods: The antibiotic resistance levels of 955 consecutive nonduplicate isolates were studied using E test and disc diffusion methods. Results were interpreted following Clinical and Laboratory Standards Institute guidelines (2005). Analysis was done according to three periods (1998-2001; 2002-2005; 2006-2008), age, and site of infection.

Results: Penicillin nonsusceptibility (PNS) increased significantly over time (15.6%, 17.8%, and 24.8%; p=0.003). Levels of PNS have changed as well: in 2006-2008, 9.1% of the isolates had an MIC ≥2 μg/ml versus 7.7% in 2002-2005 and 3.4% in 1998-2001. The PNS increase was particularly marked in pediatric isolates (21.4%, 25.5%, and 43.3%; p=0.001). There was no significant difference between the rates of PNS in invasive and noninvasive isolates from children, whereas in adults noninvasive isolates were more penicillin nonsusceptible. Amoxicillin and ceftriaxone nonsusceptible isolates were very rare. An increase of resistance rates was also noticed for erythromycin (9.4%, 12.2%, and 14.4%), tetracycline (20%, 18.6%, and 30.5%), and chloramphenicol (5.6%, 5.6%, and 8.1%). Trimethoprim-sulfamethoxazole resistance rates remained stable (22.8%, 20%, and 23.8%). Proportions of dual nonsusceptibility to penicillin and erythromycin, increased from 5.6% to 8.9%. Multiple drug resistance (resistance to 3 or more antibiotic classes) was found in 0%, 2.4%, and 7.7% of all isolates, respectively.

Conclusion: The results reported here maybe useful for guiding update of treatment recommendations and suggest the need for continuous surveillance. Increase of antibiotic resistance correlated with antibiotic consumption, stressing the need for elaboration of antibiotic policy in Morocco.