Antimicrobial susceptibility of Streptococcus pneumoniae isolates causing LRTI in Najaf, Iraq

During the period from February 2013 to April 2014, 74 (12.3%) isolates of Streptococcus pneumoniae were isolated from 600 patients (359 males and 241 females) with clinical symptoms of Lower respiratory tract infections (LRTI) (pneumonia and COPD) obtained from Najaf/Iraq Hospitals. Patients in the age groups 51-60 years had a high percentage of S. pneumoniae isolates (19.7%) compared with other age groups with a significant variation (P<0.05) between them. Males (54%) showed a higher percentage of S. pneumoniae isolates than females (45.9%) with no significant variation (P>0.05). Smokers have been shown to have increased risk to LRTI than non-smokers (P>0.05), and there was no significant variation between Urban and Rural (56.8:43.2%) patients. S. pneumoniae showed different susceptibilities towards antibiotics used in this study. The highest rate of resistance was against erythromycin (100%), azithromycin (83.8%), clindamycin (83.8%) and trimethoprim/sulfamethaxzol (81.1%) and moderate resistance to ceftriaxone (67.6%), cefotaxime (64.9%), chloramphenicol (64.9%), tetracycline (59.5%) and benzylpenicillin (45.9%) whereas there was a relatively lower resistance towards others. The results of this study showed that S. pneumoniae isolates were found to be remarkable sensitive to Vancomycin (100%) and Imipenem (100%). In this study, sixteen antibiotics were tested for (MIC) against 37 S. pneumoniae isolates by using Vitek-2 antibiotic susceptibility testing (AST) cards (41497) AST-GP74. 100% and 83.8% of S. pneumoniae isolates were resistant to erythromycin and SXT with MIC ≥1 mg/ml and 4/76 mg/ml of these antibiotic respectively, and moderately resistant to cefotaxime 64.9%, ceftriaxone 64.9% and chloramphenicol 64.9% with MIC 4 mg/ml for CTX and CRO each one, and MIC 8 mg/ml for C only. All isolates showed 100% sensitivity for each of Vancomycin and Erythromycin with MIC mg/ml and ≤1 mg/ml and ≤2 mg/ml, respectively. S. pneumoniae isolates showed a high rate of sensitivity to Ertapenem 97.3% with MIC ≤1 mg/ml, Telithromycin 89.2% with MIC ≤1, Meropenem 86.5% with MIC ≤0.25 mg/ml.