Introduction: Recent reports revealed that 10% of the worldwide burden of morbidity and
mortality relates to respiratory tract infection.
Patient and methods: Five hundreds and fifty nine clinical strains were isolated and identified from 322 patients suffering from respiratory tract infections. Patients represented different ages, sexes, and types of infections. Out of the 322 patients, 204 were suffering from upper respiratory tract infections and 118 patients were suffering from lower respiratory tract infections. Patients of upper respiratory tract infections were suffering from chronic suppurative otitis media (63 patients), tonsillitis (50 patients), pharyngitis (48 patients), and sinusitis (43 patients).
Results: Out of the total isolates, Staphylococcus aureus was the most prevalent organism, followed by Streptococcus pyogenes and Klebsiella pneumoniae (17.71, 12.34, and 11.27% respectively). Pseudomonas aeruginosa represented 6.26%. Serratia marcescens and Morganella morganii were the least isolated organisms. The results revealed that 52.42% of the strains were isolated from males and 47.58% from females. Staphylococcus aureus was the most prevalent organism in males (21.16%) while in females Strept. pyogenes was the most prevalent organism (14.29%). Also, the study revealed that Staphylococcus aureus was the most frequent isolate in age groups between 1-20, 21-40 and 41-60 years old (20.85%, 17.02% and 16.67% respectively). However, both Staphylococcus aureus and Klebsiella pneumoniae were isolated with equal incidences, 12% each, in elder patients (more than 60 years). The susceptibility pattern of the isolated bacteria to different antimicrobial agents was studied. Both levofloxacin and gatifloxacin showed the highest activity (100%), followed by ofloxacin and ciprofloxacin (96.44% and 93.39%, respectively). Those are followed by amikacin (91.86%), cefotaxime (89.31%), cefoperazone (86.26%), gentamicin (84.22%), ampicillin-sulbactam (70.48%), amoxycillin-clavulanic (62.34%), cefuroxime (62.09%), lincomycin (61.83%), vancomycin (61.07%), chloramphenicol (57%), cephalexin (48.35%), cephapirin (45.29%), erythromycin (44.78%), and trimethoprim-sulphamethoxazole (43%). Amoxycillin and tetracycline were the least active ((36.64% and 32.06% respectively). Staphylococcus aureus strains resistant to amoxycillin were tested for B-lactamase production. Out of the tested strains, 62.5% were B- lactamase producers and it may be responsible for the resistance to amoxycillin.
In conclusion, the study revealed that evaluation of respiratory tract infections and antimicrobial susceptibility is still in need for more studies. This is due to the continuous development of newly resistant strains and the relatively little number of isolates in some species. Moreover, the differences in the previous antimicrobial treatment, the history of subclinical infections and the immune status of patients involved in each study have increased the difficulty in evaluation.