RESUMEN
159 cases of post-pneumonic empyema thoracic were included in this study. They were divided into 2 groups. Comparative study between both groups revealed no difference as regard aged and sex predilection. Bacteriologically, positive cultures of pus collected from group I for aerobic bacteria were obtained in 80.6% of cases. Staph. aureus played a major role in causing empyema thoracic [43.5%]. Other isolates were: Pneumoccoci [syn. strept. pneumoniae] [25.8%], Pseudomonas sp. [14.5%], Klebsiella sp. [12.9%], Strept. pyogenes and Proteus [8% for each] and Diptheroid [4%]. Nothing recorded about anaerobic bacteria. In group II, positive cultures of pus for aerobic and anaerobic bacteria were obtained in 43.3 and 42.1%, respectively. Although Staphylococcus aureus headed the aerobic bacterial list yet, its frequency decreased to 23.7%. Other isolates were Klebsiella sp. [11.3%], Strept, pyogenes [7.2%], Strept. pneumoniae [6.2%], E. coli [5.1%], Proteus sp. [4.1%] and Pseudomonas sp. [2.1%]. Contrary to group I, Strept. pneumoniae and Pseudomonas sp. played minor roles. As regard anaerobic bacteria, the commonest was Bacteroids sp. [18.4%], followed by Peptostreptococcus [10.5%], Peptococcus [7.9%] and Fusobacterium was the least common [5.3%]. Results of sensitivity tests showed that the different isolated pathogens were sensitive to different antimicrobial drugs, so, the choice of antibiotic must usually be determined by the results of culture and sensitivity testing