The aim of the present study was to study the bacterial investigation of pneumonic calves, antibiotic susceptibility testing and analysis of some virulence and antibiotic resistance genes for the recovered isolates and evaluation of the changes of haematological indices and selected serum biochemistry variables. Bacteriological examination of nasal swabs of 40 apparently healthy and 90 pneumonic calves revealed that E. coli was the prominent pathogen (34.6%) followed by S. aureus (28.5%) and Past. Multicoda (13.1%). Antibiotic sensitivity testing exhibited high resistance rates of E. coli and S. Aureus isolates against the most used antibiotics. Past. Multocida isolates were of high sensitivity rate against most antibiotics except some resistance for tetracycline, enerofloxacin and norofloxacin. Both iss and pap < /em> C virulence genes of E. coli were detected in 80% and 60% of the examined isolates, respectively. High prevalence rate of virulence genes (spa, clfA) and (Tox A and kmt1) of S. aureus and Past. multocida recovered isolates was recorded. Genotypic detection of antibiotic resistant genes of the most yielded isolates was discussed in details. In pneumonic calves, there were significant decreases in RBCs, Hb and PCV than that of healthy one. The significant increase in WBCs with neutrophilia was detected as well as significant decrease in lymphocyte count. Serum biochemical parameters revealed significant increase in globulin, AST, ALT, urea, creatinine, P and K, while albumin, glucose, Fe, Mg and Ca were significantly decreased.