Aim of the work:The study aimed at searching for pattern of sputum bacteriology and antibiotic sensitivity for acute exacerbation of chronic obstructive pulmonary disease in patients admitted to Abbassia chest diseases hospital as a representation of Egyptian population. A trial to compare bacteriology with severity, smoking pattern and corticosteroid treatment and also to compare the bacteriologic pattern with other forms of chest infection including bronchiectasis and community acquired pneumonia. It was conducted on patients from September 2010 to July 2011.Patients & methods This study included 135 patients with community acquired respiratory infections. So this study included 3 groups of patients: 1.One hundred and ten Patients presented with acute exacerbation of chronic obstructive pulmonary disease (120 microbes)2. Ten patients suffered from community acquired pneumonia 3. Fifteen patients with acute exacerbations of bronchiectasis.•These patients were subjected to arterial blood gas on admission, spirometry, gram stain of sputum sample and sputum culture and sensitivity. ResultsKlebsiella pneumonia was the most prevalent organism in all patient groups as regard severity, presence or absence of respiratory acidosis and incidence of different micro-organisms isolated in the sputum cultures in patients admitted to ward and I.C.U. As regard hypoxemic respiratory failure (R.F), it was found that there was higher incidence of Klebsiella in patients without hypoxemic R.F than patients with hypoxemic R.F. As regard smoking habit, it was found that the most prevalent organism in ex- smokers was Klebsiella pneumoniae and the most prevalent organism in smokers was streptococci. As regard steroid therapy, it was found that there were higher incidences of Klebsiella and Pseudomonas in combined than systemic steroids and higher incidence of Klebsiella in systemic than inhaled steroids but equal incidence of Pseudomonas in both systemic and inhaled steroids.Imipenem was the most sensitive antibiotic in all patient groups as regard severity, smoking habits, presence or absence of hypoxemic respiratory failure and sensitivity rates of antibiotics in ICU and ward. It was also found that the most sensitive antibiotic for pseudomonas was Levofloxacin, the most sensitive antibiotics for Klebsiella were Imipenem and Meropenem, the most sensitive antibiotics for Enterobacter were Amikacin and Doxycycline, the most sensitive antibiotic for Acinetobacter was Doxycycline and the most sensitive antibiotic for Proteus was Imipenem. As regard sensitivity rates of highly effective antibiotics in relation to respiratory acidosis, it was found that the most sensitive antibiotics in patients without respiratory acidosis were Amikacin and Doxycycline and the most sensitive antibiotic in patients with respiratory acidosis was Imipenem. As regard sensitivity rates of highly effective antibiotics in relation to steroid therapy, it was found that the most sensitive antibiotic in inhaled group was Imipenem, the most sensitive antibiotic in systemic group was Amikacin and the most sensitive antibiotic in combined group was Levofloxacin. As regard sensitivity rates of different antibiotics combinations regardless type of organism, it was found that the most sensitive antibiotic combination in ward was Doxycycline plus Amikacin. Amikacin plus Levofloxacin and Doxycycline plus + Levofloxacin were good combinations in both ICU and ward. As regard different types of community-acquired respiratory tract infections, it was found that Klebsiella pneumoniae was the most prevalent organism in COPD and CAP and Pseudomonas was the most prevalent organism in bronchiectasis. It was also found that the most sensitive antibiotic in COPD was Imipenem, the most sensitive antibiotics in CAP were Imipenem, Levofloxacin and Doxycycline and the most sensitive antibiotics in Bronchiectasis were Levofloxacin, Amikacin and Gentamicin.