community acquired pneumonia ( cap ) is defined as an acute infection of the pulmonary parenchyma that is associated with at least some symptoms of acute infection , accompanied by the presence of an acute infiltrate on a chest radiograph or auscultatory findings consistent with pneumonia , in a patient not hospitalized or residing in a long - term care facility for 14 days before the onset of symptoms . in the absence of a chest x - ray , the british thoracic society defines pneumonia as symptoms of an acute lower respiratory tract infection , including a cough and at least one other lower respiratory tract symptom , together with at least one systemic symptom and new focal signs on chest examination . the incidence of cap is lowest in the age group of 18 - 24 years and highest in the under-5 and over-65 groups . given the emergence of antibiotic resistance and the potential hazards of antibiotic treatment failures , a definitive microbiological diagnosis is desirable . the common etiological agents causing cap include streptococcus pneumoniae ( 20 - 60% ) , hemophilus influenza ( 3 - 10% ) , chlamydia pneumoniae ( 4 - 6% ) , mycoplasma pneumoniae ( 1 - 6% ) , legionella ( 2 - 8% ) , staphylococcus aureus ( 3 - 5% ) , gram - negative bacilli ( 3 - 5% ) , viruses ( 2 - 13% ) . in 40 - 60% cases , no cause is identified and in 2 - 5% cases , two or more pathogens are identified . the main objectives of investigating patients with a clinical diagnosis of pneumonia are to obtain radiological confirmation of the diagnosis , to exclude other conditions that may mimic pneumonia , to obtain a microbiological diagnosis , to assess the severity of pneumonia and to identify the development of complications . treatment is often empirical and based on the clinical and radiological diagnosis directed at the most common organisms . hence , its antimicrobial treatment should be based on the distribution of etiological pathogens and their incidence in the community . the present study is an attempt to identify and delineate the microbiological and antimicrobial sensitivity characteristics of cap in a given community and hospital setting . the study was conducted for dissertation purpose at lourdes hospital , ernakulam which is a 750 bedded multispecialty referral hospital catering to both urban and semi - urban population . it was a prospective study of all patients who attended the medical out - patient department and were diagnosed with cap . data collection was by detailed history , clinical examination and sputum culture and sensitivity pattern . for the latter , the zone of inhibition was calculated by the diameter in mm . data analysis was by representation as tabulation and bar diagrams and calculation , in percentages , of etiological pathogens and sensitivity patterns . the exclusion criteria were patients below 16 years of age , immunocompromised patients , hospital acquired pneumonia ( onset after 4 days of hospitalization ) , aspiration pneumonia , patients with cystic fibrosis or tuberculosis and pregnant women . age and gender distribution of cap , in the studied population seven pathogens were isolated by sputum culture [ detailed in table 2 and figure 1 ] . the rate of incidence of the common pathogens based on the distribution in different age groups varied as shown in table 3 . incidence of etiological organisms of cap , with gender distribution pie diagram showing the aetiological pathogens isolated from the sputum of cap patients in this study incidence of etiological organisms of cap , with age distribution the different antimicrobial agents included in this study are mentioned in annexure 1 . the observed antimicrobial sensitivity patterns of individual pathogens are shown in table 4 . observed incidence and antimicrobial sensitivity patterns of individual pathogens in the studied population figure 2 depcits the the antimicrobial sensitivity of the most common pathogen in this study ( streptococcus pneuominae ) . bar diagram showing the antimicrobial sensitivity of the most common pathogen in this study ( streptococcus pneumoniae ) the rates of sensitivity to these antimicrobial agents shown by all the pathogens taken together are represented in terms of percentage [ figure 3 ] . here , moderate sensitivity is not taken into consideration . bar diagram showing the overall sensitivity to the tested antimicrobial agents overall , the common pathogens causing cap showed highest sensitivity to amikacin ( 44.84% ) , followed by ofloxacin ( 43.45% ) , gentamicin ( 38.62% ) , gatifloxacin ( 37.93% ) , augmentin and ciprofloxacin ( 34.48% ) , ceftriaxone ( 33.79% ) and linezolid ( 32.41% ) . the least sensitivity rates are shown to levofloxacin and penicillin g ( 0.69% ) , ampicillin and piperacillin - tazobactam ( 1.38% ) and clarithromycin , amoxicillin and cefoperazone ( 2.07% ) . a wide array of organisms can cause acute pneumonia and published reports vary in the organisms isolated due to differences in patient groups , presence of epidemic organisms and diligence of the investigation . if sputum is available and the patient has not had prior antibiotic treatment , then a gram stain is sufficient to identify the causative organism . overnight culture will provide confirmation and the chance to perform susceptibility studies , allowing modification of empirical therapy . the role of sputum as a tool in the diagnostic work - up of patients with cap remains controversial . both these findings are in agreement with indian and western reports in the literature . almost as high as 50% normal flora one study from sher - i - kashmir institute of medical sciences , srinagar has emphasized the need for further studies including the serological tests for legionella , mycoplasma and viruses to identify the microbial etiology of cap . for low - risk patients who may be safely treated in an ambulatory setting , the infectious diseases society of america ( idsa)-updated guidelines recommend doxycycline , a macrolide or an antipneumococcal fluoroquinolone as preferred agents because these agents have activity against the most likely pathogens in this setting ( s. pneumoniae , m. pneumoniae and chlamydophila pneumoniae ) . the idsa has adopted the new antipneumococcal fluoroquinolones , namely levofloxacin , sparfloxacin , moxifloxacin and gatifloxacin , as preferred agents for the treatment of both ambulatory and hospitalized patients with cap and for penicillin - resistant pneumococcal pneumonia . for empiric treatment of the moderately ill - hospitalized patient , the idsa recommends an extended - spectrum cephalosporin ( cefotaxime , ceftriaxone ) plus a macrolide or monotherapy with a fluoroquinolone . for hospitalized patients admitted to the intensive care unit , the idsa prefers agents that include combination therapy with an extended - spectrum cephalosporin plus a macrolide or a fluoroquinolone . monotherapy with a fluoroquinolone is not recommended because data with seriously ill cap patients are limited . the centers for disease control and prevention ( cdc ) working group suggests that penicillin - resistant s. pneumoniae isolates are uncommon and activity against such organisms is unnecessary for empiric treatment . their recommendations for first - line therapy of cap include a macrolide , doxycycline or an oral beta - lactam such as cefuroxime , amoxicillin or amoxicillin / clavulanate . the cdc recommends reserving the use of fluoroquinolones for treatment of gram - negative pathogens , patients with beta - lactam allergy or treatment of penicillin - resistant pneumococcal pneumonia . although this argument may be raised regarding any antibiotic , the concern with the fluoroquinolones is that resistance to one agent affects all agents to some degree . currently , pneumococcal resistance to the fluoroquinolones is low , but a report from canada has demonstrated an association between increased fluoroquinolone use and resistance in s. pneumoniae . in addition , the potential for development of resistance in other organisms ( especially pseudomonas aeruginosa ) as a result of the indiscriminate use of fluoroquinolones poses a more ominous threat to this drug class . here , the common pathogens show an overall sensitivity of 43.45% to ofloxacin , 37.93% to gatifloxacin and 34.48% to ciprofloxacin . the cdc working group recommends amoxicillin - clavulanate ( augmentin ) as one of the first - line antimicrobials . in our study , s. pneumoniae , which is the commonest etiological agent , showed nearly , 80% sensitivity to amoxicillin - clavulanate . pneumococcal susceptibility has changed significantly over the past decade . despite four decades of using penicillin , strains with minimum inhibitory concentrations ( mics ) > 0.1 mg / ml accounted for 3.8% of isolates in the 1980 's ; by 1994 - 1995 , the rate was 24% and by 1997 it was 43.8% . penicillin resistance is also associated with resistance to other antimicrobial classes , including cephalosporins , macrolides , tetracyclines and trimethoprim / sulfamethoxazole . antibiotics less affected by this broad - spectrum resistance include vancomycin , the fluoroquinolones , clindamycin , chloramphenicol and rifampin . strains are considered as sensitive if the mic is < 0.1 mg / ml . it is observed from various studies that most penicillin resistance is  relative resistance  and is readily treatable with penicillin and/or beta - lactams . most of the highly penicillin - resistant s. pneumoniae infections may also be treated with beta - lactams . alternately , doxycycline or respiratory quinolones may be used . very highly penicillin - resistant s. pneumoniae ( mic 6 g / ml ) strains are a rare cause of cap , but remain susceptible to ceftriaxone . studies suggest that empiric macrolide monotherapy should be avoided because approximately 25% of s. pneumoniae strains are naturally resistant to all macrolides . in our study , the rates of sensitivity were 11.72% to erythromycin , 10.34% to azithromycin and 2.07% to clarithromycin . it is ideal for iv - to - oral switch monotherapy in terms of patient compliance , safety and cost . mortality gradually increased with progressive delays between the time a patient presented and the time the initial dose of an antibiotic was administered . this difference reached statistical significance when the delay exceeded 8 h. many studies conclude that antibiotics should be initiated within 4 h after patient presentation . a final conclusion about the superiority of one antibacterial regimen over another in hospitalized patients with cap can not be drawn on the basis of the limited data available . monotherapy coverage of both typical and atypical pathogens in cap is preferred over double - drug therapy . serological tests to identify some rare organisms were not carried out in this study . some of these may have been reported as normal flora . antimicrobials tested for sensitivity in this study have not included the newer , costlier drugs . both these findings are in agreement with indian and western reports in the literature . almost as high as 50% normal flora one study from sher - i - kashmir institute of medical sciences , srinagar has emphasized the need for further studies including the serological tests for legionella , mycoplasma and viruses to identify the microbial etiology of cap . for low - risk patients who may be safely treated in an ambulatory setting , the infectious diseases society of america ( idsa)-updated guidelines recommend doxycycline , a macrolide or an antipneumococcal fluoroquinolone as preferred agents because these agents have activity against the most likely pathogens in this setting ( s. pneumoniae , m. pneumoniae and chlamydophila pneumoniae ) . the idsa has adopted the new antipneumococcal fluoroquinolones , namely levofloxacin , sparfloxacin , moxifloxacin and gatifloxacin , as preferred agents for the treatment of both ambulatory and hospitalized patients with cap and for penicillin - resistant pneumococcal pneumonia . for empiric treatment of the moderately ill - hospitalized patient , the idsa recommends an extended - spectrum cephalosporin ( cefotaxime , ceftriaxone ) plus a macrolide or monotherapy with a fluoroquinolone . for hospitalized patients admitted to the intensive care unit , the idsa prefers agents that include combination therapy with an extended - spectrum cephalosporin plus a macrolide or a fluoroquinolone . monotherapy with a fluoroquinolone is not recommended because data with seriously ill cap patients are limited . the centers for disease control and prevention ( cdc ) working group suggests that penicillin - resistant s. pneumoniae isolates are uncommon and activity against such organisms is unnecessary for empiric treatment . their recommendations for first - line therapy of cap include a macrolide , doxycycline or an oral beta - lactam such as cefuroxime , amoxicillin or amoxicillin / clavulanate . the cdc recommends reserving the use of fluoroquinolones for treatment of gram - negative pathogens , patients with beta - lactam allergy or treatment of penicillin - resistant pneumococcal pneumonia . although this argument may be raised regarding any antibiotic , the concern with the fluoroquinolones is that resistance to one agent affects all agents to some degree . currently , pneumococcal resistance to the fluoroquinolones is low , but a report from canada has demonstrated an association between increased fluoroquinolone use and resistance in s. pneumoniae . in addition , the potential for development of resistance in other organisms ( especially pseudomonas aeruginosa ) as a result of the indiscriminate use of fluoroquinolones poses a more ominous threat to this drug class . here , the common pathogens show an overall sensitivity of 43.45% to ofloxacin , 37.93% to gatifloxacin and 34.48% to ciprofloxacin . the cdc working group recommends amoxicillin - clavulanate ( augmentin ) as one of the first - line antimicrobials . in our study , s. pneumoniae , which is the commonest etiological agent , showed nearly , 80% sensitivity to amoxicillin - clavulanate . pneumococcal susceptibility has changed significantly over the past decade . despite four decades of using penicillin , only modest rates of reduced susceptibility to penicillin strains with minimum inhibitory concentrations ( mics ) > 0.1 mg / ml accounted for 3.8% of isolates in the 1980 's ; by 1994 - 1995 , the rate was 24% and by 1997 it was 43.8% . penicillin resistance is also associated with resistance to other antimicrobial classes , including cephalosporins , macrolides , tetracyclines and trimethoprim / sulfamethoxazole . antibiotics less affected by this broad - spectrum resistance include vancomycin , the fluoroquinolones , clindamycin , chloramphenicol and rifampin . strains are considered as sensitive if the mic is < 0.1 mg / ml . it is observed from various studies that most penicillin resistance is  relative resistance  and is readily treatable with penicillin and/or beta - lactams . most of the highly penicillin - resistant s. pneumoniae infections may also be treated with beta - lactams . alternately , doxycycline or respiratory quinolones may be used . very highly penicillin - resistant s. pneumoniae ( mic 6 g / ml ) strains are a rare cause of cap , but remain susceptible to ceftriaxone . studies suggest that empiric macrolide monotherapy should be avoided because approximately 25% of s. pneumoniae strains are naturally resistant to all macrolides . in our study , the rates of sensitivity were 11.72% to erythromycin , 10.34% to azithromycin and 2.07% to clarithromycin . it is ideal for iv - to - oral switch monotherapy in terms of patient compliance , safety and cost . mortality gradually increased with progressive delays between the time a patient presented and the time the initial dose of an antibiotic was administered . this difference reached statistical significance when the delay exceeded 8 h. many studies conclude that antibiotics should be initiated within 4 h after patient presentation . a final conclusion about the superiority of one antibacterial regimen over another in hospitalized patients with cap can not be drawn on the basis of the limited data available . monotherapy coverage of both typical and atypical pathogens in cap is preferred over double - drug therapy . serological tests to identify some rare organisms were not carried out in this study . some of these may have been reported as normal flora . antimicrobials tested for sensitivity in this study have not included the newer , costlier drugs . we have attempted to identify these in our community and study the pathogens and their sensitivity . the present study has shown s. pneumoniae as the most likely pathogen and either linezolid or amikacin as the most likely effective antimicrobial in cases of cap , in our setting . keeping the idsa and cdc recommendations in mind , we suggest that the inferences from our study should be considered when initiating antimicrobial therapy in our local setting .
objective : the objective of this study was to identify the common etiological pathogens causing community acquired pneumonia ( cap ) in our hospital and sensitivity patterns to the common antibiotics used.materials and methods : this study was undertaken in a 750 bedded multi - specialty referral hospital in kerala catering to both urban and semi - urban populations . 
 it is a prospective study of patients who attended the medical out - patient department and those admitted with a clinical diagnosis of cap , during the year 2009 . 
 data were collected based on detailed patient interview , clinical examination and laboratory investigations . the latter included sputum culture and sensitivity pattern . 
 these were tabulated and percentage incidence of etiological pathogens calculated . the antimicrobial sensitivity pattern was also classified by percentage and expressed as bar diagram.results:the study showed streptococcus pneumoniae to be the most common etiological agent for cap , in our hospital setting . 
 the other organisms isolated in order of frequency were klebsiella pneumoniae , pseudomonas aeruginosa , alpha hemolytic streptococci , escherichia coli , beta hemolytic streptococci and atypical coli . 
 s. pneumoniae was most sensitive to linezolid , followed by amoxicillin - clavulanate ( augmentin ) , cloxacillin and ceftriaxone . 
 overall , the common pathogens causing cap showed highest sensitivity to amikacin , followed by ofloxacin , gentamycin , amoxicillin - clavulanate ( augmentin ) , ceftriaxone and linezolid . 
 the least sensitivity rates were shown to amoxicillin and cefoperazone.conclusion:in a hospital setting , empirical management for cases of cap is not advisable . 
 the present study has shown s. pneumoniae as the most likely pathogen and either linezolid or amikacin as the most likely effective antimicrobial in cases of cap , in our setting .