pseudomonas aeruginosa is a common gram - negative rod - shaped bacterium that leads to significant morbidity and mortality in humans . p. aeruginosa is a prototype of  multidrug - resistant pathogen  and is recognized for its ubiquitous distribution , advanced antibiotic resistance mechanisms , and nosocomial infections . p. aeruginosa has the ability to survive on minimal nutrition and tolerate a variety of physical insults leading to its persistence in the community and hospital settings . despite the wide distribution of p. aeruginosa in nature and the potential for community - acquired infections , serious infections with this bacterium p. aeruginosa was identified as the fifth most frequently isolated nosocomial pathogen by the surveillance data from the united states . p. aeruginosa is one of the major causes of hospital - acquired infections and is responsible for about 1020% of nosocomial infections in patients admitted in the intensive care units ( icus ) . p. aeruginosa can be isolated from a wide variety of sources in the hospital , including respiratory equipment , antiseptics , soaps , sinks , mops , medicines , and physiotherapy tools . p. aeruginosa is divided into different phenotypes based on the drug resistance patterns of the organism . multidrug - resistant ( mdr ) phenotype is defined as p. aeruginosa , which is resistant to more than one antimicrobial agent in three or more antimicrobial categories . a similar resistance to more than one antimicrobial agent in <3 antimicrobial categories is defined as drug - resistant ( dr ) p. aeruginosa . the details of the antimicrobial agents and categories used to define the phenotypes are given in table 1 . extensively dr ( xdr ) phenotype is defined as p. aeruginosa , which is resistant to more than one antimicrobial agent in all the antimicrobial categories , except in two or less . pan - dr ( pdr ) phenotype is defined as a bacterium which is resistant to all antimicrobial agents in all antimicrobial categories . antimicrobial categories and agents used to define the pseudomonas aeruginosa phenotypes along with percentage of resistant strains mdr , xdr , and pdr phenotypes elaborate inactivating enzymes , such as extended - spectrum beta - lactamases ( esbl ) and metallo--lactamases ( mbl ) , that make beta - lactams and carbapenems ineffective . esbl - producing p. aeruginosa was initially detected in europe in the mid-1980s , and mbl - producing p. aeruginosa was first reported from japan in 1991 . literature is sparse regarding the incidence of different phenotypes of p. aeruginosa from our country as we could retrieve only two articles in the pubmed with the relevant ( p. aeruginosa , india , phenotype , incidence ) keywords . hence , we conducted this study to find the incidence of mdr , xdr , and pdr phenotypes of p. aeruginosa in the icu of a tertiary care hospital . this prospective , observational study was conducted at the department of microbiology of a tertiary level hospital for over a period of 2 years from january 2014 to december 2015 . we included all patients who were at least 10 years of age at the time of the admission to the icu of this hospital . as per our hospital policy , patients below 10 years of age requiring intensive are admitted to the pediatric icu . our study does not include data from the pediatric icu , thereby resulting in the exclusion of patients below 10 years of age . the patient with evidence of septicemia and known diagnosis of p. aeruginosa infection at the time of admission was excluded from the study . routine hematology and biochemistry tests were conducted as per the request of the clinical team . microbiological specimens were collected from the blood , urine , and sputum samples of the patients . other samples were collected based on the clinical suspicion from a site harboring infection , such as throat swab , wound discharge , and body fluid culture . samples obtained after an invasive procedure and from the indwelling catheters were also included in the study . a total of 100 environmental samples were collected as part of active surveillance of the hospital environment and staff , which were grouped as group 2 . these samples were collected from the medical staff ( hand , throat , and nasal swabs ) and the hospital environment ( air , surgical instruments , dressing material , floors , door , walls , beds , sinks , and antiseptic solutions ) . all blood culture and fluid samples with a minimum volume of 3 ml the bact / alert system is a continuously monitored blood culture system for detecting bacteremia and fungemia . bottles flagged as positive by the bact / alert system were subcultured and interpreted according to the standard laboratory protocols . samples other than the blood and body fluids of group 1 and all group 2 were cultured on macconkey agar and blood agar . these plates were incubated overnight at 37c and all the bacteria grown in these culture media were processed for identification and antibiotic susceptibility testing using automated bacterial system vitek 2 system ( biomrieux ) . vitek 2 system uses a new fluorescence - based technology used for the identification and susceptibility testing of bacteria and is compliant with the clinical and laboratory standard institute ( clsi ) guidelines 2014 . p. aeruginosa was identified by its colony characteristics , pigment production , grape - like odor , oxidase positivity , motility , gram - negative character of the bacilli , ability to decarboxylate arginine and to grow at 42c . antibiotic sensitivity patterns of these isolates were studied by minimal inhibitory concentration using the vitek 2 system as per the clsi 2014 guidelines . strains which had the same types of resistance patterns ( antibiotype ) were considered to be from the same clone . this prospective , observational study was conducted at the department of microbiology of a tertiary level hospital for over a period of 2 years from january 2014 to december 2015 . we included all patients who were at least 10 years of age at the time of the admission to the icu of this hospital . as per our hospital policy , patients below 10 years of age requiring intensive are admitted to the pediatric icu . our study does not include data from the pediatric icu , thereby resulting in the exclusion of patients below 10 years of age . the patient with evidence of septicemia and known diagnosis of p. aeruginosa infection at the time of admission was excluded from the study . routine hematology and biochemistry tests were conducted as per the request of the clinical team . microbiological specimens were collected from the blood , urine , and sputum samples of the patients . other samples were collected based on the clinical suspicion from a site harboring infection , such as throat swab , wound discharge , and body fluid culture . samples obtained after an invasive procedure and from the indwelling catheters were also included in the study . a total of 100 environmental samples were collected as part of active surveillance of the hospital environment and staff , which were grouped as group 2 . these samples were collected from the medical staff ( hand , throat , and nasal swabs ) and the hospital environment ( air , surgical instruments , dressing material , floors , door , walls , beds , sinks , and antiseptic solutions ) . all blood culture and fluid samples with a minimum volume of 3 ml the bact / alert system is a continuously monitored blood culture system for detecting bacteremia and fungemia . bottles flagged as positive by the bact / alert system were subcultured and interpreted according to the standard laboratory protocols . samples other than the blood and body fluids of group 1 and all group 2 were cultured on macconkey agar and blood agar . these plates were incubated overnight at 37c and all the bacteria grown in these culture media were processed for identification and antibiotic susceptibility testing using automated bacterial system vitek 2 system ( biomrieux ) . vitek 2 system uses a new fluorescence - based technology used for the identification and susceptibility testing of bacteria and is compliant with the clinical and laboratory standard institute ( clsi ) guidelines 2014 . p. aeruginosa was identified by its colony characteristics , pigment production , grape - like odor , oxidase positivity , motility , gram - negative character of the bacilli , ability to decarboxylate arginine and to grow at 42c . antibiotic sensitivity patterns of these isolates were studied by minimal inhibitory concentration using the vitek 2 system as per the clsi 2014 guidelines . strains which had the same types of resistance patterns ( antibiotype ) were considered to be from the same clone . the mean age of the patients who were included in the study was 36.2 years . a total of 597 pathogenic bacteria were isolated from the 1915 clinical specimens , giving a culture positivity rate of 31.2% for the clinical specimen . the details of all the bacterial species isolated from the study samples are shown in figure 1 . other bacteria such as coagulase - negative staphylococci , staphylococcus aureus , escherichia coli , and proteus spp . accounted for the rest of the bacterial cultures . hospital staff and group 2 samples did not grow any pathogenic bacterium , including p. aeruginosa . pattern of microbes isolated in the study sample the incidence rate of p. aeruginosa was highest ( 78% ) in the age group of patients between 20 and 50 years . urine ( 47 out of 88 ) and wound ( 38 out of 88 ) samples accounted for the majority of the positive isolates . the prevalence of p. aeruginosa phenotypes based on the resistance patterns is shown in figure 2 . our data showed that 47.7% strains were dr , 50% were mdr , and 2.3% were of xdr phenotype . no strains were resistant to all antibiotics in all antimicrobial categories as all the strains were found to be sensitive to fosfomycin and colistin ( 100% ) . our study showed the prevalence of drug resistance in almost 98% of the isolates of p. aeruginosa in the icu . the only solace is the findings of the 0% presence of pdr phenotype , thereby showing the efficacy of certain antibiotics against this organism . piperacillin resistance was found to be 70% in our study , which is comparable to a report showing it to be 73% . emergence of resistance to beta - lactams in p. aeruginosa has become a serious threat , particularly against the third- and fourth - generation cephalosporins . there are a lot of molecular mechanisms involved for resistance against these antibiotics , generation of esbl enzyme , incorporation of bla genes in integrons , and inability of porin genes to enhance their expression level and/or alteration of antibiotic target sites . ceftazidime and cefepime are the prescribed antipseudomonal third- and fourth - generation cephalosporins , respectively . the resistance to ceftazidime and cefepime observed in our study was similar to that of a previous report from india . our study showed that 80% of p. aeruginosa were resistant to carbapenem antibiotics such as imipenem and meropenem . previous studies showed a similar trend from other countries and a few authors had shown 100% resistance against carbapenems . this suggests the declining efficacy of the carbapenems as an effective antibiotic in the management of nosocomial infections . fluoroquinolone compounds are one of the important antimicrobial agents that have been used for a variety of infections . new generation fluoroquinolones are beneficial against gram - negative and gram - positive bacteria , whereas older fluoroquinolones were effective against aerobic gram - negative bacteria only . our data showed 96% resistance against ciprofloxacin and 67% resistance against levofloxacin while 100% resistance against ciprofloxacin was demonstrated earlier . our data showed similar resistance pattern between amikacin and gentamicin , which was similar to that of the published literature . similar data were not available for comparison with other authors about the sensitivity to aztreonam . similar data were reported from other countries where there is a high prevalence of p. aeruginosa infection . to the best of our knowledge , this is the first study from india that defines the prevalence of mdr , xdr , and pdr p. the strengths of our study include long duration of observation and the use of highly advanced automated bacteria identification system in the identification of p. aeruginosa . the limitations of our study include data derived from a single hospital may not be applicable to other geographic locations and inability to check resistance pattern to all the antipseudomonal drugs . mdr p. aeruginosa is responsible for serious nosocomial infections among the patients admitted in the icus of the hospital . epidemiological studies and strict laws regarding antibiotic policies should be constructed to limit the unnecessary use of antibiotics so that spread of multidrug resistance can be avoided .