previous studies showed that a. baumannii was already an emerging pathogen in the respiratory tract , wounds , blood and urine ( 3 ) . since the strains of a. baumannii were usually resistant to most available drugs , except colistin and tigecycline , they would be very sticky when detected on a patient . therefore , the urgent need to study the epidemiology of resistance , surveillance and control measures for a. baumannii in hospital infections was warned ( 4 ) . acinetobacter baumannii could be found in diverse sources such as food , water and soils . acinetobacter baumannii strains are able to survive for a long time even on a dry surface and some of them could toughly attach to human epithelial cells through fimbriae or side chains ( 5 ) . these characteristics indicate that a. baumannii could easily spread via surface , air or any other possible pathways . moreover , many studies showed that in a certain section of the hospital there was only one type of a. baumannii ( 1 , 6 ) . the sources of the harmful a. baumannii may be found by analyzing the molecular epidemiology of the strain in time . however , there are not enough studies on this subject . on the other hand , although physicians and surgeons all reported the threat of a. baumannii , most of the raised problems were from internal medicine or icu . the differences may be caused by the selective pressure from indiscriminate use of broad - spectrum antibiotics in different clinical departments ( 7 ) . analysis may lead to a new explanation for the formation and spread of carbapenem - resistant acinetobacter baumannii ( crab ) or carbapenem - susceptible acinetobacter baumannii ( csab ) ( 8) . however , by now few researches compared the differences of the distribution in different departments . the current study aimed to analyze the distribution of certain types of a. baumannii in clinical departments . authors tried to figure out the roles of the antibiotic - resistant genes and the therapies for the diseases in different departments with spread of crab and csab . eighty - one patients from three wards as icu , department of respiration medicine , department of burn and plastic surgery were studied . the current study was approved by the medical ethics committee of zhejiang university , shaoxing , china . all strains were identified by the vitek32 automatic bacteria identification system ( m - d corporation , us ) . the bacteria were cultured on mueller - hinton ( mh ) agar medium ( oxoid , uk ) and lb broth medium ( shenggong , china ) ( 2 ) . cultured isolations were collected and solved in boiling double distilled water for 10 minutes and then centrifuged at 12000 rpm . the supernatant was collected and used as the template for further mlst reaction . the housekeeping genes of ab ; glta , gyrb , gdhb , gpi , and rpod were selected as the standard template ( 9 , 10 ) . the sequences of the primers were designed according to those of the previous studies ( 3 , 11 ) ( table 2 ) . all primers were designed by jinsi rui corporation , china , and induced by rt - pcr kits ( drr063a , takara , japan ) . polymerase chain reaction ( pcr ) was performed as follows : initial denaturation , 95c for 5 minutes ; denaturation , 95c for 1 minute ; annealing , 56c for 30 seconds ; extension , 72c for 45 seconds . after the pcr reaction , the products were gathered and purified by pcr purification kit ( axygen , ap - pcr-250 , silicon , us ) . the test results were used to identify the strains collected from clinical specimens by referring to the ab mlst database ( 7 - 9 ) . the evaluation of antibiotic - resistance was induced by kirby - bauer test ( k - b ) ( 10 ) . a disk was impregnated with the antibiotic - compounds and then placed on the plate . concentrations of the compound were the highest next to the disk and decreased as distance from the disk increased . once the compound was effective against the bacteria at a certain concentration , no colonies would grow at the point where the concentration in the agar was greater than the effective concentration , i. e. the inhibition zone . pseudomonas aeruginosa atcc27853 and escherichia coli atcc25922 were used as the quality - control isolates ( 5 ) . the clinical and laboratory standards institute ( clsi ) standard was selected as the standard evaluation . the drug resistance ability was evaluated by studying the minimum inhibitory concentration ( mic ) by agar dilution method . the antibiotics used in the study were as follows : imipenem ( imp ) , aztreonam ( atm ) , cefepime ( fep ) , cefoperazone ( cfp ) , cefotaxime ( ctx ) , piperacillin ( pip ) , amikacin ( amk ) , and ciprofloxacin ( cip ) ( 7 ) . the target genes included methicillinase ( oxa-23 , oxa-24 , oxa-51 ) , carbapenemase ( sim , imp , spm ) , type i integrase intl 1 , and sulfonamides - resistance gene ( qace1-sul1 ) . abbreviations : f , forward primer ; r , reverse primer data were analyzed by spss software version17.0 . chi - square test was used to compare enumeration data between different groups while student s t - test for measurement data . one - way analysis of variance was used to analyze dependency of drug resistance and gene expression . eighty - one patients from three wards as icu , department of respiration medicine , department of burn and plastic surgery were studied . the current study was approved by the medical ethics committee of zhejiang university , shaoxing , china . all strains were identified by the vitek32 automatic bacteria identification system ( m - d corporation , us ) . the bacteria were cultured on mueller - hinton ( mh ) agar medium ( oxoid , uk ) and lb broth medium ( shenggong , china ) ( 2 ) . cultured isolations were collected and solved in boiling double distilled water for 10 minutes and then centrifuged at 12000 rpm . the supernatant was collected and used as the template for further mlst reaction . the housekeeping genes of ab ; glta , gyrb , gdhb , gpi , and rpod were selected as the standard template ( 9 , 10 ) . the sequences of the primers were designed according to those of the previous studies ( 3 , 11 ) ( table 2 ) . all primers were designed by jinsi rui corporation , china , and induced by rt - pcr kits ( drr063a , takara , japan ) . polymerase chain reaction ( pcr ) was performed as follows : initial denaturation , 95c for 5 minutes ; denaturation , 95c for 1 minute ; annealing , 56c for 30 seconds ; extension , 72c for 45 seconds . after the pcr reaction , the products were gathered and purified by pcr purification kit ( axygen , ap - pcr-250 , silicon , us ) . the test results were used to identify the strains collected from clinical specimens by referring to the ab mlst database ( 7 - 9 ) . the evaluation of antibiotic - resistance was induced by kirby - bauer test ( k - b ) ( 10 ) . a disk was impregnated with the antibiotic - compounds and then placed on the plate . concentrations of the compound were the highest next to the disk and decreased as distance from the disk increased . once the compound was effective against the bacteria at a certain concentration , no colonies would grow at the point where the concentration in the agar was greater than the effective concentration , i. e. the inhibition zone . pseudomonas aeruginosa atcc27853 and escherichia coli atcc25922 were used as the quality - control isolates ( 5 ) . the clinical and laboratory standards institute ( clsi ) standard was selected as the standard evaluation . the drug resistance ability was evaluated by studying the minimum inhibitory concentration ( mic ) by agar dilution method . the antibiotics used in the study were as follows : imipenem ( imp ) , aztreonam ( atm ) , cefepime ( fep ) , cefoperazone ( cfp ) , cefotaxime ( ctx ) , piperacillin ( pip ) , amikacin ( amk ) , and ciprofloxacin ( cip ) ( 7 ) . the target genes included methicillinase ( oxa-23 , oxa-24 , oxa-51 ) , carbapenemase ( sim , imp , spm ) , type i integrase intl 1 , and sulfonamides - resistance gene ( qace1-sul1 ) . data were analyzed by spss software version17.0 . chi - square test was used to compare enumeration data between different groups while student s t - test for measurement data . one - way analysis of variance was used to analyze dependency of drug resistance and gene expression . results of level of antibiotic - resistance of the isolates are shown in table 4 . all the isolates collected from the hospital under study had a certain level of resistance to all kinds of antibiotics . however , atm and imp were still relatively the most effective antibiotics . in order to further evaluate the properties of the isolates , group i , isolates resistant to more than four types of antibiotics ; group ii , isolates resistant to three or four types of antibiotics ; group iii isolates resistant to less than three types of antibiotics . it was identified that among the isolates , the ones isolated from blood had the highest level of drug - resistance . besides , among the three departments , species isolated from the icu had the highest level of drug - resistance . table 5 present distribution of the isolates in different clinical departments and clinical specimens . abbreviations : amk , amikacin ; atm , aztreonam ; cfp , cefoperazone ; cip , ciprofloxacin ; ctx , cefotaxime ; fep , cefepime ; mic , minimum inhibitory concentration ; pip , piperacillin ; mic50 , minimum inhibitory concentration required to inhibit the growth of 50% of organisms ; and mic90 , minimum inhibitory concentration required to inhibit the growth of 90% of organisms . abbreviations : bur and pla ; department of burn and plastic surgery ; icu , intensive care unit ; and res , department of respiratory medicine . percentage refers to the rate in total number ; for example , 39 ( 81.25 ) means 39 cases out of 48 , 39/48 = 81.25% . groups ; the groups i , ii , iii refer to the group classified by the study group . according to mlst analysis , two types of ab strains were sorted and identified from the clinical samples ; st208 and st218 . the detailed distribution of the two strains in clinical departments and specimens are listed in table 6 . the st208 isolates were distributed mainly in icu and respiration medicine ; while st218 in the burn and plastic surgery department . no significant correlation was found between the types and the sources of the clinical samples ( p value > 0.05 ) . but the departments where the strains came from seemed to be significantly related ( p value < 0.05 ) . according to the results of k - p drug sensitive test , the strains were divided into two groups , which were carbapenem resistant : the carbapenem resistant ab ( crab ) and the carbapenem sensitive ab ( csab ) ; 70.21% of st208 and 69.21% of st218 included crab strains , while 15.22% of st208 and 84.78% of st218 were csab . st208 strains isolated from icu and respiration medicine department were mainly crab ; while st218 strains isolated from burn and plastic surgery departments were mainly csab . abbreviations : bur and pla , department of burn and plastic surgery , icu , department of intensive care unit ; and res , department of respiration medicine . number refers to the number of the species isolated from a certain department or sample . percentage refers to the rate in total number ; for example , 40 ( 83.3 ) means 40 cases out of 48 , 40/48 = 83.3% . number in this group has a significant difference compared with those in other groups ( p value < 0.05 ) . pcr tests revealed that the prevalence of resistance inducing genes were as follows : oxa-23 81.3% , oxa-51 61.3% , sim 18.8% , oxa-24 5.3% , imp 12.3% , intl1 57.9% and qace1-sul1 61.2% . results of the current study showed that st208/crab / oxa-23 , 51 is the main molecular phenotype of the crab strains in the hospital . drug - resistance property of the isolates was related to the expression of oxa-23 and 51 ( p value < 0.05 ) . meanwhile , in st208 , there were more chances of expressions of oxa-23 , 51 compared with those in st218 ( p value < 0.05 ) . abbreviations : crab , carbapenem - resistant ab ; and csab , carbapenem - susceptible ab . there are significant differences in this group crab compared with those in csab , p value < 0.05 .   data are presented as number of the isolates ( which express the gene ) per number of the stains . results of level of antibiotic - resistance of the isolates are shown in table 4 . all the isolates collected from the hospital under study had a certain level of resistance to all kinds of antibiotics . however , atm and imp were still relatively the most effective antibiotics . in order to further evaluate the properties of the isolates , group i , isolates resistant to more than four types of antibiotics ; group ii , isolates resistant to three or four types of antibiotics ; group iii isolates resistant to less than three types of antibiotics . it was identified that among the isolates , the ones isolated from blood had the highest level of drug - resistance . besides , among the three departments , species isolated from the icu had the highest level of drug - resistance . table 5 present distribution of the isolates in different clinical departments and clinical specimens . abbreviations : amk , amikacin ; atm , aztreonam ; cfp , cefoperazone ; cip , ciprofloxacin ; ctx , cefotaxime ; fep , cefepime ; mic , minimum inhibitory concentration ; pip , piperacillin ; mic50 , minimum inhibitory concentration required to inhibit the growth of 50% of organisms ; and mic90 , minimum inhibitory concentration required to inhibit the growth of 90% of organisms . abbreviations : bur and pla ; department of burn and plastic surgery ; icu , intensive care unit ; and res , department of respiratory medicine . percentage refers to the rate in total number ; for example , 39 ( 81.25 ) means 39 cases out of 48 , 39/48 = 81.25% . groups ; the groups i , ii , iii refer to the group classified by the study group . according to mlst analysis , two types of ab strains were sorted and identified from the clinical samples ; st208 and st218 . the detailed distribution of the two strains in clinical departments and specimens are listed in table 6 . the st208 isolates were distributed mainly in icu and respiration medicine ; while st218 in the burn and plastic surgery department . no significant correlation was found between the types and the sources of the clinical samples ( p value > 0.05 ) . but the departments where the strains came from seemed to be significantly related ( p value < 0.05 ) . according to the results of k - p drug sensitive test , the strains were divided into two groups , which were carbapenem resistant : the carbapenem resistant ab ( crab ) and the carbapenem sensitive ab ( csab ) ; 70.21% of st208 and 69.21% of st218 included crab strains , while 15.22% of st208 and 84.78% of st218 were csab . st208 strains isolated from icu and respiration medicine department were mainly crab ; while st218 strains isolated from burn and plastic surgery departments were mainly csab .   abbreviations : bur and pla , department of burn and plastic surgery , icu , department of intensive care unit ; and res , department of respiration medicine . number refers to the number of the species isolated from a certain department or sample . percentage refers to the rate in total number ; for example , 40 ( 83.3 ) means 40 cases out of 48 , 40/48 = 83.3% . number in this group has a significant difference compared with those in other groups ( p value < 0.05 ) . pcr tests revealed that the prevalence of resistance inducing genes were as follows : oxa-23 81.3% , oxa-51 61.3% , sim 18.8% , oxa-24 5.3% , imp 12.3% , intl1 57.9% and qace1-sul1 61.2% . results of the current study showed that st208/crab / oxa-23 , 51 is the main molecular phenotype of the crab strains in the hospital . drug - resistance property of the isolates was related to the expression of oxa-23 and 51 ( p value < 0.05 ) . meanwhile , in st208 , there were more chances of expressions of oxa-23 , 51 compared with those in st218 ( p value < 0.05 ) . abbreviations : crab , carbapenem - resistant ab ; and csab , carbapenem - susceptible ab . there are significant differences in this group crab compared with those in csab , p value < 0.05 . data are presented as number of the isolates ( which express the gene ) per number of the stains . acinetobacter baumannii is widely distributed in the environment , human body and surfaces ( 12 ) . studies show that growing numbers of carbapenem - resistant pathogenic bacteria , such as crab are now appearing . the prevention and treatment of crab is an urgent issue to control nosocomial infections ( 13 - 15 ) . in the current study , all strains of a. baumannii were resistant to antibiotics in different degrees ( table 4 ) . in fact , it is a common phenomenon in hospitals in china ( 9 ) . moreover , it was found that distribution of the crab isolates were related to the wards where they came from ( table 5 ) . isolates from icu and department of respiratory medicine had higher levels of antibiotic - resistance than the strains from the surgery department . it may be due to the long - term use of antibiotics in the former wards ( 16 - 18 ) . this finding showed that the distribution of crab may be affected by the therapeutic methods . besides , authors further studied the types of the isolates in the air and hands of the doctors and nurses in the wards . it was found that in icu only st208 existed ; while in department of burn and plastic surgery only st218 was detected . considering the fact that these two departments were physically separated , it was speculated that the two different isolates may have different origins and they were separated by the spatial distance and were only epidemic in each section . currently , techniques for molecular cloning and detection are widely used to study the types of certain isolates ( 3 , 10 - 13 ) . in the current study a new technique , mlst , was used . mlst classified the strains according to the results of accurate detection of the sequences of nucleic acid from the isolates ( 19 ) . two isolates , st208 and st218 were found in the hospital , and each one had its own  territory this finding showed that a certain kind of bacteria would be dominant in a certain section . the existence of anti - carbapenemase enzymes was the key factor to the prevalence of multidrug - resistant bacteria ( 20 - 22 ) . previous reports showed that five types of anti - carbapenemase enzymes , oxa-23 , 51 , sim , imp and spm could be detected in crab ( 23 ) . the current study found that oxa-23 and 51 were the most prevalent genes in the hospital . since these antibiotic resistance inducing genes were all expressed in plasmid , their distribution was determined by gene mutation and combined effect of the antibiotics used in a certain place . thus , the final results of the distribution are the  natural selection  in the certain therapeutic milieu in the hospital . identification of the types and genes of the isolates in a certain ward would be important to restrict the prevalence . moreover , although many microbiologists believe that the nuclear - dna is not related to the plasmid - dna in bacteria , the current study findings indicated that in st208 there were more chances for the existence of oxa-23 , 51 ( table 8) . the fact revealed that there might be certain connections between the nuclear - gene types and the appearance of plasmid genes . , there may be different isolates of ab in different wards since these departments were physically separated . the levels of antibiotic - resistance were also quite different in the isolates from different locations of the human body . species isolates from blood culture had the highest level of antibiotic - resistance . st208 and the st218 were the epidemic isolates of ab , their abilities of drug - resistance were due to the existence of oxa-23 , oxa-51 , intl 1 and qace1-sul 1 . hospital managers should take measures to supervise the epidemiology and types of the crab isolates . the study of the molecular epidemiology of these isolates from different wards and specimens were significantly important . besides , further studies on the connections between the plasmid gene expression and types of the isolates are required .