Herpes Simplex Virus Type 2 Seroprevalence in Korea: Rapid Increase of HSV-2 Seroprevalence in the 30s in the Southern Part

To determine the characteristics of seroprevalence of herpes simplex virus type 2 (HSV-2) infection among Korean people, a cross-sectional study was conducted on three groups in 2004. The three groups consisted of the general public who visited public health centers, commercial sex workers (CSWs), and human immunodeficiency virus (HIV)-infected persons. Among the general public, HSV-2 seroprevalence rates for age under the 20s, in the 20s, 30s, 40s and the above 22.6%, 32.7% and 32.3%, respectively, which showed rapid increase of the rate in the 30s (p<0.0001). In case of the above of 19 yr old, women (28.0%) was higher than men (21.7%) (p<0.0001). The rate of CSWs (81.6%) was about 10 times higher than that of general women. In case of HIV-infected men (47.6%), the figure was about 2-3 times higher than that of general men. The low rate in the teens and the 20s proved that it is essential to develop sexually transmitted infections (STIs) prevention programs of education and publicity for them as a precaution measure. This study is the first major study of its kind on HSV-2 and would provide basic data for prevention of STIs including information about target groups subject to vaccination program.

Histiocytic necrotizing lymphadenitis in children : association of human herpes virus 8 and Epstein Barr virus / 소아과

PURPOSE: The aims of this study were to analyze the clinical characteristics of children with Kikuchi's disease(KD) at a medical center and to investigate the etiologic role of human herpesvirus 8(HHV 8) or Epstein-Barr virus(EBV) in children with KD. METHODS: Twenty six children who were diagnosed as KD between Jan. 1998 and Dec. 2005 were included. Medical records were reviewed on the clinical characteristics of children with KD. Follow up data were collected by chart review and telephone contact. Polymerase chain reaction(PCR) was performed in order to detect HHV 8 DNA, and in situ hybridization(ISH) was perfomed in order to detect EBV RNA from 20 lymph node tissues. RESULTS: There were 15 girls and 11 boys with a mean age of 13 years. Posterior cervical lymph nodes were involved in 72 percent(18/25) of the patients. Extracervical lymphadenopathy was associated in one patient. Fever was an associated symptom in 31 percent(8/26) of the patients. Leukopenia was observed in six (46 percent) patients. The cervical lymphadenopathy usually resolved spontaneously within 6 months. Only one patient had a recurrence of lymphadenopathy with fever during follow-up. No children with KD in our series developed systemic lupus erythematosus. HHV 8 DNA was not amplified by nested PCR in any of the cases, and all cases were negative for EBV RNA by ISH. CONCLUSION: KD should be differentiated as a cause of cervical lymphadenopathy in children. HHV 8 and EBV may not play major causative roles in KD in children.

Initial CD4+ T Cell Counts Analysis in Newly HIV-diagnosed Koreans / 감염과화학요법

BACKGROUND: In spite of active HIV/AIDS control and managements, UNAIDS estimate that 40 million people were living worldwide with HIV at the end of 2001. In Korea, The member of HIV- infected adults are continuously growing. For improvement of HIV screening and prevention, we analyzed over times the relationship between the changes in initial CD4+ T cell counts of newly HIV- diagnosed adults, sex, and exposure route. METHODS: We selected 1011 newly HIV-diagnosed adults whose initial CD4+ T cell count was determined within 6 months of HIV diagnosis between 1990 and June, 2002. Based on CD4+ T cell counts, the selected people were grouped into 4 as follows: 700 cells/mm3. The relationship between initial CD4+ T cell counts, age, sex, and HIV risk category were studied by regression statistic methods. RESULTS: The median initial CD4+ T cell counts decreased over times (P<0.001). In each major group, over 50% of initial CD4+ T cell counts were below 350 cells/mm3. For homosexually infected adults, the median age did not statistically increase (P=0.062). However, in heterosexually infected adults, the median age increased throughout the time period examined (P<0.001) with an exception of female group (P=0.427). The multi-regression analyses revealed that older age (P<0.001) and male sex (P<0.001) were independently associated with lower initial CD4+ T cell counts, but not exposure group (P=0.483). For each year cohort of newly diagnosed adults, the median initial CD4+ T cell counts in subsequent years decreased until 1998 and then increased thereafter. CONCLUSION: These results show that a large proportion of HIV-infected adults are being diagnosed late in the course of HIV infection, particularly heterosexually infected male group. Therefore, we should continuously enforce screening, prevention and prompt diagnosis of high risk groups.

Initial CD4+ T Cell Counts Analysis in Newly HIV-diagnosed Koreans / 감염과화학요법

BACKGROUND: In spite of active HIV/AIDS control and managements, UNAIDS estimate that 40 million people were living worldwide with HIV at the end of 2001. In Korea, The member of HIV- infected adults are continuously growing. For improvement of HIV screening and prevention, we analyzed over times the relationship between the changes in initial CD4+ T cell counts of newly HIV- diagnosed adults, sex, and exposure route. METHODS: We selected 1011 newly HIV-diagnosed adults whose initial CD4+ T cell count was determined within 6 months of HIV diagnosis between 1990 and June, 2002. Based on CD4+ T cell counts, the selected people were grouped into 4 as follows: 700 cells/mm3. The relationship between initial CD4+ T cell counts, age, sex, and HIV risk category were studied by regression statistic methods. RESULTS: The median initial CD4+ T cell counts decreased over times (P<0.001). In each major group, over 50% of initial CD4+ T cell counts were below 350 cells/mm3. For homosexually infected adults, the median age did not statistically increase (P=0.062). However, in heterosexually infected adults, the median age increased throughout the time period examined (P<0.001) with an exception of female group (P=0.427). The multi-regression analyses revealed that older age (P<0.001) and male sex (P<0.001) were independently associated with lower initial CD4+ T cell counts, but not exposure group (P=0.483). For each year cohort of newly diagnosed adults, the median initial CD4+ T cell counts in subsequent years decreased until 1998 and then increased thereafter. CONCLUSION: These results show that a large proportion of HIV-infected adults are being diagnosed late in the course of HIV infection, particularly heterosexually infected male group. Therefore, we should continuously enforce screening, prevention and prompt diagnosis of high risk groups.

Involvement of IS26 element in the evolution and dissemination of blaSHV-2a and blaSHV-12

A clinical isolate of Klebsiella pneumoniae K7746 produced the extended-spectrum beta-lactamase (ESBL) SHV-12. A 6.6 kb BamHI fragment containing the blaSHV-12 gene of K7746 strain was cloned into pCRScriptCAM vector resulting in the recombinant plasmid p7746-C1. The restriction map of 3.6 kb inserted DNA and sequences immediately surrounding blaSHV-12 of p7746-C1 were homologous to plasmid pMPA2a carrying blaSHV-2a. In addition, both blaSHV-12 and blaSHV-2a were expressed from a common hybrid promoter made of the -35 region derived from the left inverted repeat of IS26 and the -10 region from the blaSHV promoter itself. The results indicate that blaSHV-12 and blaSHV-2a may have evolved from a common ancestor in the sequential order of blaSHV-2a first, followed by blaSHV-12. Furthermore, by the PCR mapping method using primers corresponding to the IS26 and blaSHV, the association between IS26 and blaSHV was studied in 12 clinical isolates carrying blaSHV-2a, 27 clinical isolates carrying blaSHV-12, and 5 reference strains carrying blaSHV-1 to blaSHV-5. All 39 strains carrying blaSHV-2a or blaSHV-12 were positive by the PCR, providing confirmative evidence that IS26 has been involved in the evolution and dissemination of blaSHV-2a and blaSHV-12. But 5 reference strains carrying blaSHV-1 to blaSHV-5 were negative by the PCR. Therefore, we concluded that the molecular evolutionary pathway of blaSHV-2a and blaSHV-12 may be different from that of other blaSHV-ESBL, e.g., blaSHV-2, blaSHV-3, blaSHV-4, and blaSHV-5.

Molecular Genetic Characteristics of Trimethoprim Resistance in Clinical and Normal Fecal Isolates of Escherichia coli

One hundred and thirty trimethoprim-resistant R plasmids derived from of Escherichia coli isolated from clinical specimens and feces of healthy collegians were examined for incompatibility, EcoRI endonuclease restriction fragment pattern, and Southern hybridization with DHFR I, II, III, V, and VII probe. 1. Most trimethoprim-resistant R plasmids were resistant to ampicillin, tetracycline, chloramphenicol, gentamicin, and kanamycin, and showed multiple drug resistance and various antimicrobial resistance patterns. 2. Trimethoprim-resistant R plasmids ranged from 90 to 50 kilobase and 42.3% of R plasmids tested were classified to incompatibilty group Inc FI, Inc FII or Inc FIV, 3. Among 48 random selected R plasmids from various origin, 14 R plasmids (including 9 of 14 Inc FII plasmids and 3 of 14 Inc FI plasmids) hybridized with DHFR VII oligonucleotide probe but others did not respond to any of DHFR probes used. 4. Most R plasmids showed various EcoRI endonuclease fragments and different reaction sites by Southern hybridization. Six plasmids showed identical or nearly identical molecular weight, EcoRI endonuclease fragment patterns and different sites of Southern hybridization. But 2 Inc FII plasmids derived from urine and feces showed identical pattern. These findings, if confirmed by further studies, suggest that normal flora E. coli can act as reservoir of resistant genes and, consequently, as a factor in the dissemination of these genes among enteric pathogens and need to be examined further.

Mechanism of beta-lactam Resistance in Gram-negative Rods Isolated from Surgical Site Infection / 감염

BACKGROUND: There have been few studies about the kinds of species causing surgical site infections and their resistance pattern in Korea. An increase of extended-spectrum beta-lactamase (ESBL) producing strains is a worldwide problem. However, there is not enough data on the prevalence of ESBL-producing strains in Korea and the true extent of this problem seems to be under-recognized. METHODS: Minimal inhibitory concentrations of gram-negative bacilli isolated from surgical site infections were tested using the standard agar dilution method according to the National Committee for Clinical Laboratory Standards. To identify and characterize beta-lactamases, we performed conjugation test, isoelectric focusing, Southern hybridization, and polymerase chain reaction. RESULTS: A total of 54 strains of gram-negative enteric bacilli were identified:two strains of Acinetobacter spp., one of Citrobacter freundii, nine of Enterobacter cloacae, one of Enterobacter sakazakii, one of Escherichia coli, two of Klebsiella pneumoniae, one of Morganella morganii, one of Proteus vulgaris, 23 of Pseudomonas aeruginosa, four of Xanthomonas maltophila, and nine of Serratia marcescens. Three strains produced ESBL. CONCLUSION: Various species of gram-negative organisms isolated from surgical site infections showed complex antibiograms to various beta-lactams, even to the new generation of antibiotics. A large proportion of these strains showed conjugally transferable, plasmid-mediated, beta-lactam resistance. Some strains were ESBL-producing. This evidence suggests that there has been a molecular evolution of beta-lactamase genes to a great extent in Korea, possibly due to indiscriminate use of antibiotics.

Etest as a Method of Detecting Extended-Spectrum beta-Lactamase / 감염

BACKGROUND: Detection of extended-spectrum beta-lactamase (ESBL) expression is difficult in ordinary clinical laboratories. The Etest has been introduced into clinical settings for the rapid identification of ESBL. The principle behind the Etest is to compare the minimal inhibitory concentration (MIC) of ceftazidime alone with the MIC of ceftazidime with clavulanic acid. The aim of this study was to evaluate the efficiency of the Etest for the detection of ESBL in Korea, where antimicrobial resistance rates are high. METHODS: The double disk synergy test and the Etest were performed simultaneously. The results of the clinical isolates were compared to those of strains producing TEM-1, TEM-2, and SHV-1 as negative controls. The results of the double disk synergy test and the E-test were confirmed by isoelectric focusing of beta-lactamase extracted from suspicious ESBL-producing strains. RESULTS: MIC determination using the standard agar dilution method according to the National Committee for Clinical Laboratory Standards revealed that a total of 48 strains were resistant or intermediate against one or more antibiotics of the third generation cephalosporins. These strains included five strains of E. coli, 14 of S. marcescens, seven of K. pneumoniae, 18 of Enterobacter spp., and four of Citrobacter spp. Sixteen (33%) of the strains, including five strains of E. coli, three of S. marcescens, five of K. pneumoniae, and three of Enterobacter spp. were ESBL- producing strains that were confirmed by double disk synergy test. Thirteen (81%) of the strains of ESBL- producing organisms were detected by Etest, but the remaining three strains (19%) were undetectable by Etest alone. CONCLUSION: The accuracy of Etest for the detection of ESBL was not high, but the efficiency of Etest as the primary screening method of a large number of clinical isolates was appreciable regarding efficiency and rapidity.

Mechanism of beta-lactam Resistance in Gram-negative Rods Isolated from Surgical Site Infection / 감염

BACKGROUND: There have been few studies about the kinds of species causing surgical site infections and their resistance pattern in Korea. An increase of extended-spectrum beta-lactamase (ESBL) producing strains is a worldwide problem. However, there is not enough data on the prevalence of ESBL-producing strains in Korea and the true extent of this problem seems to be under-recognized. METHODS: Minimal inhibitory concentrations of gram-negative bacilli isolated from surgical site infections were tested using the standard agar dilution method according to the National Committee for Clinical Laboratory Standards. To identify and characterize beta-lactamases, we performed conjugation test, isoelectric focusing, Southern hybridization, and polymerase chain reaction. RESULTS: A total of 54 strains of gram-negative enteric bacilli were identified:two strains of Acinetobacter spp., one of Citrobacter freundii, nine of Enterobacter cloacae, one of Enterobacter sakazakii, one of Escherichia coli, two of Klebsiella pneumoniae, one of Morganella morganii, one of Proteus vulgaris, 23 of Pseudomonas aeruginosa, four of Xanthomonas maltophila, and nine of Serratia marcescens. Three strains produced ESBL. CONCLUSION: Various species of gram-negative organisms isolated from surgical site infections showed complex antibiograms to various beta-lactams, even to the new generation of antibiotics. A large proportion of these strains showed conjugally transferable, plasmid-mediated, beta-lactam resistance. Some strains were ESBL-producing. This evidence suggests that there has been a molecular evolution of beta-lactamase genes to a great extent in Korea, possibly due to indiscriminate use of antibiotics.

Etest as a Method of Detecting Extended-Spectrum beta-Lactamase / 감염

BACKGROUND: Detection of extended-spectrum beta-lactamase (ESBL) expression is difficult in ordinary clinical laboratories. The Etest has been introduced into clinical settings for the rapid identification of ESBL. The principle behind the Etest is to compare the minimal inhibitory concentration (MIC) of ceftazidime alone with the MIC of ceftazidime with clavulanic acid. The aim of this study was to evaluate the efficiency of the Etest for the detection of ESBL in Korea, where antimicrobial resistance rates are high. METHODS: The double disk synergy test and the Etest were performed simultaneously. The results of the clinical isolates were compared to those of strains producing TEM-1, TEM-2, and SHV-1 as negative controls. The results of the double disk synergy test and the E-test were confirmed by isoelectric focusing of beta-lactamase extracted from suspicious ESBL-producing strains. RESULTS: MIC determination using the standard agar dilution method according to the National Committee for Clinical Laboratory Standards revealed that a total of 48 strains were resistant or intermediate against one or more antibiotics of the third generation cephalosporins. These strains included five strains of E. coli, 14 of S. marcescens, seven of K. pneumoniae, 18 of Enterobacter spp., and four of Citrobacter spp. Sixteen (33%) of the strains, including five strains of E. coli, three of S. marcescens, five of K. pneumoniae, and three of Enterobacter spp. were ESBL- producing strains that were confirmed by double disk synergy test. Thirteen (81%) of the strains of ESBL- producing organisms were detected by Etest, but the remaining three strains (19%) were undetectable by Etest alone. CONCLUSION: The accuracy of Etest for the detection of ESBL was not high, but the efficiency of Etest as the primary screening method of a large number of clinical isolates was appreciable regarding efficiency and rapidity.

Epidemiology of Serratia marcescens Isolates by Transferable Resistance Gene Analysis

Conjugative R plasmids derived from 74 clinical isolates of Serratia marcescens were epidemiologically analyzed for antimicrobial resistance, EcoRI restriction endonuclease analysis and Southern hybridization with DHFR, TEM and SHV probe. 1. Resistance frequency of isolates against various B-lactam antibiotics was changed by year. 2. Twenty (27%) resistant strains transferred 32 R plasmids to E. coli or Klebsiella by mixed culture. Most strains isolated from 1994 to 1996 transferred only trimethoprim resistance but most strains isolated from 1997 did resistances against gentamicin (Gm) and B-lactams including ampicillin (Ap), carbenicillin (Cb), cefazolin (Cz), cefaloridine (Cl), cefamandole (Cn). 3. Ten plasmids of GmApCbCzC1Cn or GmApCbCzC1 pattern and 3 plasmids of TcSuGmTbApCbCzC1 pattern respectively showed identical EcoRI restriction endonuclease digestion patterns and hybridized fragment patterns with TEM-1 probe by Southern hybridization. These results indicate that the epidemic plasmids carrying blamM gene were present in this hospital in 1997 and molecular genetic analysis of R plasmids can be used to discriminate S. marcescens isolates for epidemiologic studies.

Identification of Acinetobacter calcoaceticus - Acinetobacter baumannii Complex by Ribotyping

Acinetobacter species encounters frequently with clinical specimens and now accounts for a substantial proportion of endemic nosocomial infections in Korea. Recent trends indicate that the antimicrobial resistant strains of Acinetobacter species are increasing. Sixty-one strains were isolated from specimens of patients suspected of nosocomial infections during 1991 to 1996. At present, phenotypic identification of Acinetobacter using biochemical test may not be reliable and resulted in the difficulty to clarify the source of infections and epidemiological study of hospital-acquired infections. Aware of the importance of rational taxonomic proposal for these isolates, correct species identification of these organisms by molecular typing method was carried out. A total of fifty-four strains of A. calcoaceticus-A. baumannii complex species which were identified to genospecies 2 and 13 by biochemical characteristics was subjected to identify by ribotyping using restriction endonuclease EcoRI, ClaI, and SalI. Of fifty-four strains, twenty-five strains were identified as A. baumannii (genospecies 2) and twenty-one strains as genospecies 13, and six strains changed to genospecies 3, and the rest two strains were confirmed as A. haemolyticus (genospecies 4). This result suggests that the ribotyping may be of value for identification of genospecies and epidemiological information of Acinetobacter strains.

Epidemiology of Klebsiella Isolates by Antimicrobial Resistance Gene Analysis

One hundred of clinical isolates of Klebsiella spp. from three hospitals were analyzed by phenotypic and genotypic characteristics for epidemiologic investigation. Almost all isolates of Klebsiella spp. showed highly resistance to ampicillin, and carbenicillin and 4.5-7.9% of K. pneumoniae isolates were also resistant to cefotaxime and ceftazidime, and 10-15% to aminoglycoside antibiotics except amikacin. However, all strains were highly susceptible to imipenem, cefotetan, amikacin and ciprofloxacin. All Koxytoca strains were susceptible to antimicrobials tested except Ap, Am and Cb. Twelve strains of K. pneumoniae hybridized with TEM or SHV probe and extended spectrum B-lactamases from 7 strains were TEM type. Eleven conjugative R plasmids and their parental strains were analyzed. Among them, three couples of plasmids showed identical or nearly identical resistance phenotypes of B-lactams and aminoglycosides, molecular weights, and pI values by isoelectric focusing, and hybridized fragment patterns with TEM probe by Southern hybridization, EcoR1 restriction endonuclease fragment patterns. Their parental strains were isolated from sputum, tissue, and ascites of patients and had similar characteristics. These results indicate that the epidemic strains or epidemic plasmids were present in this hospital and antimicrobial resistance anlysis can be used to discriminate clinical isolates of multi-resistant K. pneumoniae.

Molecular Epidemiologic Analysis of Enterobacter Isolated from Clinical Specimen

Eighty-nine isolates of Enterobacter spp. from two university hospitals were analyzed by phenotypic and genotypic characteristics for epidemiologic investigation. Most strains were isolated from sputum, urine, wound, pus and catheter tip. Most isolates of Enterobacter spp. were resistant to ampicillin, cefazolin and cefoxitin and 39% of E. cloacae isolates were also resistant to other cephalosporins and aminoglycoside antibiotics except amikacin but all strains were highly susceptible to imipenem and ciprofloxacin. Twenty-six antimicrobial resistance patterns were obtained from E. clacae, but E. aerogenes showed only 4 patterns. Fourty-two plasmid profiles were identified, but plasmid was not detected from 28.4% of E. cloacae and 58% of E. aerogenes. Six biotypes from E. cloacae and three biotypes from E. aerogenes were obtained by carbohydrate metabolism. Fourteen strains of E. cloacae carried conjugative R plasmids and these plasmids were further analyzed. Among them, ten plasmids showed identical antibiogram, molecular weight, and pI value by isoelectric focusing and nearly identical restriction endonuclease fragment pattern. Their parental strains had identical antibiogram, biotype, plasmid profile, and were isolated from 4 different specimens including 6 catheter tips of different patients. But most clinical isolates showed various types of combination and seemed to be different strains. These results indicate that the epidemic strain were present in this hospital and the combination of antibiogram and plasmid analysis can be used to discriminate the epidemic strains of multi-resistant E. cloacae.

Epidemiological Study of Serratia marcescens Isolates by Molecular Analysis

Ninety-two strains of Serratia marcescens isolated from 5 hospitals were analyzed for plasmid profile, antimicrobial drug resistance pattern, biotyping, and production of pigment. Ninety-three percents of strains were resistant to chloramphenicol (Cm), tetracycline (Tc), sulfisoxazole (Su), cefazolin (Cz), ampicillin (Ap), and rifampin (Rf). A majority of strains were susceptible to amikacin (Ak), ciprofloxacin (Ci), and cefotaxim (Ct). Fifty-four resistance patterns were found in 94 strains and the most prevalent resistance pattern was CmTcSuApCzRf. Seventeen (17.4%) isolates could transfer their partial resistance to E. coli or Klebsiella pneumoniae by conjugation. Twenty-seven plasmid profiles in 54 strains (58.7%) were detected, however no predominant patterns were seen in isolates from each hospital. Eleven biotypes were detected. The common types were A3b (29.4%) and A8b (27.1%), predominant types were found in each hospital. Twenty strains from 4 of 5 hospitals showed consistence of 3 types. These results indicate that plasmid profile analysis, Grimont biotyping, and resistance pattern type of strains in combination are useful as an epidemiological tool for S. marcescens isolates and some of isolates were confirmed as nosocomial strains.

Transferable Trimethoprim Resistance in Urine Isolates of Escherichia coli

One hundred and twenty-two strains of E. coli isolated from urinary tract infection were examined for antibiogram, transferability of trimethoprim (Tp) resistance, incompatibility with F group plasmid and southem hybridization with DHFR I, II, and III probe of Tp-resistant R plasmids. 1. Among 172 Gram negative bacilli isolated from urinary tract infection, 122 (70.9%) were E. coli and 75 strains of them were resistant to trimethoprim (Tp). Most of Tp-resistant isolates were also resistant to penicillins (ampicillin, carbenicillin, and ticarcillin), aminoglycosides (kanamycin and gentamicin), and sulfisoxazole but almost all strains were susceptible to cephalosporins. 2. Most of Tp-resistant strains and E. coli transconjugant derived from them showed multiple drug resistance and various antimicrobial resistance patterns. 3. Thirty-three Tp-resistant strains (45.2%) transferred 35 Tp-resistant plasmids to E. coli recipients but among them 6 transconjugants did not show retransfer of resistance and plasmid DNA were not detected in 2 transconjugants after resistance transfer. 4. Tp-resistant R plasmids ranged from 157 to 67 kb and 8 R plasmids were classified to incompatibilty group IncFI or IncFII ranging from 120 to 83 kb. Three and two R plasmids belonged to IncFII showed similar molecular weight, resistance pattern, and reaction site by southern hybridization with DHFR I probe. Twenty-five plasmids specifically responded on various EcoRI endonuclease fragments to DHFR I probe but not to DHFR II or DHFR III probe. These findings suggest that most of Tp- resistant R plasmids from urine isolates of E. coli were derived from various sources but some plasmids including IncFII R plasmids were probably originated from same or similar sources.

Molecular Epidemiologic Analysis of Nosocomial Escherichia coli Isolates

One hundred and eighteen strains of Escherichia coli isolated from clinical specimens were epidemiologically analyzed for antimicrobial resistance, EcoRI restriction endonuclease analysis, southern hybridization with TEM and SHV probe of conjugative R plasmids. 1. Sixty-two to 73% of E. coli isolates were resistant to ampicillin, carbenicillin, sulfisomidine, and tetracycline, and 20-27% to kanamycin, gentamicin, tobramycin, and nalidixic acid. However more than 93% were susceptible to cephalosporins and all strains were highly susceptible to cefotetan, imipenem, aztreonam, and amikacin. 2. Twelve strains were susceptible to all drugs tested and the multiple resistant strains showed 65 resistance pattern types. 3. Thirty-six resistant strains(34%) transferred R plasmids to E. coli RG488 or RG176 by mixed culture. Fifty-six plasmids with 31 different resistant phenotype were obtained from them. 4. Some of 15 plasmids derived from 10 strains showed identical or similar EcoRI restriction endonuclease digestion patterns, hybridized fragment patterns with TEM probe by southern hybridization, and resistance levels of j3-lactams and aminoglycosides. These results indicate that the epidemic strains or plasmids were present in this hospital and molecular genetic analysis of R plasmids can be used to discriminate clinical isolates of multi- resistant E. coli.