Comparison of Epidemiological Typing Methods for Shigella sonnei

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Use of R plasmid and bla Gene for Epidemiological Fingerprinting of Clinical Isolates of Enterobacteriaceae resistant to beta- lactam Antibiotics

Clinical isolates of Enterobacteriaceae (189 Klebsiella, 61 Enterobacter, 32 Serratia, 19 E. coli, 7 Proteus, and 3 Citrobacter) from one university hospital were epidemiologically analyzed by using transferable R plasmids resistant beta-lactam antibiotics including broad-spectrum cephalosporins. About 30% of E. cloacae and S. marcescens and about 5% of K. pneumoniae were resistant to one or more broad-spectrum j3-lactam antibiotics including cefotaxim, ceftazidime, aztreonam, or cefoxitin but all isolates of E. aerogenes, K oxytoca, and P. mirabilis were susceptible. Thirty-six conjugative R plasmids including 8 plasmids resistant expanded-spectrum cephalosporins were obtained from multiple resistant K. pneumoniae (19), E. cloacae (9), E. coli (4), and C. freundii (1). Thirty-one plasmids were subjected to R plasmid analysis and classified 20 different plasmid types. Among them 5, 2, and 2 plasmids belong to 3 different types respectively showed identical molecular size, endonuclease fragment pattern by Southem hybridization pattern by TEM-1 probe, pI value by isoelctric focusing, and also identical antibiogram and biotype of wild strains harboring plasmids. But all of plasmids resistant to cefotaxim, ceftazidime, aztreonam or cefoxitin showed different palsmid anlysis patterns. These results indicate that the epidemic strains of 3 clonal types had been present in this hospital and anlysis using transferable R plasmid and bla gene can be used to discriminate multi-resistant clinical isolates of Enterobacteriaceae.

Antimicrobial resistance and molecular epidemiologic characteristics of Stenotrophomonas maltophilia isolated from clinical specimens

Sixty-eight clinical isolates of Stenotrophomonas maltophilia from inpatients of 2 university hospitals in Taegu were epidemiologically analyzed by using the minimum inhibitory concentrations of 25 antimicrobial drugs, biochemical reaction, pulsed-field gel elctropgoresis (PFGE), and PCR with enterobacterial repetitive intergenic consensus sequences as primer (ERIC-PCR). 1. All the strains were susceptible to minocycline. More than 57% were susceptible to sulfisomidine (Su), ciprofloxacin (Ci), Ofloploxacin (Of), nalidixic acid (Na), and chloramphenicol (Cm), and 19apprx35% to ceftazidime (Cd), trimethoprim (Tp), Ticacillin-clavulanic acid, and cefoperazone-sulbactam. Most isolates were resistant to beta-lactam antibiotics such as ampicillin (Ap), carbenicillin (Cb), cefotaxim (Ct), cefoxitin (Cx), and aminoglycosides including gentamicin (Gm), tobramycin (Tb), amikacin (Ak). 2. All the isolates were multiply resistant of 5 to 17 drugs and showed 40 different resistance pattern types. 3. All the strains showed very similar biochemical reactions except beta-galactosidase and nitrate reduction test. Fourteen strains selected randomly were classified 10 different pattern type by PFGE and ERIC-PCR. These two methods showed identical result. Four strains isolated from wound in 1994 showed similar MIC pattern and identical API 20NE profile, PFGE, and ERIC-PCR pattern indicating episodes of cross-infection among patients. These results indicate that PFGE or ERIC-PCR profile has comparable discriminatory power for epidemiological typing of S. maltophilia.

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.