BACKGROUND: Increase in Escherichia coli and Klebsiella pneumoniae isolates with extended- spectrum beta-lactamase (ESBL) have been noted recently in Korea. Current NCCLS disk diffusion test is not sensitive to detect ESBL-producing strains. We have more isolates with intermediate or resistance to cefotaxime than to ceftazidime disk test. The aim of this study was to characterize the ESBLs produced by strains isolated from clinical specimens. METHODS: E. coli and K. pneumoniae strains with cefotaxime intermediate or resistance by disk method were tested for ESBL production by double-disk synergy, transfer of resistance by conjugation, and relative hydrolysis of beta-lactams and isoelectric point (pI) of cell sonicate. The types of beta-lactamase gene were determined by PCR. RESULTS: Nine of the 10 E. coli and all of the 18 K. pneumoniae strains tested were synergy test positive. The MIC of cefotaxime ranged from 1.5 to 400microgram/mL, with the inoculum of 10(4) CFU, but was much higher with larger inoculum. Some selected isolates showed that the resistance was transferable and the size of the plasmid was approximately 39 MDa. The MIC of cefotaxime was higher than that of was ceftazidime in majority of the transconjugants. The hydrolytic activity of the sonicate higher for cefotaxime than ceftazidime. TEM- and SHV-type genes were detected by PCR and the pI of the beta-lactamase was 5.9 for 4 TEM-type and 7.8 for one SHV-type. CONCLUSION: Majority of the cefotaxime intermediate or resistant E. coli and K. pneumoniae isolated from the tertiary care hospital are TEM- or SHV- type ESBL producers. The inoculum size significantly affects the MIC value of beta-lactams for the ESBL-producing strains. The ESBL hydrolyzes cefotaxime more actively than ceftazidime, and the ESBL gene is transferable by conjugation.
beta-Lactamases ; beta-Lactams ; Cefotaxime ; Ceftazidime ; Diffusion ; Escherichia coli* ; Escherichia* ; Hydrolysis ; Isoelectric Focusing ; Isoelectric Point ; Klebsiella pneumoniae* ; Klebsiella* ; Korea ; Plasmids ; Pneumonia ; Polymerase Chain Reaction ; Tertiary Healthcare

BACKGROUND: Panipenem is a carbapenem antimicrobial agent which has been shown to have broad-spectrum activities against various aerobic and anaerobic bacteria. In this study, in vitro activities of panipenem against recent clinical isolates of aerobic and anaerobic bacteria were determined. METHODS: Aerobic and anaerobic bacteria were isolated in 2001 and in 2000-2001, respectively, from a tertiary-care hospital patients. Antimicrobial susceptibility was tested by the NCCLS agar dilution method. RESULTS: MIC90s of panipenem were:similar to those of imipenem for aerobic gram-positive cocci and Enterobacteriaceae; slightly lower than those of meropenem for gram-positive cocci, but slightly higher for Enterobacteriaceae; slightly higher than imipenem for A. baumannii, but similar for anaerobic bacteria. CONCLUSION: MIC90s of panipenem were similar to those of imipenem for aerobic and anaerobic bacterial isolates, which frequently involve respiratory, urinary, intraabdominal and wound infections. When imipenem breakpoints are applied to interpret panipenem susceptibilities, panipenem can be considered useful for the treatment of various infections, including nosocomially acquired ones.
Agar ; Bacteria, Anaerobic* ; Enterobacteriaceae ; Gram-Positive Cocci ; Humans ; Imipenem ; Wound Infection

BACKGROUND: Panipenem is a carbapenem antimicrobial agent which has been shown to have broad-spectrum activities against various aerobic and anaerobic bacteria. In this study, in vitro activities of panipenem against recent clinical isolates of aerobic and anaerobic bacteria were determined. METHODS: Aerobic and anaerobic bacteria were isolated in 2001 and in 2000-2001, respectively, from a tertiary-care hospital patients. Antimicrobial susceptibility was tested by the NCCLS agar dilution method. RESULTS: MIC90s of panipenem were:similar to those of imipenem for aerobic gram-positive cocci and Enterobacteriaceae; slightly lower than those of meropenem for gram-positive cocci, but slightly higher for Enterobacteriaceae; slightly higher than imipenem for A. baumannii, but similar for anaerobic bacteria. CONCLUSION: MIC90s of panipenem were similar to those of imipenem for aerobic and anaerobic bacterial isolates, which frequently involve respiratory, urinary, intraabdominal and wound infections. When imipenem breakpoints are applied to interpret panipenem susceptibilities, panipenem can be considered useful for the treatment of various infections, including nosocomially acquired ones.
Agar ; Bacteria, Anaerobic* ; Enterobacteriaceae ; Gram-Positive Cocci ; Humans ; Imipenem ; Wound Infection

Antibiotic resistance has evolved over the past 50 years from a merely microbiological curiosity to a serious medical problem in hospitals all over the world. Resistance has been reported in almost all species of gram-positive and -negative bacteria to various classes of antibiotics including recently developed ones. Bacteria acquire resistance by reducing permeability and intracellular accumulation, by alteration of targets of antibiotic action, and by enzymatic modification of antibiotics. Inappropriate use of an antibiotic selects resistant strains much more frequently. Once resistant bacteria has emerged, the resistance can be transferred to other bacteria by various mechanisms, resulting in multiresistant strains. MRSA is one of the typical multiresistant nosocomial pathogens. A study of the PFGE pattern of endonuclease-digested chromosomal DNA showed that MRSA of a few clones were disseminated among newborns in the NICU of a Japanese hospital. In this regard, it is important to choose appropriate antibiotics and then after some time, to change to other classes to reduce the selection of resistant strains. Since the development of epoch-making new antibiotics is not expected in the near future, it has become very important to use existing antibiotics prudently based on mechanisms of antibiotic action and bacterial resistance. Control of nosocomial infection is also very important to reduce further spread of resistant bacteria.
Cross Infection/physiopathology ; Drug Resistance, Microbial/physiology* ; Enzymes/physiology ; Methicillin Resistance/physiology ; Staphylococcus aureus/physiology