Enterococci have emerged as a major nosocomial pathogen and as an ever-increasing problem in antimicrobial resistance. They are ubiquitous in the intestinal flora of humans and animals and inherently resistant to a wide array of antimicrobial agents, and, more alarmingly, they seem to have a potential facility for acquiring new resistance determinants, including beta-lactamase production, high-level resistance to aminoglycosides, and recently, glycopeptide resistance. Collectively, all of these properties make enterococci one of most difficult nosocomial pathogens to treat and control today. The purpose of this review was to examine the epidemiology, the mechanisms, and laboratory detection of resistance of enterococci to the two major groups of antibiotics: aminoglycosides and glycopeptides.
Aminoglycosides/pharmacology ; Antibiotics, Glycopeptide/pharmacology ; Drug Resistance, Microbial/physiology* ; Enterococcus/physiology* ; Enterococcus/drug effects ; Epidemiologic Methods ; Human

OBJECTIVETo determine the antibiotics resistance, aminoglycoside-modifying enzymes and homology of high-level gentamycin resistant enterococcus in clinical specimens.

METHODSThe high-level gentamicin resistant (HLGR) isolates were screened by the agar method and the resistance of 14 antimicrobial agents was determined by K-B method. The aminoglycoside-modifying enzyme genes were detected by polymerase chain reaction (PCR). Pulsed-field gel electrophoresis (PFGE) was used to analyze the homology of HLGR isolates.

RESULTSThe ratio of HLGR was 64.2% (68/106). Among the HLGR,there were no isolates resistant to linezolid, vancomycin and tecoplanin, and Enterococcus faecium was more resistant to beta-lactam antibiotics and quinolone than Enterococcus faecalis. The positive rate of aac(6')-Ie-aph(2')-Ia was 92.6% and 3 isolates had the resistance gene mostly similar to aph(2')-Id. And among 51 HLGR isolates from the hospitalized patients, PFGE grouped 17 E. faecalis isolates into 4 clusters (A-D), and 33 E. faecium isolates into 8 clusters (A-H) with A cluster as predominant.

CONCLUSIONHLGR has become the important antibiotic resistance bacteria which results in nosocomial infection; and aac(6')-Ie-aph(2')-Ia is the main aminoglycoside-modifying enzyme gene which causes HLGR.

Drug Resistance, Bacterial ; genetics ; Electrophoresis, Gel, Pulsed-Field ; Enterococcus ; drug effects ; genetics ; Enterococcus faecalis ; drug effects ; genetics ; Enterococcus faecium ; drug effects ; genetics ; Gentamicins ; pharmacology ; Humans ; Kanamycin Kinase ; genetics ; Microbial Sensitivity Tests

Drug Resistance, Bacterial ; Enterococcus ; drug effects ; Hepatitis ; microbiology ; Humans ; Microbial Sensitivity Tests

The emergence of multi-drug resistant gram-positive cocci such as methicillin-resistant (MR) staphylococci, vancomycin-resistant (VR) enterococci, and vancomycin-intermediate resistant S. aureus (VISA) has given new urgency to the development of new antimicrobial agents. One of these is quinupristin/dalfopristin (Q/D). We decided to determine the susceptibility of gram-positive cocci isolated at two university hospitals in Seoul to Q/D and compare the results with eight other antimicrobial agents. We investigated 120 isolates of S. aureus including 49 MRSAs and one VISA, 120 isolates of coagulase negative staphylococci (CNS), 64 E. faecalis and 56 E. faecium, including seven strains of VR E. faecium. Minimum inhibitory concentrations (MICs) and minimal bactericidal concentrations (MBCs) for several antimicrobials, including vancomycin and Q/D, were determined by broth microdilution. All S. aureus including VISA were susceptible to Q/D. Q/D MIC90 for both methicillin-susceptible S. aureus (MSSA) and MRSA was 0.25 g/mL. 49 (87.5%) of 56 E. faecium including six of seven VR E. faecium were susceptible to Q/D. E. faecalis were not susceptible to Q/D (only 1.5% susceptible), but were inhibited by ampicillin (94% susceptible) or vancomycin (95%). CNS was susceptible to Q/D (96% susceptible) and vancomycin (100% susceptible). One of 38 staphylococci and two of 17 E. faecium were tolerant to Q/D. In conclusion, Q/D showed excellent activity against all species of gram-positive cocci including MRSA, VISA, and VR E. faecium except E. faecalis, and may provide a valuable option for the treatment of infections caused by these emerging nosocomial pathogens of gram-positive cocci.
Antibiotics/pharmacology* ; Antibiotics, Peptide/pharmacology* ; Coagulase/analysis ; Enterococcus faecalis/drug effects ; Enterococcus faecium/drug effects ; Human ; Korea ; Microbial Sensitivity Tests* ; Staphylococcus/enzymology ; Staphylococcus/drug effects ; Staphylococcus aureus/drug effects ; Support, Non-U.S. Gov'tn ; Virginiamycin/pharmacology* ; Virginiamycin/analogs & derivatives*

OBJECTIVETo study the effect of calcium hydroxide solutions at different pH values on the cell-surface hydrophobicity of starved Enterococcus faecalis.

METHODSE. faecalis in starvation were harvested and incubated in freshly prepared calcium hydroxide solutions at the pH values ranging from 7.3 to 10.3 for 15 min or 60 min. The cell-surface hydrophobicity of the starved E. faecalis was evaluated by measuring microbial adhesion to hydrocarbons (MATH). Scanning electron microscopy was used to investigate the adhesion capability of starved E. faecalis cells incubated on human dentin at different pH levels.

RESULTSFor the same duration of treatment, increased pH value of calcium hydroxide solution significantly enhanced the cell-surface hydrophobicity of starved E. faecalis (P<0.01). At the same pH value, the cell-surface hydrophobicity of the bacterium increased significantly with time (P<0.05, 15 min vs 60 min). Scanning electron microscopy revealed a significantly increased adhesion of the starved cells on human dentin as the pH value and incubation time increased.

CONCLUSIONCalcium hydroxide solutions promote the adhesion of starved E. faecalis by modifying its cell-surface hydrophobicity.

Bacterial Adhesion ; Calcium Hydroxide ; pharmacology ; Enterococcus faecalis ; chemistry ; drug effects ; Hydrophobic and Hydrophilic Interactions ; Microbial Sensitivity Tests

OBJECTIVETo investigate the distribution and antibiotic resistance of pathogens isolated from children with complicated urinary tract infection.

METHODSA retrospective analysis was performed on the distribution and antibiotic resistance of pathogens isolated from 181 children with complicated urinary tract infection (positive urine culture). The antibiotic resistance of common pathogens was determined by the antimicrobial susceptibility test.

RESULTSGram-negative bacilli were the main pathogens (63.5%), and involved Escherichia coli (E.coli) of 42.0%. Gram-positive cocci accounted for 32.1%, and involved enterococci faecalis of 15.5%. Fungi infection was found in 4.4% of children. The resistance rate of E.coli to ampicillin was the highest (89.4%), but the rate decreased significantly by adding amoxicillin/clavulanic acid (34.2%). E.coli had a high resistance rate to cephazolin, ceftriaxone and cafalotin (>50%), but the resistance rate of E.coli to cefoperazone/sulbouam was significantly lower than other cephalosporins (P<0.01). E.coli was sensitive to imipenem and displayed a lower resistance rate to furadantin (<10%). The resistance rate of enterococci faecalis to rifampicin was high (78.3%), but was low to furadantin, vancomycin and linezolid (<10%). The multiresistant strains accounted for 77.4% of gram-negative bacilli.

CONCLUSIONSE.coli is the major pathogen in children with complicated urinary tract infection, and the enterococci-caused urinary tract infection has been increasing. These pathogens have a high antibiotic resistance, and most of them are multiresistant. Antimicrobial therapy should be based on the results of urine culture and antimicrobial susceptibility test.

Adolescent ; Child ; Child, Preschool ; Drug Resistance, Bacterial ; Enterococcus ; drug effects ; Escherichia coli ; drug effects ; Female ; Humans ; Infant ; Male ; Microbial Sensitivity Tests ; Urinary Tract Infections ; drug therapy ; microbiology

Antimicrobial resistance surveillance is necessary to determine the size of the problem and to guide empirical selection of antimicrobial agents for treating infected patients. The aim of this study was to analyze the results of susceptibility tests performed by hospitals participating in the Korean Nationwide Surveillance of Antimicrobial Resistance (KONSAR) program. The rates of oxacillin-resistant staphylococci, penicillin-nonsusceptible pneumococci, and ampicillin-resistant E. faecium were over 70%. Ampicillin-resistant H. influenzae increased to 68%. Expanded-spectrum cephalosporin-resistant K. pneumoniae, fluoroquinolone-resistant E. coli, and imipenem-resistant P. aeruginosa remained at 16% through 27%, depending on the species. The proportions of vancomycin-resistant E. faecium and imipenem-resistant P. aeruginosa were 18 - 24% and 19-21%, respectively, indicating the seriousness of antimicrobial resistance. In conclusion, the increasing prevalence of resistant bacteria indicates that more concerted effort is required to conserve the usefulness of precious new antimicrobial agents.
Anti-Bacterial Agents/*pharmacology ; Cephalosporins/*pharmacology ; *Drug Resistance, Microbial ; Enterococcus/*drug effects ; Gram-Negative Bacteria/*drug effects ; Human ; Imipenem/*pharmacology ; Korea ; *Vancomycin Resistance

The purpose of this study was to assess the efficacy of alexidine (ALX), alone and combined with N-acetylcysteine (NAC), in eradicating two Enterococcus faecalis strain biofilms. The biofilms of E. faecalis ATCC 29212 and the clinical isolate E. faecalis D1 were grown in the MBEC-high-throughput device for 24 h and were exposed to five twofold dilutions of ALX (2%-0.007 8%) alone and combined with 100 mg⋅mL(-1) NAC, for 1 and 5 min. Eradication was defined as 100% kill of biofilm bacteria. The Student's t-test was used to compare the efficacy of the associations of the two irrigants. After 1-min contact time, ALX eradicated the biofilms at all concentrations except for 0.007 8% and 0.015 6%-0.007 8% with E. faecalis ATCC 29212 and E. faecalis D1, respectively. Similar results for eradication and concentration were obtained when it was combined with 100 mg⋅mL(-1) NAC. After 5 min of contact time, ALX alone and combined with NAC eradicated all enterococci biofilms. ALX showed antimicrobial properties against the two E. faecalis strain biofilms tested at very low concentrations, and its combined use with NAC was not seen to enhance its activity.
Acetylcysteine ; pharmacology ; Anti-Infective Agents, Local ; pharmacology ; Biguanides ; pharmacology ; Biofilms ; drug effects ; Dental Pulp Cavity ; microbiology ; Drug Combinations ; Enterococcus faecalis ; drug effects ; Humans

OBJECTIVEThis study aims to compare and determine a kind of nano-hydroxyapatite composite material with good antibacterial efficacy on Enterococcusfaecalis (E. faecalis) in vitro.

METHODSWe investigated the antimicrobial activity of four kinds of nano-hydroxyapatite composites, namely, silver/hydroxyapatite composite nanoparticles (Ag/nHA), yttrium/hydroxyapatite composite nanoparticles (Yi/nHA), cerium/hydroxyapatite composite nanoparticles (Ce/nHA), and hydroxyapatite nanoparticles (nHA), against E. faecalis in vitro using the agar diffusion and broth dilution method by measuring the growth inhibition zone and the minimum inhibitory concentration (MIC), respectively.

RESULTSThe agar diffusion test results showed that Ag/nHA displayed an obvious growth inhibition zone, whereas Yi/nHA, Ce/nHA, and nHA showed no influence on E. faecalis. The MIC value of Ag/nHA was 1.0 g.L-1, and the three other materials had no effect on E.faecalis even at the high concentration of 32.0 g.L-1.

CONCLUSIONAg/nHA display a potential antimicrobial efficacy to planktonic E.faecalis. Whereas, the three other kinds of nano-hydroxyapatite composites (Yi/nHA, Ce/nHA, nHA) show no influence.

Anti-Bacterial Agents ; pharmacology ; Anti-Infective Agents ; Durapatite ; pharmacology ; Enterococcus faecalis ; drug effects ; Microbial Sensitivity Tests ; Nanocomposites ; toxicity ; Silver

OBJECTIVETo evaluate in vitro the antibacterial effectiveness of sodium hypochlorite on Enterococcus faecalis (E. faecalis) within root canals.

METHODSRoots inoculated with E. faecalis were divided into six groups, which underwent different root canal irrigation and treatment: Group 1: 5.25% NaOCl, Group 2: 2.5% NaOCl, Group 3: 0.9% NaCl, Group 4: root canal preparation + 5.25% NaOCl, Group 5: root canal preparation + 2.5% NaOCl, Group 6: root canal preparation + 0.9% NaCl. Microbiological samples were collected from root canals at three time points (before irrigation, immediately after irrigation and three days after irrigation).

RESULTSThe numbers of E. faecalis in root canal in each of the six groups were effectively reduced. Group 1 and 2 were statistically more effective than Group 3. Group 4 was statistically more effective than Group 5 and 6. Group 5 was statistically more effective than Group 6. Bacterial survival was observed in all canals of each group after a 3-day-incubation.

CONCLUSIONS2.5% NaOCl was highly effective for root canal irrigation. However residual bacteria remained in the root canals after chemical irrigation by NaOCl and mechanical preparation.

Dental Pulp Cavity ; microbiology ; Enterococcus faecalis ; drug effects ; Humans ; In Vitro Techniques ; Root Canal Irrigants ; pharmacology ; Sodium Hypochlorite ; pharmacology