OBJECTIVETo investigate the prevalence of aminoglycoside resistance and genotyping of acetyltransferase in Escherichia coli.

METHODSResistance phenotypes to 12 antibiotics of 44 Escherichia coli isolates were analyzed using agar dilution method and 3 aminoglycoside resistance genes aac(3)-I, II and aac(6')-I were determined by PCR method.

RESULTSIn 44 clinical isolates, the occurrence of ESBLs was 45.45%, resistance rates were discrepant for amikacin (18.18%), gentamicin (56.82%) and tobramycin (61.36%), the prevalence of phenotype TG (tobramycin and gentamicin) indicative of aac(3)-II production and TGA (tobramycin, gentamicin and amikacin) indicative of aac(6')-I production were 36.36% and 18.18%, respectively. The most common aminoglycoside resistance genotype of acetyltransferase was aac(3)-II (52.27%) and aac(6')-I was lower (29.55%), but no aac(3)-I was detected.

CONCLUSIONAt least 2 acetyltransferase genes exist in this area i.e. aac(3)-II and aac(6')-I.

Acyltransferases ; genetics ; Amikacin ; pharmacology ; Aminoglycosides ; pharmacology ; Drug Resistance, Bacterial ; genetics ; Escherichia coli ; enzymology ; genetics ; Genotype ; Gentamicins ; pharmacology ; Phenotype ; Tobramycin ; pharmacology

OBJECTIVETo investigate the antimicrobial resistance of clinical isolates of Stenotrophomonas matophilia (SMA) and the mechanisms of their drug resistance.

METHODSDisc diffusion method (NCCLS) was used to detect the resistant patterns of 88 initial SMA isolates resistant to 12 antibiotics isolated from a local hospital in the past 4 years. PCR was used to detect the 7 aminoglycosides modifying enzymes genes (AME) against amikacin and gentamicin. Metal-beta-lactamases (MBLs) were screened by synergic method, and extended-spectrum beta-lactamases (ESBLs) were detected by double-disk synergy test.

RESULTSThe resistance rates of the SMA isolates were 0%-9.7% to minocycline, 12.5%-22.6% to ticarcillin-clavulanic acid, 12.5%-28.6% to levofloxacin, 18.8%-33.3% to doxycycline, 18.8%-40% to sulfamethoxazole compound, 50%-65.7% to ciprofloxacin, 50%-66.7% to cehazindme, 54.8%-66.7% to amikacin, 75%-100% to gentamicin, 81.3%-100% to piperacillin, 87.5%-100% to aztreonam and 93.5%-100% to imipenem. Aac(3)-I and ant(4')-II were not detected in these strains. The positive rates of the other 5 AME genes of aac(3)-II, ant(2'')-I, aac(6')-I, aac(3)-III, aac(3)-IV were 2.3%, 5.7%, 8%, 10%, and 10%, respectively. SMA strains producing ESBLs were found at the rate of 38.6%; 25% of the strains were MBL-producing, and 13.6% produced both ESBLs and MBLs.

CONCLUSIONMost of the SMAs we isolated are multidrug-resistant through various mechanisms. The choice of antibiotics should be made according to the susceptibility results.

Amikacin ; pharmacology ; Drug Resistance, Multiple, Bacterial ; Gentamicins ; pharmacology ; Humans ; Imipenem ; pharmacology ; Microbial Sensitivity Tests ; Stenotrophomonas maltophilia ; drug effects ; isolation & purification

BACKGROUNDMycobacterium abscessus (M. abscessus) can cause a variety of human infections, involving the lung, skin and soft tissues, and is generally believed to be acquired from environmental sources. The aim of this study was to investigate the molecular diversity and antibiotic susceptibility of M. abscessus isolates as the basis for strategies to improve control and management of infection.

METHODSSeventy M. abscessus isolates from patients attending the Guangzhou Thoracic Hospital were identified from 2003 to 2005 by biochemical tests, gas chromatography, polymerase chain reaction (PCR)-restriction analysis (PRA) of heat shock protein gene hsp65, and sequencing of the quinolone resistance determining regions (QRDRs) of gyrA. Susceptibilities to six antibiotics were determined by micro-broth dilution. Isolates were genotyped using randomly amplified polymorphic DNA (RAPD) analysis.

RESULTSMost isolates (63/70; 90%) were susceptible to amikacin but rates of susceptibility to other antibiotics varied from moderate, clarithromycin (60%) and imipenem (43%), to low for ciprofloxacin and ofloxacin (3%), and 87% of isolates had intermediate susceptibility to cefoxitin. RAPD analysis showed that the 70 clinical isolates displayed 69 unique RAPD patterns.

CONCLUSIONSThe high genetic diversity of isolates suggests that they are not transmitted from person to person but, presumably, are acquired independently from environmental sources. M. abscessus isolates displayed variable levels of susceptibility to all antibiotics tested, other than amikacin, indicating a need for routine susceptibility testing to guide treatment.

Amikacin ; pharmacology ; Anti-Bacterial Agents ; pharmacology ; Cefoxitin ; pharmacology ; China ; Chromatography, Gas ; Ciprofloxacin ; pharmacology ; Clarithromycin ; pharmacology ; Imipenem ; pharmacology ; Microbial Sensitivity Tests ; Mycobacterium ; drug effects ; genetics ; Polymerase Chain Reaction ; Random Amplified Polymorphic DNA Technique

BACKGROUNDAcinetobacter baumannii has emerged as an important pathogen causing a variety of infections. Using data from the China Surveillance of Antimicrobial Resistance Program conducted biennially, we investigated the secular changes in the resistance of 2917 isolates of A. baumannii from 2004 to 2014 to differ antimicrobial agents.

METHODSPathogen samples were collected from 17 to 20 hospitals located in the eastern, central, and western regions of China. Minimum inhibitory concentrations (MICs) were determined by a 2-fold agar dilution method, and antimicrobial susceptibility was established using the 2014 Clinical Laboratory Standards Institute-approved breakpoints. Isolates not susceptible to all the tested aminoglycosides, fluoroquinolones, β-lactams, β-lactam/β-lactam inhibitors and carbapenems were defined as extensively drug resistant.

RESULTSThe rates of nonsusceptibility to common antimicrobial agents remained high (>65%) over the years with some fluctuations to certain agents. The prevalence of imipenem-resistant A. baumannii (IRAB) increased from 13.3% in 2004 to 70.5% in 2014 and that of extensively drug-resistant A. baumannii (XDRAB) increased from 11.1% in 2004 to 60.4% in 2014. The activity of tigecycline was stable with MIC90 ≤4 mg/L against A. baumannii from 2009 to 2014. Susceptibility to colistin remained high (97.0%) from 2009 to 2014. The prevalence of XDRAB increased in all the three surveillance regions over the years and was significantly higher in Intensive Care Unit (ICU) wards than non-ICU wards.

CONCLUSIONSThis longitudinal multicenter surveillance program revealed the nationwide emergence of A. baumannii in China and showed a significant increase in prevalence from 2004 to 2014. High levels of bacterial resistance were detected among samples collected from clinical settings in China, with IRAB and XDRAB being especially prevalent. This study will help to guide empirical therapy and identify at-risk groups requiring more intense interventional infection control measures, while also helping to focus surveillance efforts.

Acinetobacter baumannii ; drug effects ; Amikacin ; pharmacology ; Anti-Infective Agents ; pharmacology ; Cefoperazone ; pharmacology ; Ceftazidime ; pharmacology ; Cephalosporins ; pharmacology ; China ; Colistin ; pharmacology ; Drug Resistance, Multiple, Bacterial ; Humans ; Imipenem ; pharmacology ; Levofloxacin ; pharmacology ; Microbial Sensitivity Tests ; Minocycline ; pharmacology ; Penicillanic Acid ; analogs & derivatives ; pharmacology ; Piperacillin ; pharmacology ; Sulbactam ; pharmacology

OBJECTIVETo evaluate the antibacterial activity of Ciprofloxacin, Amikacin in combination with beta-lactams against Pseudomonas aeruginosa strains in vitro, to optimize treatment regime for antibiotics on the basis of pharmacokinetics (PK)/pharmacodynamics (PD) and drug sensitivity tests. Methods With checkerboard titration method, the minimal inhibitory concentrations (MIC) of a combination of antibiotics in different concentrations for 33 clinically isolated Pseudomonas aeruginosa strains were determined by broth dilution. Fractional inhibitory concentrations (FIC) were calculated for judging synergic effect of antibiotics.

RESULTSThe combination of Amikacin and Ceftazidime showed synergic effects (accounting for 57.6%). The combinations of Ciprofloxacin with Ceftazidime, Cefepime, Imipenem/Cilastatin, Meropenem showed synergic or additive effect. In the study with PK/PD, C(max)/MIC was the principal parameters for evaluation of aminoglycoside and fluoroquinolone antibiotics, while T > MIC was the principal parameter to be used to evaluate beta-lactams antibiotics.

CONCLUSIONWhen antibiotics are used in combination, MICs can be reduced significantly and antibacterial activities are enhanced remarkably. The combination of antibiotics results mainly in synergic or additive effect, and no inhibitory effect is observed. PK/PD analysis plays an important role in planning optimal combination regime to raise clinical efficacy.

Amikacin ; pharmacokinetics ; pharmacology ; Anti-Bacterial Agents ; pharmacokinetics ; pharmacology ; Burn Units ; Ciprofloxacin ; pharmacokinetics ; pharmacology ; Drug Therapy, Combination ; Humans ; Intensive Care Units ; Microbial Sensitivity Tests ; Pseudomonas aeruginosa ; drug effects ; isolation & purification ; beta-Lactams ; pharmacokinetics ; pharmacology

The aminoglycoside 6'-N-acetyltransferases of type Ib (aac(6')-Ib) gene confers resistance to amikacin, tobramycin, kanamycin, and netilmicin but not gentamicin. However, some isolates harboring this gene show reduced susceptibility to amikacin. The European Committee on Antimicrobial Susceptibility Testing (EUCAST) recommends a revision of the phenotypic description for isolates harboring the aac(6')-Ib gene. In this study, we determined the aminoglycoside susceptibility profiles of 58 AAC(6')-Ib-producing Enterobacter cloacae isolates. On the basis of the CLSI and EUCAST breakpoints, a large proportion (84.5% and 55.2%, respectively) of these 58 isolates were found to be susceptible to amikacin. However, among the isolates that were shown to be anikacin-susceptible according to the CLSI and EUCAST breakpoints, only 30.6% and 18.8% isolates, respectively, could be considered to have intermediate resistance on the basis of the EUCAST expert rules. Further studies should be conducted to determine the aminoglycoside susceptibility profiles of aac(6')-Ib-harboring isolates from various geographic regions and to monitor the therapeutic efficacy of amikacin in infections caused by these isolates.
Acetyltransferases/*genetics ; Amikacin/pharmacology ; Aminoglycosides/*pharmacology ; Anti-Bacterial Agents/*pharmacology ; Drug Resistance, Bacterial/genetics ; Enterobacter cloacae/*genetics/isolation & purification ; Enterobacteriaceae Infections/diagnosis/microbiology ; Humans ; Microbial Sensitivity Tests ; Polymerase Chain Reaction ; Sequence Analysis, DNA

OBJECTIVETo evaluate the free radical generation and antioxidant enzymes status in murine peritoneal macrophage during in vitro amikacin resistant Pseudomonas aeruginosa (ARPA) treatment with different time interval.

METHODSPeritoneal macrophages were treated with 1×10(8) CFU/mL ARPA cell suspension in vitro for different time interval (1, 2, 3, 6, 12, and 24 h) and super oxide anion generation, NO generation, reduced glutathione level and antioxidant enzymes status were analyzed.

RESULTSSuper oxide anion generation and NO generation got peak at 12 h, indicating maximal free radical generation through activation of NADPH oxidase in murine peritoneal macrophages during ARPA transfection. Reduced glutathione level and antioxidant enzymes status were decreased significantly (P<0.05) with increasing time of ARPA transfection. All the changes in peritoneal macrophages after 12 h in vitro ARPA transfection had significant difference (P<0.05).

CONCLUSIONSFrom this study, it may be summarized that in vitro ARPA infection not only generates excess free radical but also affects the antioxidant system and glutathione cycle in murine peritoneal macrophage.

Amikacin ; pharmacology ; Animals ; Anti-Bacterial Agents ; pharmacology ; Antioxidants ; analysis ; Cells, Cultured ; Drug Resistance, Bacterial ; Free Radicals ; analysis ; Glutathione ; analysis ; Macrophages, Peritoneal ; immunology ; microbiology ; physiology ; Male ; Mice ; Oxidative Stress ; Pseudomonas aeruginosa ; growth & development ; immunology ; Time Factors

PURPOSE: The increasing prevalence of antimicrobial resistant bacteria has become a serious worldwide problem. The aim of this study was to analyze antimicrobial resistance data generated in 2009 by hospitals and commercial laboratories participating in the Korean Nationwide Surveillance of Antimicrobial Resistance program. MATERIALS AND METHODS: Susceptibility data were collected from 24 hospitals and two commercial laboratories. In the analysis, resistance did not include intermediate susceptibility. Duplicate isolates were excluded from the analysis of hospital isolates, but not from the commercial laboratory isolates. RESULTS: Among the hospital isolates, methicillin-resistant Staphylococcus aureus, penicillin G-non-susceptible Streptococcus pneumoniae based on meningitis breakpoint, and ampicillin-resistant Enterococcus faecium remained highly prevalent. The proportion of vancomycin-resistant E. faecium gradually increased to 29%. Ceftazidime-resistant Escherichia coli and Klebsiella pneumoniae increased to 17% and 33%, respectively, and fluoroquinolone-resistant K. pneumoniae, Acinetobacter spp. and Pseudomonas aeruginosa increased to 33%, 67% and 39%, respectively. Amikacin-resistant Acinetobacter spp. increased to 48%. Imipenem-resistant Acinetobacter spp. and P. aeruginosa increased to 51% and 26%, respectively. Higher resistance rates were observed in intensive care unit (ICU) isolates than in non-ICU isolates among the isolates from hospitals. Resistance rates were higher in hospital isolates than in clinic isolates among the isolates from commercial laboratories. CONCLUSION: Among the hospital isolates, ceftazidime-resistant K. pneumoniae and fluoroquinolone-resistant K. pneumoniae, Acinetobacter spp., and P. aeruginosa further increased. The increase in imipenem resistance was slight in P. aeruginosa, but drastic in Acinetobacter spp. The problematic antimicrobial-organism combinations were much more prevalent among ICU isolates.
Acinetobacter/*drug effects/isolation & purification ; Acinetobacter Infections/drug therapy/microbiology ; Amikacin/pharmacology ; Anti-Bacterial Agents/pharmacology ; Carbapenems/pharmacology ; Cross Infection/drug therapy/microbiology ; *Drug Resistance, Bacterial ; Fluoroquinolones/pharmacology ; Humans ; Pseudomonas Infections/drug therapy/microbiology ; Pseudomonas aeruginosa/*drug effects/isolation & purification ; Republic of Korea

Monitoring temporal trends of antimicrobial resistance can provide useful information for the empirical selection of antimicrobial agents to treat infected patients and for the control of nosocomial infections. In this study, we analyzed antimicrobial resistance of clinically relevant bacteria in 2003 at Korean hospitals and at a commercial laboratory. The following organism-antimicrobial agent resistance combinations were very prevalent: oxacillin-resistant Staphylococcus aureus (68%), expanded-spectrum cephalosporin-resistant Klebsiella pneumoniae (25%), and fluoroquinolone-resistant Escherichia coli (33%), Acinetobacter spp. (58%), and Pseudomonas aeruginosa (40%). Moreover, gradual increases in vancomycin-resistant Enterococcus faecium (20%), cefoxitin-resistant E. coli (10%) and K. pneumoniae (23%), and imipenem-resistant P. aeruginosa (20%) and Acinetobacter spp. (13%) were also observed. The resistance rates of Acinetobacter spp. to most antimicrobial agents at hospitals and at the commercial laboratory were similar. Among the Acinetobacter spp. isolated at a tertiary-care hospital, 46.2% were multidrug-resistant to 9-12 of 13 antimicrobial agents, and 18.3% were panresistant. The exclusion of duplicate isolates at a tertiary-care hospital significantly lowered the proportion of oxacillin-resistant S. aureus, vancomycin-resistant E. faecium, and fluoroquinolone-resistant E. coli.
Vancomycin Resistance ; Vancomycin/pharmacology ; Population Surveillance ; Microbial Sensitivity Tests ; Korea/epidemiology ; Klebsiella pneumoniae/drug effects/isolation & purification ; Klebsiella Infections/drug therapy/epidemiology/microbiology ; Imipenem/pharmacology ; Humans ; Gram-Positive Bacterial Infections/drug therapy/epidemiology/*microbiology ; Gram-Negative Bacterial Infections/drug therapy/epidemiology/*microbiology ; Gammaproteobacteria/*drug effects/isolation & purification ; Fluoroquinolones/pharmacology ; Enterococcus faecium/*drug effects/isolation & purification ; *Drug Resistance, Bacterial ; Anti-Bacterial Agents/*pharmacology ; Amikacin/pharmacology ; Acinetobacter Infections/drug therapy/epidemiology/microbiology ; Acinetobacter/drug effects/isolation & purification