A Survey of β-Lactamase and 16S rRNA Methylase Genes Among Fluoroquinolone-Resistant Escherichia coli Isolates and Their Horizontal Transmission in Shandong, China

Characterization of Beta-Lactam Resistome of Escherichia coli Causing Nosocomial Infections

Nosocomial infections caused by Escherichia coli pose significant therapeutic challenges due to the high expression of genes encoding antimicrobial drug resistance. In this study, we investigated the conformation of the beta-lactam resistome responsible for the specific pattern of resistance against beta-lactam antibiotics. A total of 218 Escherichia coli strains were isolated from in-hospital patients diagnosed with nosocomial infections, obtained from various sources such as urine (n = 49, 22.48%), vaginal discharge (n = 46, 21.10%), catheter tips (n = 14, 6.42%), blood (n = 13, 5.96%), feces (n = 12, 5.50%), sputum (n = 11, 5.05%), biopsies (n = 8, 3.67%), cerebrospinal fluid (n = 2, 0.92%) and other unspecified discharges (n = 63, 28.90%). To characterize the beta-lactam resistome, all strains were subjected to antibiotic dilution tests and grown in beta-lactam antibiotics supplemented with Luria culture medium. Subsequently, multiplex PCR and next-generation sequencing were conducted. The results show a multi-drug-resistance phenotype, particularly against beta-lactam drugs. The primary determinant of this resistance was the expression of the blaTEM gene family, with 209 positive strains (95.87%) expressing it as a single gene (n = 47, 21.6%) or in combination with other genes. Common combinations included blaTEM + blaCTX (n = 42, 19.3%), blaTEM + blaCTX + blaSHV (n = 13, 6%) and blaTEM + blaCTX + blaBIL (n = 12, 5.5%), among others. The beta-lactam resistome of nosocomial Escherichia coli strains isolated from inpatients at the "October first" Regional Hospital of ISSSTE was predominantly composed of members of the blaTEM gene family, expressed in various configurations along with different members of other beta-lactamase gene families.

The seasonal distribution and concentration of antibiotics in rural streams and drinking wells in the piedmont of North Carolina

The present study investigated 16 residential, rural well sites and respective nearby streams in the Piedmont of North Carolina over three different seasons to determine antibiotic presence and concentration. Fifteen antibiotics were detected in stream surface water, groundwater, and stream sediment compartments. Antibiotics detected representing penicillin, sulfonamide, macrolide, aminoglycoside, lincosamide, and quinolone groups. Sulfamethoxazole (SMX), sulfamerazine (SMR), danofloxacin (DAN), and erythromycin (ETM) were the most commonly detected among samples throughout the sampling period. Concentrations reported in the study ranged from 0 to 1740 ng/L in surface water and groundwater, and 0t378 μg/kg in stream sediment. There was a seasonal influence on antibiotic concentrations in each environmental compartment. Fall had the highest antibiotic concentrations for surface water and stream sediments overall, and groundwater concentrations were highest in the winter. Principal component analysis (PCA) was used to assess the correlation between environmental variables. Antibiotic concentrations correlated with groundwater pH, surface water pH, and surface water temperature. Non-metric multidimensional scaling (NMDS), used to display seasonal and environmental compartment data, demonstrated no discernible trend in the distribution of antibiotics over time. Human health risk assessments based on risk quotients (RQs). RQs from groundwater assessment shown no risk to children 6-11 years old, or adults 18 years old or older. Results from this study illustrate that the occurrence of antibiotics in streams and groundwater in the Piedmont of North Carolina is widespread and provide a basis for future studies investigating the occurrence of antibiotics in rural areas, especially where animal density is high. This work is important because it contributes to the paucity of information on antibiotic pollution in rural areas, and because it illustrates the importance of using a combined targeted and non-targeted approach to antibiotic pollution in streams and groundwater.

Bacteriophages-a new hope or a huge problem in the food industry

Bacteriophages are viruses that are ubiquitous in nature and infect only bacterial cells. These organisms are characterized by high specificity, an important feature that enables their use in the food industry. Phages are applied in three sectors in the food industry: primary production, biosanitization, and biopreservation. In biosanitization, phages or the enzymes that they produce are mainly used to prevent the formation of biofilms on the surface of equipment used in the production facilities. In the case of biopreservation, phages are used to extend the shelf life of products by combating pathogenic bacteria that spoil the food. Although phages are beneficial in controlling the food quality, they also have negative effects. For instance, the natural ability of phages that are specific to lactic acid bacteria to destroy the starter cultures in dairy production incurs huge financial losses to the dairy industry. In this paper, we discuss how bacteriophages can be either an effective weapon in the fight against bacteria or a bane negatively affecting the quality of food products depending on the type of industry they are used.

Susceptibility breakpoint for Danofloxacin against swine Escherichia coli

Background

Improper use of antimicrobials results in poor treatment and severe bacterial resistance. Breakpoints are routinely used in the clinical laboratory setting to guide clinical decision making. Therefore, the objective of this study was to establish antimicrobial susceptibility breakpoints for danofloxacin against Escherichia coli (E.coli), which is an important pathogen of digestive tract infections.

Results

The minimum inhibitory concentrations (MICs) of 1233 E. coli isolates were determined by the microdilution broth method in accordance with the guidelines in Clinical and Laboratory Standards Institute (CLSI) document M07-A9. The wild type (WT) distribution or epidemiologic cutoff value (ECV) was set at 8 μg/mL with statistical analysis. Plasma drug concentration data were used to establish pharmacokinetic (PK) model in swine. The in vitro time kill test in our study demonstrated that danofloxacin have concentration dependent activity against E.coli. The PK data indicated that danofloxacin concentration in plasma was rapidly increased to peak levels at 0.97 h and remained detectable until 48 h after drug administration. The pharmacodynamic cutoff (CO_PD) was determined as 0.03 μg/mL using Monte Carlo simulation. To the best of our knowledge, this is the first study to establish the ECV and CO_PD of danofloxacin against E.coli with statistical method.

Conclusions

Compared to the CO_PD of danofloxacin against E.coli (0.03 μg/mL), the ECV for E.coli seemed reasonable to be used as the final breakpoint of danofloxacin against E.coli in pigs. Therefore, the ECV (MIC ≤8 μg/mL) was finally selected as the optimum danofloxacin susceptibility breakpoint for swine E.coli. In summary, this study provides a criterion for susceptibility testing and improves prudent use of danofloxacin for protecting public health.

Predominance of blaCTX-M-65 and blaCTX-M-55 in extended-spectrum β-lactamase-producing Escherichia coli from raw retail chicken in South Korea

OBJECTIVES

Extended-spectrum β-lactamase-producing Escherichia coli (ESBL-EC) are a serious public health concern worldwide. The aim of this study was to characterise ESBL-EC isolated from raw retail chicken in South Korea.

METHODS

The antimicrobial resistance, phylogenetic group and virulence gene prevalence of 67 ESBL-EC isolated from retail chicken in South Korea were investigated.

RESULTS

All of the isolates possessed bla_CTX-M genes, predominantly bla_CTX-M-65 (52.2%) and bla_CTX-M-55 (25.4%), and three isolates harboured both bla_CTX-M-65 and bla_CTX-M-55. More than one-half of the ESBL-EC strains also carried bla_TEM. Antimicrobial susceptibility testing revealed that 98.5% of the strains were multidrug-resistant (MDR). Phylogenetic analysis showed that group A was predominant (56.7%), followed by B1 (19.4%), E (8.9%), B2 (6.0%) and D (6.0%). Virulence genes associated with extraintestinal pathogenic E. coli (ExPEC) were frequently detected in isolates of phylogenetic groups B1, B2, D and E.

CONCLUSION

The results in this study demonstrate that retail chicken in South Korea is highly contaminated with MDR ESBL-EC and may serve as a reservoir for transmitting ExPEC to humans.

Identification and molecular characterization of Escherichia coli blaSHV genes in a Chinese teaching hospital

Escherichia coli (E. coli) commonly reside in human intestine and most E. coli strains are harmless, but some serotypes cause serious food poisoning. This study identified and molecularly characterized bla_SHV genes from 490 E. coli strains with multi-drug resistance in a hospital population. PCR and molecular cloning and southern blot were performed to assess functions and localizations of this resistant E. coli gene and the pulsed-field gel electrophoresis (PFGE) was utilized to demonstrate the clonal relatedness of the positive E. coli strains. The data showed that 4 of these 490 E. coli strains (4/499, 0.8%) carried bla_SHV genes that included EC D2485 (bla_SHV-5), EC D2487 (bla_SHV-5), EC D2684 (bla_SHV-11) and EC D2616 (bla_SHV-195, a novel bla_SHV). Analysis of bla_SHV open-reading frame showed that bla_SHV-5 had a high hydrolysis activity to the broad-spectrum penicillin (ampicillin or piperacillin), ceftazidime, ceftriaxone, cefotaxime and aztreonam. bla_SHV-195 and bla_SHV-11 had similar resistant characteristics with high hydrolysis activities to ampicillin and piperacillin, but low activities to cephalosporins. Moreover, the two bla_SHV-5 genes were located on a transferable plasmid (23kb), whereas the other two bla_SHV variants (bla_SHV-11 and bla_SHV-195) seemed to be located in the chromosomal material. Both EC D2485 and EC D2487 clones isolated in 2010 had the same DNA finger printing profile and they might be the siblings of clonal dissemination. The data from the current study suggest that the novel bla_SHV and clonal dissemination may be developed, although bla_SHV genes were infrequently identified in this hospital population. The results of the work demonstrate the necessity for molecular surveillance in tracking bla_SHV-producing strains in large teaching hospital settings and emphasize the need for epidemiological monitoring.

Rapid evolution of silver nanoparticle resistance in Escherichia coli

The recent exponential increase in the use of engineered nanoparticles (eNPs) means both greater intentional and unintentional exposure of eNPs to microbes. Intentional use includes the use of eNPs as biocides. Unintentional exposure results from the fact that eNPs are included in a variety of commercial products (paints, sunscreens, cosmetics). Many of these eNPs are composed of heavy metals or metal oxides such as silver, gold, zinc, titanium dioxide, and zinc oxide. It is thought that since metallic/metallic oxide NPs impact so many aspects of bacterial physiology that it will difficult for bacteria to evolve resistance to them. This study utilized laboratory experimental evolution to evolve silver nanoparticle (AgNP) resistance in the bacterium Escherichia coli (K-12 MG1655), a bacterium that does not harbor any known silver resistance elements. After 225 generations of exposure to the AgNP environment, the treatment populations demonstrated greater fitness vs. control strains as measured by optical density (OD) and colony forming units (CFU) in the presence of varying concentrations of 10 nm citrate-coated silver nanoparticles (AgNP) or silver nitrate (AgNO3). Genomic analysis shows that changes associated with AgNP resistance were already accumulating within the treatment populations by generation 100, and by generation 200 three mutations had swept to high frequency in the AgNP resistance stocks. This study indicates that despite previous claims to the contrary bacteria can easily evolve resistance to AgNPs, and this occurs by relatively simple genomic changes. These results indicate that care should be taken with regards to the use of eNPs as biocides as well as with regards to unintentional exposure of microbial communities to eNPs in waste products.

IncA/C plasmid-mediated spread of CMY-2 in multidrug-resistant Escherichia coli from food animals in China

Objectives

To obtain a broad molecular epidemiological characterization of plasmid-mediated AmpC β-lactamase CMY-2 in Escherichia coli isolates from food animals in China.

Methods

A total of 1083 E. coli isolates from feces, viscera, blood, drinking water, and sub-surface soil were examined for the presence of CMY-2 β-lactamases. CMY-2-producing isolates were characterized as follows: the bla_CMY-2 genotype was determined using PCR and sequencing, characterization of the bla_CMY-2 genetic environment, plasmid sizing using S1 nuclease pulsed-field gel electrophoresis (PFGE), PCR-based replicon typing, phylogenetic grouping, XbaI-PFGE, and multi-locus sequence typing (MLST).

Results

All 31 CMY-2 producers were only detected in feces, and presented with multidrug resistant phenotypes. All CMY-2 strains also co-harbored genes conferring resistance to other antimicrobials, including extended spectrum β-lactamases genes (bla_CTX-M-14 or bla_CTX-M-55), plasmid-mediated quinolone resistance determinants (qnr, oqxA, and aac-(6′)-Ib-cr), floR and rmtB. The co-transferring of bla_CMY-2 with qnrS1 and floR (alone and together) was mainly driven by the Inc A/C type plasmid, with sizes of 160 or 200 kb. Gene cassette arrays inserted in the class 1 or class 2 integron were amplified among 12 CMY-2 producers. CMY-2 producers belonged to avirulent groups B1 (n = 12) and A (n = 11), and virulent group D (n = 8). There was a good correlation between phylogenetic groups and sequence types (ST). Twenty-four STs were identified, of which the ST complexes (STC) 101/B1 (n = 6), STC10/A (n = 5), and STC155/B1 (n = 3) were dominant.

Conclusions

CMY-2 is the dominant AmpC β-lactamase in food animals and is associated with a transferable replicon IncA/C plasmid in the STC101, STC10, and STC155 strains.

National prevalence of resistance to third-generation cephalosporins in Escherichia coli isolates from layer flocks in France

Resistance of Escherichia coli to third-generation cephalosporin (3GC) in fecal samples representative of French egg production was studied. The susceptibility to cefotaxime of E. coli isolates obtained by culture on nonselective media was determined. Twenty-two nonsusceptible isolates were obtained (7.51%; 95% confidence interval, 4.49 to 10.54%), the majority of which came from young birds. Most isolates carried a blaCTX-M-1 group gene, and a few carried a blaCMY-2-like gene. Control of 3GC resistance in laying hens is needed.

Exogenously acquired 16S rRNA methyltransferases found in aminoglycoside-resistant pathogenic Gram-negative bacteria: an update

Exogenously acquired 16S rRNA methyltransferase (16S-RMTase) genes responsible for a very high level of resistance against various aminoglycosides have been widely distributed among Enterobacteriaceae and glucose-nonfermentative microbes recovered from human and animal. The 16S-RMTases are classified into two subgroups, N7-G1405 16S-RMTases and N1-A1408 16S-RMTases, based on the mode of modification of 16S rRNA. Both MTases add the methyl group of S-adenosyl-L-methionine (SAM) to the specific nucleotides at the A-site of 16S rRNA, which interferes with aminoglycoside binding to the target. The genetic determinants responsible for 16S-RMTase production are often mediated by mobile genetic elements like transposons and further embedded into transferable plasmids or chromosome. This genetic apparatus may thus contribute to the rapid worldwide dissemination of the resistance mechanism among pathogenic microbes. More worrisome is the fact that 16S-RMTase genes are frequently associated with other antimicrobial resistance mechanisms such as NDM-1 metallo-β-lactamase and CTX-M-type ESBLs, and some highly pathogenic microbes including Salmonella spp. have already acquired these genes. Thus far, 16S-RMTases have been reported from at least 30 countries or regions. The worldwide dissemination of 16S-RMTases is becoming a serious global concern and this implies the necessity to continue investigations on the trend of 16S-RMTases to restrict their further worldwide dissemination.