A novel reverse-line hybridization assay for identifying genotypes of CTX-M-type extended-spectrum β-lactamases

Synergistic Role of Plant Extracts and Essential Oils against Multidrug Resistance and Gram-Negative Bacterial Strains Producing Extended-Spectrum β-Lactamases

Plants, being the significant and natural source of medication for humankind against several ailments with characteristic substances hidden on them, have been recognized for many centuries. Accessibility of various methodologies for the revelation of therapeutically characteristic items has opened new avenues to redefine plants as the best reservoirs of new structural types. The role of plant metabolites to hinder the development and movement of pathogenic microbes is cherished. Production of extended-spectrum β-lactamases is an amazing tolerance mechanism that hinders the antibacterial treatment of infections caused by Gram-negative bacteria and is a serious problem for the current antimicrobial compounds. The exploration of the invention from sources of plant metabolites gives sustenance against the concern of the development of resistant pathogens. Essential oils are volatile, natural, complex compounds described by a solid odor and are framed by aromatic plants as secondary metabolites. The bioactive properties of essential oils are commonly controlled by the characteristic compounds present in them. They have been commonly utilized for bactericidal, virucidal, fungicidal, antiparasitic, insecticidal, medicinal, and antioxidant applications. Alkaloids are plant secondary metabolites that have appeared to have strong pharmacological properties. The impact of alkaloids from Callistemon citrinus and Vernonia adoensis leaves on bacterial development and efflux pump activity was assessed on Pseudomonas aeruginosa. Plant-derived chemicals may have direct antibacterial activity and/or indirect antibacterial activity as antibiotic resistance modifying agents, increasing the efficiency of antibiotics when used in combination. The thorough screening of plant-derived bioactive chemicals as resistance-modifying agents, including those that can act synergistically with antibiotics, is a viable method to overcome bacterial resistance. The synergistic assessment studies with the plant extract/essential oil and the antibiotic compounds is essential with a target for achieving a redesigned model with sustainable effects which are appreciably noticeable in specific sites of the plants compared to the entirety of their individual parts.

A comparative study for detection of extended spectrum β-lactamase (ESBL) production by Enteroaggregative Escherichia coli (EAEC) strains using double disc, nitrocefin and PCR assays

We explored and evaluated for the first time colorimetric nitrocefin assay in conjunction with the double disc test and PCR assay. We suggested the use of nitrocefin assay for rapid screening of ESBL-production by Enteroaggregative Escherichia coli.

Extended-spectrum β-lactamase-producing Escherichia coli bacteremia: Comparison of pediatric and adult populations

BACKGROUND/PURPOSE

The prevalence of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli is increasing worldwide. This study investigated the clinical features and bacteriology of pediatric patients with ESBL-producing E. coli bacteremia and compared their characteristics with those of adult patients.

METHODS

Clinical and laboratory data from all of the 41 patients aged ≤18 years diagnosed with E. coli bacteremia were collected over 5 years. Patients aged >18 years diagnosed with E. coli bacteremia, matched 1:1 for calendar time, were enrolled as the adult group. All E. coli isolates were tested for their blaCTX-M group and sequence type 131 (ST131). A novel seven-single nucleotide polymorphism-based clonotyping test was applied to detect the septatypes of each isolate.

RESULTS

In the adult group, patients with ESBL-producing E. coli bacteremia had more previous hospitalizations and antimicrobial agent use than did those with non-ESBL-producing E. coli bacteremia, but these differences were not found in pediatric group. In the pediatric group, the proportion of isolates producing CTX-M group 9 was higher than that in the adult group (85.7% vs. 42.9%; p < 0.05). Among both groups, there were more E. coli ST131 in ESBL isolates in than there were non-ESBL isolates. The distribution of septatypes was more homogenous in ESBL-producing E. coli among the pediatric patients than among the adult patients.

CONCLUSION

ST131 was the major clone causing E. coli bacteremia in both pediatric and adult populations. The pediatric population demonstrated a higher number of isolates producing CTX-M group 9 with more homogenous septatypes compared with the adult population.

Antibiotic resistance and extended spectrum beta-lactamases: Types, epidemiology and treatment

Antibiotic resistance is a problem of deep scientific concern both in hospital and community settings. Rapid detection in clinical laboratories is essential for the judicious recognition of antimicrobial resistant organisms. Production of extended-spectrum β-lactamases (ESBLs) is a significant resistance-mechanism that impedes the antimicrobial treatment of infections caused by Enterobacteriaceae and is a serious threat to the currently available antibiotic armory. ESBLs are classified into several groups according to their amino acid sequence homology. Proper infection control practices and barriers are essential to prevent spread and outbreaks of ESBL producing bacteria. As bacteria have developed different strategies to counter the effects of antibiotics, the identification of the resistance mechanism may help in the discovery and design of new antimicrobial agents. The carbapenems are widely regarded as the drugs of choice for the treatment of severe infections caused by ESBL-producing Enterobacteriaceae, although comparative clinical trials are scarce. Hence, more expeditious diagnostic testing of ESBL-producing bacteria and the feasible modification of guidelines for community-onset bacteremia associated with different infections are prescribed.

Prevalence and characterization of multidrug-resistant and extended-spectrum beta-lactamase-producing Escherichia coli from pediatric wards of a Malaysian hospital

The emergence of Escherichia coli resistant to extended-spectrum cephalosporins (ESCs) is of concern as ESC is often used to treat infections by Gram-negative bacteria. One-hundred and ten E. coli strains isolated in 2009-2010 from children warded in a Malaysian tertiary hospital were analyzed for their antibiograms, carriage of extended-spectrum beta-lactamase (ESBL) and AmpC genes, possible inclusion of the beta-lactamase genes on an integron platform, and their genetic relatedness. All E. coli strains were sensitive to carbapenems. About 46% of strains were multidrug resistant (MDR; i.e., resistant to ≥3 antibiotic classes) and almost half (45%) were nonsusceptible to ESCs. Among the MDR strains, high resistance rates were observed for ampicillin (98%), tetracycline (75%), and trimethoprim/sulfamethoxazole (73%). Out of 110 strains, bla(TEM-1) (49.1%), bla(CTX-M) (11.8%), and bla(CMY-2) (6.4%) were detected. Twenty-one strains were ESBL producers. CTX-M-15 was the predominant CTX-M variant found and this is the first report of a CTX-M-27-producing E. coli strain from Malaysia. Majority (3.1%) of the strains harbored class 1 integron-encoded integrases with a predominance of aadA and dfr genes within the integron variable region. No gene cassette encoding ESBL genes was found and integrons were not significantly associated with ESBL or non-ESBL producers. Possible clonal expansion was observed for few CTX-M-15-positive strains but the O25-ST131 E. coli clone known to harbor CTX-M-15 was not detected while CMY-2-positive strains were genetically diverse.

Multiparametric determination of genes and their point mutations for identification of beta-lactamases

More than half of all currently used antibiotics belong to the beta-lactam group, but their clinical effectiveness is severely limited by antibiotic resistance of microorganisms that are the causative agents of infectious diseases. Several mechanisms for the resistance of Enterobacteriaceae have been established, but the main one is the enzymatic hydrolysis of the antibiotic by specific enzymes called beta-lactamases. Beta-lactamases represent a large group of genetically and functionally different enzymes of which extended-spectrum beta-lactamases (ESBLs) pose the greatest threat. Due to the plasmid localization of the encoded genes, the distribution of these enzymes among the pathogens increases every year. Among ESBLs the most widespread and clinically relevant are class A ESBLs of TEM, SHV, and CTX-M types. TEM and SHV type ESBLs are derived from penicillinases TEM-1, TEM-2, and SHV-1 and are characterized by several single amino acid substitutions. The extended spectrum of substrate specificity for CTX-M beta-lactamases is also associated with the emergence of single mutations in the coding genes. The present review describes various molecular-biological methods used to identify determinants of antibiotic resistance. Particular attention is given to the method of hybridization analysis on microarrays, which allows simultaneous multiparametric determination of many genes and point mutations in them. A separate chapter deals with the use of hybridization analysis on microarrays for genotyping of the major clinically significant ESBLs. Specificity of mutation detection by means of hybridization analysis with different detection techniques is compared.

Oligonucleotide microarrays with horseradish peroxidase-based detection for the identification of extended-spectrum β-lactamases

Production of extended-spectrum β-lactamases (ESBLs) is the one of most widespread and clinically significant mechanism of Enterobacteriaceae resistance towards modern β-lactam antibiotics. There are known 400 ESBLs, with the majority represented by the enzymes of TEM, SHV and CTX-M families. Oligonucleotide microarrays with colorimetric detection have been developed for the purposes of determination of ESBLs and inhibitor-resistant β-lactamases using horseradish peroxidase (HRP). Specific oligonucleotide probes have been designed for the identification of β-lactamase family and important SNPs responsible for the broadening of substrate specificity and tolerance to inhibitors. Multiplex PCR has been developed for simultaneous amplification and labeling of full-size genes of TEM-, SHV- and CTX-M-type β-lactamases with biotin. The labeled target DNA is then hybridized with specific oligonucleotide probes immobilized on a porous membrane support. After hybridization, biotin-labeled DNA duplexes are stained with the streptavidin-HRP conjugate detected colorimetrically. Design of oligonucleotide probes and optimization of hybridization conditions ensure the specificity of all control ESBLs identification. The newly developed method has been successfully used to identify bla(TEM), bla(SHV) and bla(CTX-M) genes in 90 clinical isolates of Enterobacteriaceae: 70% were found to carry bla(TEM), 50% bla(SHV), 50% bla(CTX-M); with the following distribution of CTX-M subclusters: 68% bla(CTX-M-1), 4% bla(CTX-M-2), and 14% bla(CTX-M-9). No ESBL of TEM-type and IRT phenotype assigned to TEM- or SHV-type β-lactamases had been detected; 24.6% of clinical samples show two types of ESBLs simultaneously. A mixture of CTX-M-1-like and SHV-5-like genes was the most abundant combination detected. Membrane microarray technique with colorimetric detection provides both high specificity and effectiveness of screening for ESBL- and IRT-producing samples.

Evaluation of a DNA microarray, the check-points ESBL/KPC array, for rapid detection of TEM, SHV, and CTX-M extended-spectrum beta-lactamases and KPC carbapenemases

Extended-spectrum beta-lactamases (ESBLs) and Klebsiella pneumoniae carbapenemases (KPC carbepenemases) have rapidly emerged worldwide and require rapid identification. The Check-Points ESBL/KPC array, a new commercial system based on genetic profiling for the direct identification of ESBL producers (SHV, TEM, and CTX-M) and of KPC producers, was evaluated. Well-characterized Gram-negative rods (Enterobacteriaceae, Pseudomonas aeruginosa, Acinetobacter baumannii) expressing various ss-lactamases (KPC-2, SHV, TEM, and CTX-M types) were used as well as wild-type reference strains and isolates harboring ss-lactamase genes not detected by the assay. In addition, phenotypically confirmed ESBL producers isolated in clinical samples over a 3-month period at the Bicetre hospital were analyzed using the Check-Points ESBL/KPC array and by standard PCR. The Check-Points ESBL/KPC array allowed fast detection of all TEM, SHV, and CTX-M ESBL genes and of the KPC-2 gene. The assay allowed easy differentiation between non-ESBL TEM and SHV and their ESBL derivatives. None of the other tested ss-lactamase genes were detected, underlining its high specificity. The technique is suited for Enterobacteriaceae but also for P. aeruginosa and A. baumannii. However, for nonfermenters, especially P. aeruginosa, a 1:10 dilution of the total DNA was necessary to detect KPC-2 and SHV-2a genes reliably. The Check-Points ESBL/KPC array is a powerful high-throughput tool for rapid identification of ESBLs and KPC producers in cultures. It provided definitive results within the same working day, allowing rapid implementation of isolation measures and appropriate antibiotic treatment. It showed an interesting potential for routine laboratory testing.

Rapid characterization of beta-lactamases by multiplex PCR

The rising prevalence of the members of the Enterobacteriaceae, Pseudomonas spp. and Acinetobacter baumannii that produce extended-spectrum beta-lactamases (ESBLs) and carbapenem-hydrolysing beta-lactamases (carbapenemases) represents one of the largest "new" resistance problems faced by clinicians and microbiologists during the last 10 years. These diverse enzymes have emerged globally and represent serious health challenges, compromising therapeutic choice and complicating patient management. The rapid detection of strains that produce these beta-lactamases in clinical bacteriology laboratories allows appropriate therapy to be implemented promptly, which reduces patient mortality. This chapter describes three multiplex PCR assays, which may be used to detect genes that encode five families of CTX-M-type ESBLs (groups 1, 2, 8, 9, and 25), five families of metallo-carbapenemases (IMP, VIM, SPM, GIM, and SIM enzymes), and four families of OXA-carbapenemases (OXA-23-like, OXA-40-like, OXA-51-like, and OXA-58-like enzymes). The CTX-M ESBLs are the most prevalent of these enzyme groups, particularly, though not exclusively, in isolates of Escherichia coli and in Klebsiella spp.; metallo-carbapenemases are often found in Pseudomonas spp. and other "non-fermenters," but are also emerging problems in members of the Enterobacteriaceae in some countries and locales; with a few exceptions, the OXA-carbapenemases detected by the assay described are limited to isolates of Acinetobacter spp. These assays are suitable for deployment in national reference laboratories, but should also be considered for use in regional centres and in tertiary referral hospitals.

Characterization of multidrug resistant ESBL-producing Escherichia coli isolates from hospitals in Malaysia

The emergence of Escherichia coli that produce extended spectrum beta-lactamases (ESBLs) and are multidrug resistant (MDR) poses antibiotic management problems. Forty-seven E. coli isolates from various public hospitals in Malaysia were studied. All isolates were sensitive to imipenem whereas 36 were MDR (resistant to 2 or more classes of antibiotics). PCR detection using gene-specific primers showed that 87.5% of the ESBL-producing E. coli harbored the blaTEM gene. Other ESBL-encoding genes detected were blaOXA, blaSHV, and blaCTX-M. Integron-encoded integrases were detected in 55.3% of isolates, with class 1 integron-encoded intI1 integrase being the majority. Amplification and sequence analysis of the 5'CS region of the integrons showed known antibiotic resistance-encoding gene cassettes of various sizes that were inserted within the respective integrons. Conjugation and transformation experiments indicated that some of the antibiotic resistance genes were likely plasmid-encoded and transmissible. All 47 isolates were subtyped by PFGE and PCR-based fingerprinting using random amplified polymorphic DNA (RAPD), repetitive extragenic palindromes (REPs), and enterobacterial repetitive intergenic consensus (ERIC). These isolates were very diverse and heterogeneous. PFGE, ERIC, and REP-PCR methods were more discriminative than RAPD in subtyping the E. coli isolates.

Characterization of multidrug-resistant and extended-spectrum beta-lactamase-producing Klebsiella pneumoniae strains from Malaysian hospitals

The emergence of multidrug-resistant (MDR) and extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae poses a serious antibiotic management problem as resistance genes are easily transferred from one organism to another. Fifty-one strains of K. pneumoniae isolated from sporadic cases in various hospitals throughout Malaysia were analysed by antimicrobial susceptibility testing, PCR detection of ESBL-encoding genes and DNA fingerprinting. Although 27 of the 51 K. pneumoniae strains were MDR (i.e. resistant to three or more classes of antibiotics), the majority of the strains (98 %) were sensitive to imipenem. PCR detection using ESBL gene-specific primers showed that 46 of the K. pneumoniae strains harboured bla(SHV), 19 harboured bla(CTX-M), 5 harboured bla(OXA-1) and 4 harboured bla(TEM-1). Class 1 integron-encoded intI1 integrase was detected in 21 of the 51 K. pneumoniae strains and amplification of the integron 5'CS region showed the presence of several known antibiotic resistance gene cassettes of various sizes. Results of conjugation and transformation experiments indicated that some of the ESBL-encoding genes (i.e. bla(SHV), bla(CTX-M) and bla(TEM-1)) were transmissible and were likely plasmid-encoded. DNA fingerprinting using PFGE and PCR-based methods indicated that the 51 K. pneumoniae strains were genetically diverse and heterogeneous.

Extended-spectrum beta-lactamase-producing Enterobacteriaceae: an emerging public-health concern

The medical community relies on clinical expertise and published guidelines to assist physicians with choices in empirical therapy for system-based infectious syndromes, such as community-acquired pneumonia and urinary-tract infections (UTIs). From the late 1990s, multidrug-resistant Enterobacteriaceae (mostly Escherichia coli) that produce extended-spectrum beta lactamases (ESBLs), such as the CTX-M enzymes, have emerged within the community setting as an important cause of UTIs. Recent reports have also described ESBL-producing E coli as a cause of bloodstream infections associated with these community-onset UTIs. The carbapenems are widely regarded as the drugs of choice for the treatment of severe infections caused by ESBL-producing Enterobacteriaceae, although comparative clinical trials are scarce. Thus, more rapid diagnostic testing of ESBL-producing bacteria and the possible modification of guidelines for community-onset bacteraemia associated with UTIs are required.

Prevalence and clonality of extended-spectrum beta-lactamases in Asia

Asia is almost certainly a part of the world in which extended-spectrum beta-lactamases (ESBLs) have emerged de novo, with some early antimicrobial resistance studies showing high levels of the ESBL phenotype, particularly among Klebsiella, and most notably in China, Korea, Japan and India. There is a lack of genotyping studies but work from the late 1990s suggests that SHV-5 and SHV-12 were most common then, with only very rare reports of TEM-related ESBL genes. As in other parts of the world, quite marked differences have since been seen in the pattern of ESBL genes, particularly in relation to the CTX-M family. The early emergence of TOHO CTX-M-2 in Japan contrasted with CTX-M-3 and -14 in China and many other parts of the Far East, suggesting the separate transfer of genes from the genome of Kluyvera spp. to mobile genetic elements in human-associated Enterobacteriaceae. ESBL production rates are now very high compared with Europe. In most countries, there are mixtures of CTX-M types, with VEB appearing significantly in Vietnam and Thailand, and ESBL isolates from India being completely dominated by the presence of bla(CTX-M-15) alone, with no other CTX-M types reported. With the total population of India and China being c. 2.4 billion and with faecal carriage rates of, probably, c. 10%, these countries represent major reservoirs of bla(CTX-M) genes. Increasing international travel and trade will lead to the movement of many of these ESBL genes. The high prevalence of ESBL genes in Asia means that the empirical treatment of serious infections with beta-lactam antibiotics, except carbapenems, is seriously compromised.

Activity of faropenem against cephalosporin-resistant Enterobacteriaceae

BACKGROUND

There is a need for new oral agents active against extended-spectrum beta-lactamase (ESBL) producers, as these increasingly cause community-onset infections. We therefore evaluated faropenem, a penem in Phase III development, against recently collected oxyimino-cephalosporin-resistant bacteria.

METHODS

We tested 847 consecutive cephalosporin-resistant Enterobacteriaceae collected at 16 centres in South-East England in 2004, 501 of them with CTX-M enzymes; we also tested reference strains and transconjugants with acquired beta-lactamases and various modes of AmpC expression. MICs were determined by the BSAC agar dilution method.

RESULTS

Modal MICs of faropenem for Escherichia coli or Klebsiella spp. with CTX-M or non-CTX-M ESBLs or high-level AmpC enzyme were 0.5-1 mg/L, with over 95% of producers susceptible to <or=2 mg/L. Modal MICs for Enterobacter and Citrobacter spp. with ESBLs or derepressed AmpC were 2-4 mg/L, although around 5% of AmpC-derepressed Enterobacter spp. required faropenem MICs of 16 mg/L. MICs of 8-16 mg/L were seen also for most AmpC-derepressed Serratia spp. isolates. Derepression of AmpC in isogenic mutant series typically raised faropenem MICs by one doubling dilution; among the beta-lactamases introduced into E. coli, only NMC-A (Class A) and IMP (Class B) carbapenemases caused substantive rises in faropenem MICs.

CONCLUSIONS

Faropenem has good activity against E. coli and Klebsiella spp. with ESBLs, including the CTX-M types now proliferating in Europe, but was less active against AmpC-derepressed and ESBL-producing Enterobacter spp. Its clinical utility will depend on levels achieved in the urinary tract, the site of most of the community infections caused by ESBL producers, and more work is needed in this area.