Phenotypic and molecular detection of CTX-M-beta-lactamases produced by Escherichia coli and Klebsiella spp

A novel flow cytometric assay for rapid detection of extended-spectrum beta-lactamases

The rapid detection of extended-spectrum beta-lactamases (ESBLs) is a challenge for most clinical microbiology laboratories because inaccurate identification of ESBL producers has important clinical implications for both antibiotic treatment and infection control. The aim of our study was to develop a rapid detection assay of ESBL producers based upon flow cytometric analysis. Antimicrobial susceptibility testing followed by molecular characterization of bla(TEM) , bla(SHV) or bla(CTX-M) genes was performed on clinical isolates (41 ESBL positive and 20 ESBL negative) and isolates expressing well-characterized beta-lactamases, including ESBLs (n = 13), plasmid AmpCs (n = 3), oxacillinases (n = 5) and carbapenemases (n = 3). Additionally, two ATCC strains recommended by CLSI for susceptibility testing were used as controls. The flow cytometry analysis protocol involved an incubation of bacterial cells with different concentrations of ceftazidime (1, 2 and 4 mg/L) and cefotaxime (4, 8 and 16 mg/L) for 1 and 2 hours, in the presence and absence of clavulanic acid; subsequently, cells were stained with the fluorescent dye Bis-(1,3-dibutylbarbituric acid) trimethine oxonol [DiBAC(4) (3)], a lipophilic anion able to diffuse across depolarized membranes. Additionally, CFU counts were performed. Susceptible isolates displayed increased fluorescence after 1 hour of incubation; conversely, the increase of the depolarized population was only observed after incubation with clavulanic acid associated with ceftazidime or cefotaxime in ESBL producers. An excellent correlation was obtained between the number of non-depolarized bacteria quantified by flow cytometry and by conventional CFU assays. A novel, accurate and fast flow cytometric assay is available to detect the presence of ESBLs.

Prevalence and spread of multidrug resistant Escherichia coli isolates among nursing home residents in the southern part of The Netherlands

OBJECTIVES

Empiric antibiotic treatment should be based on recent surveillance data. Therefore, we conducted a surveillance of (multidrug) resistance of Escherichia coli and antibiotic use among Dutch nursing home (NH) residents. Pulsed-field gel electrophoresis and multilocus sequence typing were used to describe the spread of multidrug-resistant strains.

DESIGN

Observational study.

SETTING

Five NHs in the southern part of The Netherlands.

PARTICIPANTS

A total of 337 NH residents from both somatic and psychogeriatric wards.

MEASUREMENTS

The prevalence and spread of antibiotic resistance and multidrug resistant E. coli isolates collected from urine samples and antibiotic use among the NH residents were investigated.

RESULTS

A total of 208 E. coli isolates were collected from 308 urine samples. Resistance to amoxicillin-clavulanic acid was 23% and resistance to ciprofloxacin was 16%. Resistance to trimethoprim-sulfamethoxazole was 19%, whereas nitrofurantoin resistance was less than 1%. Multidrug resistance was observed in 28 of the 208 isolates (13%). Several isolates showed a similar pulsed-field gel electrophoresis pulsotype and multilocus sequence typing type. Sequence type (ST) 131 was the most prevalent (48%) and was demonstrated in all NHs and with four different pulsotypes. Consumption of antibiotics for systemic use was 64.4 defined daily dose (DDD)/1000 residents/day. Amoxicillin-clavulanic acid was most frequently prescribed (20.92 DDD/1000 residents/day), followed by the quinolones (14.8 DDD/1000 residents/day).

CONCLUSION

We observed a high prevalence of antibiotic resistance and antibiotic use. In particular, the use of and resistance to fluoroquinolones is concerning. Because of the high prevalence of resistance, many agents are no longer suitable for empiric treatment. E. coli ST131, which has also been demonstrated in this study, poses a potential risk to this vulnerable population. We have clearly demonstrated that the resistance among NH residents is different from elderly living at home and hospitalized patients, and with the emergence of resistant strains, such as ST131, NHs are a potential reservoir for multidrug resistant bacteria.

Frequency and diversity of CTX-M enzymes among extended-spectrum beta-lactamase-producing Enterobacteriaceae isolates from Caracas, Venezuela

CTX-M-type extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae have been previously reported in Venezuela. We assessed the frequency and diversity of CTX-M enzymes among 97 ESBL-producing Enterobacteriaceae isolates as well as to establish the genetic relationship among CTX-M producers collected from six hospitals in Caracas. Polymerase chain reaction (PCR) assays identified the bla(CTX-M) genes in 42 isolates (43.3%). The bla(CTX-M-1) group was the most common in Escherichia coli (91 %) and the bla(CTX-M-2) in Klebsiella pneumoniae (56.6%). Presence of bla(CTX-M-1), bla(CTX-M-2), bla(CTX-M-15), and bla(CTX-M-14) was revealed by sequencing analysis. The CTX-M producers were mainly isolated from urine samples (46%). Antimicrobial susceptibility tests showed that a high proportion of CTX-M-producing isolates was resistant to ciprofloxacin and trimethoprim-sulfamethoxazole. Analysis of enterobacterial repetitive intergenic consensus PCR and repetitive extragenic palindromic PCR profiles revealed several genetic clusters between isolates carrying the bla(CTX-M-1) group, while complete genotypic diversity among isolates carrying the bla(CTX-M-2) group was observed. This study documented that CTX-M has achieved a citywide distribution, with the CTX-M-1 group as the most frequent (66.7%). The CTX-M clusters detected suggest that patient-patient transmission may have played an important role in the widespread and high prevalence of the CTX-M-1 group. To our knowledge, this is the first report of the CTX-M-15 in Venezuela.

Prevalence of bla (CTX M) extended spectrum beta lactamase gene in enterobacteriaceae from critical care patients

Context:

Critical care units provide a favourable environment for the antimicrobial resistant organisms to disseminate. There is recent increase in number of extended spectrum beta lactamase (ESBL) producers because of the emergence of CTX M Beta lactamases produced by Enterobacteriaceae. They colonize the intestinal flora and spread with greater intensity in the community and hospital. Usage of Carbapenems becomes mandatory as the ESBL inhibitor combination antibiotics (Amoxicillin/Clavulanate) are not effective especially against CTX M ESBLs.

Aim:

The aim of this study is to detect ESBL producing bla CTX M gene in Enterobacteriaceae from infections in Critical care patients and to stress on the intensity of the problem and to make interventions to curb the emergence and dissemination of CTX M ESBLs.

Materials and Methods:

A total of 118 Enterobacteriaceae isolates from Critical care unit patients were recovered from a variety of clinical specimens. Antimicrobial susceptibility test was done and isolates with resistance or with reduced susceptibility to any of the third generation Cephalosporins were selected for the study. Phenotypic confirmation of ESBL production was done by Double Disc Synergy Test and confirmed by minimum inhibitory concentration. Multiplex polymerase chain reaction was performed to screen the four groups of CTX-M ESBLs.

Results:

Among the 118 isolates of Enterobacteriaceae 54 isolates were positive for CTX-M group I ESBL which constitutes 45.7 %.

Conclusions:

Early detection of CTX M producing Enterobacteriaceae by continuous surveillance and thereby reducing their spread and restricted use of third generation Cephalosporins (3GC) antibiotics could be the possible routes to prevent the emergence and spread of CTX M ESBL producing organisms.

Electron microscopic structures, serum resistance, and plasmid restructuring of New Delhi metallo-β-lactamase-1 (NDM-1)-producing ST42 Klebsiella pneumoniae emerging in Japan

Enterobacteriaceae, carrying the New Delhi metallo-β-lactamase-1 (NDM-1) gene (bla (NDM-1)), have emerged and posed a threat since 2006. In Japan, bla (NDM-1)-carrying Escherichia coli was first described in 2010. In this study, we characterized NDM-1-positive Klebsiella pneumoniae strain 419 in Japan, which was isolated from the urine of a 90-year-old Japanese patient who had never been to the Indian subcontinent. K. pneumoniae 419 belonged to ST42. It possessed a surface capsule (with untypeable capsular PCR types) and was resistant to serum killing. K. pneumoniae 419 cells were occasionally flagellated or piliated and autoaggregated. K. pneumoniae 419 was resistant to β-lactams (including carbapenems), aminoglycosides, and fluoroquinolones, and was susceptible to imipenem (or biapenem), aztreonam, polymixin B, and colistin. It possessed at least eight plasmids; of those, a 74-kb plasmid (pKPJ1) of the replicon FIIA carried bla (NDM-1) and was conjugally transferred to E. coli strains, with a 71-kb transferable azithromycin-resistant (mphA (+)) plasmid of the replicon F (pKPJ2), as a large (145-kb) plasmid (pKPJF100) through a transposition event. In addition to bla (NDM-1), pKPJ1 carried arr-2, pKPJ2 carried mphA, and pKPJF100 carried both. They were negative for the 16S rRNA methylase gene, e.g., which is frequently associated with bla (NDM-1). The data demonstrate that K. pneumoniae 419 possessed virulence- and fitness-associated surface structures, was resistant to serum killing, and possessed a unique (or rare) genetic background in terms of ST type and bla (NDM-1)-carrying plasmid.

Analysis of β-lactamase phenotypes and carriage of selected β-lactamase genes among Escherichia coli strains obtained from Kenyan patients during an 18-year period

Background

Although β-lactam antibiotics are heavily used in many developing countries, the diversity of β-lactamase genes (bla) is poorly understood. We screened for major β-lactamase phenotypes and diversity of bla genes among 912 E. coli strains isolated from clinical samples obtained between 1992 and 2010 from hospitalized and non-hospitalized patients.

Results

None of the isolates was resistant to carbapenems but 30% of all isolates were susceptible to cefepime, cephamycins and piperacillin-tazobactam. Narrow spectrum β-lactamase (NSBL) phenotype was observed in 278 (30%) isolates that contained bla_TEM-1 (54%) or bla_SHV-1 (35%) or both (11%). Extended Spectrum β-lactamase (ESBL) phenotype was detected in 247 (27%) isolates which carried bla_CTX-M-14 (29%), bla_CTX-M-15 (24%), bla_CTX-M-9 (2%), bla_CTX-M-8 (4%), bla_CTX-M-3 (11%), bla_CTX-M-1 (6%), bla_SHV-5 (3%), bla_SHV-12 (5%), and bla_TEM-52 (16%). Complex Mutant TEM-like (CMT) phenotype was detected in 220 (24%) isolates which carried bla_TEM-125 (29%), while bla_TEM-50, bla_TEM-78, bla_TEM-109, bla_{TEM −152} and bla_TEM-158 were detected in lower frequencies of between 7% and 11%. Majority of isolates producing a combination of CTX-M-15 + OXA-1 + TEM-1 exhibited resistance phenotypes barely indistinguishable from those of CMT-producers. Although 73 (8%) isolates exhibited Inhibitor Resistant TEM-like (IRT) phenotype, bla_TEM-103 was the only true IRT-encoding gene identified in 18 (25%) of strains with this phenotype while the rest produced a combination of TEM-1 + OXA-1. The pAmpCs-like phenotype was observed in 94 (10%) isolates of which 77 (82%) carried bla_CMY-2 while 18% contained bla_CMY-1.

Isolates from urine accounted for 53%, 53%, 74% and 72% of strains exhibiting complex phenotypes such as IRT, ESBL, CMT or pAmpC respectively. On the contrary, 55% isolates from stool exhibited the relatively more susceptible NSBL-like phenotype. All the phenotypes, and majority of the bla genes, were detected both in isolates from hospitalized and non-hospitalized patients but complex phenotypes were particularly common among strains obtained between 2000 and 2010 from urine of hospitalized patients.

Conclusions

The phenotypes and diversity of bla genes in E. coli strains implicated in clinical infections in non-hospitalized and hospitalized patients in Kenya is worryingly high. In order to preserve the efficacy of β-lactam antibiotics, culture and susceptibility data should guide therapy and surveillance studies for β-lactamase-producers in developing countries should be launched.

First description of Escherichia coli producing CTX-M-15- extended spectrum beta lactamase (ESBL) in out-patients from south eastern Nigeria

We studied the presence of extended spectrum beta lactamases (ESBLs) in 44 clinical isolates of Escherichia coli collected from out-patients in two university teaching hospitals in South-Eastern Nigeria. Species identification was performed by standard microbiology methods and re-confirmed by MALDI-TOF technology. Phenotypic characterization of ESBL enzymes was done by double disc synergy test and presence of ESBL genes was determined by specific PCR followed by sequencing. Transfer of plasmid DNA was carried out by transformation using E. coli DH5 as recipient strain. Phenotypic characterization identified all isolates to be ESBL positive. 77% of strains were from urine, 13.6% from vaginal swabs and 9.0% from wound swabs. 63.6% were from female patients, 68% were from outpatients and 95.5% from patients younger than 30 years. All ESBL producers were positive in a PCR for bla_CTX-M-1 cluster, in exemplary strains bla_CTX-M-15 was found by sequencing. In all strains ISEcp1 was found upstream and ORF477 downstream of bla_CTX-M. PCR for bla_TEM and bla_OXA-1 was positive in 93.1% of strains, whereas bla_SHV was not detected, aac(6′)-Ib-cr was found in 97.7% of strains. RAPD analysis revealed seven different clonal groups named A through G with the majority of the strains (65.9%) belonging to clone A. Transfer of an ESBL plasmid with co-resistance to gentamicin, kanamycin, tobramycin, doxycycline and trimethropim-sulfamethoxazole was successful in 19 (43.2%) strains. This study showed a high rate of CTX-M-1 cluster - ESBLs in South-Eastern Nigeria and further confirms the worldwide spread of CTX-M ESBL in clinical isolates.

Antibiotic resistance patterns of Escherichia coli isolates from different aquatic environmental sources in León, Nicaragua

Antibiotic-resistant bacteria have emerged due to the selective pressure of antimicrobial use in humans and animals. Water plays an important role in dissemination of these organisms among humans, animals and the environment. We studied the antibiotic resistance patterns among 493 Escherichia coli isolates from different aquatic environmental sources collected from October 2008 to May 2009 in León, Nicaragua. High levels of antibiotic resistance were found in E. coli isolates in hospital sewage water and in eight of 87 well-water samples. Among the resistant isolates from the hospital sewage, ampicillin, chloramphenicol, ciprofloxacin, nalidixic acid, trimethoprim-sulphamethoxazole was the most common multi-resistance profile. Among the resistant isolates from the wells, 19% were resistant to ampicillin, ceftazidime, ceftriaxone, cefotaxime, chloramphenicol, ciprofloxacin, gentamicin, nalidixic acid and trimethoprim-sulphamethoxazole. E. coli producing ESBL and harbouring bla(CTX-M) genes were detected in one of the hospital sewage samples and in 26% of the resistant isolates from the well-water samples. The bla(CTX-M-9) group was more prevalent in E. coli isolates from the hospital sewage samples and the bla(CTX-M-1) group was more prevalent in the well-water samples.

Prevalence and pathogenesis of extended-spectrum beta-lactamase producing Escherichia coli causing urinary tract infection in hospitalized patients

A total of 296 E. coli strains isolated from hospitalized patients with urinary tract infection were included in this study. These strains were tested for their resistance to 22 antimicrobial drugs and the presence of ESBLs genes coding for TEM, SHV, OXA, and CTX-M. We further characterized them for their interaction with a renal cell line (A-498) and a gastrointestinal cell line (Caco-2). Strains were also typed using a combination of RAPD-PCR, PhP-typing and phylogenetic grouping. Only eight strains (2.7 %) were confirmed as ESBLs producers. The most common clonal type contained 35 isolates and only two of them were ESBLs producers and both showed a high degree of adhesion to both cell lines but only one was able to translocate in Caco-2 cells. These strains belonged to phylogenetic group B2, were resistant to nine antibiotics and carried CTX-M-type of ESBL. The remaining six strains belonged to single clones with different phylogenetic groups and ESBL genotypes and were resistant to between 12 and 15 antibiotics. They also showed a high rate of adhesion to A-498 cells (19 ± 2 to 35 ± 3 CFU/cell) and all translocated in this cell line. The rate of adhesion of ESBL-producing strains to Caco-2 cells (11 ± 3.4 CFU/cell) was significantly lower than A-498 cells (26 ± 8 CFU/cell) (p = 0.0002) and only four of them translocated in Caco-2 cells. Our results suggest that the ESBL-producing clones of E. coli have a potential to translocate and cause septicemia in hospitalized patients with UTI.

Transmission dynamics of extended-spectrum β-lactamase-producing Enterobacteriaceae in the tertiary care hospital and the household setting

Transmission of extended-spectrum β-lactamase (ESBL)–producing Enterobacteriaceae in households outweighs nosocomial dissemination in the non-outbreak setting. Importation of ESBL producers into the hospitals is as frequent as transmission during hospital stay. ESBL–Klebsiella pneumoniae might be more efficiently transmitted within the hospital than ESBL–Escherichia coli.

Background. Studies about transmission rates of extended-spectrum β-lactamase (ESBL)–producing Enterobacteriaceae in hospitals and households are scarce.

Methods. Eighty-two index patients with new carriage of ESBL-producing Escherichia coli (ESBL-Ec; n = 72) or ESBL-producing Klebsiella pneumoniae (ESBL-Kp; n = 10) and their hospital (n = 112) and household (n = 96) contacts were studied prospectively from May 2008 through September 2010. Isolates were phenotypically and molecularly characterized (sequencing of bla genes, repetitive extragenic palindromic polymerase chain reaction, pulse-field gel electrophoresis, and multilocus sequence typing). Transmission was defined as carriage of a clonally-related ESBL producer with identical bla_ESBL gene(s) in the index patient and his or her contact(s).

Results. CTX-M-15 was the most prevalent ESBL in ESBL-Ec (58%) and ESBL-Kp (70%) in the index patients. Twenty (28%) ESBL-Ec isolates were of the hyperepidemic clone ST131. In the hospital, transmission rates were 4.5% (ESBL-Ec) and 8.3% (ESBL-Kp) and the incidences of transmissions were 5.6 (Ec) and 13.9 (Kp) per 1000 exposure days, respectively. Incidence of ESBL-Kp hospital transmission was significantly higher than that of ESBL-Ec (P < .0001), despite implementation of infection control measures in 75% of ESBL-Kp index patients but only 22% of ESBL-Ec index patients. Detection of ESBL producers not linked to an index patient was as frequent (ESBL-Ec, 5.7%; ESBL-Kp, 16.7%) as nosocomial transmission events. In households, transmission rates were 23% for ESBL-Ec and 25% for ESBL-Kp.

Conclusions. Household outweighs nosocomial transmission of ESBL producers. The effect of hospital infection control measures may differ between different species and clones of ESBL producers.

Epidemiology of Escherichia coli, Klebsiella species, and Proteus mirabilis strains producing extended-spectrum β-lactamases from clinical samples in the Kinki Region of Japan

In the present study, nonduplicate, clinical isolates of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli, Klebsiella spp, and Proteus mirabilis were collected during a 10-year period from 2000 to 2009 at several hospitals in the Kinki region, Japan. The detection rate of E coli markedly increased from 0.24% to 7.25%. The detection rate of Klebsiella pneumoniae increased from 0% to 2.44% and that of P mirabilis from 6.97% to 12.85%. The most frequently detected genotypes were the CTX-M9 group for E coli, the CTX-M2 group for K pneumoniae, and the CTX-M2 group for P mirabilis. E coli clone O25:H4-ST131 producing CTX-M-15, which is spreading worldwide, was first detected in 2007. The most common replicon type of E coli was the IncF type, particularly FIB, detected in 466 strains (69.7%). Of the K pneumoniae strains, 47 (55.3%) were of the IncN type; 77 P mirabilis strains (96.3%) were of the IncT type. In the future, the surveillance of various resistant bacteria, mainly ESBL-producing Enterobacteriaceae, should be expanded to prevent their spread.

Incidence of temonera, sulphuhydryl variables and cefotaximase genes associated with β-lactamase producing escherichia coli in clinical isolates

Background:

the occurrence of the different types of Extended spectrum beta Lactamase producing Escherichia coli with the, Sulphurhydryl variable, Temonera and the Cefotaximase have been on the rise

Aim:

The study was to determine the prevalence of extended spectrum beta lactamase gene resistance across the clinical isolates of hospitalized patients.

Materials and Method:

Three hundred and fifty isolates of Escherichia coli were received from different clinical specimens. The susceptibility profile of the isolates against 10 different antibiotics was examined, the MICs (Minimum Inhibitory Concentration) for ceftazidime were also determined using micro-broth dilution assay. Isolates showing MIC ≥ 6 μg/ml for ceftazidime were screened for ESBL (PCT)phenotypic confirmatory test and subjected to PCR (polymerase chain reaction) to further.

Results:

By disk diffusion test, there was resistance to ceftazidime and cefotaxime were 180(51.4%) and 120 (34.2%) respectively. However, all strains were susceptible to imipenem. 250 isolates showed MICs≥ 6 μg/ml for ceftazidime of which 180 (72%) were positive for extended spectrum beta lactamase. The prevalence of Sulphurhydryl variable, Temonera and the Cefotaximase among these isolates were 17.1%, 6.6% and 17%, respectively.

Conclusion:

For the identification of extended spectrum beta lactamase producing isolates it is recommended that clinical laboratories adopt simple test based on Cinical laboratory standard institute recommendation for confirming extended spectrum beta lactamase production in enterobacteriacea species.

Human-associated extended-spectrum β-lactamase in the Antarctic

Escherichia coli bacteria with extended-spectrum β-lactamase (ESBL) type CTX-M resistance were isolated from water samples collected close to research stations in Antarctica. The isolates had bla(CTX-M-1) and bla(CTX-M-15) genotypes and sequence types (ST) indicative of a human-associated origin. This is the first record of ESBL-producing enterobacteria from Antarctica.

Molecular characterization of CTX-Mβ-lactamases among Klebsiella pneumoniae isolated from patients at Tehran hospitals

PURPOSE

Plasmid-encoded CTX-M-group of extended-spectrum β-lactamases (ESBLs) represent a significant and rapidly emerging problem in most part of the world. The aim of the present study was to describe the prevalence of CTX-M producing Klebsiella pneumoniae at Tehran hospitals.

MATERIALS AND METHODS

Clinical isolates of K. pneumoniae (n=250) were collected from 10 hospitals of Tehran. Susceptibility to antimicrobial agents, MIC of cefotaxime and ESBLs production of collected isolates were detected. All ESBL-producing isolates were screened for bla CTX-M genes using PCR and DNA sequencing. Molecular typing of bla(CTX-M) harboring isolates was performed by Pulsed-field gel electrophoresis assay.

RESULTS

Of 250 K. pneumoniae clinical isolates, 102 isolates revealed ESBLs - phenotype. PCR assay and sequencing detected bla(CTX-M) genes in 71.5% (n= 73) of ESBL-producing isolates. The prevalence of CTX-M -I and CTX-M-III clusters among these isolates was 35.61% (n=26) and 21.9 % (n=16) respectively. Coexistence of CTX-M -I and CTX-M-III clusters was found among 42.5% (n= 31) of isolates. Of 102 isolates that were positive in the phenotypic confirmatory test (PCT), 29 isolates (28.4%) did not produce any amplicons in PCR for bla(CTX-M) gene. The results of PCR for CTX-M -II and CTX-M-IV clusters were also negative. Analysis of the 31 CTX-M producing K. pneumoniae isolates by PFGE typing showed 26 distinct patterns.

CONCLUSIONS

The bla CTX-M genes are widespread among Iranian isolates of K. pneumoniae. PFGE demonstrated the high diversity of K. pneumoniae harboring bla(CTX-M) in our study.

Phylogenetic groups and cephalosporin resistance genes of Escherichia coli from diseased food-producing animals in Japan

A total of 318 Escherichia coli isolates obtained from different food-producing animals affected with colibacillosis between 2001 and 2006 were subjected to phylogenetic analysis: 72 bovine isolates, 89 poultry isolates and 157 porcine isolates. Overall, the phylogenetic group A was predominant in isolates from cattle (36/72, 50%) and pigs (101/157, 64.3%) whereas groups A (44/89, 49.4%) and D (40/89, 44.9%) were predominant in isolates from poultry. In addition, group B2 was not found among diseased food-producing animals except for a poultry isolate. Thus, the phylogenetic group distribution of E. coli from diseased animals was different by animal species. Among the 318 isolates, cefazolin resistance (minimum inhibitory concentrations: ≥32 μg/ml) was found in six bovine isolates, 29 poultry isolates and three porcine isolates. Of them, 11 isolates (nine from poultry and two from cattle) produced extended spectrum β-lactamase (ESBL). The two bovine isolates produced bla_CTX-M-2, while the nine poultry isolates produced bla_CTX-M-25 (4), bla_SHV-2 (3), bla_CTX-M-15 (1) and bla_CTX-M-2 (1). Thus, our results showed that several types of ESBL were identified and three types of β-lactamase (SHV-2, CTX-M-25 and CTX-M-15) were observed for the first time in E. coli from diseased animals in Japan.

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.

Susceptibility of extended-spectrum-beta-lactamase-producing Enterobacteriaceae according to the new CLSI breakpoints

In 2010 the Clinical and Laboratory Standards Institute (CLSI) lowered the susceptibility breakpoints of some cephalosporins and aztreonam for Enterobacteriaceae and eliminated the need to perform screening for extended-spectrum β-lactamases (ESBLs) and confirmatory tests. The aim of this study was to determine how many ESBL-producing strains of three common species of Enterobacteriaceae test susceptible using the new breakpoints. As determined with the CLSI screening and confirmatory tests, 382 consecutive ESBL-producing strains were collected at Huashan Hospital between 2007 and 2008, including 158 strains of Escherichia coli, 164 of Klebsiella pneumoniae, and 60 of Proteus mirabilis. Susceptibility was determined by the CLSI agar dilution method. CTX-M-, TEM-, and SHV-specific genes were determined by PCR amplification and sequencing. bla(CTX-M) genes alone or in combination with bla(SHV) were present in 92.7% (354/382) of these ESBL-producing strains. Forty-two (25.6%) strains of K. pneumoniae harbored SHV-type ESBLs alone or in combination. No TEM ESBLs were found. Utilizing the new breakpoints, all 382 strains were resistant to cefazolin, cefotaxime, and ceftriaxone, while 85.0 to 96.7% of P. mirabilis strains tested susceptible to ceftazidime, cefepime, and aztreonam, 41.8 to 45.6% of E. coli strains appeared to be susceptible to ceftazidime and cefepime, and 20.1% of K. pneumoniae were susceptible to cefepime. In conclusion, all ESBL-producing strains of Enterobacteriaceae would be reported to be resistant to cefazolin, cefotaxime, and ceftriaxone by using the new CLSI breakpoints, but a substantial number of ESBL-containing P. mirabilis and E. coli strains would be reported to be susceptible to ceftazidime, cefepime, and aztreonam, which is likely due to the high prevalence of CTX-M type ESBLs.

Association of IS5 with divergent tandem blaCMY-2 genes in clinical isolates of Escherichia coli

OBJECTIVE

To characterize a unique tandem bla(CMY-2) gene arrangement found in two non-identical clinical strains of Escherichia coli.

METHODS

Both plasmid and chromosomal DNA were evaluated using PFGE, restriction digest analysis, plasmid profiling and Southern hybridization. bla(CMY-2) gene expression and gene copy number were evaluated by real-time PCR. Susceptibilities to selected β-lactam antibiotics were determined by agar dilution.

RESULTS

A tandem arrangement for bla(CMY-2) was identified in both isolates and was the only arrangement for bla(CMY-2) observed. These isolates had distinct PFGE and plasmid profiles. Each strain exhibited 2-fold higher bla(CMY-2) mRNA expression and up to 8-fold lower β-lactam susceptibility compared with a strain with a single copy of bla(CMY-2).

CONCLUSION

This is the first report of IS5 being associated with tandem bla(CMY-2). IS5 has previously been associated with antibiotic resistance through tandem gene amplification. The unique tandem arrangement provides a mechanism for increased bla(CMY-2) expression.

Analysis of risk factors for a high prevalence of extended-spectrum {beta}-lactamase-producing Enterobacteriaceae in asymptomatic individuals in rural Thailand

The prevalence of and risk factors associated with extended-spectrum β-lactamase (ESBL)-producing micro-organisms have not been well studied in healthy individuals. The aim of this study was to determine this in healthy individuals in Thailand. Stool samples and questionnaires obtained from 445 participants from three provinces in Thailand were analysed. The antimicrobial susceptibility of the isolates was assessed using phenotypic and genotypic methods. PCR analysis was performed to detect and group the bla(CTX-M) genes. The prevalence of CTX-M-type ESBL-producing Enterobacteriaceae in the three provinces was as follows: 29.3 % in Nan (43/147), 29.9 % in Nakhon Si Thammarat (43/144) and 50.6 % in Kanchanaburi (78/154) (P<0.001). Of the 445 samples, 33 (7.4 %), 1 (0.2 %) and 127 (28.5 %) isolates belonged to the bla(CTX-M) gene groups I, III and IV, respectively. Escherichia coli was the predominant member of the Enterobacteriaceae producing CTX-M-type ESBLs (40/43, 39/43 and 70/78 isolates in Nan, Nakhon Si Thammarat and Kanchanaburi, respectively). No statistically significant association was observed between the presence of ESBL-producing bacteria and gender, age, education, food habits or antibiotic usage. However, the provinces that had the highest prevalence of ESBL-producing Enterobacteriaceae also had the highest prevalence of use and purchase of antibiotics without a prescription. Thus, this study revealed that faecal carriage of ESBL-producing Enterobacteriaceae is very high in asymptomatic individuals in Thailand, with some variations among the provinces. This high prevalence may be linked to antibiotic abuse.

Antibiotic resistance patterns of intestinal Escherichia coli isolates from Nicaraguan children

In developing countries, diarrhoeal diseases are one of the major causes of death in children under 5 years of age. It is known that diarrhoeagenic Escherichia coli (DEC) is an important aetiological agent of infantile diarrhoea in Nicaragua. However, there are no recent studies on antimicrobial resistance among intestinal E. coli isolates in Nicaraguan children. The aim of the present study was to determine the antimicrobial resistance pattern in a collection of 727 intestinal E. coli isolates from the faeces of children in León, Nicaragua, between March 2005 and September 2006. All samples had been screened previously for the presence of DEC by multiplex PCR. Three hundred and ninety-five non-DEC isolates (270 from children with diarrhoea and 125 from children without diarrhoea) and 332 DEC isolates (241 from children with diarrhoea and 91 from children without diarrhoea) were analysed in this study. In general, antimicrobial resistance among the 727 intestinal E. coli isolates was high for ampicillin (60 %), trimethoprim–sulfamethoxazole (64 %) and chloramphenicol (11 %). Among individual E. coli categories, enteroaggregative E. coli isolates from children with and without diarrhoea exhibited significantly higher levels of resistance (P<0.05) to ampicillin and trimethoprim–sulfamethoxazole compared to the other E. coli categories. Resistance to ceftazidime and/or ceftriaxone and a pattern of multi-resistance was related to CTX-M-5- or CTX-M-15-producing E. coli isolates. The results suggest that E. coli isolates from Nicaraguan children have not reached the high levels of resistance to the most common antibiotics used for diarrhoea treatment as in other countries.

Study of CTX-M Type of Extended Spectrum β-Lactamase among Nosocomial Isolates of Escherichia coli and Klebsiella pneumoniae in South India

Data on CTX-M type extended-spectrum β-lactamase (ESBL) produced by Gram-negative bacteria by molecular methods are limited from India. This study was conducted to investigate the prevalence of CTX-M type ESBL producing Escherichia coli and Klebsiella pneumoniae from nosocomial isolates in a tertiary care hospital in southern India. A total of 179 clinical isolates of K. pneumoniae (n = 72) and E. coli (n = 107) were obtained in a period of 3 months and assessed for ESBL production phenotypically. Associated resistance to a panel of antibiotics and Minimum Inhibitory Concentration for 3rd generation cephalosporins was determined. Phenotypically ESBL positive isolates were subjected to PCR for blaCTX-M gene using two sets of primers for the simultaneous detection of all the five major groups of CTX-M types. All the positive isolates were then subjected to a group specific PCR to detect the prevalent group. Out of 179 isolates, 156 (87.1%) were positive for ESBL phenotypically, which includes 39.2% of K. pneumoniae and 60.8% of E. coli. All of them were examined by PCR using two primers for the presence of blaCTX-M genes. Among the 156 phenotypic positive isolates, 124 (79.4%) were positive for blaCTX-M genes, of which 45 (36.2%) were K. pneumoniae, 79 (63.7%) were E. coli. When the 124 positive clinical isolates were further tested with CTX-M group-specific primers, all were positive for the CTX-M-1 group. Our findings document evidence of the high prevalence of multidrug resistant CTX-M group 1 type ESBL among nosocomial isolates in this region. High co-resistance to other non-β-lactam antibiotics is a major challenge for management of ESBL infections. This is alarming and calls for the judicious use of carbapenems, especially in developing countries. This has significant implications for patient management, and indicates the need for increased surveillance and for further molecular characterization of these isolates.

CTX-M-producing non-Typhi Salmonella spp. isolated from humans, United States

CTX-M-type beta-lactamases are increasing among US Enterobacteriaceae isolates. Of 2,165 non-Typhi Salmonella isolates submitted in 2007 to the National Antimicrobial Resistance Monitoring System, 100 (4.6%) displayed elevated MICs (≥2 mg/L) of ceftriaxone or ceftiofur. Three isolates (serotypes Typhimurium, Concord, and I 4,5,12:i:-) contained bla(CTX-M-5), bla(CTX-M-15), and bla(CTX-M-55/57), respectively.

Antibiotic-resistant Escherichia coli bacteria, including strains with genes encoding the extended-spectrum beta-lactamase and QnrS, in waterbirds on the Baltic Sea Coast of Poland

Individual cloacal swabs of mallards (Anas platyrhynchos) and of herring gulls (Larus argentatus), as well as samples of waterbird feces obtained in 2008 and 2009, were cultivated for Escherichia coli. Isolates of E. coli were tested for susceptibilities to 12 antimicrobial agents by the disk diffusion method. Moreover, the samples were subcultivated on MacConkey agar (MCA) containing cefotaxime (2 mg liter(-1)) to detect E. coli with extended-spectrum beta-lactamase (ESBL) and subsequently on MCA supplemented with ciprofloxacin (0.05 mg liter(-1)) and MCA with nalidixic acid (20 mg liter(-1)) to isolate fluoroquinolone-resistant E. coli. PCR was used to detect specific antibiotic resistance genes. We found 9 E. coli isolates producing ESBL with bla genes: bla(CTX-M-1) (6 isolates), bla(CTX-M-9) plus bla(TEM-1b) (1 isolate), bla(CTX-M-15) plus bla(OXA-1) (1 isolate), and bla(SHV-12) (1 isolate). In the isolate with bla(CTX-M-15), the gene aac(6)-Ib-cr was also detected. The bla genes were harbored by transferable plasmids of the IncN and IncI1 groups. Nine quinolone-resistant E. coli isolates with qnrS genes were found and characterized. The gene qnrS was associated with a Tn3-like transposon on the IncX1 plasmid together with bla(TEM-1) in two isolates. The gene qnrS was also harbored by conjugative plasmids of the IncN and IncX2 groups. Even if populations of wild birds are not directly influenced by antibiotic practice, we have demonstrated that antibiotic-resistant E. coli strains, including strains with various ESBL and qnrS genes, are found in the feces of wild birds on the coast of the Baltic Sea in Poland.

Determinants of beta-lactam resistance in meningitis-causing Enterobacteriaceae in Brazil

This study analyzed resistance determinants in extended-spectrum beta-lactamase (ESBL)-producing enterobacteria and the epidemiology of 11 Escherichia coli isolates obtained from meningitis patients in a region of Brazil from 2000 to 2005. ESBL-encoding genes and their genetic environment were investigated by PCR and sequencing. The gene blaCTX-M-2 was identified in 3 different enterobacteria (E. coli, Serratia marcescens, and Proteus mirabilis) downstream of the insertion sequence ISCR1 (localized in class 1 integrons), but not as part of the resistance cassettes region. Multilocus sequence typing (MLST) was used to investigate genetic relationships between the 11 E. coli isolates in this study and strains associated with meningitis in the E. coli MLST database. MLST analysis indicated high genetic diversity among isolates, and no significant genetic relationship was identified with meningitis-causing E. coli in the database. The results in this report reinforce the need to be attentive to meningitis suspected to be due to ESBL-producing enterobacterial isolates, especially where ESBL epidemiology is well known.

Foreign travel is a major risk factor for colonization with Escherichia coli producing CTX-M-type extended-spectrum beta-lactamases: a prospective study with Swedish volunteers

Foreign travel has been suggested to be a risk factor for the acquisition of extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae. To our knowledge, this has not previously been demonstrated in a prospective study. Healthy volunteers traveling outside Northern Europe were enrolled. Rectal swabs and data on potential travel-associated risk factors were collected before and after traveling. A total of 105 volunteers were enrolled. Four of them did not complete the study, and one participant carried ESBL-producing Escherichia coli before travel. Twenty-four of 100 participants with negative pretravel samples were colonized with ESBL-producing Escherichia coli after the trip. All strains produced CTX-M enzymes, mostly CTX-M-15, and some coproduced TEM or SHV enzymes. Coresistance to several antibiotic subclasses was common. Travel to India was associated with the highest risk for the acquisition of ESBLs (88%; n = 7). Gastroenteritis during the trip was an additional risk factor (P = 0.003). Five of 21 volunteers who completed the follow-up after 6 months had persistent colonization with ESBLs. This is the first prospective study demonstrating that international travel is a major risk factor for colonization with ESBL-producing Enterobacteriaceae. Considering the high acquisition rate of 24%, it is obvious that global efforts are needed to meet the emergence and spread of CTX-M enzymes and other antimicrobial resistances.

Distribution of bla(TEM), bla(SHV), bla(CTX-M) genes among clinical isolates of Klebsiella pneumoniae at Labbafinejad Hospital, Tehran, Iran

Extended-spectrum beta-lactamase (ESBL)-producing isolates of Klebsiella pneumoniae have been increasingly recognized in the hospital settings in Iran as well as throughout the world. The aim of this study was to detect and determine the genes encoding the ESBLs including bla(TEM), bla(SHV), and bla(CTX-M) groups among the K. pneumoniae isolates at Labbafinejad Hospital by polymerase chain reaction (PCR) and characterize them by direct sequencing of PCR products. Eighty-nine isolates were isolated from patients at different wards during March 2008-March 2009. They were identified as K. pneumoniae using biochemical tests. Susceptibility of isolates to 17 different antimicrobial agents was determined using agar disk diffusion method. The phenotypic confirmatory test was used to screen the isolates for production of ESBLs. To amplify the bla(SHV) the template DNA was extracted by boiling method. Plasmid DNA was extracted using minipreparation kit and used as template in PCR for detection of bla(TEM) and bla(CTX-M). The selected PCR products were sequenced and analyzed. All 89 strains were susceptible to imipenem. The rates of resistance to different antibiotics were in the following order: aztronam (79.7%), cefexime (67.4%), cefpodoxime (66.2%), cefotaxime (65.1%), ceftazidime (61.7%). The phenotypic confirmatory test detected 62 isolates (69.7%) as ESBL-producing K. pneumoniae. The prevalence of genes encoding ESBLs were as follows: bla(TEM) 54% (n = 48), bla(SHV) 67.4% (n = 60), bla(CTX-M-I) 46.51% (n = 40), and bla(CTX-M-III) 29% (n = 25). The bla(CTX-M-II) and bla(CTX-M-IV) were not detected. All bla(TEM) types were characterized as bla(TEM-1) and all bla(CTX-M-I) were identified as bla(CTX-M-15). The SHV types were characterized as SHV-5, SHV-11, and SHV-12. The rate of ESBL at Labbafinejad Hospital was 25% increase in a 4-year study that ended in March 2009. It appears that bla(TEM-1), bla(SHV-5), bla(SHV-11), bla(SHV-12), and bla(CTX-M-15) are the dominant ESBLs among the resistant strains of K. pneumoniae in Iran.

Evaluation of a commercial microarray system for detection of SHV-, TEM-, CTX-M-, and KPC-type beta-lactamase genes in Gram-negative isolates

We evaluated the ability of a commercial microarray system (Check KPC/ESBL; Check-Points Health BV) to detect clinically important class A beta-lactamase genes. A total of 106 Gram-negative strains were tested. The following sensitivity and specificity results were recorded, respectively: for bla(SHV), 98.8% and 100%; for bla(TEM), 100% and 96.4%; and for bla(CTX-M) and bla(KPC), 100% and 100%.

Prevalência das famílias TEM, SHV e CTX-M de β-lactamases de espectro estendido em Escherichia coli e Klebsiella spp no Hospital Universitário de Santa Maria, Estado do Rio Grande do Sul

Neste estudo estimou-se a distribuição e prevalência de β-lactamases de espectro estendido pertencentes às famílias TEM, SHV e CTX-M entre amostras de Escherichia coli e Klebsiella spp. no Hospital Universitário de Santa Maria, Rio Grande do Sul. Durante 14 meses, 90 microrganismos foram selecionados como prováveis produtores de ESBL. Os isolados foram submetidos a testes fenotípicos confirmatórios para a presença de ESBL. A seguir, os tipos de ESBLs presentes em cada microrganismo foram determinados através da pesquisa dos respectivos genes através da reação em cadeia da polimerase. Empregando-se o método do disco combinado, a presença de ESBLs foi confirmada em 55 (61,1%) amostras; quando o método do duplo disco foi utilizado, 57 (63,3%) amostras foramprodutoras de ESBLs. Com base na PCR, as ESBLs do tipo TEM e SHV foram mais presentes em Klebsiella pneumoniae enquanto que ESBL do tipo CTX-M foram mais presentes em Klebsiella oxytoca.

Phenotypic and molecular characterization of a novel beta-lactamase carried by Klebsiella pneumoniae, CTX-M-72, derived from CTX-M-3

This study reports phenotypic and molecular characterization of a novel CTX-M beta-lactamase carried by two Klebsiella pneumoniae isolates collected from two hospitals in China. Conjugation experiment, Southern hybridization, susceptibility testing, isoelectric focusing, PCR, and sequencing techniques as well as clone, expression, purification and kinetics were carried out to describe the characterization of the novel CTX-M-type enzyme. The analyses of plasmid profiling and pulsed-field gel electrophoresis of the novel enzyme were performed to investigate epidemiology. The PCR products had 967 nucleotides and a novel CTX-M enzyme with a pI of 8.5 was implicated in this resistance: CTX-M-72. Two strains exhibited a clavulanic acid-inhibited substrate profile that included extended-spectrum cephalosporins. The amino acid sequence of the CTX-M-72 beta-lactamase differed from that of the CTX-M-3 beta-lactamase by the Arg-->Gly change at position 164. The novel enzyme was susceptible to ceftazidime, the same response being observed for other CTX-M enzymes. The substrates of the beta-lactamase were also characterized. Furthermore, two resistant genes of clinical strains were closely related. The emergence of a novel CTX-M-type extended-spectrum beta-lactamase was rarely described in other areas. This study illustrated the importance of molecular surveillance in tracking CTX-M-producing strains in large teaching hospitals, suggested the horizontal transfer of plasmid-borne bla(CTX-M) genes contributed to the dissemination of CTX-M enzymes in hospital environments, and emphasized the need for epidemiological monitoring.

A 7-year surveillance for ESBL-producing Escherichia coli and Klebsiella pneumoniae at a university hospital in Taiwan: the increase of CTX-M-15 in the ICU

To monitor the changing trend of extended-spectrum beta-lactamase (ESBL)-producing bacteria, a 7-year continuous study was launched in 2001 at the largest tertiary hospital in Taiwan. A significant increase over the study period was evident for ESBL-producing isolates of Escherichia coli (4.8-10.0%) and Klebsiella pneumoniae (15.0-23.4%). Molecular investigation conducted in three separate periods revealed the prevalent ESBL types and their genetic relatedness. CTX-M-producing isolates (73.8%) were more prevalent than SHV-type ESBLs (37.0%), the most frequent being CTX-M-14 (34.3%), CTX-M-3 (25.9%), and SHV-12 (25.7%). However, a marked increase of CTX-M-15-producing isolates from 2.1% in 2002 to 29.6% in 2007 was also noted. The increase of ESBL-producing isolates in both species may be mainly due to the horizontal transmission of resistance plasmids, while clonal expansion of some epidemic strains further added to the dispersion of ESBL-producing K. pneumoniae.

Genetic analysis of multi-drug resistance and the clonal dissemination of beta-lactam resistance in Salmonella Infantis isolated from broilers

An epidemiologic study was conducted to investigate the incidence and characterize the antimicrobial resistance determinants, analyzing plasmid profiles, and establishing the genetic relationship among beta-lactam-resistant isolates of Salmonella Infantis from broilers in Southern Japan. A total of 120 isolates were recovered from 56 flocks belonging to 44 holdings during 2004-2006. The percentages of resistance were as follows: ampicillin (24%), cephalothin (23%), cefoxitin (0%), ceftazidime (11%), cefotaxime (11%), chloramphenicol (0%), kanamycin (7.5%), ofloxacin (20%), oxytetracycline, streptomycin and sulfamethoxazole (100%) and trimethoprim (75%). The incidence of bla(TEM)-encoded beta-lactam resistance in 2004-2006 was significantly higher than in 1998-2003 (P<0.001). BlnI-digested PFGE patterns generated two related clusters implicated in the dissemination of beta-lactam resistance. Two types of plasmid profiles were observed and two plasmids of ca. 50 and 180-kb size were carried by beta-lactam-resistant isolates. Streptomycin resistance was conferred by aadA1 (n=116), aadA1-aadA2 (n=1), and aadA1-strA-strB (n=3). Resistances to kanamycin, oxytetracycline, sulfamethoxazole and trimethoprim were conferred by aphA1 (n=9, 100%), tetA (n=120, 100%) sul1 (n=120, 100%) and dfrA5 (n=90, 100%), respectively. Two types of class 1 integrons were detected: 1.0 kb (n=120) and, 1.0/1.5 kb (n=3). Integrons of 1.0/1.5 kb were found in isolates with the aadA1-strA-strB gene combination. For the first time, all S. Infantis isolates showed resistance to at least three classes of antimicrobial agents; and the intestinal tract of healthy poultry was a reservoir of the extended-spectrum cephalosporin-resistant isolates of serovar Infantis.

Dissemination of Escherichia coli with CTX-M type ESBL between humans and yellow-legged gulls in the south of France

Extended Spectrum beta-Lactamase (ESBL) producing Enterobacteriaceae started to appear in the 1980s, and have since emerged as some of the most significant hospital-acquired infections with Escherichia coli and Klebsiella being main players. More than 100 different ESBL types have been described, the most widespread being the CTX-M beta-lactamase enzymes (bla(CTX-M) genes). This study focuses on the zoonotic dissemination of ESBL bacteria, mainly CTX-M type, in the southern coastal region of France. We found that the level of general antibiotic resistance in single randomly selected E. coli isolates from wild Yellow-legged Gulls in France was high. Nearly half the isolates (47.1%) carried resistance to one or more antibiotics (in a panel of six antibiotics), and resistance to tetracycline, ampicillin and streptomycin was most widespread. In an ESBL selective screen, 9.4% of the gulls carried ESBL producing bacteria and notably, 6% of the gulls carried bacteria harboring CTX-M-1 group of ESBL enzymes, a recently introduced and yet the most common clinical CTX-M group in France. Multi locus sequence type and phylogenetic group designations were established for the ESBL isolates, revealing that birds and humans share E. coli populations. Several ESBL producing E. coli isolated from birds were identical to or clustered with isolates with human origin. Hence, wild birds pick up E. coli of human origin, and with human resistance traits, and may accordingly also act as an environmental reservoir and melting pot of bacterial resistance with a potential to re-infect human populations.

Characterization of CTX-M ESBLs in Enterobacter cloacae, Escherichia coli and Klebsiella pneumoniae clinical isolates from Cairo, Egypt

Background

A high rate of resistance to 3^rd generation cephalosporins among Enterobacteriaceae isolates from Egypt has been previously reported. This study aims to characterize the resistance mechanism (s) to extended spectrum cephalosporins among resistant clinical isolates at a medical institute in Cairo, Egypt.

Methods

Nonconsecutive Klebsiella pneumoniae (Kp), Enterobacter cloacae (ENT) and Escherichia coli (EC) isolates were obtained from the clinical laboratory at the medical institute. Antibiotic susceptibility was tested by CLSI disk diffusion and ESBL confirmatory tests. MICs were determined using broth microdilution. Isoelectric focusing (IEF) was used to determine the pI values, inhibitor profiles, and cefotaxime (CTX) hydrolysis by the β-lactamases. PCR and sequencing were performed using bla_CTX-M and ISEcp1-specific primers, with DNA obtained from the clinical isolates. Conjugation experiments were done to determine the mobility of bla_CTX-M.

Results

All five clinical isolates were resistant to CTX, and were positive for ESBL screening. IEF revealed multiple β-lactamases produced by each isolate, including a β-lactamase with a pI of 8.0 in Kp and ENT and a β-lactamase with a pI of 9.0 in EC. Both β-lactamases were inhibited by clavulanic acid and hydrolyzed CTX. PCR and sequence analysis identified bla_CTX-M-14 in Kp and ENT and a bla_CTX-M-15 in EC. Both bla_CTX-M-14 and bla_CTX-M-15 were preceded by ISEcp1 elements as revealed by partial sequence analysis of the upstream region of the bla_CTX-M genes. bla_CTX-M-15 was transferable but not bla_CTX-M-14.

Conclusion

This is the first report of CTX-M-14 in Kp and ENT isolates from Egypt, the Middle East and North Africa.

Prevalence of plasmid-mediated quinolone resistance determinants in ESBL Enterobacteriaceae clinical isolates over a 1-year period in a French hospital

The prevalence of plasmid-mediated quinolone resistance (PMQR) determinants (qnrA, qnrB, qnrS, aac(6')-Ib-cr, and qepA) was investigated in a collection of 47 extended-spectrum β-lactamase (ESBL) producing enterobacterial isolates with reduced susceptibility to fluoroquinolones, recovered at Nantes University hospital, in 2006. qnr, aac(6')-Ib-cr, and qepA genes were screened by PCR, and positive results were subsequently confirmed by sequencing. The epidemiological relationship between positive isolates was studied by pulsed-field gel electrophoresis (PFGE). qnr-positive isolates were analyzed for antimicrobial susceptibility and presence of mutations in the quinolone resistance-determining region (QRDR) of gyrA and parC genes. ESBL genes were characterized by PCR and sequencing. Conjugation experiments were performed to determine whether the qnr-carrying plasmids were self-transferable. Two Klebsiella pneumoniae isolates (4.3%), not clonally related, harboured a qnrS1 gene, whereas no qnrA- or qnrB-positive isolate was detected. The aac(6')-Ib-cr gene was detected in 11 Escherichia coli and one K. pneumoniae isolates. None of the 47 isolates carried the qepA gene. ESBLs associated with QnrS1 were CTX-M-14 and CTX-M-15. The CTX-M-15 producing isolate was highly resistant to fluoroquinolones and harboured three mutations in the QRDR and two PMQR determinants (qnrS1 and aac(6')-Ib-cr). The CTX-M-14-producing isolate exhibited reduced susceptibility or resistance to fluoroquinolones without resistance to nalidixic acid. This strain harboured only a qnr gene on a single 170 kb transferable plasmid, without any mutation in the QRDR. In conclusion, our study showed that aac(6')-Ib-cr gene had occurred in multiclonal ESBL-producing enterobacterial isolates collected at Nantes University hospital in 2006, with a higher prevalence than qnr genes.