A preliminary survey of extended-spectrum beta-lactamases (ESBLs) in clinical isolates of Klebsiella pneumoniae and Escherichia coli in Japan

Disappearance and prevalence of extended-spectrum β-lactamase-producing Escherichia coli and other coliforms in the wastewater treatment process

Antibiotic-resistant bacteria (ARBs) can now be detected not only in clinical institutions but also in wastewater treatment plants (WWTPs), extending the range of emergence to residential areas. In this study, we investigated the change of antibiotic-resistant Escherichia coli (E. coli) and other coliforms in each treatment process at WWTPs. Throughout the treatment process, the numbers of E. coli and other coliforms were significantly reduced to less than 5.7 ± 0.5 CFU/100 ml and 2.4 ± 0.0×102 CFU/100 ml, respectively. However, ESBL-producing E. coli and other coliforms were detected in each treatment process (even after chlorination) at 5.6% and 4.8%, compared to the total E. coli and other coliforms counts. Then, ESBL-producing-related genes were identified via PCR analyses, and the most predominant gene was CTX-M-9 in both E. coli (47.2%) and other coliforms (47.3%). Although actual WWTPs greatly reduced the number of bacteria, the relative prevalence of ESBL-producing bacteria was increased, suggesting that ESBL-producing bacteria remain in the effluent at minimal concentrations and could be diffusing to water bodies.

Whole-genome analyses of extended-spectrum or AmpC β-lactamase-producing Escherichia coli isolates from companion dogs in Japan

The emergence and global spread of extended-spectrum or AmpC β-lactamase (ESBL/AmpC)-producing Enterobacteriaceae in companion animals have led to the hypothesis that companion animals might be reservoirs for cross-species transmission because of their close contact with humans. However, current knowledge in this field is limited; therefore, the role of companion animals in cross-species transmission remains to be elucidated. Herein, we studied ESBL/AmpC-producing Enterobacteriaceae, Escherichia coli in particular, isolated from extraintestinal sites and feces of companion dogs. Whole-genome sequencing analysis revealed that (i) extraintestinal E. coli isolates were most closely related to those isolated from feces from the same dog, (ii) chromosomal sequences in the ST131/C1-M27 clade isolated from companion dogs were highly similar to those in the ST131/C1-M27 clade of human origin, (iii) certain plasmids, such as IncFII/pMLST F1:A2:B20/bla_CTX-M-27, IncI1/pMLST16/bla_CTX-M-15, or IncI1/bla_CMY-2 from dog-derived E. coli isolates, shared high homology with those from several human-derived Enterobacteriaceae, (iv) chromosomal bla_CTX-M-14 was identified in the ST38 isolate from a companion dog, and (v) eight out of 14 tested ESBL/AmpC-producing E. coli isolates (i.e., ST131, ST68, ST405, and ST998) belonged to the human extraintestinal pathogenic E. coli (ExPEC) group. All of the bla-coding plasmids that were sequenced genome-wide were capable of horizontal transfer. These results suggest that companion dogs can spread ESBL/AmpC-producing ExPEC via their feces. Furthermore, at least some ESBL/AmpC-producing ExPECs and bla-coding plasmids can be transmitted between humans and companion dogs. Thus, companion dogs can act as an important reservoir for ESBL/AmpC-producing E. coli in the community.

Antibiogram Signatures of Some Enterobacteria Recovered from Irrigation Water and Agricultural Soil in two District Municipalities of South Africa

This study was undertaken to evaluate the antibiogram fingerprints of some Enterobacteria recovered from irrigation water and agricultural soil in two District Municipalities of the Eastern Cape Province, South Africa using standard culture-based and molecular methods. The prevalent resistance patterns in the isolates follow the order: Salmonella enterica serovar Typhimurium [tetracycline (92.3%), ampicillin (69.2%)]; Enterobacter cloacae [amoxicillin/clavulanic acid (77.6%), ampicillin (84.5%), cefuroxime (81.0%), nitrofurantoin (81%), and tetracycline (80.3%)]; Klebsiella pneumoniae [amoxicillin/clavulanic acid (80.6%), ampicillin (88.9%), and cefuroxime (61.1%)]; and Klebsiella oxytoca [chloramphenicol (52.4%), amoxicillin/clavulanic acid (61.9%), ampicillin (61.9%), and nitrofurantoin (61.9%)]. Antibiotic resistance genes detected include tetC (86%), sulII (86%), and bla_AmpC (29%) in Salmonella enterica serovar Typhimurium., tetA (23%), tetB (23%), tetC (12%), sulI (54%), sulII (54%), catII (71%), bla_AmpC (86%), bla_TEM (43%), and bla_PER (17%) in Enterobacter cloacae., tetA (20%), tetC (20%), tetD (10%), sulI (9%), sulII (18%), FOX (11%) and CIT (11%)-type plasmid-mediated AmpC, bla_TEM (11%), and bla_SHV (5%) in Klebsiella pneumoniae and bla_AmpC (18%) in Klebsiella oxytoca. Our findings document the occurrence of some antibiotic-resistant Enterobacteria in irrigation water and agricultural soil in Amathole and Chris Hani District Municipalities, Eastern Cape Province of South Africa, thus serving as a potential threat to food safety.

Molecular-diversity, Prevalence and Antibiotic Susceptibility of Pathogenic Klebsiella Pneumoniae under Saudi Condition

BACKGROUND AND OBJECTIVE

Klebsiella pneumoniae is an important multi-drug-resistant Gram-negative pathogen, associated with nosocomially acquired infections. This study aimed to determine the genotypic and phenotypic characterization of Klebsiella pneumoniae isolates and to correlate the antibiotic resistance with the presence of virulence genes revealed by molecular genotypic testing in Riyadh, Saudi Arabia.

MATERIALS AND METHODS

About 23 Klebsiella pneumoniae isolates were collected from various specimen types. Identification of the organisms was carried out. Antimicrobial susceptibility performed against 12 antibiotics. The DNA was isolated and purified then genotypic confirmation was done through polymerase chain reactions (PCR) to detect TEM, SHV, CTX-M, IMP and KPC genes. PCR products were sequenced and aligned with GenBank sequences.

RESULTS

Out of 23 isolates of K. pneumoniae, the majority (43.5%) was from tracheal aspirate. The percentage of females (65.2%) was more than males (34.8%). The highest isolates prevalence was found in the age group of >58 (39.1%). About 100% of isolates were resistant to cefotaxime, ceftriaxone, ceftazidime, cefepime and ampicillin and 91.3% were sensitive to amikacin and Imipenem. Most isolates were SHV-9 gene positive (52.2%). It was found that tested isolates had 99-100% similarity when compared to GenBank sequences.

CONCLUSION

There was a preponderance of SHV-9 gene which suggests dissemination of the gene in the tested isolates.

Systematic research to overcome newly emerged multidrug-resistant bacteria

In the 1980s, I found that the chromosomal β-lactamase of Klebsiella pneumoniae LEN-1 showed a very high similarity to the R-plasmid-mediated penicillinase TEM-1 on the amino acid sequence level, and this strongly suggested the origination of TEM-1 from the chromosomal penicillinases of K. pneumoniae or related bacteria. Moreover, the chromosomal K1 β-lactamase (KOXY) of Klebsiella oxytoca was found to belong to the class A β-lactamases that include LEN-1 and TEM-1, although KOXY can hydrolyze cefoperazone (CPZ) like the chromosomal AmpC-type cephalosporinases of various Enterobacteriaceae that can hydrolyze several cephalosporins including CPZ. Furthermore, my collaborators and I found plural novel serine-type β-lactamases, such as MOX-1, SHV-24, TEM-91, CTX-M-64, CMY-9, CMY-19, GES-3, GES-4, and TLA-3, mediated by plasmids. Besides these serine-type β-lactamases, we also first identified exogenously acquired metallo-β-lactamases (MBLs), IMP-1 and SMB-1, in imipenem-resistant Serratia marcescens, and the IMP-1-producing S. marcescens TN9106 became the index case for carbapenemase-producing Enterobacteriaceae. I developed the sodium mercaptoacetic acid (SMA)-disk test for the simple identification of MBL-producing bacteria. We were also the first to identify a variety of plasmid-mediated 16S ribosomal RNA methyltransferases, RmtA, RmtB, RmtC, and NpmA, from various Gram-negative bacteria that showed very high levels of resistance to a wide range of aminoglycosides. Furthermore, we first found plasmid-mediated quinolone efflux pump (QepA) and fosfomycin-inactivating enzymes (FosA3 and FosK). We also first characterized penicillin reduced susceptible Streptococcus agalactiae, macrolide-resistant Mycoplasma pneumoniae, as well as Campylobacter jejuni, and Helicobacter pylori, together with carbapenem-resistant Haemophilus influenzae. We constructed a PCR-based open reading frame typing method for rapid identification of Acinetobacter baumannii international clones.

Difference of Phenotype and Genotype Between Human and Environmental: Isolated Vibrio cholerae in Surabaya, Indonesia

Cholera due to Vibrio cholerae has been spreading worldwide, although the reports focusing on Indonesian V. cholerae are few. In this study, in order to investigate how V. cholerae transmitted to human from environment. We extended an epidemiological report that had investigated the genotype of V. cholerae isolated from human pediatric samples and environmental samples. We examined 44 strains of V. cholerae isolated from pediatric diarrhea patients and the environment such as shrimps or oysters collected in three adjacent towns in Surabaya, Indonesia. Susceptibilities were examined for 11 antibiotics. Serotype O1 or O139 genes and pathogenic genes including cholera toxin were detected. Multi-locus sequence typing (MLST) and enterobacterial repetitive intergenic consensus (ERIC)-PCR were also performed to determine genetic diversity of those isolates. Serotype O1 was seen in 17 strains (38.6%) with all pathogenic genes among 44 isolates. Other isolates were non-O1/non-O139 V. cholerae. Regarding antibiotic susceptibilities, those isolates from environmental samples showed resistance to ampicillin (11.4%), streptomycin (9.1%) and nalidixic acid (2.3%) but those isolates from pediatric stools showed no resistance to those 3 kinds of antibiotics. MLST revealed sequence type (ST) 69 in 17 strains (38.6%), ST198 in 3 strains (6.8%) and non-types in 24 strains (54.5%). All the ST69 strains were classified to O1 type with more than 95% similarity by ERIC-PCR, including all 6 (13.6%) isolates from environmental samples with resistance to streptomycin. In conclusion, V. cholerae O1 ST69 strains has been clonally spreading in Surabaya, exhibiting pathogenic factors and antibiotic resistance to streptomycin, especially in the isolates from environment.

Truncated Class 1 Integron Gene Cassette Arrays Contribute to Antimicrobial Resistance of Diarrheagenic Escherichia coli

Class 1 integrons (c1-integrons) are associated with multidrug resistance in diarrheagenic Escherichia coli (DEC). However, little is known about gene cassettes located within these c1-integrons, particularly truncated c1-integrons, in DEC strains. Therefore, the aims of the present study were to reveal the relationship between antimicrobial resistance and the presence of truncated c1-integrons in DEC isolates derived from human stool samples in Japan. A total of 162 human stool-derived DEC isolates from Japan were examined by antimicrobial susceptibility testing, PCR-based gene detection, and next-generation sequencing analyses. Results showed that 44.4% (12/27) of c1-integrons identified in the DEC isolates harbored only intI1 (an element of c1-integrons) and were truncated by IS26, Tn3, or IS1-group insertion sequences. No difference in the frequency of antimicrobial resistance was recorded between intact and truncated c1-integron-positive DEC isolates. Isolates containing intact/truncated c1-integrons, particularly enteroaggregative E. coli isolates, were resistant to a greater number of antimicrobials than isolates without c1-integrons. aadA and dfrA were the most prevalent antimicrobial resistance genes in the intact/truncated c1-integrons examined in this study. Therefore, gene cassettes located within these intact/truncated c1-integrons may only play a limited role in conferring antimicrobial resistance among DEC. However, DEC harboring truncated c1-integrons may be resistant to a greater number of antimicrobials than c1-integron-negative DEC, similar to strains harboring intact c1-integrons.

Enterohaemorrhagic Escherichia coli O121:H19 acquired an extended-spectrum β-lactamase gene during the development of an outbreak in two nurseries

Enterohaemorrhagic Escherichia coli (EHEC) is an important human pathogen worldwide. Although serotype O157 is currently the most dominant and important EHEC strain, serotypes O26, O111, O91, O103 and O121 are also recognized as serious pathogens that affect public health. EHEC outbreaks often occur in nurseries and elderly care facilities. In 2012, a nursery outbreak of EHEC O121 occurred during which the bacterium acquired a plasmid-borne extended-spectrum β-lactamase (ESBL) gene. ESBL-producing E. coli O86 was concurrently isolated from one of the EHEC patients. Therefore, we investigated the isolates by whole-genome sequence (WGS) analysis to elucidate the transmission dynamics of the EHEC strains and the ESBL plasmid. According to WGS-based phylogeny, all 17 EHEC O121 isolates were clonal, while E. coli O86 was genetically distant from the EHEC O121 isolates. The complete sequence of an ESBL plasmid encoding the CTX-M-55 β-lactamase was determined using S1-PFGE bands, and subsequent mapping of the WGS reads confirmed that the plasmid sequences from EHEC O121 and E. coli O86 were identical. Furthermore, conjugation experiments showed that the plasmid was capable of conjugative transfer. These results support the hypothesis that EHEC O121 acquired an ESBL-producing plasmid from E. coli O86 during the outbreak. This report demonstrates the importance of implementing preventive measures during EHEC outbreaks to control both secondary infection and the spread of antimicrobial resistance factors.

Investigation of multidrug-resistant ST2 Acinetobacter baumannii isolated from Saint George hospital in Lebanon

BACKGROUND

Acinetobacter baumannii is an opportunistic pathogen causing various nosocomial infections. The spread of multidrug-resistant A. baumannii is a major public health problem. The aim of this study was to investigate the molecular epidemiology and the genetic support of multidrug-resistant A. baumannii isolates collected from Saint-Georges Hospital in Lebanon.

METHODS

Between January and August 2016, 31 A. baumannii isolates were collected from sputum samples of patients infected with ventilator-associated pneumonia (VAP) and treated with colistin-carbapenem combination therapy. Antibiotic susceptibility testing was performed using the disk diffusion method. Carbapenemases, extended spectrum β-lactamases encoding genes and mcr-1/2 genes were investigated by RT-PCR and standard PCR. The epidemiological relatedness of the strains was studied using MLST analysis.

RESULTS

Most of the isolates exhibited multidrug-resistant phenotypes. All the isolates were carbapenem-resistant and among them, 30 carried the class D carbapenemase bla_oxa-23 gene while one isolate carried bla_oxa-72 gene. MLST results revealed three sequence types, namely ST2, ST699, and ST627. Isolates having ST2 were the most prevalent clone (29/31, 93.5%).

CONCLUSIONS

This study shows a nosocomial spread of multidrug-resistant A. baumannii ST2 having bla_OXA-23 gene in Saint-George in Lebanon. Monitoring and control measures need to be adopted to avoid the spread of A. baumannii to patients.

The Growing Genetic and Functional Diversity of Extended Spectrum Beta-Lactamases

The β-lactams-a large class of diverse compounds-due to their excellent safety profile and broad antimicrobial spectrum are considered to be the most widely used therapeutic class of antibacterials prescribed in human and veterinary clinical practices. This, unfortunately, has also given rise to a continuous increased resistance globally in health care settings as well as in the community due to their permanent selective force driving diversification of the resistance mechanism. Resistance against β-lactams is increasing rapidly as novel β-lactamases, enzymes that degrade β-lactams, are being discovered each day such as recent emergence of extended spectrum β-lactamases (ESBL) that have the ability to inactivate most of the cephalosporins. The complexity and diversity of ESBL are increasing so rapidly that more than 170 variants have thus far been described for only a single genotype, the blaCTX-M -encoding ESBL. This review is to organize all the current updated literature describing genomic features, organization, and mechanism of resistance and mode of dissemination of all known ESBLs.

Population structure of Japanese extraintestinal pathogenic Escherichia coli and its relationship with antimicrobial resistance

Objectives

To define the population structure of extraintestinal pathogenic Escherichia coli (ExPEC) in Japan and its relationship with antimicrobial resistance and the major resistance mechanisms for fluoroquinolones and β-lactams, we designed a multicentre prospective study.

Methods

A total of 329 ExPEC isolates were collected at 10 Japanese acute-care hospitals during December 2014. We defined the clonal groups of ExPEC by fumC and fimH sequencing (CH typing). Antimicrobial susceptibility testing of 18 agents and the detection of mutations in quinolone resistance-determining regions (QRDRs) and β-lactamases were performed.

Results

Among the study isolates, 103 CH types were found, and CH40-30 (25%) and another 10 CH types (35% in total) constituted the major ExPEC population. Ciprofloxacin non-susceptibility, ESBLs and MDR phenotypes were found in 34%, 22% and 33%, respectively. CH40-30, corresponding to the C/H30 clade of the global pandemic ST131 clone, was associated with four QRDR mutations (100%) and bla CTX-M (60%) and was the most frequent type in 15 antimicrobial-non-susceptible populations (dominating 39%-75% of each population, the highest prevalence for ciprofloxacin), the ESBL producers (70%) and the MDR isolates (59%). Isolates that were non-susceptible to nalidixic acid and low-level resistant to ciprofloxacin with one or two QRDR mutations represented 16% of the study isolates and were distributed among the eight major and non-major CH types.

Conclusions

More than half of the ExPEC population in Japan consisted of 11 major clones. Of these clones, the CH40-30-ST131-C/H30 clone was the predominant antimicrobial-resistant population. The presence of major clones with low-level ciprofloxacin resistance supports the potential future success of a non-ST131 fluoroquinolone-resistant clone.

Prevalence and clonal relationship of ESBL-producing Salmonella strains from humans and poultry in northeastern Algeria

BACKGROUND

The aims of this study were to investigate Salmonella contamination in broiler chicken farms and slaughterhouses, to assess the antibiotic resistance profile in avian and human Salmonella isolates, and to evaluate the relationship between avian and human Extended Spectrum β-Lactamase (ESBL)-producing isolates. Salmonella was screened in different sample matrices collected at thirty-two chicken farms and five slaughterhouses. The human isolates were recovered from clinical specimens at the University Teaching Hospital of Constantine (UTH). All suspected colonies were confirmed by MALDI-TOF (Matrix Assisted Laser Desorption Ionization Time OF light) and serotyped. Susceptibility testing against 13 antibiotics including, amoxicillin/clavulanic acid, ticarcillin, cefoxitin, cefotaxime, aztreonam, imipenem, ertapenem, gentamicin, amikacin, ciprofloxacin, colistin, trimethoprim/sulfamethoxazole and fosfomycin, was performed using the disk diffusion method on Mueller-Hinton agar. ESBL-production was screened by the double-disk synergy test and confirmed by molecular characterization using PCR (polymerase chain reaction) amplification and sequencing of ESBL encoding genes. Clonality of the avian and human strains was performed using the Multi Locus Sequencing Typing method (MLST).

RESULTS

Forty-five isolated avian Salmonella strains and 37 human collected ones were studied. Five S. enterica serotypes were found in avian isolates (mainly Kentucky) and 9 from human ones (essentially Infantis). 51.11% and 26.6% of the avian isolates were resistant to ciprofloxacin and cefotaxime, respectively, whereas human isolates were less resistant to these antibiotics (13.5% to ciprofloxacin and 16.2% to cefotaxime). Eighteen (12 avian and 6 human) strains were found to produce ESBLs, which were identified as bla _CTX-M-1 (n = 12), bla _CTX-M-15 (n = 5) and bla _TEM group (n = 8). Interestingly, seven of the ESBL-producing strains (5 avian and 2 human) were of the same ST (ST15) and clustered together, suggesting a common origin.

CONCLUSION

The results of the combined phenotypic and genotypic analysis found in this study suggest a close relationship between human and avian strains and support the hypothesis that poultry production may play a role in the spread of multidrug-resistant Salmonella in the human community within the study region.

Antibiotic-Resistant Extended Spectrum ß-Lactamase- and Plasmid-Mediated AmpC-Producing Enterobacteriaceae Isolated from Retail Food Products and the Pearl River in Guangzhou, China

We conducted a survey in 2015 to evaluate the presence of extended spectrum β-lactamase (ESBL)- and plasmid-mediated AmpC-producing Enterobacteriaceae in retail food and water of the Pearl River in Guangzhou, China, as well as their antibiotic resistance profiles. Samples (88 fresh food samples and 43 water samples) from eight different districts were analyzed by direct plating and after enrichment. Multidrug-resistant strains were found in 41.7 and 43.4% of food and water samples, respectively. ESBLs were found in 3.4 and 11.6% of food and water samples, respectively, and AmpC producers were found in 13.6 and 16.3% of food and water samples, respectively. Molecular characterization revealed the domination of bla_CTX−Mgenes; plasmidic AmpC was of the type DHA-1 both in food and water samples. Thirteen of Fifty one β-lactamase-producing positive isolates were detected to be transconjugants, which readily received the β-lactamase genes conferring resistance to β-lactam antibiotics as well as some non-β-lactam antibiotics. These findings provide evidence that retail food and the river water may be considered as reservoirs for the dissemination of β-lactam antibiotics, and these resistance genes could readily be transmitted to humans through the food chain and water.

Clinical and microbiologic characteristics of cefotaxime-non-susceptible Enterobacteriaceae bacteremia: a case control study

Background

Cefotaxime plays an important role in the treatment of patients with bacteremia due to Enterobacteriaceae, although cefotaxime resistance is reported to be increasing in association with extended-spectrum β-lactamase (ESBL) and AmpC β-lactamase (AmpC).

Methods

We conducted a case-control study in a Japanese university hospital between 2011 and 2012. We assessed the risk factors and clinical outcomes of bacteremia due to cefotaxime-non-susceptible Enterobacteriaceae (CTXNS-En) and analyzed the resistance mechanisms.

Results

Of 316 patients with Enterobacteriaceae bacteremia, 37 patients with bacteremia caused by CTXNS-En were matched to 74 patients who had bacteremia caused by cefotaxime-susceptible Enterobacteriaceae (CTXS-En). The most common CTXNS-En was Escherichia coli (43%), followed by Enterobacter spp. (24%) and Klebsiella spp. (22%). Independent risk factors for CTXNS-En bacteremia included previous infection or colonization of CTXNS-En, cardiac disease, the presence of intravascular catheter and prior surgery within 30 days. Patients with CTXNS-En bacteremia were less likely to receive appropriate empirical therapy and to achieve a complete response at 72 h than patients with CTXS-En bacteremia. Mortality was comparable between CTXNS-En and CTXS-En patients (5 vs. 3%). CTXNS-En isolates exhibited multidrug resistance but remained highly susceptible to amikacin and meropenem. CTX-M-type ESBLs accounted for 76% of the β-lactamase genes responsible for CTXNS E. coli and Klebsiella spp. isolates, followed by plasmid-mediated AmpC (12%). Chromosomal AmpC was responsible for 89% of CTXNS Enterobacter spp. isolates.

Conclusions

CTXNS-En isolates harboring ESBL and AmpC caused delays in appropriate therapy among bacteremic patients. Risk factors and antibiograms may improve the selection of appropriate therapy for CTXNS-En bacteremia. Prevalent mechanisms of resistance in CTXNS-En were ESBL and chromosomal AmpC.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-016-2150-6) contains supplementary material, which is available to authorized users.

[Epidemiological Survey of the Extended-spectrum β-lactamase-producing Bacteria in Hospitals and Nursing Homes in Morioka Secondary Medical Area Zone of Iwate Prefecture]

The spread of ESBL-producing bacteria (ESBLs) in local communities is a crucially important issue related to infection control. We investigated the relevance of isolation of ESBLs and the risk factors influencing the isolation rates of these organisms at medical facilities (4 rural hospitals, A-D; 4 nursing homes, a-d) located in the Morioka medical area. The isolation rates of ESBLs at 4 hospitals were estimated from the patient medical records from April 2013 to March 2014. Also, ESBLs were isolated from stool samples from residents in 4 nursing homes during almost the same period, and were analyzed to ascertain their genotypes. Furthermore, we compared the isolation rates of ESBLs among four hospitals to determine the influence of use of third-generation cephalosporins and alcohol-based hand rubs, and also among four nursing homes to identify the clinical backgrounds of the nursing home residents influencing the isolation rates. The isolation rates of ESBLs in hospitals and nursing homes were 13.3% (3.6-25.0%) and 9.3% (3.4-21.0%), respectively. Hospital B, which had the highest isolation rate of ESBLs, showed the highest rate of use of third-generation cephalosporins. On the other hand, Hospital A, with a lower isolation rate of ESBLs, showed the highest frequency of use of alcohol rubs. The rate of use of enteral nutrition was significantly higher in the nursing homes with higher isolation rate of ESBLs than those with lower isolation rates (odds ratio 2.71, p < 0.05). Nursing home c, with a significantly higher isolation rate of ESBLs, showed higher usage of adult diapers as well as higher rates of residents with recent hospitalization and high-level care. All ESBLs (13 Escherichia coli) isolated from nursing home c showed the same genotype: CTX-M-3. Although numerous ESBLs were isolated from the hospitals and nursing homes investigated in this study, the isolation rates of ESBLs and the clinical backgrounds of the patients differed greatly among the medical facilities in the same area. Furthermore, as patients and residents were transferred reciprocally among the hospitals and nursing homes, it was suggested that infection control for ESBLs at any individual facility alone was not sufficient and also that cooperative education and information sharing on ESBLs among facilities in the same area might be important.

Acquisition of Extended-Spectrum β-Lactamases by Escherichia coli and Klebsiella pneumoniae in Gut Microbiota of Pilgrims during the Hajj Pilgrimage of 2013

We reported the acquisition of extended-spectrum-β-lactamase (ESBL)-producing bacteria in rectal samples of 129 pilgrims during the 2013 Hajj (pilgrimage to Makkah). When returning from the Hajj, there was a significant increase in the number of pilgrims carrying E. coli resistant to ceftriaxone (P = 0.008). The CTX-M gene was detected in rectal samples, with the detection rate increasing from 10.08% to 32.56% of samples after the Hajj (P < 0.001).

In Vitro and In Vivo Activities of OP0595, a New Diazabicyclooctane, against CTX-M-15-Positive Escherichia coli and KPC-Positive Klebsiella pneumoniae

Gram-negative bacteria are evolving to produce β-lactamases of increasing diversity that challenge antimicrobial chemotherapy. OP0595 is a new diazabicyclooctane serine β-lactamase inhibitor which acts also as an antibiotic and as a β-lactamase-independent β-lactam "enhancer" against Enterobacteriaceae Here we determined the optimal concentration of OP0595 in combination with piperacillin, cefepime, and meropenem, in addition to the antibacterial activity of OP0595 alone and in combination with cefepime, in in vitro time-kill studies and an in vivo infection model against five strains of CTX-M-15-positive Escherichia coli and five strains of KPC-positive Klebsiella pneumoniae An OP0595 concentration of 4 μg/ml was found to be sufficient for an effective combination with all three β-lactam agents. In both in vitro time-kill studies and an in vivo model of infection, cefepime-OP0595 showed stronger efficacy than cefepime alone against all β-lactamase-positive strains tested, whereas OP0595 alone showed weaker or no efficacy. Taken together, these data indicate that combinational use of OP0595 and a β-lactam agent is important to exert the antimicrobial functions of OP0595.

Long-Term Colonization by bla(CTX-M)-Harboring Escherichia coli in Healthy Japanese People Engaged in Food Handling

The actual state of intestinal long-term colonization by extended-spectrum β-lactamase (ESBL)-producing Escherichia coli in healthy Japanese people remains unclear. Therefore, a total of 4,314 fecal samples were collected from 2,563 food handlers from January 2010 to December 2011. Approximately 0.1 g of each fecal sample was inoculated onto a MacConkey agar plate containing cefotaxime (1 μg/ml). The bacterial colonies that grew on each plate were checked for ESBL production by the double-disk synergy test, as recommended by the Clinical and Laboratory Standards Institute. The bacterial serotype, antimicrobial susceptibility, pulsotype, sequence type (ST), and ESBL genotype were checked, and the replicon types of plasmids harboring the ESBL gene were also determined after conjugation experiments. ESBL producers were recovered from 70 (3.1%) of 2,230 participants who were checked only once. On the other hand, ESBL producers were isolated at least once from 52 (15.6%) of 333 participants who were checked more than twice, and 13 of the 52 participants carried ESBL producers for from more than 3 months to up to 2 years. Fluoroquinolone (FQ)-resistant E. coli strains harboring bla(CTX-M) were repeatedly recovered from 11 of the 13 carriers of bla(CTX-M)-harboring E. coli. A genetically related FQ-resistant E. coli O25b:H4-ST131 isolate harboring bla(CTX-M)-27 was recovered from 4 of the 13 carriers for more than 6 months. Three FQ-resistant E. coli O1:H6-ST648 isolates that harbored bla(CTX-M-15) or bla(CTX-M)-14 were recovered from 3 carriers. Moreover, multiple CTX-M-14- or CTX-M-15-producing E. coli isolates with different serotypes were recovered from 2 respective carriers. These findings predict a provable further spread of ESBL producers in both community and clinical settings.

[Serovars and Drug-Resistance of Salmonella Strains Isolated from Domestic Chicken Meat in Tokyo (1992-2012)]

A total of 477 Salmonella strains isolated from retail domestic chicken meat during 1992-2012 in Tokyo, were examined regarding their serovars and drug-resistance. These strains were detected in 469 (29.8%) of 1,576 samples. The detection rate in every two years was 10.1% to 46.3% of the range. Serological typing results showed that 477 strains were classified into 22 serovars excepting 2 untypable strains. Among them, S. Infantis (312 strains) was the most prevalent, followed by II O4: b: [e, n, x] (S. II Sofia) (71 strains), S. Hadar (20 strains), S. Typhimurium (20 strains), S. Manhattan (12 strains), S. Schwarzengrund (9 strains), S. Agona (7 strains), and other 15 serovars (24 strains). Results of the antibacterial drug susceptibility test for 477 strains revealed that 89.9% was resistant to some of the 12 drugs tested, and multidrug-resistant strains accounted for 90.2% among them. The frequencies of resistance to each drug were 81.8%; 77.8%, 45.5%, 33.3%, 11.3%, 9.6%, 2.9%, 0.6%, 0.6% and 0.2%, in order with high frequency, for SM, TC, KM, ST, NA, ABPC, CP, FOM, CTX and CAZ, respectively. None of the strains was resistant to NFLX or IPM. Three CTX-resistant strains were CTX-M type extended-spectrum β-lactamase (ESBL) producers, and the group of CTX-M type ESBL genes were CTX-M-2 group (2 strains) and CTX-M-9 group (1 strain). CAZ-resistant 1 strain was an ESBL producer, but the ESBL gene was not determined.

Characterization of CTX-M-Type Extend-Spectrum β-Lactamase Producing Klebsiella spp. in Kashan, Iran

CONTEXT

The CTX-M family consists of more than 50 β-lactamases, which are grouped on the basis of sequences into five subtypes including CTX-M-1, CTX-M-2, CTX-M-8, CTX-M-9 and CTX-M-25.

OBJECTIVES

The current study aimed to detect subtypes of CTX-M extended-spectrum β-lactamases (ESBLs) among ESBL positive Klebsiella isolates from patients in Kashan, Iran.

MATERIALS AND METHODS

A total of 100 clinical isolates of Klebsiella were collected and the isolates, which showed resistance or reduced susceptibility to cefotaxime, ceftazidime and/or aztreonam by the disk diffusion method were selected. These isolates were identified as ESBL-producing isolates by double disk synergy tests using clavulanic acid, cefotaxime, ceftazidime and aztreonam. The blaCTX-M type determinants were identified by the Polymerase Chain Reaction (PCR) method followed by DNA sequencing.

RESULTS

Of the 100 Klebsiella isolates, 41 (41%) demonstrated resistance or reduced susceptibility to ceftazidime and/or aztreonam and 35% (n = 35) were ESBL-producers. Twenty-eight (8o%) of the ESBL-producing isolates carried the blaCTX-M type genes. Based on PCR assays and sequencing of blaCTX-M genes, CTX-M-1, CTX-M-2 and CTX-M-9 were identified in 21 (60%), 15 (42%) and nine (34%) of these isolates, respectively (GenBank accession numbers KJ803828-KJ803829).

CONCLUSIONS

Our study showed that the frequency of blaCTX-M genes among Klebsiella isolates in our region is at an alarming rate. Also, we found a high prevalence of blaCTX-M-1 β-lactamase in Klebsiella isolates in Kashan.

The prevalence of Escherichia coli strains with extended spectrum beta-lactamases isolated in China

The extended-spectrum-lactamases-producing Escherichia coli has rapidly spread worldwide. Escherichia coli has been becoming much more resistant to β-lactam antibiotics and other commonly available antimicrobials. We investigated the prevalence, resistance, and probable gene type of extended spectrum beta-lactamases (ESBLs) using minimum inhibitory concentrations (MICs) testing and polymerase chain reaction (PCR). We have collected 289 single-patient E. coli Isolates based on samples of China from July 2013 to August 2014. This article explored that the prevalence of ESBL-producing Isolates showed multi-resistant to antimicrobials such as fluoroquinolones, trimethoprim, tetracycline and aminoglycosides, and so on. The frequencies of resistance in Isolates were as follows: Ciprofloxacin, 74%, gentamicin, 69.5%, levofloxacin, 63%, tobramycin, 39%, and minocycline, 7.9%. According to our results, 197(68.2%) of the total 289 Isolates were ESBL-producing strains; further, 172 (87.3%) producers contained genes encoding CTX-M enzymes and 142(72.1%) producers contained genes encoding TEM enzymes. Most ESBL-producing Escherichia coli has produced more than one type of β-lactamase. Nucleotide sequence analysis has revealed the diversity of ESBLs types: CTX-M -15 is in the majority and TEM-135, CTX-M-3, CTX-M-98, CTX-M-14, CTX-M-142, CTX-M-65, CTX-M-55, CTX-M-27, and CTX-M-123 have been recovered. The results confirm that ESBL producers which are common in hospital strains of Escherichia coli are resistant to cephalosporins and other antibiotics in China. It is important to monitor such strains closely and provide scientific evidence of rational application of antibiotics to prevent their spread.

CTX-M-27- and CTX-M-14-producing, ciprofloxacin-resistant Escherichia coli of the H30 subclonal group within ST131 drive a Japanese regional ESBL epidemic

OBJECTIVES

The global increase in ESBL-producing Escherichia coli is associated with the ST131 clonal group, especially its CTX-M-15-producing H30Rx subset. To understand the rapid spread of ESBL-producing E. coli in Japan, we investigated the molecular epidemiology and ESBL-associated genetic environments of Japanese ST131 isolates.

METHODS

Between 2001 and 2012, 1079 ESBL-producing E. coli isolates were collected at 10 Japanese acute-care hospitals. ESBL types, ST131 status, fimH allele, H30Rx-defining sequences and ESBL-associated genetic environments were defined using PCR and sequencing. Subclonal groups were defined based on fimH allele and H30Rx status.

RESULTS

Overall, 461 (43%) of the 1079 ESBL-producing E. coli isolates represented ST131. According to fimH-based subclonal typing, the ST131 isolates included 398 fimH allele 30 (H30) isolates, 49 H41 isolates, 10 H22 isolates and 4 other fimH-type isolates. The 398 H30 isolates included 396 ciprofloxacin-resistant H30R isolates, of which 64 (16%) represented the H30Rx subset. Between 2001 and 2007, the CTX-M-14-producing H30R subgroup predominated, accounting for 46% of ST131 isolates, whereas the CTX-M-27-producing H30R and CTX-M-15-producing H30Rx subgroups were rarely detected. In contrast, from 2008 onward the latter two subgroups rose to dominance, accounting for 45% and 24% of ST131 isolates, respectively, versus only 15% for the (formerly dominant) CTX-M-14-producing H30R subgroup. The emergent CTX-M-27-H30R subgroup frequently had an IS26-ΔISEcp1-blaCTX-M-27-ΔIS903D-IS26-like structure, whereas the older CTX-M-14-H30R subgroup frequently had an ISEcp1-blaCTX-M-14-IS903D-like structure.

CONCLUSIONS

This Japanese regional ESBL-producing E. coli epidemic is closely associated with newly identified CTX-M-27- and CTX-M-14-producing ST131 H30R subclonal groups and with mobile elements IS26, ISEcp1 and IS903D.

Antimicrobial Susceptibility Profile of Extended Spectrum β-Lactamase (ESBL) Producing Escherichia coli from Various Clinical Samples

BACKGROUND

Extended spectrum β-lactamase (ESBL) producing Escherichia coli has tremendously increased worldwide and it is one of the most common causes of morbidity and mortality associated with hospital-acquired infections. This could be attributed to association of multi drug resistance in ESBL producing isolates. The present study was aimed to determine the antimicrobial sensitivity profile of ESBL producing E. coli isolates from various clinical samples.

MATERIALS AND METHODS

Clinical samples, which consist of pus, urine, blood, cerebrospinal fluid (CSF), stool, sputum, swabs, and different body fluids, are included in the study. Samples were processed and identified as per routine laboratory protocol. ESBL screening and confirmation along with antimicrobial susceptibility test was done according to the Clinical Laboratory Standards Institute (CLSI) guidelines.

RESULTS

Out of 180 third generation cephalosporins resistant E. coli, 100 (55.55%) isolates were ESBL producers showing a greater degree of resistance to antibiotics.

CONCLUSION

The prevalence of ESBL is increasing day by day in nearly every center of different countries and necessary steps to prevent the spread and emergence of resistance should be taken.

CTX-M-15-producing Morganella morganii from Hôpital Principal de Dakar, Senegal

We report the detection and molecular characterization of extended spectrum β-lactamases in a series of 112 clinical isolates of Enterobacteriaceae from the Hôpital Principal de Dakar, Senegal, including five CTX-M-15-producing Morganella morganii isolates, which are reported for the first time in this country.

Prevalence and epidemiological relationship of CMY-2 AmpC β-lactamase and CTX-M extended-spectrum β-lactamase-producing Escherichia coli isolates from broiler farms in Japan

To evaluate the prevalence of extended-spectrum cephalosporin (ESC)-resistant Enterobacteriaceae in broiler chickens, 41 rectal samples taken from 4 commercial farms were examined. Desoxycholate hydrogen sulfide lactose agars, supplemented with either 4 μg/ml cefotaxime or 16 μg/ml ceftazidime, were used to screen ESC-resistant bacteria. ESC-resistant bacteria were isolated from all samples. Of the 164 ESC-resistant bacteria (included 4 isolates per a sample), 163 were Escherichia coli, while 1 isolate was identified as Enterobacter cloacae. Extended-spectrum β-lactamase (ESBL) genes and plasmid-mediated AmpC β-lactamase genes in the isolates were determined by PCR and sequencing. One AmpC β-lactamase gene, bla(CMY-2) (66%), and 4 ESBL genes, bla(CTX-M-1) (26%), bla(CTX-M-55) (10%), bla(SHV-5) (4%) and bla(CTX-M-2) (3%), were detected in the E. coli isolates. The epidemiological relationship of the CMY-2 and CTX-M β-lactamase-producing isolates among the farms was analyzed by pulsed-field gel electrophoresis using the XbaI restriction enzyme. Forty-one (Y1-Y41) and 14 (X1-X14) clusters were found in the CMY-2 and CTX-M-carrying E. coli isolates, respectively. Some clusters included isolates derived from more than 1 farm, indicating some cross-contamination of clonal strains and spread of CMY-2 AmpC β-lactamase or CTX-M ESBL among the farms.

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.

[Analysis of extended-spectrum CTX-M-14 beta-lactamase (ESBLs) producing Escherichia coli isolates in the same ward over the long term]

We bacteriologically and genetically analysed 30 cephalosporin-resistant Escherichia coli strains isolated from specimens from 19 neurology-ward inpatients at our hospital over the 3 years from April 2006 to March 2009, surveying and comparing subjects' backgrounds. Of the 30, 19 (63%) were urine, 6 (20%) sputum, and 3 (10%) blood. We tested extended-spectrum beta-lactamase (ESBLs) production, found in all samples. PCR and gene sequencing showed that 25 strains (83%) were CTX-M-14 and 5 (17%) CTX-M-2. Among CTX-M-14 strains, two cluster groups I and II, were obtained using pulsed-field gel electrophoresis (PFGE). Cluster group I in particular, continued to be detected for 18 months in the same hospital room. The detection rate was high at 13 (68%) in subjects with urinary catheters and morbidity was high in those with a history of cerebrovascular disease, diabetes, and hypertension. Our findings suggest that genetically identical strains may become established and spread in hospitals possibly due to inadequate contact prevention, subjects' immune status, and risk factor existence.

Extended-spectrum Beta-lactamase gene sequences in gram-negative saprophytes on retail organic and nonorganic spinach

A substantial proportion of infections caused by drug-resistant Gram-negative bacteria (GNB) in community and health care settings are recognized to be caused by evolutionarily related GNB strains. Their global spread has been suggested to occur due to human activities, such as food trade and travel. These multidrug-resistant GNB pathogens often harbor mobile drug resistance genes that are highly conserved in their sequences. Because they appear across different GNB species, these genes may have origins other than human pathogens. We hypothesized that saprophytes in common human food products may serve as a reservoir for such genes. Between July 2007 and April 2008, we examined 25 batches of prepackaged retail spinach for cultivatable GNB population structure by 16S rRNA gene sequencing and for antimicrobial drug susceptibility testing and the presence of extended-spectrum beta-lactamase (ESBL) genes. We found 20 recognized GNB species among 165 (71%) of 231 randomly selected colonies cultured from spinach. Twelve strains suspected to express ESBLs based on resistance to cefotaxime and ceftazidime were further examined for bla(CTX-M) and bla(TEM) genes. We found a 712-bp sequence in Pseudomonas teessidea that was 100% identical to positions 10 to 722 of an 876-bp bla(CTX-M-15) gene of an E. coli strain. Additionally, we identified newly recognized ESBL bla(RAHN-2) sequences from Rahnella aquatilis. These observations demonstrate that saprophytes in common fresh produce can harbor drug resistance genes that are also found in internationally circulating strains of GNB pathogens; such a source may thus serve as a reservoir for drug resistance genes that ultimately enter pathogens to affect human health.

Molecular characteristics of extended spectrum beta-lactamases in Escherichia coli and Klebsiella pneumoniae and the prevalence of qnr in Extended spectrum beta-lactamase isolates in a tertiary care hospital in Korea

PURPOSE

Extended spectrum beta-lactamases (ESBLs) are cephalosporinases that confer resistance to a wide variety of oxyimino cephalosporins and create serious therapeutic problems. In addition, the quinolone resistance qnr genes are becoming increasingly prevalent in clinical isolates, some of which also produce ESBL. This study was designed to evaluate the occurrence and genotypic distribution of ESBL producing Escherichia coli (E. coli) and Klebsiella pneumoniae (K. pneumoniae) as well as the prevalence and distribution of qnr genes in ESBL-producing isolates in a tertiary care hospital in Korea.

MATERIALS AND METHODS

We tested a total of 111 ESBL-producing isolates of E. coli and K. pneumoniae, which were collected at Kyung Hee Medical Center from November 2006 to June 2008. ESBL production was determined by the Clinical and Laboratory Standards Institute (CLSI) ESBL confirmatory test. The cefotaxime and ceftazidime resistance of the ESBL-producers were transferred to azide-resistant E. coli J53 by conjugation. The presence and identity of ESBL and qnr genes were determined by polymerase chain reaction (PCR) and nucleotide sequencing.

RESULTS

The prevalence of ESBLs was 17.7% (297/1,680) of E. coli and 26.5% (240/904) of K. pneumoniae in our hospital during the study periods. Of the 111 collected isolates, 69 isolates were E. coli and 42 isolates were K. pneumoniae. The most prevalent ESBL genotype was CTX-M15. Among the ESBL-producing isolates, 4 E. coli (5.8%) and 17 K. pneumoniae (40.5%) contained qnr genes. qnrB4 was the most frequent type in both E. coli and K. pneumoniae.

CONCLUSION

CTX-M15 was the most frequently encountered ESBL. In addition, a high prevalence of qnr genes among ESBL-producing K. pneumoniae was identified in this study.

Acquisition of a transposon encoding extended-spectrum beta-lactamase SHV-12 by Pseudomonas aeruginosa isolates during the clinical course of a burn patient

Three of seven clonally related Pseudomonas aeruginosa strains isolated from a burn patient produced the extended-spectrum beta-lactamase (ESBL) SHV-12. Its gene was flanked by two IS26 elements with a large transposon (>24 kb). The transposon also contained at least five IS26 elements and a gene encoding the amikacin resistance determinant aminoglycoside 6'-N-acetyltransferase type Ib [aac(6')-Ib]. It was inserted into the gene PA5317 in the P. aeruginosa chromosome.

First detection of CTX-M and SHV extended-spectrum beta-lactamases in Escherichia coli urinary tract isolates from dogs and cats in the United States

One hundred fifty canine and feline Escherichia coli isolates associated with urinary tract infections were screened for the presence of extended-spectrum beta-lactamase (ESBL) genes. Out of 60 isolates suspected to be ESBL positive based on antimicrobial susceptibility testing, 11 ESBLs were identified, including one SHV-12 gene, one CTX-M-14 gene, and nine CTX-M-15 genes. This study provides the first report of CTX-M- and SHV-type ESBLs in dogs and cats in the United States.

Extended Spectrum beta-Lactamases among Gram-Negative Bacterial Isolates from Clinical Specimens in Three Major Hospitals in Northern Jordan

Background and Objectives. Extended spectrum β-lactamase (ESBL) production is increasing all over the world, and organisms other than E. coli and K. pneumoniae are acquiring this character. ESBL production is detectable by automation, E-test, double disk diffusion (DDD), and PCR. This study aimed to determine the prevalence of ESBL production among clinical isolates of gram-negative rods, and to evaluate the effectiveness of augmentation of clavunate with Cefotaxime, Ceftazoxime, Aztreonam, Ceftriaxone, and Cefpodoxime in detecting ESBL production. Methods. 472 clinical gram-negative isolates identified by standard methods were tested for ESBL-production by (DDD) method using six cephalosporins and amoxicillin-clavulinate discs. Results. 108/472 (22.9%) of the isolates were ESBL producers, and were prevalent in tertiary care hospitals. 88.2% of E. cloacae, 71.4% of K. pneumoniae, 28.6% of K. oxytoca, 12.5% of C. freundii, 11.1% of A. calcoacceticus, and 10.8% of E. coli were ESBL producers. The DDD test demonstrated some variations in the efficacy of the different cephalosporins in detecting all the ESBL producers. The inclusion of ceftizoxime discs increased the efficacy of the test. It is concluded that ESBL-producing bacteria were prevalent among our hospitalized patients, and involved genera other than Klebsiella and Escherichia, and the inclusion of ceftizoxime increased the efficacy of ESBL detection by the DDD test.

Genetic basis of multidrug resistance in Acinetobacter baumannii clinical isolates at a tertiary medical center in Pennsylvania

A total of 49 unique clinical isolates of multidrug-resistant (MDR) Acinetobacter baumannii identified at a tertiary medical center in Pittsburgh, Pennsylvania, between August 2006 and September 2007 were studied for the genetic basis of their MDR phenotype. Approximately half of all A. baumannii clinical isolates identified during this period qualified as MDR, defined by nonsusceptibility to three or more of the antimicrobials routinely tested in the clinical microbiology laboratory. Among the MDR isolates, 18.4% were resistant to imipenem. The frequencies of resistance to amikacin and ciprofloxacin were high at 36.7% and 95.9%, respectively. None of the isolates was resistant to colistin or tigecycline. The presence of the carbapenemase gene bla(OXA-23) and the 16S rRNA methylase gene armA predicted high-level resistance to imipenem and amikacin, respectively. bla(OXA-23) was preceded by insertion sequence ISAba1, which likely provided a potent promoter activity for the expression of the carbapenemase gene. The structure of the transposon defined by ISAba1 differed from those reported in Europe, suggesting that ISAba1-mediated acquisition of bla(OXA-23) may occur as an independent event. Typical substitutions in the quinolone resistance-determining regions of the gyrA and parC genes were observed in the ciprofloxacin-resistant isolates. Plasmid-mediated quinolone resistance genes, including the qnr genes, were not identified. Fifty-nine percent of the MDR isolates belonged to a single clonal group over the course of the study period, as demonstrated by pulsed-field gel electrophoresis.

Human Salmonella and concurrent decreased susceptibility to quinolones and extended-spectrum cephalosporins

For complicated infections, decreased susceptibility could compromise treatment with drugs from either antimicrobial class.

The National Antimicrobial Resistance Monitoring System monitors susceptibility among Enterobacteriaceae in humans in the United States. We studied isolates exhibiting decreased susceptibility to quinolones (nalidixic acid MIC >32 µg/mL or ciprofloxacin MIC >0.12 µg/mL) and extended-spectrum cephalosporins (ceftiofur or ceftriaxone MIC >2 µg/mL) during 1996–2004. Of non-Typhi Salmonella, 0.19% (27/14,043) met these criteria: 11 Senftenberg; 6 Typhimurium; 3 Newport; 2 Enteridis; and 1 each Agona, Haifa, Mbandaka, Saintpaul, and Uganda. Twenty-six isolates had gyrA mutations (11 at codon 83 only, 3 at codon 87 only, 12 at both). All Senftenberg isolates had parC mutations (S80I and T57S); 6 others had the T57S mutation. The Mbandaka isolate contained qnrB2. Eight isolates contained bla_CMY-2; 1 Senftenberg contained bla_CMY-23. One Senftenberg and 1Typhimurium isolate contained bla_SHV-12; the Mbandaka isolate contained bla_SHV-30. Nine Senftenberg isolates contained bla_OXA-1; 1 contained bla_OXA-9. Further studies should address patient outcomes, risk factors, and resistance dissemination prevention strategies.

Multiclonal outbreak of Klebsiella pneumoniae producing extended-spectrum beta-lactamase CTX-M-2 and novel variant CTX-M-59 in a neonatal intensive care unit in Brazil

An outbreak of cephalosporin-resistant Klebsiella pneumoniae occurred in a neonatal intensive care unit in São Paulo, Brazil. Of the 10 pulsotypes identified during the outbreak and follow-up periods, nine produced CTX-M-2 or its new variant CTX-M-59 and one produced SHV-5. bla(CTX-M-2/59) genes were located on closely related plasmids that were transferable.

qnrB, another plasmid-mediated gene for quinolone resistance

A novel plasmid-mediated quinolone resistance gene, qnrB, has been discovered in a plasmid encoding the CTX-M-15 beta-lactamase from a Klebsiella pneumoniae strain isolated in South India. It has less than 40% amino acid identity with the original qnr (now qnrA) gene or with the recently described qnrS but, like them, codes for a protein belonging to the pentapeptide repeat family. Strains with qnrB demonstrated low-level resistance to all quinolones tested. The gene has been cloned in an expression vector attaching a polyhistidine tag, which facilitated purification to >or=95% homogeneity. As little as 5 pM of QnrB-His6 protected purified DNA gyrase against inhibition by 2 microg/ml (6 microM) ciprofloxacin. With a PCR assay qnrB has been detected in Citrobacter koseri, Enterobacter cloacae, and Escherichia coli isolates from the United States, linked to SHV-12 beta-lactamase and coding for a product differing in five amino acids from the Indian (now QnrB1) variety. The qnrB gene has been found near Orf1005 in some, but not all, plasmids and in association with open reading frames matching known chromosomal genes, suggesting that it too was acquired by plasmids from an as-yet-unknown bacterial source.

PCR classification of CTX-M-type beta-lactamase genes identified in clinically isolated gram-negative bacilli in Japan

Of 1,456 strains isolated from 2001 to 2003 demonstrating resistance to either oxyimino-cephalosporin, 317 strains, isolated in 57 of 132 clinical facilities, were found to harbor bla(CTX-M) genes by PCR. Fifty-seven, 161, and 99 strains harbored bla(CTX-M) genes belonging to the bla(CTX-M-1), bla(CTX-M-2), and bla(CTX-M-9) clusters, respectively.

Molecular analysis of the simultaneous production of two SHV-type extended-spectrum beta-lactamases in a clinical isolate of Enterobacter cloacae by using single-nucleotide polymorphism genotyping

Bacteria that simultaneously produce multiple extended-spectrum beta-lactamases are frequently isolated. We report an Enterobacter cloacae isolate, ES24, producing four different beta-lactamases (AmpC type beta-lactamase, TEM-1, SHV-7, and a novel extended-spectrum beta-lactamase, SHV-30). Direct sequencing of bla(SHV) gene products gave a "double peak" at position 703, suggesting the presence of more than one allele. Using fluorescence resonance energy transfer real-time PCR to detect single-nucleotide polymorphisms, we were able to distinguish two different bla(SHV) genes in a single isolate. This may prove to be a useful technique in surveys of beta-lactamase production in contemporary clinical isolates.

Extended-spectrum-beta-lactamase-producing Escherichia coli strains isolated from farm animals from 1999 to 2002: report from the Japanese Veterinary Antimicrobial Resistance Monitoring Program

A nationwide surveillance for antimicrobial susceptibility in Escherichia coli strains isolated from food-producing animals in Japan was conducted from 1999 to 2002. Eighteen cefazolin-resistant E. coli strains were isolated from broilers. Six were CTX-M-type producing, and eight were CMY-2 producing, while eight had mutations at the ampC promoter region.

Practical methods using boronic acid compounds for identification of class C beta-lactamase-producing Klebsiella pneumoniae and Escherichia coli

Detection of the resistance mediated by class C beta-lactamases remains a challenging issue, considering that transferable plasmid-mediated class C beta-lactamases are of worldwide concern. Methods for the identification of strains that produce extended-spectrum beta-lactamases (ESBLs) or metallo-beta-lactamases (MBLs) have been developed and applied for routine use in clinical microbiology laboratories, but no practical methods for identification of plasmid-mediated class C producers have been established to date. We therefore developed three simple methods for clinical microbiology laboratories that allow identification of plasmid-mediated class C beta-lactamase-producing bacteria using a boronic acid derivative, 3-aminophenylboronic acid (APB), one of the specific inhibitors of class C beta-lactamases. Detection by the disk potentiation test was based on the enlargement of the growth-inhibitory zone diameter (by greater than or equal to 5 mm) around a Kirby-Bauer disk containing a ceftazidime (CAZ) or a cefotaxime (CTX) disk in combination with APB. In a double-disk synergy test, the discernible expansion of the growth-inhibitory zone around the CAZ or the CTX disk toward a disk containing APB was indicative of class C beta-lactamase production. A greater than or equal to eightfold decrease in the MIC of CAZ or CTX in the presence of APB was the criterion for detection in the microdilution test. By using these methods, Escherichia coli and Klebsiella pneumoniae isolates producing plasmid-mediated class C beta-lactamases, ACT-1, CMY-2, CMY-9, FOX-5, LAT-1, and MOX-1, were successfully distinguished from those producing other classes of beta-lactamases, such as ESBLs and MBLs. These methods will provide useful information needed for targeted antimicrobial therapy and better infection control.

Extended-spectrum beta-lactamase-producing Shiga toxin gene (Stx1)-positive Escherichia coli O26:H11: a new concern

Escherichia coli strain TUM2139 was isolated from a stool sample from a 9-year-old girl on 16 June 2004. This strain was categorized as Shiga toxin-producing Escherichia coli (STEC) because the Shiga-like toxin gene stx(1) was detected by immunochromatography and PCR assay. The strain was highly resistant to cefotaxime (256 microg/ml) and was also resistant to cefepime, cefpodoxime, ceftriaxone, and aztreonam. In the presence of 4 microg of clavulanic acid per ml, the MIC of cefotaxime decreased to < or =0.12 microg/ml, indicating that this strain was an extended-spectrum beta-lactamase (ESBL) producer. Cefotaxime resistance was transferred to E. coli C600 by conjugation at a frequency of 3.0 x 10(-6). A PCR assay was performed with primer sets specific for TEM-type and SHV-type ESBLs and for the CTX-M-2 (Toho-1), CTX-M-3, and CTX-M-9 groups of ESBLs. A specific signal was observed with the primer set specific for the CTX-M-9 group of beta-lactamases. This beta-lactamase was confirmed to be the ESBL CTX-M-18 by DNA sequencing. This is the first report of an ESBL-producing STEC isolate.

Nosocomial transmission of CTX-M-2 beta-lactamase-producing Acinetobacter baumannii in a neurosurgery ward

Three strains of cefotaxime (CTX)-resistant Acinetobacter baumannii, FM0209680, FM0300106, and FM0301433, were isolated from transtracheal aspirate cultures of three patients with probable nosocomial infections in a neurosurgery ward in Japan. The CTX MICs for these isolates were greater than 128 microg/ml but were drastically reduced in the presence of 4 microg of clavulanic acid per ml. These strains were also resistant to ceftriaxone, cefpodoxime, and aztreonam but were susceptible to ceftazidime and imipenem. The profile of resistance to various broad-spectrum beta-lactams was transferred by conjugation. Strain FM0209680 was not eradicated from case patient 1 by administration of imipenem, ceftazidime, and levofloxacin, even after a 6-month hospitalization period. Strains FM0300106 and FM0301433 were isolated from case patients 2 and 3 during the sixth week following admission, respectively, and then each patient was colonized for 3 weeks. Eradication of FM0300106 was successfully obtained from case patient 2 by imipenem treatment, while administration of imipenem was continued to prevent pneumonia. Prophylactic antimicrobial therapy was discontinued in case patient 3 because of the lack of pneumonic symptoms, and FM0301433 disappeared after the discontinuation of antimicrobial chemotherapy. All three strains carried the bla(CTX-M-2) gene, and the appearance of colonies in the growth-inhibitory zones around disks of CTX and aztreonam in double-disk synergy tests suggested inducible beta-lactamase production in these A. baumannii strains. The ribotyping investigation suggested that all these strains belong to the same clonal lineage. The plasmids harbored by A. baumannii had the same restriction profile as those harbored by Proteus mirabilis strains previously isolated in a urology ward of the Funabashi Medical Center.

Inhibitor-sensitive AmpC beta-lactamase variant produced by an Escherichia coli clinical isolate resistant to oxyiminocephalosporins and cephamycins

Escherichia coli HKY28, a ceftazidime-resistant strain isolated from a urine specimen in Japan, produced an inhibitor-sensitive AmpC beta-lactamase variant. The deduced amino acid sequence of the enzyme contained a number of substitutions and a tripeptide deletion (Gly286-Ser287-Asp288) compared with the sequence of native AmpC of E. coli. When the deletion was reverted by a 9-base insertion at the relevant site of ampC in the clone, the typical inhibitor-resistant phenotype of AmpC was restored, while at the same time the levels of resistance to ceftazidime, cefpirome, and cefepime were reduced eightfold or more. Molecular modeling studies indicated that a structural change took place in the H-10 helix as a result of the deletion, and this change caused an alteration of the substrate binding site, leading to a unique phenotype analogous to that of inhibitor-sensitive class A extended-spectrum beta-lactamases. The degree of inhibition was greater with sulbactam and tazobactam than with clavulanic acid. To our knowledge, this is the first report to have characterized an E. coli ampC that encodes chromosomal AmpC beta-lactamase sensitive to the available beta-lactamase inhibitors.

Nosocomial spread of ceftazidime-resistant Klebsiella pneumoniae strains producing a novel class a beta-lactamase, GES-3, in a neonatal intensive care unit in Japan

Klebsiella pneumoniae strain KG525, which showed high-level resistance to broad-spectrum cephalosporins, was isolated from the neonatal intensive care unit (NICU) of a Japanese hospital in March 2002. The ceftazidime resistance of strain KG525 was transferable to Escherichia coli CSH-2 by conjugation. Cloning and sequence analysis revealed that production of a novel extended-spectrum class A beta-lactamase (pI 7.0), designated GES-3, which had two amino acid substitutions of M62T and E104K on the basis of the sequence of GES-1, was responsible for resistance in strain KG525 and its transconjugant. The bla(GES-3) gene was located as the first gene cassette in a class 1 integron that also contained an aacA1-orfG fused gene cassette and one unique cassette that has not been described in other class 1 integrons and ended with a truncated 3' conserved segment by insertion of IS26. Another five ceftazidime-resistant K. pneumoniae strains, strains KG914, KG1116, KG545, KG502, and KG827, which were isolated from different neonates during a 1-year period in the same NICU where strain KG525 had been isolated, were also positive for GES-type beta-lactamase genes by PCR. Pulsed-field gel electrophoresis and enterobacterial repetitive intergenic consensus-PCR analyses displayed genetic relatedness among the six K. pneumoniae strains. Southern hybridization analysis with a GES-type beta-lactamase gene-specific probe showed that the locations of bla(GES) were multiple and diverse among the six strains. These findings suggest that within the NICU setting genetically related K. pneumoniae strains carrying the bla(GES) gene were ambushed with genetic rearrangements that caused the multiplication and translocation of the bla(GES) gene.

Role of a mutation at position 167 of CTX-M-19 in ceftazidime hydrolysis

CTX-M-19 is a recently identified ceftazidime-hydrolyzing extended-spectrum beta-lactamase, which differs from the majority of CTX-M-type beta-lactamases that preferentially hydrolyze cefotaxime but not ceftazidime. To elucidate the mechanism of ceftazidime hydrolysis by CTX-M-19, the beta-lactam MICs of a CTX-M-19 producer, and the kinetic parameters of the enzyme were confirmed. We reconfirmed here that CTX-M-19 is also stable at a high enzyme concentration in the presence of bovine serum albumin (20 micro g/ml). Under this condition, we obtained more accurate kinetic parameters and determined that cefotaxime (k(cat)/K(m), 1.47 x 10(6) s(-1) M(-1)), cefoxitin (k(cat)/K(m), 62.2 s(-1) M(-1)), and aztreonam (k(cat)/K(m), 1.34 x 10(3) s(-1) M(-1)) are good substrates and that imipenem (k(+2)/K, 1.20 x 10(2) s(-1) M(-1)) is a poor substrate. However, CTX-M-18 and CTX-M-19 exhibited too high a K(m) value (2.7 to 5.6 mM) against ceftazidime to obtain their catalytic activity (k(cat)). Comparison of the MICs with the catalytic efficiency (k(cat)/K(m)) of these enzymes showed that some beta-lactams, including cefotaxime, ceftazidime, and aztreonam showed a similar correlation. Using the previously reported crystal structure of the Toho-1 beta-lactamase, which belongs to the CTX-M-type beta-lactamase group, we have suggested characteristic interactions between the enzymes and the beta-lactams ceftazidime, cefotaxime, and aztreonam by molecular modeling. Aminothiazole-bearing beta-lactams require a displacement of the aminothiazole moiety due to a severe steric interaction with the hydroxyl group of Ser167 in CTX-M-19, and the displacement affects the interaction between Ser130 and the acidic group such as carboxylate and sulfonate of beta-lactams.

Escherichia coli producing CTX-M-2 beta-lactamase in cattle, Japan

From November 2000 to June 2001, Escherichia coli strains producing CTX-M-2 β-lactamase were isolated from 6 (1.5%) of 396 cattle fecal samples and 2 (0.7%) of 270 surface swabs of cattle carcasses in Japan. The bla_CTX-M-2 gene responsible for CTX-M-2 production was encoded on transferable plasmids, and the gene was transferred to E. coli CSH2 with a very high frequency (2 x 10^-4 to 6 x 10^-1 per donor cells) by conjugation. Random amplified polymorphic DNA analysis of nine isolates showed at least five different patterns. These findings suggest that CTX-M-2 producers might have originated from cattle through the use of cephalosporins such as ceftiofur and that cattle could be a reservoir of CTX-M-2–producing E. coli. Continuous and strategic surveillance of antimicrobial-resistant bacteria in livestock is essential to suppress further dissemination of these bacteria into society at large.

Prevalence and molecular epidemiology of CTX-M extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae in Russian hospitals

A total of 904 consecutive nosocomial isolates of Escherichia coli and Klebsiella pneumoniae collected from 28 Russian hospitals were screened for production of extended-spectrum beta-lactamases (ESBLs). The ESBL phenotype was detected in 78 (15.8%) E. coli and 248 (60.8%) K. pneumoniae isolates. One hundred fifteen isolates carried the genes for CTX-M-type beta-lactamases, which, as shown by PCR-restriction fragment length polymorphism analysis, were distributed into the two genetic groups of CTX-M-1 (93%)- and CTX-M-2 (7%)-related enzymes. Isolates producing the enzymes of the first group were found in 20 hospitals from geographically distant regions of the country and were characterized by considerable diversity of genetic types, as was demonstrated by enterobacterial repetitive consensus PCR typing. Within this group the CTX-M-3 and the CTX-M-15 beta-lactamases were identified. In contrast, the enzymes of the CTX-M-2 group (namely, CTX-M-5) were detected only in eight clonally related E. coli isolates from a single hospital. Notably, the levels of resistance to ceftazidime were remarkably variable among the CTX-M producers. This study provides further evidence of the global dissemination of CTX-M type ESBLs and emphasizes the need for their epidemiological monitoring.

A new TEM-derived extended-spectrum beta-lactamase (TEM-91) with an R164C substitution at the omega-loop confers ceftazidime resistance

A new plasmid-mediated TEM-derived extended-spectrum beta-lactamase, TEM-91, was identified in a ceftazidime-resistant (MIC, >128 microg per ml) Escherichia coli strain isolated in 1996 in Japan. TEM-91 has three amino acid substitutions, R164C, M184T, and E240K, compared with TEM-1 penicillinase. The isoelectric point (pI), K(m), and k(cat) of TEM-91 for ceftazidime were 5.7, 179 microM, and 29.0 s(-1), respectively. The K(i) of clavulanic acid for ceftazidime hydrolysis was 30.3 nM.