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Objectives: In England, group B streptococci (GBS; Streptococcus agalactiae) are considered universally susceptible to penicillin. Reports from Africa, Asia, North America and a few European countries have described GBS isolates with penicillin MICs above the epidemiological cut-off (0.125 mg/L). Our aim was to characterize a penicillin-resistant GBS (PRGBS) isolate recovered in 2016 from a patient treated with long-term antimicrobials in the UK., Methods: Antibiotic susceptibility of a referred isolate from a discharging sinus overlying a chronic prosthetic joint infection was determined using gradient strip testing for seven antibiotics. Illumina short read sequencing was carried out using a HiSeq 2500 platform to determine MLST, capsular type, to detect mutations in the pbp genes, and to compare the isolate with contemporaneous GBS isolates circulating in the UK., Results: The GBS isolate belonged to capsular type Ia and MLST 144. We observed resistance to penicillin (MIC = 1 mg/L) and tetracycline (32 mg/L) with susceptibility to linezolid (1 mg/L), erythromycin (0.064 mg/L), clindamycin (0.064 mg/L), teicoplanin (0.064 mg/L) and vancomycin (0.25 mg/L). Deduced amino acid sequences revealed substitutions and non-synonymous changes in PBP2x and PBP2b. Genomic analysis of contemporaneous cases (n = 34) from across the UK identified single nucleotide polymorphism (SNP) variation ranged from 153-6596 SNPs., Conclusions: We confirm the first identification of a PRGBS isolate amongst referrals to the UK's national reference laboratory. Substitutions in pbp1a, pbp2a, pbp2x and pbp2b were identified that likely developed in the face of long-term beta-lactam antibiotic use., (© The Author(s) 2024. Published by Oxford University Press on behalf of British Society for Antimicrobial Chemotherapy.)

Background: Ceftazidime/avibactam combines an established oxyimino-cephalosporin with the first diazabicyclooctane β-lactamase inhibitor to enter clinical use. We reviewed its activity against Gram-negative isolates, predominantly from the UK, referred for resistance investigation in the first year of routine testing, beginning in July 2015., Methods: Isolates were as received from referring laboratories; there is a bias to submit those with suspected carbapenem resistance. Identification was by MALDI-TOF mass spectroscopy, and susceptibility testing by BSAC agar dilution. Carbapenemase genes were sought by PCR; other resistance mechanisms were inferred using genetic data and interpretive reading., Results: Susceptibility rates to ceftazidime/avibactam exceeded 95% for: (i) Enterobacteriaceae with KPC, GES or other Class A carbapenemases; (ii) Enterobacteriaceae with OXA-48-like enzymes; and (iii) for ESBL or AmpC producers, even when these had impermeability-mediated ertapenem resistance. Almost all isolates with metallo-carbapenemases were resistant. Potentiation of ceftazidime by avibactam was seen for 87% of ceftazidime-resistant Enterobacteriaceae with 'unassigned' ceftazidime resistance mechanisms, including two widely referred groups of Klebsiella pneumoniae where no synergy was seen between cephalosporins and established β-lactamase inhibitors. Potentiation here may be a diazabicyclooctane/cephalosporin enhancer effect. Activity was seen against Pseudomonas aeruginosa with derepressed AmpC, but not for those with efflux-mediated resistance., Conclusions: Of the available β-lactams or inhibitor combinations, ceftazidime/avibactam has the widest activity spectrum against problem Enterobacteriaceae, covering all major types except metallo-carbapenemase producers; against P. aeruginosa it has a slightly narrower spectrum than ceftolozane/tazobactam, which also covers efflux-type resistance.

Objectives: Detection of rarer carbapenemases is challenging, as it requires molecular assays with comprehensive coverage or the use of phenotypic methods for the detection of carbapenemase activity. We describe a new class A carbapenemase, FRI-2, in an Enterobacter cloacae complex isolate following implementation of an in-house multiplex PCR for the detection of 'rare' class A carbapenemases., Methods: MICs were determined by agar dilution. A carbapenem-resistant E. cloacae complex isolate was tested by PCR for the class A carbapenemases blaKPC, blaFRI, blaIMI, blaGES and blaSME. Carbapenemase activity was assessed using Carba NP and the carbapenem inactivation method. Whole genome and plasmid analyses of the clinical isolate and the FRI-2 transformant were performed by WGS, respectively. Typing was carried out by PFGE., Results: The E. cloacae complex isolate showed resistance to imipenem (MIC = 16 mg/L), meropenem (MIC = 8 mg/L) and ertapenem (MIC = 8 mg/L), but remained susceptible to piperacillin/tazobactam (MIC = 8 mg/L). Carbapenemase activity was confirmed in the isolate by both phenotypic methods. A blaFRI-1-like gene was detected by PCR and analysis of WGS data of the clinical isolate identified an ORF of 885 bp, which showed 97% nucleotide identity with blaFRI-1 and was named blaFRI-2. WGS of the transformant indicated blaFRI-2 was located on a 108 kb IncF/IncR plasmid. The FRI-2-positive E. cloacae complex isolate belonged to a novel ST (ST829)., Conclusions: The possible circulation of rarer carbapenemases in clinical settings highlights the role of phenotypic tests to detect carbapenemase activity when molecular assays are negative for the 'big 5' carbapenemase families., (© Crown copyright 2017.)

Background: We assessed the activity of ceftolozane/tazobactam against consecutive isolates collected in the BSAC Bacteraemia Surveillance from 2011 to 2015 and against 'problem' isolates sent to the UK national reference laboratory from July 2015, when routine testing began., Methods: Susceptibility testing was by BSAC agar dilution with resistance mechanisms identified by PCR and interpretive reading., Results: Data were reviewed for 6080 BSAC surveillance isolates and 5473 referred organisms. Ceftolozane/tazobactam had good activity against unselected ESBL producers in the BSAC series, but activity was reduced against ertapenem-resistant ESBL producers, which were numerous among reference submissions. AmpC-derepressed Enterobacter spp. were widely resistant, but Escherichia coli with raised chromosomal AmpC frequently remained susceptible, as did Klebsiella pneumoniae with acquired DHA-1-type AmpC. Carbapenemase-producing Enterobacteriaceae were mostly resistant, except for ceftazidime-susceptible isolates with OXA-48-like enzymes. Ceftolozane/tazobactam was active against 99.8% of the BSAC Pseudomonas aeruginosa isolates; against referred P. aeruginosa it was active against 99.7% with moderately raised efflux, 94.7% with strongly raised efflux and 96.6% with derepressed AmpC. Resistance in P. aeruginosa was largely confined to isolates with metallo-β-lactamases (MBLs) or ESBLs. MICs for referred Burkholderia spp. and Stenotrophomonas maltophilia were 2-4-fold lower than those of ceftazidime., Conclusions: Ceftolozane/tazobactam is active against ESBL-producing Enterobacteriaceae; gains against other problem Enterobacteriaceae groups were limited. Against P. aeruginosa it overcame the two most prevalent mechanisms (up-regulated efflux and derepressed AmpC) and was active against 51.9% of isolates non-susceptible to all other β-lactams, rising to 80.9% if ESBL and MBL producers were excluded., (© The Author 2017. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy.)

Objectives: OXA-48-like carbapenemases have spread worldwide since 2001. We analysed patient and microbiological data for UK isolates with these enzymes as confirmed by the national reference laboratory from November 2007 to December 2014., Methods: MICs were determined using BSAC agar dilution. Isolates with reduced susceptibility or resistance to at least one carbapenem and high-level resistance to both piperacillin/tazobactam (MICs ≥64 mg/L) and temocillin (MICs ≥128 mg/L) were screened by PCR for bla OXA-48-like genes. The genomes of about half of the isolates were sequenced, with MLST types, resistance genes and plasmid replicon types inferred. Patient data provided by sending laboratories were reviewed., Results: Isolates ( n  =   741) with OXA-48-like carbapenemases were submitted from 111 UK laboratories, representing 536 patients. Almost all (99%; 736 of 741) were Enterobacteriaceae, predominantly Klebsiella pneumoniae (55%; 408), and most (80%; 595) were from inpatients. WGS of 351 non-duplicate isolates identified bla OXA-48 as the most common variant, found in two-thirds (235 of 351) of isolates, followed by bla OXA-181 (68), bla OXA-232 (32), bla OXA-244 (10), bla OXA-484 (5) and bla OXA-245 (1). Among K. pneumoniae (163 of 351), Escherichia coli (114 of 351) and Enterobacter cloacae (42 of 351), 119 STs were identified. Mapping analyses revealed that 63% (222 of 351) of isolates harboured plasmids that shared >99% identity to one of four known plasmids [pOXA-48a (44%; 154 of 351), pOXA-232 (10%; 34 of 351), pOXA181 (9%; 30 of 351) and pKP3-A (1%; 4 of 351)]; the remaining 37% of isolates harboured bla OXA-48-like in unknown environments., Conclusions: OXA-48-like carbapenemases are an increasing problem in the UK. This study highlights both the role of successful plasmids and the polyclonal nature of their dissemination., (© Crown copyright 2017.)

Objectives: Carbapenemase-producing Enterobacteriaceae (CPE) have been increasingly reported in the UK since 2003. We analysed patient and isolate data for CPE confirmed by the national reference laboratory from laboratories in the West Midlands region from November 2007 to December 2014., Methods: MICs were determined by BSAC agar dilution methodology and isolates exhibiting resistance to one or more carbapenems were screened for carbapenemase genes by PCR. Plasmid analyses were performed after electro-transformation of carbapenemase-encoding plasmids. WGS was performed on both transformants and clinical isolates. Patient data provided by the sending laboratories were reviewed., Results: During the study period, CPE ( n  = 139) were submitted from 13 laboratories in the West Midlands region, originating from 108 patients and including one environmental isolate. CPE submissions increased significantly from 2009 onwards. Isolates were predominantly Klebsiella pneumoniae (89/139) obtained from inpatients. WGS was performed on all clinical isolates and transformants. After deduplication 119 isolates and 96 transformants remained for analysis. Within these, four families of carbapenemase genes were identified: bla NDM (69/119), bla KPC (26/119), bla OXA-48-like (16/119) and bla VIM (7/119); one isolate carried both bla NDM and bla OXA-48-like . Isolates represented diverse STs and plasmid replicon types. Plasmid analyses identified plasmids of different replicon types encoding bla KPC , bla NDM and bla OXA-48-like genes, found across several species and STs., Conclusions: CPE have been reported increasingly in the West Midlands region over a 7 year period. bla NDM , bla KPC and bla OXA-48-like were the dominant carbapenemase genes and were found in a range of diverse genomic/plasmid environments, highlighting their ability to mobilize across different plasmids, often impeding the detection of outbreaks., (© Crown copyright 2017.)

Objectives: To estimate UK prevalence and incidence of clinically significant carbapenemase-producing Enterobacteriaceae (CPE), and to determine epidemiological characteristics, laboratory methods and infection prevention and control (IPC) measures in acute care facilities., Methods: A 6 month survey was undertaken in November 2013-April 2014 in 21 sentinel UK laboratories as part of the European Survey on Carbapenemase-Producing Enterobacteriaceae (EuSCAPE) project. Up to 10 consecutive, non-duplicate, clinically significant and carbapenem-non-susceptible isolates of Escherichia coli or Klebsiella pneumoniae were submitted to a reference laboratory. Participants answered a questionnaire on relevant laboratory methods and IPC measures., Results: Of 102 isolates submitted, 89 (87%) were non-susceptible to ≥1 carbapenem, and 32 (36%) were confirmed as CPE. CPE were resistant to most antibiotics, except colistin (94% susceptible), gentamicin (63%), tigecycline (56%) and amikacin (53%). The prevalence of CPE was 0.02% (95% CI = 0.01%-0.03%). The incidence of CPE was 0.007 per 1000 patient-days (95% CI = 0.005-0.010), with north-west England the most affected region at 0.033 per 1000 patient-days (95% CI = 0.012-0.072). Recommended IPC measures were not universally followed, notably screening high-risk patients on admission (applied by 86%), using a CPE 'flag' on patients' records (70%) and alerting neighbouring hospitals when transferring affected patients (only 30%). Most sites (86%) had a laboratory protocol for CPE screening, most frequently using chromogenic agar (52%) or MacConkey/CLED agars with carbapenem discs (38%)., Conclusions: The UK prevalence and incidence of clinically significant CPE is currently low, but these MDR bacteria affect most UK regions. Improved IPC measures, vigilance and monitoring are required., (© Crown copyright 2016.)

Objectives: Klebsiella pneumoniae carbapenemases (KPCs) have been increasingly reported in the UK since 2003. We analysed patient and isolate data for KPC-positive bacteria confirmed by the national reference laboratory from UK laboratories from August 2003 to August 2014, excluding North-West England, where the epidemiology has previously been studied., Methods: MICs were determined by BSAC agar dilution. Carbapenem-resistant isolates lacking imipenem/EDTA synergy were tested by PCR for blaKPC. MLST and blaKPC sequencing were performed on a subset of isolates. Plasmid analysis was performed by transformation, PCR-based replicon typing and, in some cases, whole-plasmid sequencing. Patient data provided by the sending laboratories were reviewed., Results: Two hundred and ten isolates with KPC enzymes were submitted from 71 UK laboratories outside North-West England, representing 160 patients. All were Enterobacteriaceae, predominantly K. pneumoniae (82%; 173/210), and most (91%; 191/210) were from hospitalized patients. Analysis of 100 isolates identified blaKPC-2 (62%), blaKPC-3 (30%) and blaKPC-4 (8%). Clonal group (CG) 258 was dominant among K. pneumoniae (64%; 54/84), but 21 unrelated STs were also identified. Plasmid analysis identified a diverse range of plasmids representing >11 different replicon types and found in multiple STs and species. Most (34/35) plasmids with IncFIB/FIIK replicons exhibited >99% sequence identity to pKpQIL., Conclusions: KPC enzymes are increasingly detected in Enterobacteriaceae in the UK, albeit without the major outbreaks seen in North-West England. K. pneumoniae CG258 are the dominant hosts, but plasmid spread plays a major role in KPC dissemination between other K. pneumoniae STs and enterobacterial species., (© The Author 2016. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.)

Objectives: Gram-negative bacteria with diverse carbapenemases, including New Delhi metallo-β-lactamase (NDM) enzymes, have been increasingly recorded in the UK since 2007. We analysed patient data for NDM-positive isolates confirmed by the national reference laboratory from UK laboratories from February 2008 to July 2013., Methods: Isolates resistant to carbapenems and with imipenem MICs reduced ≥8-fold by EDTA were tested by PCR for genes encoding acquired class B carbapenemases. MICs were determined by BSAC agar dilution methodology. When requested by the sender, or when they were members of apparent clusters, NDM-positive isolates were typed by variable number tandem repeat (VNTR) analysis or PFGE. Data provided by the sending laboratories were collated and reviewed., Results: From February 2008 to July 2013 the reference laboratory confirmed 326 NDM-positive isolates from 250 patients, submitted by 83 laboratories. Most (85%, 213/250) patients were already hospitalized when the NDM-positive bacteria were detected, were male (61%, 152/250) and were aged >60 years (58%, 145/250). Travel history was available for only 40% of patients, but 52% (53/101) of these had documented healthcare contact within or travel to the Indian subcontinent. Most NDM-positive isolates (94%, 306/326) were Enterobacteriaceae with just 6% (20/326) non-fermenters; the predominant hosts were Klebsiella spp. (55%, 180/326) and Escherichia coli (25%, 80/326). Almost all NDM-positive isolates were resistant to multiple antibiotic classes, but 90% remained susceptible to colistin., Conclusions: Gram-negative bacteria with NDM carbapenemases are a growing challenge, especially for elderly hospitalized patients, including those with healthcare contact in the Indian subcontinent, and leave few therapeutic options. UK outbreaks remain rare and contained., (© Crown copyright 2014.)

Objectives: To characterize UK clinical isolates of Enterobacteriaceae producing OXA-48-like carbapenemases and to compare their resistance plasmids., Methods: Twenty-six enterobacteria producing OXA-48-like enzymes were studied. These were from 22 diverse hospitals in the UK. Isolates of Escherichia coli and Klebsiella pneumoniae were assigned to clonal lineages by multilocus sequence typing. Carbapenemase genes and their genetic environments were characterized by PCR and sequencing. Resistance plasmids were transferred by transformation or conjugation and compared by restriction analysis and PCR for genes encoding critical plasmid functions., Results: Thirteen isolates of K. pneumoniae, 10 E. coli and 2 Enterobacter cloacae harboured a classical bla(OXA-48) gene; the K. pneumoniae isolates belonged to 11 sequence types (STs) and the E. coli to 7 STs, including ST131 and ST38. The bla(OXA-48) genes were located within either Tn1999 or Tn1999.2 transposons on related ≈ 50 kb or ≈ 62 kb plasmids, which lacked other resistance genes or, in one isolate, on an ≈ 140 kb plasmid that also encoded OXA-9 and CTX-M group-9 β-lactamases. One India-linked K. pneumoniae isolate had a bla(OXA-181) gene in association with an ISEcp1 insertion sequence on a 7 kb plasmid., Conclusions: Horizontal transfer of related plasmids has facilitated the spread of OXA-48 carbapenemase into multiple strains of several Enterobacteriaceae species. The clonal diversity of the producers suggests repeated introduction into the UK. Low carbapenem MICs for some producers complicates detection and creates a risk for unrecognized spread.

Background: The global accumulation of Escherichia coli with CTX-M extended-spectrum β-lactamases partly reflects the dissemination of clonal lineages, notably ST131 and ST405. More recently, E. coli have emerged that produce NDM carbapenemase. We sought to determine the clonal diversity of E. coli with this enzyme from English hospitals, and to compare them with isolates from Pakistan and India., Methods: The 18 NDM-positive E. coli were from hospitals in England (n = 10), Pakistan (n = 7) and India (n = 1). Isolates were compared by phylogenetic grouping, multilocus sequence typing and PFGE of XbaI-digested DNA. Isolates were screened by PCR for acquired AmpC genes, bla(CTX-M), and the 16S rRNA methylase genes armA and rmtC., Results: Most of the isolates belonged to phylogenetic groups B1 (n = 9) or D (n = 7); two were group A and none was group B2. Nine isolates from England and Pakistan belonged to the B1 lineage ST101, with seven of these clustering at >77% similarity by PFGE. Other lineages included ST405 (n = 3, group D), ST648 (n = 3, group D), the ST23 complex (one each of ST90 and ST410, both group A) and ST156 (n = 1, group D). Sixteen of 18 isolates had a group 1 CTX-M gene, 13 had a CIT-type acquired AmpC, and 16 had either or both of armA and rmtC., Conclusions: The E. coli isolates producing NDM-1 carbapenemase belonged to six sequence types and included diverse clonal lineages. Nevertheless, isolates of B1-ST101 accounted for half the collection, and included isolates from both England and Pakistan. None of the isolates belonged to ST131 or to phylogroup B2.

Objectives: To describe the emergence of linezolid-resistant methicillin-resistant Staphylococcus aureus (MRSA) of sequence type (ST)36 lineage in two paediatric patients with cystic fibrosis, after long-term low-dose linezolid treatment., Methods: Two paediatric males with cystic fibrosis had sputum samples quantitatively cultured during hospitalization. After the isolation of MRSA from both patients, oral treatment with 300 mg linezolid twice daily was initiated for periods of 1-2 months separated by up to 6 months. Isolates cultured 9 months after the start of treatment were tested for resistance to linezolid by agar dilution (BSAC). Resistant isolates were examined for 23S rDNA mutations, and typed by phage and macrorestriction with SmaI. Isolates from follow-up sputum samples were obtained until 44-51 months after treatment with linezolid., Results: Colonization with MRSA was at a density of approximately 10(6) cfu/mL sputum for both subjects. Initial isolates were susceptible to linezolid, but, 9 months later, isolates from both patients were resistant (MICs > 16 mg/L). Both isolates were epidemic MRSA-16 variant A1 (ST36-MRSA-II), which is widespread in UK hospitals. Both isolates were heterozygous for a G2576T mutation in their 23S rDNA genes, but one was resistant to fusidic acid and tetracycline. In follow-up sampling, the younger patient yielded linezolid-resistant EMRSA-16 for a further 42 months, whilst the other lost the linezolid-resistant MRSA and had alternately Pseudomonas aeruginosa or linezolid-susceptible EMRSA-16 variant A1 isolated over 35 further months., Conclusions: Linezolid resistance emerged in two isolates of ST36 MRSA colonizing the lungs of two paediatric cystic fibrosis patients. Subtherapeutic levels of linezolid may have facilitated the selection of resistance.

Objectives: To determine the distribution of acquired AmpC beta-lactamases in 173 isolates of Escherichia coli and Klebsiella spp. submitted to the UK's national reference laboratory for antibiotic resistance., Methods: MICs were determined and interpreted according to BSAC guidelines. Candidate isolates were those resistant to cefotaxime and/or ceftazidime, irrespective of addition of clavulanic acid. Genes encoding six phylogenetic groups of acquired AmpC enzymes were sought by PCR. Selected isolates were compared by pulsed-field gel electrophoresis (PFGE), and one bla(AmpC) amplicon was sequenced., Results: Genes encoding acquired AmpC enzymes were detected in 67 (49%) candidate E. coli and 21 (55%) Klebsiella spp. Sixty isolates produced CIT-type enzymes, 14 had ACC types, 11 had FOX types and 3 had DHA enzymes. The low-level cephalosporin resistance of the remaining isolates (n = 85; 49%) was inferred to result from reduced permeability or, in E. coli, from hyperexpression of chromosomal ampC. Twenty-four E. coli isolates from one hospital produced a CIT-type enzyme, with 20 of these additionally producing a group 1 CTX-M extended-spectrum beta-lactamase. PFGE indicated that these isolates belonged to UK epidemic strain A, which normally produces CTX-M-15, but no acquired AmpC. Sequencing a representative bla(AmpC) amplicon indicated that in one centre this strain had acquired a novel CMY-2 variant, designated CMY-23., Conclusions: Diverse acquired AmpC enzymes occur in E. coli and Klebsiella spp. isolates in the UK and Ireland, with CIT types the most common. Producers are geographically scattered, but with some local outbreaks. Acquisition of a CMY-2-like enzyme by E. coli epidemic strain A suggests that these enzymes may be poised to become an important public health issue.

Objectives: The UK, like other countries worldwide, has a growing problem with CTX-M beta-lactamase-producing Escherichia coli. Five major clonally related strains have been identified among CTX-M-15 producers. We characterize here the plasmids from clonal strains A and D., Methods: Plasmids were extracted and transformed into E. coli DH5alpha; conjugative mating was attempted on agar. MICs were determined by agar dilution. beta-Lactamases were typed by isoelectric focusing; antibiotic resistance genes and integrons were identified by PCR and sequenced. Plasmid incompatibility groups were determined by replicon PCR., Results: bla(CTX-M-15) was carried by a 150 kb plasmid in strain A and a 70 kb plasmid in strain D. Conjugative transfer of cefotaxime resistance was only achieved from strain D; plasmids from both strains were transferred by transformation. The plasmid from strain A additionally carried bla(TEM-1) (variably), bla(OXA-1), aac(6')-Ib-cr and tet(A), as well as a class 1 integron with the gene cassettes aadA5 and dfr(17); the plasmid from strain D carried bla(TEM-1) consistently, also bla(OXA-1), aac(6')-Ib-cr, aac3-IIa and tet(A). Both plasmids belonged to incompatibility group FII., Conclusions: bla(CTX-M-15) was plasmid-mediated in both strains A and D and was linked to other antibiotic resistance genes including aac(6')-Ib-cr, which encodes an acetyltransferase, not previously found in Europe, acting on both aminoglycosides and some fluoroquinolones. Although the plasmids from the two strains differed in size, both were related and conferred similar multi-drug resistance phenotypes, suggesting that they may share a similar genetic scaffold. Both shared features with plasmids encoding CTX-M-15 beta-lactamases in E. coli from Canada and India.

ISAba1 was found in all widespread clones of Acinetobacter baumannii in the United Kingdom. All isolates studied had a blaOXA-51-like carbapenemase gene; some also had blaOXA-23-like and/or blaOXA-58-like. Among isolates with blaOXA-51-like as sole carbapenemase gene, only those with ISAba1 adjacent to blaOXA-51-like were carbapenem resistant. Minor differences in blaOXA-51-like sequence were observed in resistant and susceptible isolates. Isolates with blaOXA-23-like in addition were consistently resistant to carbapenems; in all of these ISAba1 lay upstream of blaOXA-23-like, but was not associated with blaOXA-51-like. These results suggest that ISAba1 is providing the promoter for blaOXA-51-like and, probably, for blaOXA-23-like.

Objectives: During 2003, the Health Protection Agency's Antibiotic Resistance Monitoring and Reference Laboratory began to receive isolates of Escherichia coli for confirmation of extended-spectrum beta-lactamase production with a phenotype implying a CTX-M-type beta-lactamase, i.e. MICs of cefotaxime > or = 8-fold higher than MICs of ceftazidime. Many were referred as being from community patients. We examined 291 CTX-M-producing isolates from the UK and investigated the genetic basis of their phenotype., Methods: PCR was used to detect alleles encoding CTX-M enzymes and to assign these to their blaCTX-M phylogenetic groups. Selected alleles were sequenced. Producers were compared by analysis of banding patterns generated by pulsed-field gel electrophoresis of XbaI-digested genomic DNA. MICs were determined by an agar dilution method or by Etest., Results: Of 291 CTX-M-producing E. coli isolates studied from 42 UK centres, 70 (24%) were reportedly from community patients, many of whom had only limited recent hospital contact. Community isolates were referred by 12 centres. Two hundred and seventy-nine (95.9%) producers contained genes encoding group 1 CTX-M enzymes and 12 contained blaCTX-M-9-like alleles. An epidemic CTX-M-15-producing strain was identified, with 110 community and inpatient isolates referred from six centres. Representatives of four other major strains also produced CTX-M-15, as did several sporadic isolates examined. Most producers were multi-resistant to fluoroquinolones, trimethoprim, tetracycline and aminoglycosides as well as to non-carbapenem beta-lactams., Conclusions: CTX-M-producing E. coli are a rapidly developing problem in the UK, with CTX-M-15 particularly common. The diversity of producers and geographical scatter of referring laboratories indicates wide dissemination of blaCTX-M genes. Because of the public health implications, including for the treatment of community-acquired urinary tract infections, the spread of these strains--and CTX-M-15 beta-lactamase in particular--merits close monitoring.

Mercury-resistant bacteria isolated from the oral cavities of children carried one of two types of merA gene that appear to have evolved from a common ancestor. Streptococcus oralis, Streptococcus mitis and a few other species had merA genes that were very similar to merA of Bacillus cereus strain RC607. Unlike the B. cereus RC607 merA gene, however, the streptococcal merA genes were not carried on Tn5084-like transposons. Instead, comparisons with microbial genomic sequences suggest the merA gene is located on a novel type II transposon. Coagulase-negative staphylococci and Streptococcus parasanguis had identical merA genes that represent a new merA variant.

Genes encoding resistance to mercury and to antibiotics are often carried on the same mobile genetic element and so it is possible that mercury-containing dental materials may select for bacteria resistant to mercury and to antibiotics. The main aim of this study was to determine whether the prevalence of Hg-resistant oral bacteria was greater in children with mercury amalgam fillings than in those without. A secondary aim was to determine whether the Hg-resistant isolates were also antibiotic resistant. Bacteria in dental plaque and saliva from 41 children with amalgam fillings and 42 children without such fillings were screened for mercury resistance by cultivation on a HgCl(2)-containing medium. Surviving organisms were identified and their susceptibility to mercury and to several antibiotics was determined. Seventy-eight per cent and 74% of children in the amalgam group and amalgam-free group, respectively, harboured Hg-resistant bacteria; this difference was not statistically significant. Nor was there any significant difference between the groups in terms of the proportions of Hg-resistant bacteria in the oral microflora of the children. Of Hg-resistant bacteria, 88% and 92% from the amalgam group and the amalgam-free group, respectively, were streptococci; 41% and 33% were resistant to at least one antibiotic, most frequently tetracycline. The results of this study show that there was no significant difference between children with amalgam fillings and those without such fillings with regard to the prevalence, or the proportion, of Hg-resistant bacteria in their oral microflora. The study also found that Hg-resistant bacteria were common in children regardless of whether or not they had amalgam fillings and that many of these organisms were also resistant to antibiotics.