Extended-spectrum beta-lactamases from Klebsiella pneumoniae strains isolated at an Italian hospital

Eighteen strains of Klebsiella pneumoniae recently isolated from hospitalized patients were resistant or moderately resistant to oxyimino-cephalosporins (ceftazidime and/or cefotaxime), aztreonam, cefoxitin and all but one were susceptible to imipenem. Analysis of enzymes produced by these clinical isolates revealed a wide pattern of extended-spectrum beta-lactamases. All isolates produced one or more beta-lactamases that were characterized preliminarily by their isoelectric point. Strains isolated early were from patients in the Intensive Care Unit and produced an ES beta-lactamase with an apparent pI of 7.6, whereas the later isolates were from surgical and medical wards of the same hospital and produced ES beta-lactamases with apparent pI of 8.2 and 8.4, respectively. This suggests the emergence of SHV-5 and MIR-1 beta-lactamases in our hospital. Agarose gel electrophoresis of plasmid DNA revealed the presence of a similar plasmid of approximate size 60 Kb in all isolates.     

Antibiotic resistance in Pseudomonas aeruginosa: an Italian survey

In order to assess the current level of resistance to widely used antipseudomonal antibiotics in clinical isolates of Pseudomonas aeruginosa, a national survey was undertaken. Fifteen hospitals throughout Italy participated in the study. The University of Catania tested the antibiotic susceptibility of 1005 consecutive clinically significant P. aeruginosa collected from March to June 1995. Lack of susceptibility, according to NCCLS breakpoints, was at the following rates: meropenem, 9.1%; imipenem, 19.3%; ceftazidime, 13.4%; carbenicillin, 27.3%; piperacillin, 12%; ticarcillin/clavulanic acid, 22.8%; amikacin, 10.6%; and ciprofloxacin, 31.9%. About half of the isolates (44.4%) were not susceptible to at least one of the antibiotics tested.     

Contribution of beta-lactamases to beta-lactam susceptibilities of susceptible and multidrug-resistant Mycobacterium tuberculosis clinical isolates

The beta-lactamases in 154 clinical Mycobacterium tuberculosis strains were studied. Susceptibilities to beta-lactam antibiotics, their combination with clavulanate (2:1), and two fluoroquinolones were determined in 24 M. tuberculosis strains susceptible to antimycobacterial drugs and in nine multiresistant strains. All 154 M. tuberculosis isolates showed a single chromosomal beta-lactamase pattern (pI 4.9 and 5.1). M. tuberculosis beta-lactamase hydrolyzes cefotaxime with a maximum rate of 22.5 +/- 2.19 IU/liter (strain 1382). Neither amoxicillin, carbenicillin, cefotaxime, ceftriaxone, nor aztreonam was active alone. Except for aztreonam, beta-lactam combinations with clavulanate produced better antimycobacterial activity.     

Novel OXA-10-derived extended-spectrum beta-lactamases selected in vivo or in vitro

A clinical isolate of Pseudomonas aeruginosa, PAe191, was found to be highly resistant to all anti-Pseudomonas beta-lactam antibiotics (except imipenem) and resistant also to aminoglycosides. It produced a beta-lactamase (with an apparent pI of 7.6) which was not inhibited by clavulanic acid. Cloning and characterization of the beta-lactamase gene showed that it coded for a novel extended-spectrum OXA-10 variant, called OXA-19, which differed from OXA-10 by nine amino acids and from OXA-13 by two, i.e., Asn in position 73 (Asn73) instead of Ser and Asp157 instead of Gly. Asparagine in position 157 is implicated in resistance to ceftazidime, while the amino acid in position 73, in this variant, seems to condition the level of resistance to penicillins. The oxa19 gene was found to be inserted, in a typical integron structure, immediately downstream from an aac(6')-Ib gene coding for an aminoglycoside acetyltransferase variant, which was called AAC(6')-Ib9.     

A comparison of three measures of estimating premorbid intellectual level in dementia of the Alzheimer type

Forty-four patients receiving intensive care were studied prospectively to assess the utility of serial rectal swab cultures and clinical correlates of resistance for Pseudomonas aeruginosa, Enterobacter spp., Citrobacter spp., Morganella morganii, and Serratia marcescens strains resistant to ceftazidime or imipenem. Strains of Pseudomonas aeruginosa, Enterobacter spp., Citrobacter spp., or Morganella morganii were found in 26 of 44 (59%) patients: 17 (65%) in clinical sites (11 with concomitant rectal isolates) and nine (35%) in a rectal site only. Of 49 total isolates, 13 (26.5%) were resistant: 10 (20.4%) to ceftazidime and three (6.1%) to imipenem. Surveillance rectal swabs from 27 patients without a clinical isolate identified two patients with resistant organisms (15% of all resistant isolates). The majority of resistance to ceftazidime or imipenem among Pseudomonas or Enterobacter can be detected by the use of clinical specimens alone.     

Analysis of genome-type, serovar and antibiotic susceptibility of Pseudomonas aeruginosa isolated in Beijing Hospital China in 1991 to 1993]

We analyzed the in vitro antibiotic susceptibility pattern and serovar for 192 strains of Pseudomonas aeruginosa isolated at Beijing Hospital(China) from October 1991 to October 1993. The frequency of resistant strains was high, more than 15%, for ceftazidime, cefsulodin, cefoperazone, aztreonam, gentamicin, tobramycin, tosufloxacin, ofloxacin and fosfomycin. The incidence of resistants against piperacillin and imipenem was significantly low. Among the 192 strains, 16 were designated as being multi-drug resistant strains(i.e.; resistant to more than 8 drugs out of 11 drugs), and all of the multi-drug resistant strains were isolated from inpatients. Predominant serovar of 192 strains were 60(31.3%) for G, 28(14.7%) for E, and 24(12.5%) for I. Multi-drug resistant strains have no characteristic serovar. Restriction enzyme SpeI digestion analysis(using pulse field electrophoresis) of P. aeruginosa-genome yielded several common patterns, and was shown to be useful for tracing the route of nosocomial infection. Further, isolates with closely related genome type, in which the size of one digested band was different, showed a different minimum inhibitory concentration of fosfomycin in one genome type or new quinolones in the other genome type. Analysis of genome type and antibiotic susceptibility pattern may exhibit the antibiotic resistant gene.     

Imipenem resistance in Pseudomonas aeruginosa

In 1997 in western Austria, 9.9% of Pseudomonas aeruginosa strains from patients of general practitioners were resistant to imipenem as well as 18.2% of the isolates from hospitals and 20.2% of the strains at a university teaching hospital. Within the hospital the imipenem resistance varied from 9.9% among out-patients to 28.7% in isolates from intensive care units. In medical/surgical words, up to 15.1% of P. aeruginosa strains were resistant to imipenem. The incidence of imipenem-resistant P. aeruginosa strains correlates to the use of carbapenems. In June 1997, 10 consecutive isolates from 8 patients were obtained and typed using restriction fragment length polymorphism analysis (RFLP) and Pyocin typing. All 10 isolates were resistant to meropenem as well as to imipenem. The finding (by RFLP and Pyocin typing) of individual bacterial types in each isolate strongly contradicts the spread of infection by cross infection. However, all patients were proven to have been treated with imipenem during the 3 months prior to testing. In 1997, 13,880 g of imipenem were used at the university hospital in Innsbruck. The use of carbapenems appears to be the main cause for the increased incidence of imipenem-resistant P. aeruginosa strains.     

In vitro and in vivo properties of murine monoclonal antibody for a novel immature thymocyte-differentiated antigen, JL1

Bactericidal activities of 8 antibiotics (ticarcillin, piperacillin, piperacillin-tazobactam, ceftazidime, cefepime, imipenem, amikacin, ciprofloxacin) and of 7 combinations have been studied by time-killing curve technique for 16 Pseudomonas aeruginosa selected for their beta-lactams resistance phenotypes (3 wild strains, 5 penicillinases, 2 extended-spectrum beta-lactamases, 3 high level cephalosporinases and 3 non enzymatic resistance). Bactericidal activities of beta-lactams used alone were as follows: imipenem > cefepime > ceftazidime, piperacillin, piperacillin-tazobactam > ticarcillin. All the antibiotics combinations were synergistic or additive. However, only the combination of imipenem with amikacin was bactericidal for all strains. For the strains with penicillinases, piperacillin-tazobactam was not more effective than piperacillin. For the extended-spectrum beta-lactamases, we have observed a synergy with piperacillin-tazobactam and ciprofloxacin or amikacin.     

Infection and antibiotic therapy in 4000 burned patients treated in Milan, Italy, between 1976 and 1988

The pathogenic flora, isolated from burn wounds of patients admitted to a burn care unit during the years between 1976 and 1988 were typed and the in vitro susceptibility to antibacterial agents was recorded. Between 1976 and 1988 the general therapeutic approach was changed three times, in congruence with the prevalent nosocomial bacterial resistance. The most frequent isolates were: Pseud. aeruginosa, Staphylococcus aureus, Enterococcus spp., Proteus mirabilis, Escherichia coli, Enterobacter cloacae, Klebsiella spp. and other Enterobacteriaceae, such as Acinetobacter, Citrobacter. The most striking finding was the increase in antibiotic-resistant Enterococcus isolates. Staph. aureus, Klebsiella and E. cloacae showed susceptibility to cephalosporins, imipenem, pefloxacin, vancomycin; Enterococcus susceptibility to pefloxacin and vancomycin, and Pseud. aeruginosa sensitivity to piperacillin, amikacin, tobramycin was generally good. E. coli showed a satisfactory susceptibility on average, and P. mirabilis showed a good sensitivity to piperacillin, cephalosporins, amikacin, tobramycin, aztreonam and imipenem. Thus, the general bacterial flora and susceptibility have remained mostly unchanged over the years, with the conspicuous exception of Enterococcus spp. and E. cloacae, which demonstrated a marked increase in incidence, with a concomitant dramatic decrease in the sensitivity of Enterococcus spp. to antibiotics.     

Pathogenicity of human anti-platelet factor 4 (PF4)/heparin in vivo: generation of mouse anti-PF4/heparin and induction of thrombocytopenia by heparin

Acinetobacter baumannii strain A148, a clinical isolate resistant to imipenem (MIC = 32 mg l-1), synthesized two beta-lactamases with pIs 6.3 and > 9.2. The pI 6.3 enzyme hydrolyzed the penicillins, including isoxazoylpenicillins, first-, second- and, to a lesser extent, third-generation cephalosporins. It was inhibited by chloride ions and by the penem beta-lactamase inhibitor BRL 42715. Clavulanate was a weak inhibitor and EDTA did not affect the beta-lactamase activity. This enzyme also hydrolyzed imipenem with a catalytic efficiency (Kcat/Km) of 1500 mM-1 s-1. Moreover, this purified beta-lactamase produced a positive microbiological clover-leaf test with imipenem. Therefore, the pI 6.3 beta-lactamase was considered to be involved in the imipenem resistance of A. baumannii strain A148.     

A TEM-derived extended-spectrum beta-lactamase in Pseudomonas aeruginosa

A clinical strain of Pseudomonas aeruginosa, PAe1100, was found to be resistant to all antipseudomonal beta-lactam antibiotics and to aminoglycosides, including gentamicin, amikacin, and isepamicin. PAe1100 produced two beta-lactamases, TEM-2 (pI 5.6) and a novel, TEM-derived extended-spectrum beta-lactamase called TEM-42 (pI 5.8), susceptible to inhibition by clavulanate, sulbactam, and tazobactam. Both enzymes, as well as the aminoglycoside resistance which resulted from AAC(3)-IIa and AAC(6')-I production, were encoded by an 18-kb nonconjugative plasmid, pLRM1, that could be transferred to Escherichia coli by transformation. The gene coding for TEM-42 had four mutations that led to as many amino acid substitutions with respect to TEM-2: Val for Ala at position 42 (Ala42), Ser for Gly238, Lys for Glu240, and Met for Thr265 (Ambler numbering). The double mutation Ser for Gly238 and Lys for Glu240, which has so far only been described in SHV-type but not TEM-type enzymes, conferred concomitant high-level resistance to cefotaxime and ceftazidime. The novel, TEM-derived extended-spectrum beta-lactamase appears to be the first of its class to be described in P. aeruginosa.     

Ceftazidime-resistant Klebsiella pneumoniae and Escherichia coli isolates producing TEM-10 and TEM-43 beta-lactamases from St. Louis, Missouri

Ceftazidime-resistant Escherichia coli and Klebsiella pneumoniae (49 and 102 isolates, respectively) were collected from Barnes-Jewish Hospital, St. Louis, Mo., from 1992 to 1996. They were uniformly resistant to ceftazidime, generally resistant to aztreonam, and variably susceptible to cefotaxime. Four representative E. coli strains and 15 Klebsiella strains were examined. From one to four beta-lactamases were produced per strain, with three possible enzymes related to ceftazidime resistance: enzymes with pI values of 5.6, 6.1, or 7.6. By pulsed-field gel electrophoresis there were at least 13 different Klebsiella strain types and 3 different E. coli strain types, indicating that the outbreak was not clonal. After cloning and sequencing of the beta-lactamase-encoding genes, the enzyme with a pI of 5.6 was identified as TEM-10. The enzyme with a pI of 6.1 was a novel TEM variant (TEM-43) with Lys at 104, His at 164, and Thr at 182. TEM-43 showed broad-spectrum hydrolytic activity against all penicillins, with the highest hydrolysis rate for ceftazidime compared to those for the other expanded-spectrum cephalosporins. Aztreonam was also a good substrate for TEM-43, with hydrolytic activity similar to that of ceftazidime and affinity higher than that of ceftazidime. The TEM-43 beta-lactamase was well inhibited by clavulanic acid and tazobactam at concentrations of < 10 nM. Sulbactam was less effective than the other inhibitors. The Thr182 mutation previously reported in an inhibitor-resistant beta-lactamase did not cause the TEM-43 enzyme to become resistant to any of the inhibitors.     

Interpretation of Mini-Mental State Examination scores in community-dwelling elderly and geriatric neuropsychiatry patients

Detection of Klebsiella pneumoniae strains with extended-spectrum beta-lactamase (ESBL)-related resistance phenotypes is becoming important in clinical microbiology laboratories. In this study, we investigated the usefulness of three screening methods, the Etest ESBL screen, the double-disk synergy test, and the ceftazidime disk test, for identifying ESBL-producing K. pneumoniae strains. The agar dilution method was used as the standard. We also determined the in vitro activity of several new antimicrobial agents against these organisms. Strains that exhibited an increase in the minimum inhibitory concentration (MIC) to the third-generation cephalosporins or aztreonam of 2 micrograms/mL or more, but were susceptible to the three cephamycins tested, were considered to have ESBL-related resistance phenotypes. The frequency of ESBL-producing K. pneumoniae isolates (according to the disk-diffusion method) has increased markedly in recent years, from 3.4% in 1993 to 10.3% in 1997. A total of 93 preserved isolates of K. pneumoniae collected from December 1995 through March 1997 were found to be resistant to at least one of the third-generation cephalosporins (cefotaxime and ceftazidime) or aztreonam using the routine disk diffusion method. Among these isolates, 35 were classified as having an ESBL phenotype using the agar dilution method. The remaining 58 isolates were classified as cephamycin resistant, which indicated resistance to both cephamycins and third-generation cephalosporins or aztreonam. The susceptibility rates of the ESBL-producing isolates were 11% for cefotaxime, 14% for ceftazidime, and 6% for aztreonam. The susceptibility rates of these 35 isolates to imipenem, ciprofloxacin, and ofloxacin were 100%, 80%, and 86%, respectively. Both the MIC50 and MIC90 of meropenem were 0.06 microgram/mL, while the MIC50 and MIC90 of BAY 12-8039 were 0.125 and 2 micrograms/mL, respectively. Thirty-two (91%) of the 35 isolates of K. pneumoniae with the ESBL-related resistance phenotype were detected by the Etest ESBL screen, while the ceftazidime disk screen test detected 77% of these isolates, and the double-disk synergy test detected 74%. The Etest ESBL screen appears to be an acceptable, convenient, and sensitive method for the detection of ESBL-producing isolates in the clinical microbiology laboratory.     

Inducible amp C beta-lactamase producing gram-negative bacilli from blood stream infections: frequency, antimicrobial susceptibility, and molecular epidemiology in a national surveillance program (SCOPE)

A surveillance study of nosocomial blood stream infections [Surveillance and Control of Pathogens of Epidemiologic Importance (SCOPE)] was conducted during a 14-month period in 1995 to 1996 in approximately 50 American medical centers. Among the 4725 blood stream infections, the etiologic agent was Enterobacter spp. in 230, Citrobacter freundii in 24, and Serratia marcescens in 65. The vast majority of these isolates (89%) had been sent to the University of Iowa including 198 Enterobacter spp. (46 Enterobacter aerogenes, 141 Enterobacter cloacae, 11 other Enterobacter spp.), 23 C. freundii, and 62 S. marcescens. Because these species are capable of producing Amp C beta-lactamase, we examined their susceptibility to 12 broad-spectrum antimicrobial agents. The frequency of resistance to ceftazidime and the molecular epidemiology of ceftazidime-resistant strains was also examined. Among the Enterobacter spp. and C. freundii isolates, resistance to third generation cephalosporins (ceftazidime, ceftriaxone) and broad-spectrum semisynthetic penicillins (piperacillin), with or without an enzyme inhibitor (piperacillin/tazobactam), was high, e.g., 35 to 50%. The S. marcescens isolates were quite susceptible to all agents tested. Both imipenem and cefepime were active against virtually all isolates tested including 84 stably derepressed Amp C-producing ceftazidime-resistant strains of Enterobacter spp. and C. freundii. The overall rank order of activity for the six best agents against these Amp C-producing strains was: imipenem (100% susceptible) > amikacin = cefepime (98.6%) > ciprofloxacin = gentamicin = ofloxacin (93.6 to 94.0%). Molecular typing studies of ceftazidime-resistant E. cloacae using an automated ribotyping system, as well as pulsed-field gel electrophoresis, indicated that although clonal spread of a single strain occurred in some of the medical centers, most of the episodes of bacteremia were caused by patient-unique strains. Control of these resistant organisms will require attention to microbiologic recognition of phenotypes, to infection control practices, and to limiting the overuse of certain extended spectrum beta-lactams.     

Antimicrobial resistance and epidemiological study of Haemophilus influenzae strains isolated in Portugal. The Multicentre Study Group

In the course of a multicentric surveillance study, nine laboratories sent 375 isolates of Haemophilus influenzae to the Sector de Resistência aos Antibióticos (SRA) from the National Institute of Health in Lisbon, between 1 January and 31 December 1992. The majority of the H. influenzae isolates were from the respiratory tract (84.8%); only 5.1% were of invasive origin. Overall resistance for ampicillin was 11.7%, tetracycline 3.7%, and chloramphenicol 2.4%. All isolates tested were fully susceptible to cefotaxime, ceftriaxone, ciprofloxacin and rifampicin. Multiresistance was rare, occurring only in 2.4% of the isolates, although 50% of the ampicillin resistant strains had at least one additional resistance marker. Forty two isolates (11.2%) produced a TEM-1 type beta-lactamase, as shown by isoelectric focusing. beta-lactamase production was not detected in two of the ampicillin resistant strains. Fifteen of the 42 beta-lactamase producing strains (35.7%) contained detectable DNA plasmid: nine harboured large plasmids with an apparent molecular mass of 45 or 54 kb depending on their resistance phenotype and six harboured a small plasmid of 5 kb. In order to study transfer of resistance in both ampicillin and multiresistant strains conjugation experiments were performed for 14 isolates, seven of which harboured a large plasmid and seven had no detectable plasmid DNA. All 14 transferred their resistance phenotype but only a single large plasmid could be demonstrated in ten transconjugants. Restriction endonuclease analysis of plasmids from six representative transconjugants, isolated in different hospitals, revealed that there was no dissemination of a single R plasmid, which suggests an independent process of acquisition of resistance genes.     

Role of mutations in DNA gyrase genes in ciprofloxacin resistance of Pseudomonas aeruginosa susceptible or resistant to imipenem

In Pseudomonas aeruginosa, resistance to imipenem is mainly related to a lack of protein OprD and resistance to fluoroquinolones is mainly related to alterations in DNA gyrase. However, strains cross resistant to fluoroquinolones and imipenem have been selected in vitro and in vivo with fluoroquinolones. We investigated the mechanisms of resistance to fluoroquinolones in 30 clinical strains of P. aeruginosa resistant to ciprofloxacin (mean MIC, >8 micrograms/ml), 20 of which were also resistant to imipenem (mean MIC, >16 micrograms/ml). By immunoblotting, OprD levels were markedly decreased in all of the imipenem-resistant strains. Plasmids carrying the wild-type gyrA gene (pPAW207) or gyrB gene (pPBW801) of Escherichia coli were introduced into each strain by transformation. MICs of imipenem did not change after transformation, whereas those of ciprofloxacin and sparfloxacin dramatically decreased (25- to 70-fold) for all of the strains. For 28 of them (8 susceptible and 20 resistant to imipenem), complementation was obtained with pPAW207 but not with pPBW801. After complementation, the geometric mean MICs of ciprofloxacin and sparfloxacin (MICs of 0.3 microgram/ml and 0.5 microgram/ml, respectively) were as low as those for wild-type strains. Complementation was obtained only with pPBW801 for one strain and with pPAW207 and pPBW801 for one strain highly resistant to fluoroquinolones. These results demonstrate that in clinical practice, gyrA mutations are the major mechanism of resistance to fluoroquinolones even in the strains of P. aeruginosa resistant to imipenem and lacking OprD, concomitant resistance to these drugs being the result of the addition of at least two independent mechanisms.     

Epidemiology of community-acquired Pseudomonas aeruginosa infections in children

The epidemiology of community-acquired Pseudomonas aeruginosa infections in children during a one-year period (January through December 1993) was evaluated. A total of 6,859 clinical samples, each one representing a separate individual with suspected infection, were cultured. Pseudomonas aeruginosa was isolated from 218 children with various infections occurring in the following order of frequency: chronic suppurative otitis media, 76.3%; appendicitis/peritonitis, 10.3%; osteomyelitis, 8.9%; skin or soft tissue infection, 6.3%; acute conjunctivitis, 3.0%; and urinary tract infection, 0.1%. A variety of O serogroups were identified: O1 (15.2%), O6 (14.7%), O11 (12.4%), O10 (11.5%), O3 (10.6%), O5 (5.1%), and O9 (4.6%). Other serogroups and nontypable strains were recovered at a frequency of 11.2% and 14.7%, respectively. Nontypable strains predominated in chronic otitis media (18.9%), while serogroups O1 (18.3%), O6 (17.5%), and O11 (17.5%) were recovered most frequently among the typable isolates. Susceptibility of Pseudomonas aeruginosa to antipseudomonadal agents was extremely high. The rate of susceptibility to ceftazidime was 99.6%, to azlocillin 98.6%, to piperacillin 98.2%, to aztreonam 97.3%, to gentamicin and netilmicin 97.7%, and to ciprofloxacin 99.1%. All isolates were susceptible to tobramycin, imipenem, and amikacin. The results might suggest that community-acquired Pseudomonas aeruginosa infections in children can be treated successfully with any antipseudomonadal antibiotic.     

Pseudomonas aeruginosa isolates from patients with cystic fibrosis have different beta-lactamase expression phenotypes but are homogeneous in the ampC-ampR genetic region

Pseudomonas aeruginosa isolates from 1 of 17 cystic fibrosis patients produced secondary beta-lactamase in addition to the ampC beta-lactamase. Isolates were grouped into three beta-lactamase expression phenotypes: (i) beta-lactam sensitive, low basal levels and inducible beta-lactamase production; (ii) beta-lactam resistant, moderate basal levels and hyperinducible beta-lactamase production; (iii) beta-lactam resistant, high basal levels and constitutive beta-lactamase production. Apart from a base substitution in the ampR-ampC intergenic region of an isolate with moderate-basal-level and hyperinducible beta-lactamase production, sensitive and resistant strains were identical in their ampC-ampR genetic regions. Thus, enhanced beta-lactamase expression is due to mutations in regulatory proteins other than AmpR.     

Norepinephrine loss selectively enhances chronic nigrostriatal dopamine depletion in mice and rats

A total of 3,700 Pseudomonas aeruginosa isolates were collected from 17 general hospitals in Japan from 1992 to 1994. Of these isolates, 132 carbapenem-resistant strains were subjected to DNA hybridization analysis with the metallo-beta-lactamase gene (blaIMP)-specific probe. Fifteen strains carrying the metallo-beta-lactamase gene were identified in five hospitals in different geographical areas. Three strains of P. aeruginosa demonstrated high-level imipenem resistance (MIC, > or = 128 micrograms/ml), two strains exhibited low-level imipenem resistance (MIC, < or = 4 micrograms/ml), and the rest of the strains were in between. These results revealed that the acquisition of a metallo-beta-lactamase gene alone does not necessarily confer elevated resistance to carbapenems. In several strains, the metallo-beta-lactamase gene was carried by large plasmids, and carbapenem resistance was transferred from P. aeruginosa to Escherichia coli by electroporation in association with the acquisition of the large plasmid. Southern hybridization analysis and genomic DNA fingerprinting profiles revealed different genetic backgrounds for these 15 isolates, although considerable similarity was observed for the strains isolated from the same hospital. These findings suggest that the metallo-beta-lactamase-producing P. aeruginosa strains are not confined to a unique clonal lineage but proliferated multifocally by plasmid-mediated dissemination of the metallo-beta-lactamase gene in strains of different genetic backgrounds. Thus, further proliferation of metallo-beta-lactamase-producing strains with resistance to various beta-lactams may well be inevitable in the future, which emphasizes the need for early recognition of metallo-beta-lactamase-producing strains, rigorous infection control, and restricted clinical use of broad-spectrum beta-lactams including carbapenems.     

Transcontinental importation into the UK of Escherichia coli expressing a plasmid-mediated AmpC-type beta-lactamase exposed during an outbreak of SHV-5 extended-spectrum beta-lactamase in a Leeds hospital

Sixteen strains of Escherichia coli with high-level resistance to extended-spectrum cephalosporins and other classes of antibiotic have been isolated at St James' University Hospital, Leeds. They produce up to three separate beta-lactamases: TEM-1, SHV-5 and, in five isolates, a plasmid-mediated AmpC-type enzyme. With the exception of carbapenems, the isolates reported in this study were resistant to all beta-lactam antibiotics including extended-spectrum cephalosporins and the monobactam aztreonam. There was evidence of the spread of a plasmid encoding SHV-5, particularly amongst patients on the liver transplant unit. Sensitivity to beta-lactam antibiotics in five isolates expressing the AmpC-type beta-lactamase was not restored by the beta-lactamase inhibitor clavulanic acid. These bacteria also carried blaSHV-5 on a large plasmid. PCR-amplification of the structural gene and digestion with restriction endonucleases demonstrated that the plasmid-mediated blaAmpC probably identified as BIL-1 using the criteria available. Four of the five patients carrying isolates that carried the plasmid-located blaAmpC gene had recently visited the Indian subcontinent and we presume that they returned carrying these bacteria. Restriction fragment length polymorphism analysis using pulsed field gel electrophoresis (PFGE) suggests that at least four distinct strains existed amongst these five isolates. The two isolates that had very similar PFGE patterns had different plasmid profiles and were isolated from different locations in the hospital and at different times. This study demonstrates the ease with which highly resistant bacteria can be imported into the UK and spread within hospitals.