Molecular epidemiology of extended-spectrum beta-lactamase-producing Klebsiella pneumoniae isolates in a district hospital in Taiwan

Thirty-one of 104 clinical isolates of Klebsiella pneumoniae collected over a period of 8 months were found to be putative extended-spectrum beta-lactamase (ESBL) producers. Isoelectric focusing and an iodine overlay agar method were used for preliminary identification of the ESBLs. They were further identified by DNA sequencing. Seventy-one percent of the isolates were found to produce SHV-5. The variation in the ESBL patterns of these isolates was slight, with only five patterns being identified. The strains were typed by pulsed-field gel electrophoresis (PFGE), and 16 different genotypes were identified. When the PFGE patterns were analyzed by the algorithmic clustering method called the unweighted-pair group method using arithmetic averages, five clusters were found. However, significant genetic variations were found among 11 isolates and between each cluster. A plasmid of 36 kb was found in all clinical isolates and in the transconjugants. Our results indicate that the increase in the number of ESBL-producing K. pneumoniae isolates in this hospital is due mainly to the dissemination of a resistance plasmid rather than to the clonal spread of a few epidemic strains.     

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.     

Extended-spectrum beta-lactamase-producing Klebsiella pneumoniae strains causing nosocomial outbreaks of infection in the United Kingdom

Representative isolates from 10 distinct extended-spectrum beta-lactamase-producing strains of Klebsiella pneumoniae that caused hospital outbreaks in the United Kingdom from 1991 to 1994 were examined for relationships between their enzymes and plasmids. The beta-lactamases were identified by a combination of isoelectric focusing and gene sequencing. SHV-2 beta-lactamase was produced by isolates from four outbreaks, SHV-5 was involved in three, and SHV-4, TEM-15, and TEM-26 were involved in one outbreak each. All of the extended-spectrum beta-lactamases were encoded by self-transmissible plasmids, with sizes ranging from about 70 to 160 kb. No similarities between the restriction digest patterns of the extended-spectrum beta-lactamase-encoding plasmids were detected, except to some extent between those that produced TEM-15 and TEM-26. Thus, outbreaks of hospital infection with these organisms in the United Kingdom from 1991 to 1994 involved distinct organisms and resistance plasmids and appeared to be unrelated.     

Outbreak of ceftazidime-resistant Klebsiella pneumoniae in a pediatric hospital in Warsaw, Poland: clonal spread of the TEM-47 extended-spectrum beta-lactamase (ESBL)-producing strain and transfer of a plasmid carrying the SHV-5-like ESBL-encoding gene

In 1996 a large, 300-bed pediatric hospital in Warsaw, Poland, started a program of monitoring infections caused by extended-spectrum beta-lactamase (ESBL)-producing microorganisms. Over the first 3-month period eight Klebsiella pneumoniae isolates were identified as being resistant to ceftazidime. Six of these were found to produce the TEM-47 ESBL, which we first described in a K. pneumoniae strain recovered a year before in a pediatric hospital in Lód?, Poland, which is 140 km from Warsaw. Typing results revealed a very close relatedness among all these isolates, which suggested that the clonal outbreak in Warsaw was caused by a strain possibly imported from Lód?. The remaining two isolates expressed the SHV-5-like ESBL, which resulted from the horizontal transfer of a plasmid carrying the blaSHV gene between nonrelated strains. The data presented here exemplify the complexity of the epidemiological situation concerning ESBL producers typical for large Polish hospitals, in which no ESBL-monitoring programs were in place prior to 1995.     

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.     

Leukocyte CD14 and CD45 expression during hemodialysis: polysulfone versus cuprophane

Four Klebsiella pneumoniae isolates (LB1, LB2, LB3, and LB4) with increased antimicrobial resistance were obtained from the same patient. The four isolates were indistinguishable in biotype, plasmid content, lipopolysaccharide, and DNA analysis by pulse-field gel electrophoresis. Isolate LB1 made TEM-1 and SHV-1 beta-lactamases. Isolates LB2, LB3, and LB4 produced SHV-5 in addition to TEM-1 and SHV-1. MICs of cefoxitin, ceftazidime, and cefotaxime against LB1 were 4, 1, and 0.06 micrograms/ml, respectively. MICs of ceftazidime against K. pneumoniae LB2, LB3, and LB4 were > 256 micrograms/ml, and those of cefotaxime were 2, 4, and 64 micrograms/ml, respectively. MICs of cefoxitin against K. pneumoniae LB2 and LB3 were 4 micrograms/ml, but that against K. pneumoniae LB4 was 128 micrgrams/ml. K. pneumoniae LB4 could transfer resistance to ceftazidime and cefotaxime, but not that to cefoxitin, to Escherichia coli. Isolate LB4 and cefoxitin-resistant laboratory mutants lacked an outer membrane protein of about 35 kDa whose molecular mass, mode of isolation, resistance to proteases, and reaction with a porin-specific antiserum suggested that it was a porin. MICs of cefoxitin and cefotaxime reverted to 4 and 2 micrograms/ml, respectively, when isolate LB4 was transformed with a gene coding for the K. pneumoniae porin OmpK36. We conclude that the increased resistance to cefoxitin and expanded-spectrum cephalosporins of isolate LB4 was due to loss of a porin channel for antibiotic uptake.     

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.     

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.     

Chromosomally encoded ampC-type beta-lactamase in a clinical isolate of Proteus mirabilis

A clinical strain of Proteus mirabilis (CF09) isolated from urine specimens of a patient displayed resistance to amoxicillin (MIC >4,096 microg/ml), ticarcillin (4,096 microg/ml), cefoxitin (64 microg/ml), cefotaxime (256 microg/ml), and ceftazidime (128 microg/ml) and required an elevated MIC of aztreonam (4 microg/ml). Clavulanic acid did not act synergistically with cephalosporins. Two beta-lactamases with apparent pIs of 5.6 and 9.0 were identified by isoelectric focusing on a gel. Substrate and inhibition profiles were characteristic of an AmpC-type beta-lactamase with a pI of 9.0. Amplification by PCR with primers for ampC genes (Escherichia coli, Enterobacter cloacae, and Citrobacter freundii) of a 756-bp DNA fragment from strain CF09 was obtained only with C. freundii-specific primers. Hybridization results showed that the ampC gene is only chromosomally located while the TEM gene is plasmid located. After cloning of the gene, analysis of the complete nucleotide sequence (1,146 bp) showed that this ampC gene is close to blaCMY-2, from which it differs by three point mutations leading to amino acid substitutions Glu --> Gly at position 22, Trp --> Arg at position 201, and Ser --> Asn at position 343. AmpC beta-lactamases derived from that of C. freundii (LAT-1, LAT-2, BIL-1, and CMY-2) have been found in Klebsiella pneumoniae, E. coli, and Enterobacter aerogenes and have been reported to be plasmid borne. This is the first example of a chromosomally encoded AmpC-type beta-lactamase observed in P. mirabilis. We suggest that it be designated CMY-3.     

Characterization of ceftriaxone-resistant Enterobacteriaceae: a multicentre study in 26 French hospitals. Vigil'Roc Study Group

During a multicentre study performed in 26 French hospitals, 287 (3.2%) of 9038 Enterobacteriaceae isolated, mainly Enterobacter spp., Serratia spp., Citrobacter spp. and Klebsiella spp. were classified as ceftriaxone resistant on the basis of an MIC > 4 mg/L or the presence of an extended-spectrum beta-lactamase. Extended-spectrum beta-lactamase was present mainly in Klebsiella pneumoniae (65 strains, 10.2%) and very rarely in Escherichia coli, Proteus mirabilis, Klebsiella oxytoca, Citrobacter spp. and Enterobacter spp. The extended-spectrum beta-lactamases conferred low-level resistance to ceftriaxone in nearly 60% of the strains harbouring them, emphasizing the need for routine testing for the presence of these enzymes. Among transconjugants three types of extended-spectrum beta-lactamase were identified. Those resembling TEM-3 were the most common, but TEM-21, and SHV-4 were also found. Clavulanate and to a lesser extent sulbactam inhibited all the extended-spectrum beta-lactamases encountered in this study.     

beta-Lactamases responsible for resistance to expanded-spectrum cephalosporins in Klebsiella pneumoniae, Escherichia coli, and Proteus mirabilis isolates recovered in South Africa

Although resistance to the expanded-spectrum cephalosporins among members of the family Enterobacteriaceae lacking inducible beta-lactamases occurs virtually worldwide, little is known about this problem among isolates recovered in South Africa. Isolates of Klebsiella pneumoniae, Escherichia coli, and Proteus mirabilis resistant to expanded-spectrum cephalosporins recovered from patients in various parts of South Africa over a 3-month period were investigated for extended-spectrum beta-lactamase production. Antibiotic susceptibility was determined by standard disk diffusion and agar dilution procedures. Production of extended-spectrum beta-lactamases was evaluated by using the double-disk test, and the beta-lactamases were characterized by spectrophotometric hydrolysis assays and an isoelectric focusing overlay technique which simultaneously determined isoelectric points and general substrate or inhibitor characteristics. DNA amplification and sequencing were performed to confirm the identities of these enzymes. The P. mirabilis and E. coli isolates were found to produce TEM-26-type, SHV-2, and SHV-5 extended-spectrum beta-lactamases. An AmpC-related enzyme which had a pI of 8.0 and which conferred resistance to cefoxitin as well as the expanded-spectrum cephalosporins was found in a strain of K. pneumoniae. This is the first study which has identified organisms producing different extended-spectrum beta-lactamases from South Africa and the first report describing strains of P. mirabilis producing a TEM-26-type enzyme. The variety of extended-spectrum beta-lactamases found among members of the family Enterobacteriaceae isolated from major medical centers in South Africa is troubling and adds to the growing list of countries where these enzymes pose a serious problem for antimicrobial therapy.     

Cloning and sequencing of the gene encoding Toho-2, a class A beta-lactamase preferentially inhibited by tazobactam

Escherichia coli TUM1083, which is resistant to ampicillin, carbenicillin, cephaloridine, cephalothin, piperacillin, cefuzonam, and aztreonam while being sensitive to cefoxitin, moxalactam, cefmetazole, ceftazidime, and imipenem, was isolated from the urine of a patient treated with beta-lactam antibiotics. The beta-lactamase (Toho-2) purified from the bacteria hydrolyzed beta-lactam antibiotics such as penicillin G, carbenicillin, cephaloridine, cefoxitin, cefotaxime, ceftazidime, and aztreonam and especially had increased relative hydrolysis rates for cephalothin, cephaloridine, cefotaxime, and ceftizoxime. Different from other extended-spectrum beta-lactamases, Toho-2 was inhibited 16-fold better by the beta-lactamase inhibitor tazobactam than by clavulanic acid. Resistance to beta-lactams was transferred by conjugation from E. coli TUM1083 to E. coli ML4909, and the transferred plasmid was about 54.4 kbp, belonging to the incompatibility group IncFII. The cefotaxime resistance gene for Toho-2 was subcloned from the 54.4-kbp plasmid. The sequence of the gene was determined, and the open reading frame of the gene was found to consist of 981 bases. The nucleotide sequence of the gene (DDBJ accession no. D89862) designated as bla(toho) was found to have 76.3% identity to class A beta-lactamase CTX-M-2 and 76.2% identity to Toho-1. It has 55.9% identity to SHV-1 beta-lactamase and 47.5% identity to TEM-1 beta-lactamase. Therefore, the newly isolated beta-lactamase designated as Toho-2 produced by E. coli TUM1083 is categorized as an enzyme similar to Toho-1 group beta-lactamases rather than to mutants of TEM or SHV enzymes. According to the amino acid sequence deduced from the DNA sequence, the precursor consisted of 327 amino acid residues. Comparison of Toho-2 with other beta-lactamase (non-Toho-1 group) suggests that the substitutions of threonine for Arg-244 and arginine for Asn-276 are important for the extension of the substrate specificity.     

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.     

Inhibitor-resistant OXY-2-derived beta-lactamase produced by Klebsiella oxytoca

Klebsiella oxytoca strains are generally moderately resistant to amoxicillin and ticarcillin due to the activities of the chromosomally encoded OXY-1 and OXY-2 class A beta-lactamase families. These enzymes have the ability to hydrolyze not only penicillins but also cephalosporins, including cefuroxime, ceftriaxone, and aztreonam, and are inhibited by clavulanic acid. A Klebsiella oxytoca strain was isolated from a culture of blood from a patient who had been treated with amoxicillin-clavulanate (3 g/day) for 10 days 1 month earlier. This strain harbored an unusual phenotype characterized by resistance to amoxicillin-clavulanate. It produced an OXY-2-type beta-lactamase (pI 6.3), as confirmed by PCR amplification with primers specific for the OXY-2-encoding gene. Gene sequencing revealed a point mutation (A-->G) corresponding to the amino acid substitution Ser-->Gly at position 130. This mutant enzyme was poorly inhibited by inhibitors, and its kinetic constants compared to those of the parent enzyme were characterized by an increased Km value for ticarcillin, with a drastically reduced activity against cephalosporins, as is observed with inhibitor-resistant TEM enzymes. The substitution Ser-->Gly-130 was previously described in the inhibitor-resistant beta-lactamase SHV-10 derived from an SHV-5 variant, but this is the first report of such a mutant in OXY enzymes from K. oxytoca.     

Topographic variation in biglycan and decorin synthesis by articular cartilage in the early stages of osteoarthritis: an experimental study in sheep

From October 1988 to January 1992, nine isolates of Pseudomonas aeruginosa carrying transferable plasmids encoding imipenem-hydrolyzing beta-lactamase (pI = c. 9.5) were recovered from nine different patients in a neurosurgical ward of a hospital in Japan. The beta-lactamase activities of the sonicated extracts from the transconjugants were inhibited by EDTA and this was partially reversible by the addition of zinc cation. The substrate specificity and pI of the beta-lactamase were similar to those of the metallo beta-lactamases from P. aeruginosa and Serratia marcescens TN9106. All strains were resistant to imipenem, carbenicillin and antipseudomonal cephems including ceftazidime, cefsulodin, cefpirome, while four and five strains were susceptible to piperacillin and aztreonam, respectively. Both low level imipenem resistance and high level cephem resistance were co-transferred with the production of metallo beta-lactamase, while resistance to piperacillin, aztreonam, and high level imipenem-resistance were not selected. Production of chromosomal cephalosporinase in piperacillin resistant strains was derepressed, and production of outer membrane protein of D2 was diminished in highly imipenem resistant strains. Six strains were isolated in 1991, and the amounts of antipseudomonal agents, especially imipenem, used in the neurosurgical ward increased markedly in this year. Only three of the nine isolates had the same serotype, pyocin type and phage type. Our results suggest that the repeated isolation of imipenem and cephem-resistant P. aeruginosa producing metallo beta-lactamase was related to the high usage of antipseudomonal beta-lactam antibiotics such as imipenem, and was exacerbated by the dissemination of a plasmid.     

A novel chronic and detachable indwelling jugular catheterization procedure for mice

SHV-6 was previously identified by its susceptibility pattern and biochemical criteria in a clinical isolate of Klebsiella pneumoniae which was resistant to ceftazidime. It contains only a single point difference with the beta laSHV-1 gene as determined by PCR amplification and nucleotide sequencing. This is the result of a single amino acid substitution, Ala for Asp, at position 179. Directed mutagenesis experiments have shown this substitution to confer selective resistance to ceftazidime in the TEM family.     

Characterization of plasmids which mediate resistance to multiple antibiotics in gram-negative bacteria of nosocomial origin

BACKGROUND: The genetic and molecular mechanisms involved in antimicrobial resistance of 10 strains of gramnegative bacilli (1 Serratia marcescens; 2 Escherichia coli; 1 Proteus mirabilis; 4 Klebsiella pneumoniae; 1 Enterobacter cloacae y 1 Alcaligenes faecalis), isolated from adult patients with nosocomial pulmonary infection at the in-patient facilities of the University Hospital of Los Andes, Mérida, Venezuela, have been studied. METHODS: The antimicrobial susceptibility was determined by minimum inhibitory concentrations using the dilution method in agar. The study of extrachromosomal genes was carried out by conjugation, bacterial infection with the bacteriophage M13 and curing of plasmid by acridine orange. The plasmids were isolated by alkaline lysis and analysis of restriction endonuclease digestion was carried out separately using the enzymes EcoRI and HindIII. A DNA probe, derived from the region which encodes the TEM-1 beta-lactamase of the plasmid pBR322 was used for dot-blot hybridization tests. RESULTS: All of the gramnegative bacilli showed resistance to ampicillin, carbenicillin and cephalothin (> 128 micrograms/ml) and 3 strains also showed resistance to gentamicin (> 64 micrograms/ml). Genetic and molecular procedures showed the presence of conjugative plasmids of approximately 54 kb in all the 10 strains. The restriction patterns obtained by using EcoRI and HindIII indicated common DNA fragments in most of the plasmids studied. The dot-blot hybridization tests confirmed homology between the plasmids and the DNA probe used (TEM-1 beta-lactamase). CONCLUSIONS: In this study, the gramnegative bacteria of nosocomial origin harbored self-transferable plasmids of approximately 54 kb, which mediate resistance to gentamicin and encode a beta-lactamase of the TEM group.     

Extended spectrum beta-lactamases in Danish Klebsiella isolates

This study presents the first two cases of infections with Klebsiella pneumoniae producing extended spectrum betalactamases (ESBL) that have been recorded in Denmark. They presented as a urinary tract infection and a generalized infection in a patient admitted to an intensive care unit. Both patients had been treated with broad spectrum antibiotics prior to infection. Presumably, one of the strains had been imported from Turkey. The ESBL of the two strains were characterized as SHV-2 and SHV-5, respectively. Patients transferred from hospitals abroad should be screened for Klebsiella producing ESBL, in addition to MRSA and other multiresistant organisms. A restrictive antibiotic policy and strict hygienic precautions are essential measures to control the selection and spread of such organisms in the hospital environment.     

Penectomy: a technique to reduce blood loss

Twelve SHV-type extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli lac mutant isolates were recovered in October 1997 from 11 patients of the neonatal ward in a Warsaw hospital. The outbreak was clonal; however, some of the isolates expressed a much higher level of resistance to several beta-lactam antibiotics, including expanded-spectrum cephalosporins. This phenotype has been attributed to beta-lactamase hyperproduction correlating with the multiplication of ESBL gene copies, as was demonstrated for representative isolates.     

First characterization of inhibitor-resistant TEM (IRT) beta-lactamases in Klebsiella pneumoniae strains

Two clinical strains of Klebsiella pneumoniae, TP 01 and TP 02, presented resistance to amoxicillin-clavulanate and were fully susceptible to cephalothin. These strains produced two beta-lactamases, SHV-1 and a TEM enzyme with a pI of 5.2. The previously described changes Arg-244-->Cys and Arg-244-->Ser in IRT-1 and IRT-2 (A. Belaaouaj, C. Lapoumeroulie, M. M. Cani?a, G. Vedel, P. Nevot, R. Krishnamoorthy, and G. Paul, FEMS Microbiol. Lett. 120:75-80, 1994) were found in TEM enzymes from the TP 01 and TP 02 strains, respectively. This is the first report of inhibitor-resistant TEM (IRT) in species other than Escherichia coli from the family Enterobacteriaceae.