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Carbapenem-hydrolysing IMP-1 β-lactamase in Klebsiella pneumoniae from Singapore
events. The DRA came to know about fulminant hepatic failure with nimesulide through an e-mail discussion group (“E-drug”) in May. The paediatric nimesulide preparation has now been withdrawn from sale in and Israel.4 These Portugal3 discoveries were fortuitous—the DRA simply does not have the funds to subscribe to medical journals or the personnel to monitor reports. Nimesulide is now unlikely to be registered in Sri Lanka because of these reports. As Figueras and colleagues underline, the World Trade Organisation and the International Conference on Harmonisation are driving the procedures for registration of drugs. What should a developing country with little or no information exchange, and inadequate regulation of drugs do, when the harmonised dossiers of the new drugs are submitted for registration? In the few situations in which the new drug has a clear advantage over existing drugs, it should properly be assessed and registered promptly. However for the “me-too” drugs with no advantage over existing drugs, which make-up most of the applications, such speed may not be needed. There is a simple way to decide on “me-too” drugs; the approved product information (indications, adverse effects) for an existing drug from a reference DRA would show little or no difference from that of the newer “me-too”. Sri Lanka used this method and did not register mibefradil,5 the caution was well placed since the drug was subsequently withdrawn worldwide. An important issue in registering new drugs in developing countries is whether health or trade should come first. Registering new drugs without delay would help trade and free circulation of goods; adopting a cautious attitude would serve health. Should not the government ensure that citizens are healthy before they begin to trade? K Weerasuriya *Department of Pharmacology, Faculty of Medicine, University of Colombo, Colombo 00800, Sri Lanka; and Drug Evaluation Sub Committee Ministry of Health, Colombo 1
Figueras A, Estevez F, Laporte J-R. New drugs, new adverse reactions, and bibliographic databases. Lancet 1999; 3 5 3 : 1447–48. 2 Nimesulide ADR controversy in Portugal. Scrip 1999; no 2406: 8. 3 Portugal suspends paediatric nimesulide. Scrip 1990; no 2431: 20. 4 Israel nimesulide suspension inquiry. Scrip 1999; no 2434: 23. 5 Weerasuriya K. Mibefradil: the sole exception. Lancet 1998; 351: 1829–30.
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Carbapenem-hydrolysing IMP-1 -lactamase in Klebsiella pneumoniae from Singapore Sir—The carbapenems (meropenem and imipenem) are the -lactams with the broadest spectrum and are stable to most -lactamases. They are invaluable against multiresistant gram-negative bacteria, but resistance is beginning to appear. Carbapenem-resistant Klebsiella pneumoniae from the USA1 and Scotland 2 had impermeability together with hyperproduction of chromosomal or acquired -lactamases with weak carbapenemase activity. More ominously, potent acquired carbapenemases have been reported in a few Pseudomonas aeruginosa and Enterobacteriaceae, and in rather greater numbers of Acinetobacter spp.3 Only one such enzyme—IMP-1—has become established on any scale, and that only in Japan,4 where it is scattered in P aeruginosa and Serratia marcescens. IMP-1, which is often plasmid mediated, has also been reported once from Klebsiella spp in Japan.4 When expressed efficiently, IMP-1 confers resistance to all carbapenems, penicillins, and cephalosporins, and this resistance cannot be overcome with any -lactamase inhibitor.3 Aztreonam is stable, but producers are often resistant by other mechanisms.3 G Cornaglia and colleagues (March 13, p 899)5 reported IMP-1 from Acinetobacter baumannii in Italy and wider dissemination outside Japan is increasingly feared. In 1996, a 25-year-old Chinese man with acute myeloid leukaemia was treated for neutropenic fever in Singapore. He received several courses of antibiotics, including imipenem. 3 days after he started imipenem, a carbapenem-resistant K pneumoniae strain (identified with an API20E strip) was isolated from blood culture. He responded to combined therapy with amikacin, co-trimoxazole, and ceftazidime, and subsequent blood cultures were negative. The minimum inhibitory concentrations of penicillins, cephalosporins, carbapenems, and other antibiotics for the K pneumoniae isolate were 128 mg/L or greater, apart from amikacin (1 mg/L) and ciprofloxacin (8 mg/L). Crude extracts of the K pneumoniae isolate hydrolysed imipenem in bioassays and this activity was confirmed by spectrophotometry. Imipenemase activity was almost completely inhibited by 10 mmol/L edetic acid, and this inhibition was reversed by 10 mmol/L zinc sulphate indicating a metallo--lactamase.
Isoelectric focusing revealed multiple -lactamase bands with isoelectric points between 7·6 and 9·0. All except the isoelectric point 7·6 activity aligned with bands given by an IMP-1 control from P aeruginosa 101/1477 and all except this 7·6 activity were partially inhibited if the gel was overlaid with 10 mmol/L edetic acid before adding nitrocefin as the indicator substrate. PCR with primers for the IMP-1 gene (bla IMP-1) gave a positive result, confirming the presence of this gene or of a close relative. Conjugative transfer of the imipenem resistance to Escherichia coli K-12 J53-2 was achieved by broth mating followed by counter selection on agar that contained imipenem and rifampicin. The transconjugant showed an eightfold increase in imipenem minimum inhibitory concentration (from 0·25 to 2 mg/L) and acquired IMP-1 enzyme and a 150 kb plasmid. Given the extended resistance conferred, that IMP-1 enzyme can be encoded by plasmids and integrons which facilitate its spread and recombination,3 and that K pneumoniae is notorious for its ability to spread among patients and to act as a vector for resistance plasmids, we believe the discovery of IMP-1-positive K pneumoniae in Singapore to be a serious cause for concern. This study was funded by a grant from the British Society of Antimicrobial Chemotherapy.
*T H Koh, G S Babini, N Woodford, L-H Sng, L M C Hall, D M Livermore *Department of Medical Microbiology, Royal London Hospital, London E1 1BB, UK; Antibiotic Resistance Monitoring and Reference Laboratory, Central Public Health Laboratory, London; Department of Pathology, Singapore General Hospital, Singapore; and Department of Medical Microbiology, St Bartholomew’s and the Royal London School of Medicine and Dentistry, London 1
Bradford PA, Urban C, Mariano N, Projan SJ, Rahal JJ, Bush K. Imipenem resistance in Klebsiella pneumoniae is associated with the combination of ACT-1, a plasmid mediated AmpC -lactamase, and the loss of an outer membrane protein. Antimicrob Agents Chemother 1997; 41: 563–69. 2 MacKenzie FM, Forbes KJ, Dorai-John T, Amyes SGB, Gould IM. Emergence of a carbapenem-resistant Klebsiella pneumoniae. Lancet 1997; 350: 783. 3 Livermore DM. Acquired carbapenemases. J Antimicrob Chemother 1997; 39: 673–76. 4 Senda K, Arakawa Y, Nakashima K, et al. Multifocal outbreaks of metallo-lactamase-producing Pseudomonas aeruginosa resistant to broad-spectrum -lactams, including carbapenems. Antimicrob Agents Chemother 1996; 40: 349–53. 5 Cornaglia G, Riccio ML, Mazzariol A, Lauretti L, Fontana R, Rossolini GM. Appearance of IMP-1 metallo--lactamase in Europe. Lancet 1999; 353: 899–900.
THE LANCET • Vol 353 • June 19, 1999
Figueras A, Estevez F, Laporte J-R. New drugs, new adverse reactions, and bibliographic databases. Lancet 1999; 3 5 3 : 1447–48. 2 Nimesulide ADR controversy in Portugal. Scrip 1999; no 2406: 8. 3 Portugal suspends paediatric nimesulide. Scrip 1990; no 2431: 20. 4 Israel nimesulide suspension inquiry. Scrip 1999; no 2434: 23. 5 Weerasuriya K. Mibefradil: the sole exception. Lancet 1998; 351: 1829–30.
2162
Carbapenem-hydrolysing IMP-1 -lactamase in Klebsiella pneumoniae from Singapore Sir—The carbapenems (meropenem and imipenem) are the -lactams with the broadest spectrum and are stable to most -lactamases. They are invaluable against multiresistant gram-negative bacteria, but resistance is beginning to appear. Carbapenem-resistant Klebsiella pneumoniae from the USA1 and Scotland 2 had impermeability together with hyperproduction of chromosomal or acquired -lactamases with weak carbapenemase activity. More ominously, potent acquired carbapenemases have been reported in a few Pseudomonas aeruginosa and Enterobacteriaceae, and in rather greater numbers of Acinetobacter spp.3 Only one such enzyme—IMP-1—has become established on any scale, and that only in Japan,4 where it is scattered in P aeruginosa and Serratia marcescens. IMP-1, which is often plasmid mediated, has also been reported once from Klebsiella spp in Japan.4 When expressed efficiently, IMP-1 confers resistance to all carbapenems, penicillins, and cephalosporins, and this resistance cannot be overcome with any -lactamase inhibitor.3 Aztreonam is stable, but producers are often resistant by other mechanisms.3 G Cornaglia and colleagues (March 13, p 899)5 reported IMP-1 from Acinetobacter baumannii in Italy and wider dissemination outside Japan is increasingly feared. In 1996, a 25-year-old Chinese man with acute myeloid leukaemia was treated for neutropenic fever in Singapore. He received several courses of antibiotics, including imipenem. 3 days after he started imipenem, a carbapenem-resistant K pneumoniae strain (identified with an API20E strip) was isolated from blood culture. He responded to combined therapy with amikacin, co-trimoxazole, and ceftazidime, and subsequent blood cultures were negative. The minimum inhibitory concentrations of penicillins, cephalosporins, carbapenems, and other antibiotics for the K pneumoniae isolate were 128 mg/L or greater, apart from amikacin (1 mg/L) and ciprofloxacin (8 mg/L). Crude extracts of the K pneumoniae isolate hydrolysed imipenem in bioassays and this activity was confirmed by spectrophotometry. Imipenemase activity was almost completely inhibited by 10 mmol/L edetic acid, and this inhibition was reversed by 10 mmol/L zinc sulphate indicating a metallo--lactamase.
Isoelectric focusing revealed multiple -lactamase bands with isoelectric points between 7·6 and 9·0. All except the isoelectric point 7·6 activity aligned with bands given by an IMP-1 control from P aeruginosa 101/1477 and all except this 7·6 activity were partially inhibited if the gel was overlaid with 10 mmol/L edetic acid before adding nitrocefin as the indicator substrate. PCR with primers for the IMP-1 gene (bla IMP-1) gave a positive result, confirming the presence of this gene or of a close relative. Conjugative transfer of the imipenem resistance to Escherichia coli K-12 J53-2 was achieved by broth mating followed by counter selection on agar that contained imipenem and rifampicin. The transconjugant showed an eightfold increase in imipenem minimum inhibitory concentration (from 0·25 to 2 mg/L) and acquired IMP-1 enzyme and a 150 kb plasmid. Given the extended resistance conferred, that IMP-1 enzyme can be encoded by plasmids and integrons which facilitate its spread and recombination,3 and that K pneumoniae is notorious for its ability to spread among patients and to act as a vector for resistance plasmids, we believe the discovery of IMP-1-positive K pneumoniae in Singapore to be a serious cause for concern. This study was funded by a grant from the British Society of Antimicrobial Chemotherapy.
*T H Koh, G S Babini, N Woodford, L-H Sng, L M C Hall, D M Livermore *Department of Medical Microbiology, Royal London Hospital, London E1 1BB, UK; Antibiotic Resistance Monitoring and Reference Laboratory, Central Public Health Laboratory, London; Department of Pathology, Singapore General Hospital, Singapore; and Department of Medical Microbiology, St Bartholomew’s and the Royal London School of Medicine and Dentistry, London 1
Bradford PA, Urban C, Mariano N, Projan SJ, Rahal JJ, Bush K. Imipenem resistance in Klebsiella pneumoniae is associated with the combination of ACT-1, a plasmid mediated AmpC -lactamase, and the loss of an outer membrane protein. Antimicrob Agents Chemother 1997; 41: 563–69. 2 MacKenzie FM, Forbes KJ, Dorai-John T, Amyes SGB, Gould IM. Emergence of a carbapenem-resistant Klebsiella pneumoniae. Lancet 1997; 350: 783. 3 Livermore DM. Acquired carbapenemases. J Antimicrob Chemother 1997; 39: 673–76. 4 Senda K, Arakawa Y, Nakashima K, et al. Multifocal outbreaks of metallo-lactamase-producing Pseudomonas aeruginosa resistant to broad-spectrum -lactams, including carbapenems. Antimicrob Agents Chemother 1996; 40: 349–53. 5 Cornaglia G, Riccio ML, Mazzariol A, Lauretti L, Fontana R, Rossolini GM. Appearance of IMP-1 metallo--lactamase in Europe. Lancet 1999; 353: 899–900.
THE LANCET • Vol 353 • June 19, 1999