Dissemination of genetically related IMP-6-producing multidrug-resistant Pseudomonas aeruginosa ST235 in South Korea

It is unclear whether the genetic background of drug-resistant Pseudomonas aeruginosa was disseminated from a certain clone. Thus, we performed MLST (multilocus sequence typing) of 896 P. aeruginosa isolates that were nonsusceptible to imipenem, meropenem, or ceftazidime. This revealed 254 sequence types (STs), including 104 new STs and 34 STs with novel alleles. Thirtythree clonal complexes and 404 singletons were found. In conclusion, drug-resistant P. aeruginosa clones can be developed from diverse genetic backgrounds. Pseudomonas aeruginosa is one of the most common opportunistic pathogens and can cause severe diseases in humans, especially patients in intensive care units, burn centers, and cystic fibrosis centers (1-4). Infections caused by P. aeruginosa are often difficult to treat and are a great challenge to physicians and patients, raising morbidity and mortality rates (5, 6). Previous studies have revealed that the number of drug-resistant P. aeruginosa strains is increasing and the rate of resistance to carbapenems goes up every year (7-9). For instance, The CAPITAL surveillance program tested the susceptibility of 2,722 P. aeruginosa isolates, which revealed that the rates of resistance to imipenem, meropenem, and ceftazidime were 21.9, 15.4, and 15.2%, respectively (10). MLST (multilocus sequence typing) is an unambiguous molecular typing method that is used mostly to assess local outbreaks of infections (11-13). Study of population genetic backgrounds is also an application for MLST. For example, previous studies have indicated that the P. aeruginosa population structure is nonclonal (14-17). Specifically, Kidd et al. collected 501 P. aeruginosa isolates from an extensive region and various sources and identified 274 different sequence types (STs) that were confirmed as nonclonal (18). Some studies have focused on different geographic areas, but the samples used were of limited size or from the environment (16,18). A large-scale epidemiological study of drug-resistant P. aeruginosa based on MLST has not been conducted in China. This study was conducted in order to investigate the drug resistance of P. aeruginosa in China and its genetic background based on MLST.A total of 2,818 P. aeruginosa isolates were collected in 2010 from 65 hospitals in 22 regions of China. Susceptibilities to 16 antimicrobial agents were evaluated by the disk diffusion method. The results were interpreted according to the 2012 Clinical and Laboratory Standards Institute (CLSI) guidelines (19), and P. aeruginosa ATCC 27853 was used as the control. The results showed that carbapenems (imipenem and meropenem), cephalosporins (cefepime and ceftazidime), penicillins (piperacillin and tazobactam-piperacillin), quinolones (ciprofloxacin), and aminoglycosides (amikacin and gentamicin) were more active than other drugs, with susceptibility rates ranging from 71.2 to 85.2%. The rates of isolate resistance to imipenem, meropenem, and ceftazidime were 23.1, 18.1, and 15.3%, respectively. Cefoperazone, sulbactam-cefoperazone, and aztre...

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confidence: 99%

Multilocus Sequence Typing Reveals Genetic Diversity of Carbapenem- or Ceftazidime-Nonsusceptible Pseudomonas aeruginosa in China

Wang

Zhou

et al. 2013

“…(7,14). IMP-6, which differs from IMP-1 by an S262G mutation, was first isolated in 1996 in Japan, also from Serratia marcescens (27), and has also been identified in P. aeruginosa and Enterobacteriaceae in Japan (28) and South Korea (20,21,29). The biochemical properties of IMP-1 and IMP-6 have been compared extensively (10,16,18,27).…”

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confidence: 99%

“…When virtually mutating Gly235 in both crystal structures to serine using the "mutate" tool in Swiss-PDB Viewer (http://spdbv.vital-it.ch/), which selects the most favorable rotamer, the serine hydroxyl group is placed within hydrogen bonding distance (Յ3.2 Å between heavy atoms) of the Asn233 side chain (Fig. 1A) (20,21,29), suggesting that it might be a derivative of IMP-6, which in turn could be a derivative of IMP-1 (19). When going from IMP-1 over IMP-6 to IMP-25, the resistance levels to meropenem steadily increase, consistent with the idea that they present an evolutionary pathway for the adaptation to meropenem exposure.…”

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confidence: 99%

The Sequence-Activity Relationship between Metallo-β-Lactamases IMP-1, IMP-6, and IMP-25 Suggests an Evolutionary Adaptation to Meropenem Exposure

Liu

Pegg

Oelschlaeger

2012

b Metallo-␤-lactamases are important determinants of antibacterial resistance. In this study, we investigate the sequence-activity relationship between the closely related enzymes IMP-1, IMP-6, and IMP-25. While IMP-1 is the more efficient enzyme across the overall spectrum of tested ␤-lactam antibacterial agents, IMP-6 and IMP-25 seem to have evolved to specifically inactivate the newer carbapenem meropenem. Molecular modeling indicates that the G235S mutation distinguishing IMP-25 from IMP-1 and IMP-6 may affect enzyme activity via Asn233. Antibacterial resistance in combination with few new antibacterial agents being developed raises concerns for the future treatment of bacterial infections (13). ␤-Lactamases (EC 3.5.2.6.), enzymes that hydrolyze and inactivate ␤-lactam antibacterials, and in particular metallo-␤-lactamases (MBLs), present a serious challenge to public health (4). The IMP-type enzymes are among the clinically most important MBLs (7,14). These enzymes hydrolyze penicillins, cephalosporins, and carbapenems, and they are not inhibited by traditional serine ␤-lactamase inhibitors, such as clavulanic acid and sulbactam (25). They utilize two Zn(II) ions as metal cofactors to bind antibiotics and activate a water molecule for nucleophilic attack. Although they cannot hydrolyze aztreonam, they are often coproduced in bacteria that produce aztreonam-hydrolyzing extended-spectrum ␤-lactamases (3).The IMP-1 enzyme was first isolated in 1991 in Japan from Serratia marcescens (19) and has since been found in several countries worldwide, as well as in multiple microorganisms, including Pseudomonas aeruginosa, members of the family Enterobacteriaceae, and Acinetobacter spp. (7,14). IMP-6, which differs from IMP-1 by an S262G mutation, was first isolated in 1996 in Japan, also from Serratia marcescens (27), and has also been identified in P. aeruginosa and Enterobacteriaceae in Japan (28) and South Korea (20,21,29). The biochemical properties of IMP-1 and IMP-6 have been compared extensively (10,16,18,27). Interestingly, IMP-1 confers higher resistance levels to the carbapenem imipenem and several other antibiotics (10, 16), whereas IMP-6 confers higher resistance levels to the newer carbapenems meropenem (27) and doripenem (this study).IMP-25, which differs from IMP-6 by a G235S mutation and from IMP-1 by two mutations, S262G and G235S (Fig. 1A), was recently isolated from P. aeruginosa in South Korea (GenBank accession no. EU541448). In this study, we investigate the sequence-activity relationship between these closely related enzymes by determining and comparing their biochemical characteristics and abilities to confer ␤-lactam resistance to Escherichia coli cells. Furthermore, we use molecular modeling to examine the role of residue 235.Plasmids pET30a-bla IMP-6 for heterologous overexpression and pBC SK(ϩ)-bla IMP-6 for MIC assays were created by PCRbased site-directed mutagenesis using pET30a-bla IMP-1 and pBC SK(ϩ)-bla IMP-1 [obtained by subcloning bla IMP-1 with leader sequence from pET26b into pBC ...

“…ST235 is an international clone detected in Europe (31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41), Russia (42), Asia (7,(43)(44)(45)(46)(47)(48)(49), and the Middle East (50). ST235, ST111, and ST175 are regarded as epidemic high-risk clones, and ST235 lacks pyocyanin and pyoverdine production (51).…”

Section: Figmentioning

confidence: 99%

“…ST235, ST111, and ST175 are regarded as epidemic high-risk clones, and ST235 lacks pyocyanin and pyoverdine production (51). The association of ST235 with a variety of carbapenem resistance acquired by horizontal transfer of the genes such as bla PER (31,36,40,41,50), bla OXA (36,43,50), bla GES (31,39), bla SPM (36), bla VIM (31-34, 36-38, 42, 44, 52), bla IMP (36,(43)(44)(45)(46)(47)(48)(49), bla FIM (53), and bla NDM (54) suggests its importance in public health and in P. aeruginosa's flexibility in adaptation. Recently, IMP-6-producing P. aeruginosa ST235 has become endemic in Korea (48).…”

Section: Figmentioning

confidence: 99%

Persistence and Epidemic Propagation of a Pseudomonas aeruginosa Sequence Type 235 Clone Harboring an IS 26 Composite Transposon Carrying the bla _IMP-1 Integron in Hiroshima, Japan, 2005 to 2012

Shimizu

Kayama

Kouda

et al. 2015

A 9-year surveillance for multidrug-resistant (MDR) Pseudomonas aeruginosa in the Hiroshima region showed that the number of isolates harboring the metallo-␤-lactamase gene bla IMP-1 abruptly increased after 2004, recorded the highest peak in 2006, and showed a tendency to decline afterwards, indicating a history of an epidemic. PCR mapping of the variable regions of the integrons showed that this epidemic was caused by the clonal persistence and propagation of an MDR P. aeruginosa strain harboring the bla IMP-1 gene and an aminoglycoside 6=-N-acetyltransferase gene, aac(6=)-Iae in a class I integron (In113), whose integrase gene intl1 was disrupted by an IS26 insertion. Sequence analysis of the representative strain PA058447 resistance element containing the In113-derived gene cassette array showed that the element forms an IS26 transposon embedded in the chromosome. It has a Tn21 backbone and is composed of two segments sandwiched by three IS26s. In Japan, clonal nationwide expansion of an MDR P. aeruginosa NCGM2.S1 harboring chromosomally encoded In113 with intact intl1 is reported. Multilocus sequence typing and genomic comparison strongly suggest that PA058447 and NCGM2.S1 belong to the same clonal lineage. Moreover, the structures of the resistance element in the two strains are very similar, but the sites of insertion into the chromosome are different. Based on tagging information of the IS26 present in both resistance elements, we suggest that the MDR P. aeruginosa clone causing the epidemic in Hiroshima for the past 9 years originated from a common ancestor genome of PA058447 and NCGM2.S1 through an IS26 insertion into intl1 of In113 and through IS26-mediated genomic rearrangements. P seudomonas aeruginosa is an opportunistic human pathogen and a leading cause of nosocomial infections. It also causes mastitis in dairy cows as mild chronic persistent inflammation (1). Carbapenems have been used to treat P. aeruginosa infections; however, P. aeruginosa isolates resistant to carbapenems are reported in many countries and an acquired resistance to carbapenems by metallo-␤-lactamase (MBL) genes causes a serious therapeutic problem in clinical settings. Carbapenem-resistant P. aeruginosa strains producing MBLs were first discovered in Japan (2, 3) and have since been reported in many countries all over the world (4).Specifically, IMP, VIM, SPM, and NDM are the most important types of MBL with worldwide distribution, and their genes are frequently carried on class 1 integrons (4, 5). Class 1 integrons are often found on plasmids or as a part of transposons or resistance genetic elements that are able to integrate into chromosomal elements, resulting in an increase in the number of resistant Gramnegative bacilli (6). MBL-producing P. aeruginosa strains often behave as multidrug-resistant (MDR) strains. The recent increase of nosocomial infections caused by MDR P. aeruginosa has raised a serious concern.In the Hiroshima prefecture, we have conducted a multihospital surveillance for drug-resistant P. aeruginosa i...