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

Abstract

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...

Similar Frequencies of Pseudomonas aeruginosa Isolates Producing KPC and VIM Carbapenemases in Diverse Genetic Clones at Tertiary-Care Hospitals in Medellín, Colombia

“…In Colombia, this ST has also been reported in an isolate harboring bla KPC-2 and bla VIM-2 , similar to one of the isolates harboring both genes found in this study (22). Previous studies in China and Spain have shown that clones of carbapenem-resistant P. aeruginosa can emerge from diverse genetic backgrounds and that MLST diversity could actually be higher than detected (29,30). In accordance with this, it appears that the population structure of carbapenem-resistant P. aeruginosa isolates in Colombia is also diverse, with several distinctive clones currently able to harbor KPC and VIM carbapenemases, mainly ST235 and ST111, respectively, but with the parallel emergence of other clones.…”

Applying a PCR-based open-reading frame typing method for easy genotyping and molecular epidemiological analysis of Pseudomonas aeruginosa

“…On the other hand, Ps. aeruginosa isolates show high diversity even in MLST analyses (Kidd et al 2011;Gomila et al 2013;Ji et al 2013). Although 70% of the isolates here were collected in one hospital, Simpson's index of the POT in this study was 0Á986.…”

“…; Ji et al . ). Although 70% of the isolates here were collected in one hospital, Simpson's index of the POT in this study was 0·986.…”

“…; Ji et al . ). However, only particular STs were frequently observed among metallo‐β‐lactamase (MBL)‐producing Ps.…”

“…aeruginosa isolates. The sequence types (STs) of clinical isolates obtained by MLST show high diversity (Kidd et al 2011;Gomila et al 2013;Ji et al 2013). However, only particular STs were frequently observed among metallo-b-lacta-mase (MBL)-producing Ps.…”