During the COMParative Activity of Carbapenems Testing (COMPACT) surveillance study, 448 Pseudomonas aeruginosa clinical isolates were obtained from 16 Spanish hospitals. Nonsusceptibility (EUCAST breakpoints) to imipenem (35%), meropenem (33%), and/or doripenem (33%) was observed with 175 isolates (39%). Simultaneous resistance to these three drugs was observed with 126 of the 175 isolates (72%). Except for colistin, high resistance rates were observed among noncarbapenem antibiotics. Clonal relatedness was investigated by pulsed-field gel electrophoresis (PFGE) with SpeI, discriminating 68 patterns. Multilocus sequence typing (MLST) was performed on 84 isolates representing different PFGE types and all participating hospitals. Thirty-nine sequence types (STs) could be distinguished, and of these, ST175 (48 isolates, 10 hospitals), ST646 (16 isolates, 4 hospitals), ST532 (13 isolates, 3 hospitals), and ST111 (13 isolates, 7 hospitals) were the most frequently encountered. Minimum-spanning tree analysis confirmed a wide dissemination of different clones among participant hospitals, particularly ST175. PFGE pattern comparison within the four most frequent STs revealed that ST175 isolates were relatively uniform, while ST646, ST532, and ST111 isolates were highly diverse, with almost every isolate belonging to a unique pulsotype, even when originating from the same center. The population of carbapenem-nonsusceptible P. aeruginosa isolates from 16 hospitals is highly diverse, with one ST (ST175) representing a highly conserved clone disseminated in 10 of the 16 participant hospitals. This ST175 clone should be added to the list of P. aeruginosa clones at high risk for epidemic spread, such as the Liverpool, Manchester, and Melbourne clones previously found in cystic fibrosis patients and ST235 in the nosocomial setting.Antibiotic surveillance studies are necessary not only for the better understanding of bacterial epidemiology, but also for the design of control strategies for preventing bacterial resistance and establishing therapeutic guidelines. In this context, the COMParative Activity of Carbapenems Testing (COMPACT) multicenter study was performed in 16 European countries, including Spain (23). The main objectives of this surveillance study were to test the activity of currently used carbapenems against Pseudomonas aeruginosa clinical isolates and to detect carbapenem nonsusceptible isolates (12).In this multicenter study, Spanish authors concluded that percentages of carbapenem resistance among P. aeruginosa clinical isolates in their country (range of 21.4% to 32.6%) are very similar to those previously reported in other European countries. Doripenem was the most active drug against these resistant isolates (12). The presence of carbapenem-nonsusceptible P. aeruginosa isolates has been described worldwide, particularly in relation to outbreaks (1,5,6,17,18,25,28,30,31,37). Most of these studies focused on clinical isolates, and genetic relatedness was established using molecular typing tools based on macror...

Many bacterial typing methods are specific for one species only, time-consuming, or poorly reproducible. DiversiLab (DL; bioMérieux) potentially overcomes these limitations. In this study, we evaluated the DL system for the identification of hospital outbreaks of a number bacterial species. Appropriately typed clinical isolates were tested with DL. DL typing agreed with pulsed-field gel electrophoresis (PFGE) for Acinetobacter (n ‫؍‬ 26) and Stenotrophomonas maltophilia (n ‫؍‬ 13) isolates. With two exceptions, DL typing of Klebsiella isolates (n ‫؍‬ 23) also correlated with PFGE, and in addition, PFGE-nontypeable (PFGE-NT) isolates could be typed. Enterobacter (n ‫؍‬ 28) results also correlated with PFGE results; also, PFGE-NT isolates could be clustered. In a larger study (n ‫؍‬ 270), a cluster of 30 isolates was observed that could be subdivided by PFGE. The results for Escherichia coli (n ‫؍‬ 38) correlated less well with an experimental multilocus variable number of tandem repeats analysis (MLVA) scheme. Pseudomonas aeruginosa (n ‫؍‬ 52) showed only a limited number of amplification products for most isolates. When multiple Pseudomonas isolates were assigned to a single type in DL, all except one showed multiple multilocus sequence types. Methicillin-resistant Staphylococcus aureus generally also showed a limited number of amplification products. Isolates that belonged to different outbreaks by other typing methods, including PFGE, spa typing, and MLVA, were grouped together in a number of cases. For Enterococcus faecium, the limited variability of the amplification products obtained made interpretation difficult and correlation with MLVA and esp gene typing was poor. All of the results are reflected in Simpson's index of diversity and adjusted Rand's and Wallace's coefficients. DL is a useful tool to help identify hospital outbreaks of Acinetobacter spp., S. maltophilia, the Enterobacter cloacae complex, Klebsiella spp., and, to a somewhat lesser extent, E. coli. In our study, DL was inadequate for P. aeruginosa, E. faecium, and MRSA. However, it should be noted that for the identification of outbreaks, epidemiological data should be combined with typing results.

The patient-to-patient transmission of highly prevalent Pseudomonas aeruginosa clones which are associated with enhanced disease progression has led to strict segregation policies for cystic fibrosis (CF) patients in many countries. However, little is known about the population structure of P. aeruginosa among CF patients. The aim of the present cross-sectional study was to determine the prevalence and genetic relatedness of P. aeruginosa isolates from CF patients who visited two major CF centers in The Netherlands in 2007 and 2008. These patients represented 45% of the Dutch CF population. P. aeruginosa carriage in the respiratory tract was determined by standard microbiological culture techniques, and all phenotypically different isolates in the first specimens recovered in 2007 and 2008 were genotyped by multilocus sequence typing. A total of 313 (57%) of 551 patients whose samples were cultured carried P. aeruginosa. Two sequence types (STs), ST406 and ST497, were found in 15% and 5% of the patients, respectively, and 60% of the patients harbored a strain that was also found in at least two other patients. The risk ratios for carrying ST406 and ST497 were 17.8 (95% confidence interval [CI], 7.2 to 43.6) for those aged between 15 and 24 years and 6 (95% CI, 1.4 to 26.1) for those aged >25 years. ST406 and ST497 were not genetically linked to previously described epidemic clones, which were also not found in this CF population. The population structure of P. aeruginosa in Dutch CF patients is characterized by the presence of two prevalent STs that are associated with certain age groups and that are not genetically linked to previously described epidemic clones.Pseudomonas aeruginosa is a ubiquitous, versatile bacterium that can infect humans as well as plants and animals. The species is infamous for causing nosocomial infections in immunocompromised patients and patients in intensive care units and is a major cause of morbidity and mortality in patients with cystic fibrosis (CF) (26).The widely held belief that CF patients acquire P. aeruginosa strains mainly from their inanimate environment, with most patients being colonized by unique strains, has been challenged by reports indicating that P. aeruginosa clones may frequently be transmitted between CF patients (3,6,18,19,23,24). Some of these clones, such as the Liverpool epidemic strain and the Melbourne epidemic strain, have been associated with enhanced disease progression and higher rates of mortality, respectively (1, 13). In The Netherlands, the patient-to-patient transmission of P. aeruginosa was documented during a summer camp (4). These findings have led to strict segregation policies for CF patients in many countries, including The Netherlands. However, despite these studies, there is little information on the population structure of P. aeruginosa within populations of CF patients. We therefore investigated the prevalence and genetic relatedness of P. aeruginosa isolates compared to those of the international known genotypes in an unbiased cohort re...

ObjectiveTo determine whether highly prevalent P. aeruginosa sequence types (ST) in Dutch cystic fibrosis (CF) patients are specifically linked to CF patients we investigated the population structure of P. aeruginosa from different clinical backgrounds. We first selected the optimal genotyping method by comparing pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST) and multilocus variable number tandem-repeat analysis (MLVA).MethodsSelected P. aeruginosa isolates (n = 60) were genotyped with PFGE, MLST and MLVA to determine the diversity index (DI) and congruence (adjusted Rand and Wallace coefficients). Subsequently, isolates from patients admitted to two different ICUs (n = 205), from CF patients (n = 100) and from non-ICU, non-CF patients (n = 58, of which 19 were community acquired) were genotyped with MLVA to determine distribution of genotypes and genetic diversity.ResultsCongruence between the typing methods was >79% and DIs were similar and all >0.963. Based on costs, ease, speed and possibilities to compare results between labs an adapted MLVA scheme called MLVA9-Utrecht was selected as the preferred typing method. In 363 clinical isolates 252 different MLVA types (MTs) were identified, indicating a highly diverse population (DI  = 0.995; CI  = 0.993–0.997). DI levels were similarly high in the diverse clinical sources (all >0.981) and only eight genotypes were shared. MTs were highly specific (>80%) for the different patient populations, even for similar patient groups (ICU patients) in two distinct geographic regions, with only three of 142 ICU genotypes detected in both ICUs. The two major CF clones were unique to CF patients.ConclusionThe population structure of P. aeruginosa isolates is highly diverse and population specific without evidence for a core lineage in which major CF, hospital or community clones co-cluster. The two genotypes highly prevalent among Dutch CF patients appeared unique to CF patients, suggesting specific adaptation of these clones to the CF lung.