Clinical and molecular characteristics and risk factors for patients acquiring carbapenemase-producing and non-carbapenemase-producing carbapenem-nonsusceptible-Enterobacterales bacteremia

Molecular characterization of class 1 integrons in carbapenem-resistant Enterobacterales isolates

OBJECTIVE

Carbapenem-resistant Enterobacterales (CRE) infections result in higher treatment costs and mortality rates. Integrons play important roles in emergence and spread of antibiotic resistant genes. To get a better understand on the effects of integron on CRE resistance, distribution of common carbapenemase genes and class 1 integron in clinical CRE isolates were investigated.

METHOD

Carbapenemase genes, including bla_KPC, bla_VIM, bla_IMP, bla_NDM, bla_GES, bla_VEB and bla_OXA-23, were screened in 161 CRE isolates and subtypes of these genes were confirmed through sequence analysis. Class 1 integron was screened and common promoter and gene cassette arrays were determined by sequencing. The resistant rates to clinical commonly used antibiotics between integron positive and integron negative CRE isolates were compared.

RESULTS

Of 161 CRE isolates, the most prevalent carbapenemase gene was bla_KPC-2, which was detected in 139 isolates, including 99 Klebsiella pneumoniae. Class 1 integron was detected in 78 isolates. Twenty different gene cassettes, including two carbapenemase genes bla_VEB-1 and bla_IMP-4, and nine different gene cassette arrays, including bla_VEB-1-aadB-arr-2-cmlA5-bla_OXA-10-aadA1, aadB-catB8-bla_OXA-10-aadA1-dfrA1-aacA4 and bla_IMP-4-qacG-aacA4-catB3, were detected. Five types of common promoters were identified. Relative weak promoter PcH1 was the dominant type. Resistant rates of CRE isolates containing class 1 integrons to ceftazidime, amikacin, trimethoprim/sulfamethoxazole and gentamicin were higher than those without class 1 integrons (P < 0.05).

CONCLUSION

Class 1 integrons play important roles in the emergence and spread of CRE resistance. To the best of our knowledge, this is the first report of aadB-catB8-bla_OXA-10-aadA1-dfrA1-aacA4 and bla_IMP-4-qacG-aacA4-catB3 in the same Providencia rettgeri isolate and bla_VEB-1-aadB-arr-2-cmlA5-bla_OXA-10-aadA1 in P. rettgeri.

Clinical characteristics and outcomes of carbapenem-resistant Enterobacterales bacteremia in pediatric patients

BACKGROUND/PURPOSE

Clinical data on carbapenem-resistant Enterobacterales (CRE) bacteremia in the pediatric population are limited. This study investigated the clinical characteristics and outcomes of pediatric CRE bacteremia.

METHODS

Clinical data on bacteremia caused by carbapenem-susceptible and carbapenem-resistant Enterobacterales, including Escherichia coli, Klebsiella spp., Enterobacter spp., Serratia marcescens, Proteus mirabilis, Citrobacter spp., and Morganella spp., in pediatric patients from a children's hospital in Taiwan were retrospectively retrieved and analyzed.

RESULTS

From January 2013 to December 2021, 471 clinical isolates of Enterobacterales bacteremia were identified in 451 episodes from 379 pediatric patients. Among all the isolates, the predominant species were E. coli (199/471, 42.2%), Klebsiella spp. (168/471, 35.6%), and Enterobacter spp. (59/471, 12.5%), with carbapenem-resistance rates of 1.5%, 11.9%, and 25.0%, respectively. Overall, 40 (8.4%) showed a carbapenem resistance phenotype. Patients' all-cause mortality rate at 14 days was significantly higher in CRE bacteremia episodes than non-CRE ones (12.5% vs. 3.6%, p < 0.05). The predicting factor of a CRE bacteremia episode was the causative agent of Enterobacter spp. (adjusted OR of 2.551, CI 1.073-6.066, p < 0.05) and ESBL-producing phenotype (adjusted OR 14.268, CI 5.120-39.762, p < 0.001).

CONCLUSION

Bloodstream infections caused by CRE are associated with a higher mortality rate in the pediatric population. Attention must be paid to preventing and managing pediatric patients with CRE infections.

A Longitudinal Nine-Year Study of the Molecular Epidemiology of Carbapenemase-Producing Enterobacterales Isolated From a Regional Hospital in Taiwan: Predominance of Carbapenemase KPC-2 and OXA-48

Enterobacterales clinical isolates are now being resistant to clinically achievable concentrations of most commonly used antibiotics that makes treatment of hospitalized patients very challenging. We hereby determine the molecular characteristics of carbapenemase genes in carbapenem-resistant Enterobacterales (CRE) isolates in Taiwan. A total of 455 CRE isolates were identified between August 2011 to July 2020. Minimum inhibitory concentrations for selected carbapenems were tested using Vitek 2, and carbapenemase genes were determined using polymerase chain reaction in combination with sequencing. Phenotypic detection of carbapenemase was determined by modified carbapenem inactivation method (mCIM) and EDTA-modified carbapenem inactivation method (eCIM) to validate our PCR screening results. Pulsed-field gel electrophoresis (PFGE) was used to determine the clonality of carbapenemase-producing Enterobacterales (CPE) isolates, and the transferability of carbapenemase-carrying plasmids was determined by conjugation assays. A slight increase in carbapenem-resistant E. coli (CREC) was observed, however, the prevalence of carbapenem-resistant K. pneumoniae (CRKP) was steady, during 2011–2020. The dominant species among our CRE was K. pneumoniae (270/455, 59.3%), followed by E. coli (81/455, 17.8%), Morganella morganii (32/455, 7.0%), and Enterobacter cloacae (25/455, 5.5%). From 2011 to 2020, the total percentage of CPE increased steadily, accounting for 61.0% of CRE in 2020. Moreover, 122 of 455 CRE isolates (26.8%) were CPE. Among the CPE isolates, the dominant carbapenemase gene was bla_{OXA–48–like} (54/122, 44.3%), and the second most common carbapenemase gene was bla_KPC–2 (47/122, 38.5%). The sensitivity and specificity for mCIM to detect carbapenemase in the 455 isolates were both 100% in this study. The PFGE results showed that 39 carbapenemase-producing E. coli and 69 carbapenemase-producing K. pneumoniae isolates carrying bla_KPC–2 and/or bla_NDM–5 could be classified into 5 and 12 clusters, respectively. In conclusion, our results showed an increase in CPE isolates in Taiwan. Moreover, the distribution of carbapenemase and antimicrobial susceptibility in CPE were associated with PFGE typing.