Molecular Mechanism of the β-Lactamase Mediated β-Lactam Antibiotic Resistance of Pseudomonas aeruginosa Isolated From a Chinese Teaching Hospital

Prioritization of Critical Factors for Surveillance of the Dissemination of Antibiotic Resistance in Pseudomonas aeruginosa: A Systematic Review

Pseudomonas aeruginosa is the primary opportunistic human pathogen responsible for a range of acute and chronic infections; it poses a significant threat to immunocompromised patients and is the leading cause of morbidity and mortality for nosocomial infections. Its high resistance to a diverse array of antimicrobial agents presents an urgent health concern. Among the mechanisms contributing to resistance in P. aeruginosa, the horizontal acquisition of antibiotic resistance genes (ARGs) via mobile genetic elements (MGEs) has gained recognition as a substantial concern in clinical settings, thus indicating that a comprehensive understanding of ARG dissemination within the species is strongly required for surveillance. Here, two approaches, including a systematic literature analysis and a genome database survey, were employed to gain insights into ARG dissemination. The genome database enabled scrutinizing of all the available sequence information and various attributes of P. aeruginosa isolates, thus providing an extensive understanding of ARG dissemination within the species. By integrating both approaches, with a primary focus on the genome database survey, mobile ARGs that were linked or correlated with MGEs, important sequence types (STs) carrying diverse ARGs, and MGEs responsible for ARG dissemination were identified as critical factors requiring strict surveillance. Although human isolates play a primary role in dissemination, the importance of animal and environmental isolates has also been suggested. In this study, 25 critical mobile ARGs, 45 critical STs, and associated MGEs involved in ARG dissemination within the species, are suggested as critical factors. Surveillance and management of these prioritized factors across the One Health sectors are essential to mitigate the emergence of multidrug-resistant (MDR) and extensively resistant (XDR) P. aeruginosa in clinical settings.

Resistance genomics and molecular epidemiology of high-risk clones of ESBL-producing Pseudomonas aeruginosa in young children

Introduction

The emergence of multidrug-resistant Pseudomonas aeruginosa poses a global threat, but the distribution and resistance profiling are unclear, especially in young children. Infections due to P. aeruginosa are common, associated with high mortality, and increasingly β-lactam drug resistant.

Methods

We studied the molecular epidemiology and antibiotic resistance mechanisms in 294 clinicalisolates of P. aeruginosa from a pediatric hospital in China. Non-duplicate isolates were recovered from clinical cases and were identified using an API-20 kit followed by antimicrobial susceptibility testing using the VITEK®2 compact system (BioMerieux, France) and also by broth dilution method. In addition, a double-disc synergy test for the ESBL/E-test for MBL was performed. The presence of beta-lactamases, plasmid types, and sequence types was determined by PCR and sequencing.

Results

Fifty-six percent (n = 164) of the isolates were resistant to piperacillin-tazobactam, followed by cefepime (40%; n = 117), ceftazidime (39%; n = 115), imipenem (36%; n = 106), meropenem (33%; n = 97), and ciprofloxacin (32%; n = 94). Forty-two percent (n = 126) of the isolates were positive for ESBL according to the double-disc synergy test. The blaCTX-M-15 cephalosporinase was observed in 32% (n = 40/126), while 26% (n = 33/126) werepositive for blaNDM-1 carbapenemase. Aminoglycoside resistance gene aac(3)IIIawas observed in 16% (n = 20/126), and glycylcyclines resistance gene tet(A) was observed in 12% (n = 15/126) of the isolates. A total of 23 sequence types were detected, including ST1963 (12%; n = 16), followed by ST381 (11%; n = 14), ST234 (10%; n = 13), ST145 (58%; n = 10), ST304 (57%; n = 9), ST663 (5%; n = 7), and a novel strain. In ESBL-producing P. aeruginosa, 12 different Incompatibility groups (Inc) were observed, the most common being IncFI, IncFIS, and IncA/C. The MOBP was the most common plasmid type, followed by MOBH, MOBF, and MOBQ.

Discussion

Our data suggest that the spread of antibiotic resistance is likely due toclonal spread and dissemination of different clinical strains of P. aeruginosa harbouring different plasmids. This is a growing threat in hospitals particularly in young children which needs robust prevention strategies.

Phenotypic and genotypic discrepancies for carbapenemase-producing Citrobacter freundii in multiple isolates from a single patient

BACKGROUND

Carbapenemase-producing gram-negative organisms continue to be a significant healthcare concern and a therapeutic challenge. Members of the genus Citrobacter have emerged as increasingly multidrug resistant and versatile healthcare-associated pathogens. In this study we investigated five KPC-producing Citrobacter freundii isolates, from the same patient, that presented unusual phenotypic characteristics including false susceptibility to carbapenems detection by culture-based methods.

METHODS

The isolates were tested for antimicrobial susceptibility using broth microdilution and disk diffusion. Production of serine carbapenemase was confirmed with the mCIM (modified carbapenem inactivation method) test. Genotypes were determined by PCR and whole genome sequencing analysis.

RESULTS

The five isolates were susceptible to meropenem by broth microdilution and presented varying colonial morphologies and levels of susceptibility to carbapenems by multiple phenotypic methods, despite being positive for carbapenemase production by mCIM and positive for bla_KPC by PCR. Whole genome sequence analysis showed that three of the five highly related isolates harbor an additional gene cassette, including bla_CARB-2, ant(2''), aadA2, dfrA19, catB3, cmlA1, mph(E), msr(E), and qnrA1. The presence of these genes explains the difference in phenotypes observed.

CONCLUSION

Failure to detect and completely eradicate the carbapenemase-producing C. freundii in the urine with ertapenem therapy, likely due to the presence of a heterogeneous population, resulted in the phenotypic and genotypic adaptations of the organism as it disseminated to the bloodstream and kidneys. The fact that carbapenemase-producing C. freundii can elude detection by phenotypic methods and can so easily acquire and transfer resistance gene cassettes is of concern.