Hidden Carbapenem Resistance in OXA-48 and Extended-Spectrum β-Lactamase-Positive Escherichia coli

Bloodstream Infections by AmpC-Producing Enterobacterales: Risk Factors and Therapeutic Outcome

Bloodstream infections associated with AmpC-producing Enterobacterales are severe medical conditions which, without prompt and effective treatment, may have dire ramifications. This study aimed to assess whether certain comorbidities and previous surgical procedures coincide with resistance determinants of AmpC-producing Enterobacterales associated with bloodstream infections. Antibiotic resistance patterns and therapy outcome were also determined. The patients' data obtained revealed that the prevalence of recent surgical procedures, solid organ tumors, metabolic diseases, kidney and liver failure, and hematological malignancies do not differ between resistant and susceptible isolates of AmpC-producing Enterobacterales. Furthermore, no difference was reported in mortality rates. Regarding antibiotic resistance, 34.52% of isolates were confirmed to be resistant (AmpC hyperproduction, ESBL, or carbapenemase). More than one in five AmpC hyperproducers were reported amid Providencia spp., K. aerogenes, E. cloacae, and C. freundii. strains. Carbapenemases were mostly noted in Providencia spp. followed by M. morganii and K. aerogenes strains. Serratia marcescens had the highest proportion of ESBLsof ESBLs. Resistance to expanded-spectrum cephalosporins of Providencia spp. and K. aerogenes strains exceeded 50%, and resistance to meropenem over 10% was observed only in C. freundii strains. Enterobacterales' ever-growing resistance to antibiotics is becoming quite a challenge for clinicians and new treatment options are required.

Emergence and Spread of Enterobacterales with Multiple Carbapenemases after COVID-19 Pandemic

Resistance to carbapenems in Enterobacterales has become a matter of the highest concern in the last decade. Recently, Enterobacterales harboring multiple carbapenemases were detected in three hospital centers in Croatia and in the outpatient setting, posing a serious therapeutic challenge for clinicians. In this study, we analyzed eight Klebsiella pneumoniae and two Enterobacter cloacae complex isolates with multiple carbapenemases, with regard to antibiotic susceptibility, β-lactamase production and plasmid content. The isolates demonstrated uniform resistance to amoxicillin/clavulanate, piperacillin/tazobactam, cefuroxime, ceftazidime, cefotaxime, ceftriaxone and ertapenem. Among novel β-lactam/inhibitor combinations, ceftazidime/avibactam exhibited moderate activity, with 50% of isolates susceptible. All isolates demonstrated resistance to imipenem/cilastatin/relebactam, and all but one to ceftolozane/tazobactam. Four isolates exhibited a multidrug-resistant phenotype (MDR), whereas six were allocated to an extensively drug-resistant phenotype (XDR). OKNV detected three combinations of carbapenemases: OXA-48+NDM (five isolates), OXA-48+VIM (three isolates) and OXA-48+KPC (two isolates). Inter-array testing identified a wide variety of resistance genes for β-lactam antibiotics: bla_CTX-M-15, bla_TEM, bla_SHV, bla_OXA-1, bla_OXA-2, bla_OXA-9, aminoglycosides: aac6, aad, rmt, arm and aph, fluoroquinolones: qnrA, qnrB and qnrS, sulphonamides: sul1 and sul2 and trimethoprim: dfrA5, dfrA7, dfrA14, dfrA17 and dfrA19. mcr genes were reported for the first time in Croatia. This study demonstrated the ability of K. pneumoniae and E. cloacae to acquire various resistance determinants under the selection pressure of antibiotics widely used during the COVID-19 pandemic. The novel inter-array method showed good correlation with OKNV and PCR, although some discrepancies were found.

Antibiotic resistance spectrum of E. coli strains from different samples and age-grouped patients: a 10-year retrospective study

OBJECTIVE

Escherichia coli (E. coli) is the most common opportunistic clinical micro-organism with high drug resistance. This study aimed to analyse the resistance pattern of E. coli according to patient age and clinical sample type.

DESIGN AND SETTING

This retrospective observational study was conducted in a tertiary hospital in southeastern China.

PARTICIPANTS

E. coli strains were isolated from blood, urine and sputum of infected inpatients. The patients were divided into four age groups: children (0-14 years old, including neonatal and non-neonatal groups), youths (15-40 years old), middle-aged (41-60 years old) and old (>60 years old).

RESULTS

A total of 7165 E. coli strains were collected from all samples. Compared with urine and blood isolates, more sputum isolates were resistant against 12 tested antibiotics. Furthermore, urine isolates were more resistant to levofloxacin than sputum and blood isolates. Although the patients' age was not associated with resistance rates of E. coli strains isolated from blood, a larger proportion of urine-derived strains from youths were resistant to sulfamethoxazole-trimethoprim and piperacillin-tazobactam than those from old people. The sputum strains from the elderly were more resistant to most of the tested antibiotics compared with sputum strains isolated from children.

CONCLUSIONS

The resistance profile of E. coli is different among age groups and specimen sources and should be considered during E. coli infection treatment.

Submarine Outfalls of Treated Wastewater Effluents are Sources of Extensively- and Multidrug-Resistant KPC- and OXA-48-Producing Enterobacteriaceae in Coastal Marine Environment

The rapid and ongoing spread of carbapenemase-producing Enterobacteriaceae has led to a global health threat. However, a limited number of studies have addressed this problem in the marine environment. We investigated their emergence in the coastal waters of the central Adriatic Sea (Croatia), which are recipients of submarine effluents from two wastewater treatment plants. Fifteen KPC-producing Enterobacteriaceae (nine Escherichia coli, four Klebsiella pneumoniae and two Citrobacter freundii) were recovered, and susceptibility testing to 14 antimicrobials from 10 classes showed that four isolates were extensively drug resistant (XDR) and two were resistant to colistin. After ERIC and BOX-PCR typing, eight isolates were selected for whole genome sequencing. The E. coli isolates belonged to serotype O21:H27 and sequence type (ST) 2795, while K. pneumoniae isolates were assigned to STs 37 and 534. Large-scale genome analysis revealed an arsenal of 137 genes conferring resistance to 19 antimicrobial drug classes, 35 genes associated with virulence, and 20 plasmid replicons. The isolates simultaneously carried 43–90 genes encoding for antibiotic resistance, while four isolates co-harbored carbapenemase genes blaKPC-2 and blaOXA-48. The blaOXA-48 was associated with IncL-type plasmids in E. coli and K. pneumoniae. Importantly, the blaKPC-2 in four E. coli isolates was located on ~40 kb IncP6 broad-host-range plasmids which recently emerged as blaKPC-2 vesicles, providing first report of these blaKPC-2-bearing resistance plasmids circulating in E. coli in Europe. This study also represents the first evidence of XDR and potentially virulent strains of KPC-producing E. coli in coastal waters and the co-occurrence of blaKPC-2 and blaOXA-48 carbapenemase genes in this species. The leakage of these strains through submarine effluents into coastal waters is of concern, indicating a reservoir of this infectious threat in the marine environment.

Direct detection of OXA-48-like carbapenemase variants with and without co-expression of an extended-spectrum β-lactamase from bacterial cell lysates using mass spectrometry

INTRODUCTION

Antibiotic-resistant Gram-negative bacteria are of a growing concern globally, especially those producing enzymes conferring resistance. OXA-48-like carbapenemases hydrolyze most β-lactam antibiotics, with typically low-level hydrolysis of carbapenems, but have limited effect on broad-spectrum cephalosporins. These are frequently co-expressed with extended spectrum β-lactamases, especially CTX-M-15, which typically shows high level resistance to broad-spectrum cephalosporins, yet is carbapenem susceptible. The combined resistance profile makes the need for successful detection of these specific resistance determinants imperative for effective antibiotic therapy.

OBJECTIVES

The objective of this study is to detect and identify OXA-48-like and CTX-M-15 enzymes using mass spectrometry, and to subsequently develop a method for detection of both enzyme types in combination with liquid chromatography.

METHODS

Cells grown in either broth or on agar were harvested, lysed, and, in some cases buffer-exchanged. Lysates produced from bacterial cells were separated and analyzed via liquid chromatography with mass spectrometry (LC-MS) and tandem mass spectrometry (LC-MS/MS).

RESULTS

The intact proteins of OXA-48, OXA-181, and OXA-232 (collectively OXA-48-like herein) and CTX-M-15 were characterized and detected. Acceptance criteria based on sequence-informative fragments from each protein group were established as confirmatory markers for the presence of the protein(s). A total of 25 isolates were successfully tested for OXA-48 like (2), CTX-M-15 (3), or expression of both (7) enzymes. Thirteen isolates served as negative controls.

CONCLUSIONS

Here we present a method for the direct and independent detection of both OXA-48-like carbapenemases and CTX-M-15 β-lactamases using LC-MS/MS. The added sensitivity of MS/MS allows for simultaneous detection of at least two co-eluting, co-isolated and co-fragmented proteins from a single mass spectrum.

β-Lactamases and β-Lactamase Inhibitors in the 21st Century

The β-lactams retain a central place in the antibacterial armamentarium. In Gram-negative bacteria, β-lactamase enzymes that hydrolyze the amide bond of the four-membered β-lactam ring are the primary resistance mechanism, with multiple enzymes disseminating on mobile genetic elements across opportunistic pathogens such as Enterobacteriaceae (e.g., Escherichia coli) and non-fermenting organisms (e.g., Pseudomonas aeruginosa). β-Lactamases divide into four classes; the active-site serine β-lactamases (classes A, C and D) and the zinc-dependent or metallo-β-lactamases (MBLs; class B). Here we review recent advances in mechanistic understanding of each class, focusing upon how growing numbers of crystal structures, in particular for β-lactam complexes, and methods such as neutron diffraction and molecular simulations, have improved understanding of the biochemistry of β-lactam breakdown. A second focus is β-lactamase interactions with carbapenems, as carbapenem-resistant bacteria are of grave clinical concern and carbapenem-hydrolyzing enzymes such as KPC (class A) NDM (class B) and OXA-48 (class D) are proliferating worldwide. An overview is provided of the changing landscape of β-lactamase inhibitors, exemplified by the introduction to the clinic of combinations of β-lactams with diazabicyclooctanone and cyclic boronate serine β-lactamase inhibitors, and of progress and strategies toward clinically useful MBL inhibitors. Despite the long history of β-lactamase research, we contend that issues including continuing unresolved questions around mechanism; opportunities afforded by new technologies such as serial femtosecond crystallography; the need for new inhibitors, particularly for MBLs; the likely impact of new β-lactam:inhibitor combinations and the continuing clinical importance of β-lactams mean that this remains a rewarding research area.