Increased frequency of integrons and β-lactamase-coding genes among extraintestinal Escherichia coli isolated with a 7-year interval

Cefiderocol against Multi-Drug and Extensively Drug-Resistant Escherichia coli: An In Vitro Study in Poland

Cefiderocol (CFDC) is a novel, broad-spectrum siderophore cephalosporin with potential activity against multi-drug (MDR) and extensively drug-resistant (XDR) Enterobacterales, including carbapenem-resistant strains. We assessed the in vitro susceptibility to CFDC of MDR, and XDR E. coli isolates derived from clinical samples of hospitalized patients. Disk diffusion (DD) and MIC (minimum inhibitory concentration) test strip (MTS) methods were used. The results were interpreted based on EUCAST (version 12.0 2022) recommendations. Among all E. coli isolates, 98 (94.2%) and 99 (95.2%) were susceptible to CFDC when the DD and MTS methods were used, respectively (MIC range: <0.016−4 µg/mL, MIC50: 0.19 µg/mL, MIC90: 0.75 µg/mL). With the DD and MTS methods, all (MIC range: 0.016−2 µg/mL, MIC50: 0.19 µg/mL, MIC90: 0.75 µg/mL) but three (96.6%) ESBL-positive isolates were susceptible to CFDC. Out of all the metallo-beta-lactamase-positive E. coli isolates (MIC range: 0.016−4 µg/mL, MIC50: 0.5 µg/mL, MIC90: 1.5 µg/mL), 16.7% were resistant to CFDC with the DD method, while 11.1% were resistant to CFDC when the MTS method was used. CFDC is a novel therapeutic option against MDR and XDR E. coli isolates and is promising in the treatment of carbapenem-resistant E. coli strains, also for those carrying Verona integron-encoded metallo-beta-lactamases, when new beta-lactam-beta-lactamase inhibitors cannot be used.

Efficacy of Urine Dipstick Test in Diagnosing Urinary Tract Infection and Detection of the blaCTX-M Gene among ESBL-Producing Escherichia coli

A urine dipstick test used for prompt diagnosis of urinary tract infection (UTI) is a rapid and cost-effective method. The main objective of this study was to compare the efficacy of the urine dipstick test with culture methods in screening for UTIs along with the detection of the bla_CTX-M gene in extended spectrum β-lactamase (ESBL)-producing Escherichia coli. A total of 217 mid-stream urine samples were collected from UTI-suspected patients attending Bharatpur Hospital, Chitwan, and tested by dipstick test strip (COMBI-10SL, Germany) prior to the culture. E. coli isolates were identified by standard microbiological procedures and subjected to antimicrobial susceptibility testing by Kirby Bauer disc diffusion method following CLSI guideline. Primary screening of ESBL-producing E. coli isolates was conducted using ceftriaxone, cefotaxime and ceftazidime discs and phenotypically confirmed by combined disk diffusion test. Plasmid DNA of ESBL-producing strains was extracted by phenol-chloroform method and subjected to PCR for detection of the bla_CTX-M gene. Out of 217 urine samples, 48 (22.12%) showed significant bacteriuria. Among 46 (21.20%) Gram negative bacteria recovered, the predominant one was E. coli 37 (77.08%) of which 33 (89.19%) were multidrug resistant (MDR). E. coli isolates showed a higher degree of resistance towards cefazolin (62.16%) while 81.08% of the isolates were sensitive towards amikacin followed by nitrofurantoin (70.27%). Among 14 (37.84%) phenotypically confirmed ESBL isolates, only eight (21.62%) isolates carried the bla_CTX-M gene. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of urine dipstick test were 43.75%, 77.51%, 35.59% and 82.91%, respectively. Besides, the use of dipstick test strip for screening UTI was associated with many false positive and negative results as compared to the gold standard culture method. Hence, dipstick nitrite test alone should not be used as sole method for screening UTIs.

Antimicrobial susceptibility of multi-drug and extensively-drug-resistant Escherichia coli to ceftolozane-tazobactam and ceftazidime-avibactam: An in vitro study*

Aim: <i>Escherichia coli</i> is one of the Gram-negative bacteria, known to cause many nosocomial infections. Multi-drug (MDR) and extensively-drug resistant (XDR). <i>E. coli</i> are of particular note, due to significant limitations in antibiotic therapy. Ceftolozane-tazobactam and ceftazidime-avibactam are novel therapeutic options against Gram-negative bacteria; hence the aim of this study was to evaluate and compare the <i> in vitro </i> activity of ceftolozane-tazobactam and ceftazidime-avibactam against MDR and XDR clinical <i>E. coli</i> isolates. Material/Methods: The study included 100 non-replicate <i>E. coli</i> isolates derived from clinical samples of patients hospitalized in teaching hospitals. Bacteria were identified by applying mass spectrometry in the MALDI Biotyper system (Bruker). ESBL (bla_CTX-M-1group, bla_CTX-M-9group) and carbapenemase (bla_KPC, bla_VIM, bla_NDM, bla_OXA-48, bla_OXA-181) genes were detected using the eazyplex® SuperBug CRE test, based on a loop-mediated isothermal amplification (LAMP). The in vitro susceptibility to ceftolozane-tazobactam and ceftazidime-avibactam was tested using validated MIC Test strips (Liofilchem). Results: All 84 extended-spectrum β-lactamase-producing (ESBL) <i>E. coli</i> isolates were susceptible to ceftazidime-avibactam and 83 to ceftolozane-tazobactam. Among 17 <i>E. coli</i> isolates with resistance to at least one of the carbapenems, three (17.6%) were susceptible to ceftolozane-tazobactam and ceftazidime-avibactam. All 14 blaVIM gene-positive <i>E. coli</i> isolates were resistant to both ceftolozane-tazobactam and ceftazidime-avibactam. Both antibiotics were active against bla_CTX-M-9group and bla_OXA-48 gene-positive <i>E. coli</i> isolates, but they were not active against bla_CTX-M-1group and bla_VIM gene-positive isolates. Conclusions: Ceftolozane-tazobactam and ceftazidime-avibactam are alternative, non-carbapenem therapeutic options for ESBL-positive <i>E. coli</i> strains, and they are promising in the treatment of carbapenem-resistant <i>E. coli</i> strains, but not for those carrying the metallo-β-lactamase enzymes. Both drug combinations have comparable activity against ESBL, however, lower MIC values were found for ceftazidime-avibactam.

The genetic background of antibiotic resistance among clinical uropathogenic Escherichia coli strains

The spreading mechanisms of antibiotic resistance are related to many bacterial and environment factors. The overuse of antibiotics is leading to an unceasing emergence of new multidrug resistant strains. This problem also concerns uropathogenic Escherichia coli strains, which is the most common pathogen causing urinary tract infections. The aim of this study was the genetic analysis of antibiotic resistance in comparison to the phenotypic background of E. coli strains. The characterized collection of E. coli strains isolated 10 years ago from the urine samples of patients with urinary tract infections was used for antimicrobial susceptibility testing (the disc diffusion method) and analysis of antibiotic resistance genes (PCR reaction, sequencing). Additionally, the presence of ESBL strains was analyzed. Fourteen genes were associated with resistance to beta-lactams, aminoglycosides, sulfonamides and quinolones. The genetic analysis revealed that bla_TEM-1 and sul2 were present in almost all of the studied strains. Other drug-resistance genes were very rare or non-existent. Otherwise, the phenotypic resistance to fluoroquinolones was well correlated with the genotypic background of the studied bacteria. The presence of particular genes and specific mutations indicate a high bacterial potential to multidrug resistance. On the other hand, it needs to be emphasized that the standard disk diffusion test for the routine antimicrobial susceptibility analysis is still the best way to estimate the current situation of bacterial drug-resistance.

Distribution of Integrons and Gene Cassettes Among Uropathogenic and Diarrheagenic Escherichia coli Isolates in Iran

Integrons are considered to play a significant role in the evolution and spread of antimicrobial resistance genes. A total of 200 uropathogenic (UPEC) and diarrheagenic Escherichia coli (DEC) isolates from outpatients were investigated for antimicrobial susceptibility and the presence of class 1, 2, and 3 integron-associated integrase (intI) genes and gene cassettes. Conjugal transfer and Southern hybridization were performed to determine the genetic localization of class 1 integrons. One hundred ninety-two (96%) isolates were resistant to one or more antimicrobial agents. Antimicrobial resistance among DEC isolates was higher compared with the UPEC. Integrons were highly prevalent in both pathotypes (92.5%). Comparison of integrons among UPEC and DEC showed that DEC isolates harbored integrases (94% for intI1, 8% for intI2) with a slightly higher frequency than in UPEC isolates (87% for intI1, 7% for intI2) (p>0.05). Dihydrofolate reductase (dfrA) and aminoglycoside adenyl transferase (aad) gene cassettes were found most frequently in intI1-positive isolates. All isolates carried their class 1 integrons on conjugative plasmids. These results indicate that class 1 integrons are widespread among E. coli isolates. Therefore, appropriate surveillance and control measures are essential to prevent the further spread of integron-producing isolates.

Molecular characterization of integrons in clinical isolates of betalactamase-producing Escherichia coli and Klebsiella pneumoniae in Iran

Integrons are considered to play a significant role in the evolution and spread of antibiotic resistance genes. A total of 349 clinical isolates of Escherichia coli and Klebsiella pneumoniae were investigated for molecular characterization of integrons and betalactamases. Antimicrobial susceptibility testing was also performed as the Clinical and Laboratory Standards Institute (CLSI) guidelines. The frequency of extended spectrum betalactamases (ESBL) or metallo-betalactamases (MBL)-producing isolates, patient demographics, and the susceptibility to various antimicrobial agents were described. BlaCTX-M was the most frequently detected betalactamase in all isolates. Moreover, MBL producing K. pneumoniae carried blaIMP and blaVIM at 100 and 41·6%, respectively but no MBL-positive E. coli was detected. Class 1 integrons were more frequent among E. coli and K. pneumoniae isolates in comparison with class 2 integrons and the frequency of intI2 in K. pneumoniae was significantly higher than E. coli isolates. Five different resistance gene arrays were identified among class 1 integrons. Dihydrofolate reductase (dfrA) and aminoglycoside adenyltransferase (aad) gene cassettes were found to be predominant in the class 1 integrons. These results indicate that class 1 integrons are widespread among ESBL-producing isolates of K. pneumoniae and E. coli and appropriate surveillance and control measures are essential to prevent further dissemination of these elements among Enterobacteriaceae in our country.