Characterization of CTX-M-14 and CTX-M-15 ProducingEscherichia coliStrains Causing Neonatal Sepsis

Risk Factors Associated with Multi-Drug Resistance in Neonatal Sepsis Caused by Escherichia coli

Background and Objective

An increasing number of cases of neonatal sepsis due to extended-spectrum beta-lactamase (ESBL)-producing multi-drug resistant (MDR) Escherichia coli (E. coli) have been reported worldwide. The aim of this study was to explore the risk factors associated with ESBL-producing MDR E. coli among neonates with culture-confirmed E. coli sepsis and thereby to help selection of appropriate empirical antibiotics.

Patients and Methods

All newborn infants with a confirmed pathogen isolated from blood or cerebrospinal fluid (CSF) from 2016 to 2021 were identified and those with E. coli infection were included in this analysis. We compared a group of neonatal patients with ESBL-producing MDR E. coli sepsis (n=69) to a group with ESBL-negative E. coli (n=70) based on antimicrobial susceptibility reports. We used multivariable regression analysis to determine the risk factors associated with ESBL-producing MDR E. coli strains among the neonates with culture-confirmed E. coli sepsis.

Results

ESBL-producing MDR E. coli sepsis was more common in premature infants and newborns with hospital-acquired late-onset sepsis (HALOS). The mortality rate of neonatal sepsis caused by ESBL-producing E. coli was about twice as that of sepsis caused by ESBL-negative E. coli. Antepartum exposure to cephalosporins (OR=25.191, 95% CI: 3.184-199.326, P<0.01) and parenteral nutrition for more than 1 week (OR=4.495, 95% CI: 2.009-10.055, P<0.01) were independent risk factors for neonatal infection with ESBL-producing stains among infants with E. coli sepsis.

Conclusion

E. coli remains the most common Gram-negative bacterial pathogen causing neonatal sepsis. A higher proportion of ESBL-producing MDR E. coli is seen in premature infants and those newborns with HALOS and is associated with higher mortality. Antepartum use of cephalosporins and prolonged use of parenteral nutrition may be important factors to consider in the selection of empirical antibiotics for use in neonatal sepsis caused by gram-negative rods prior to the availability of the results of antimicrobial susceptibility.

Genetic Background and Expression of the New qepA4 Gene Variant Recovered in Clinical TEM-1- and CMY-2-Producing Escherichia coli

A new QepA4 variant was detected in an O86:H28 ST156-fimH38 Escherichia coli, showing a multidrug-resistance phenotype. PAβN inhibition of qepA4-harboring transconjugant resulted in increase of nalidixic acid accumulation. The qepA4 and catA1 genes were clustered in a 26.0-kp contig matching an IncF-type plasmid, and containing a Tn21-type transposon with multiple mobile genetic elements. This QepA variant is worrisome because these determinants might facilitate the selection of higher-level resistance mutants, playing a role in the development of resistance, and/or confer higher-level resistance to fluoroquinolones in association with chromosomal mutations.

Prevalence, risk factors, outcomes, and molecular epidemiology of mcr-1-positive Enterobacteriaceae in patients and healthy adults from China: an epidemiological and clinical study

BACKGROUND

The mcr-1 gene confers transferable colistin resistance. mcr-1-positive Enterobacteriaceae (MCRPE) have attracted substantial medical, media, and political attention; however, so far studies have not addressed their clinical impact. Herein, we report the prevalence of MCRPE in human infections and carriage, clinical associations of mcr-1-positive Escherichia coli (MCRPEC) infection, and risk factors for MCRPEC carriage.

METHODS

We undertook this study at two hospitals in Zhejiang and Guangdong, China. We did a retrospective cross-sectional assessment of prevalence of MCRPE infection from isolates of Gram-negative bacteria collected at the hospitals from 2007 to 2015 (prevalence study). We did a retrospective case-control study of risk factors for infection and mortality after infection, using all MCRPEC from infection isolates and a random sample of mcr-1-negative E coli infections from the retrospective collection between 2012 and 2015 (infection study). We also did a prospective case-control study to assess risk factors for carriage of MCRPEC in rectal swabs from inpatients with MCRPEC and mcr-1 negative at the hospitals and collected between May and December, 2015, compared with mcr-1-negative isolates from rectal swabs of inpatients (colonisation study). Strains were analysed for antibiotic resistance, plasmid typing, and transfer analysis, and strain relatedness.

FINDINGS

We identified 21 621 non-duplicate isolates of Enterobacteriaceae, Acinetobacter spp, and Pseudomonas aeruginosa from 18 698 inpatients and 2923 healthy volunteers. Of 17 498 isolates associated with infection, mcr-1 was detected in 76 (1%) of 5332 E coli isolates, 13 (<1%) of 348 Klebsiella pneumoniae, one (<1%) of 890 Enterobacter cloacae, and one (1%) of 162 Enterobacter aerogenes. For the infection study, we included 76 mcr-1-positive clinical E coli isolates and 508 mcr-1-negative isolates. Overall, MCRPEC infection was associated with male sex (209 [41%] vs 47 [63%], adjusted p=0·011), immunosuppression (30 [6%] vs 11 [15%], adjusted p=0·011), and antibiotic use, particularly carbapenems (45 [9%] vs 18 [24%], adjusted p=0·002) and fluoroquinolones (95 [19%] vs 23 [30%], adjusted p=0·017), before hospital admission. For the colonisation study, we screened 2923 rectal swabs from healthy volunteers, of which 19 were MCRPEC, and 1200 rectal swabs from patients, of which 35 were MCRPEC. Antibiotic use before hospital admission (p<0·0001) was associated with MCRPEC carriage in 35 patients compared with 378 patients with mcr-1-negative E coli colonisation, whereas living next to a farm was associated with mcr-1-negative E coli colonisation (p=0·03, univariate test). mcr-1 could be transferred between bacteria at high frequencies (10^-1 to 10^-3), and plasmid types and MCRPEC multi-locus sequence types (MLSTs) were more variable in Guangdong than in Zhejiang and included the human pathogen ST131. MCRPEC also included 17 unreported ST clades.

INTERPRETATION

In 2017, colistin will be formally banned from animal feeds in China and switched to human therapy. Infection with MRCPEC is associated with sex, immunosuppression, and previous antibiotic exposure, while colonisation is also associated with antibiotic exposure. MLST and plasmid analysis shows that MCRPEC are diversely spread throughout China and pervasive in Chinese communities.

FUNDING

National Key Basic Research Program of China, National Natural Science Foundation of China/Zhejiang, National Key Research and Development Program, and MRC, UK.

Molecular Characterization of Escherichia coli Strains Isolated from Retail Meat That Harbor blaCTX-M and fosA3 Genes

A total of 55 cefotaxime-resistantEscherichia coliisolates were obtained from retail meat products purchased in Shenzhen, China, during the period November 2012 to May 2013. Thirty-seven of these 55 isolates were found to harbor ablaCTX-Mgene, with theblaCTX-M-1group being the most common type.blaCMY-2was detected in 16 isolates, alone or in combination with other extended-spectrum β-lactamase (ESBL) determinants. Importantly, thefosA3gene, which encodes fosfomycin resistance, was detected in 12 isolates, with several being found to reside in the conjugative plasmid that harbored theblaCTX-Mgene. The insertion sequence IS26was observed upstream of some of theblaCTX-M-55andfosA3genes. Conjugation experiments showed thatblaCTX-Mgenes from 15 isolates were transferrable, with Inc I1 and Inc FII being the most prevalent replicons. High clonal diversity was observed among theblaCTX-Mproducers, suggesting that horizontal transfer of theblaCTX-Mgenes amongE. colistrains in retail meats is a common event and that such strains may constitute an important reservoir ofblaCTX-Mgenes, which may be readily disseminated to other potential human pathogens.

In vivo horizontal gene transfer of the carbapenemase OXA-48 during a nosocomial outbreak

BACKGROUND

OXA-48 is a highly prevalent carbapenemase and has been isolated worldwide. Here, we investigate the in vivo horizontal gene transfer (HGT) of blaOXA-48 from Klebsiella pneumoniae to Escherichia coli in an infected patient.

METHODS

Bacterial isolates were characterized by susceptibility testing, multilocus sequence typing, DiversiLab, and plasmid analyses. Transferability of blaOXA-48 was evaluated by in vitro transconjugation using the outbreak strain and E. coli J53. In vivo transconjugation was investigated using the larvae of the greater wax moth (Galleria mellonella) and low-complexity-microbiota mice.

RESULTS

OXA-48-harboring K. pneumoniae isolates belonging to ST14 were isolated during a nosocomial outbreak from 6 patients. Molecular and epidemiological analyses revealed the HGT of an approximately 60-kb OXA-48-containing IncL/M-type plasmid from K. pneumoniae to E. coli belonging to the novel ST666 in a patient. In vitro conjugation experiments revealed a transconjugation frequency of 8.7 × 10(-7). HGT of OXA-48 in a newly developed in vivo model using G. mellonella larvae revealed a higher transconjugation frequency of 1.3 × 10(-4). The conjugation frequency of OXA-48 from K. pneumoniae and E. coli in the gut of low-complexity-microbiota mice was determined to be 2.9 × 10(-5).

CONCLUSIONS

The in vivo intergenus gene transfer of OXA-48 in the gut of an infected patient was verified in vitro and in 2 in vivo models, which both showed even higher transmission frequencies vs in vitro conditions. This implies that the current in vitro protocols might not correctly reflect the HGT of carbapenemase genes in vivo.