Colonization With Fluoroquinolone-Resistant Enterobacterales Decreases the Effectiveness of Fluoroquinolone Prophylaxis in Hematopoietic Cell Transplant Recipients.

BACKGROUND: Levofloxacin prophylaxis is recommended to prevent gram-negative bloodstream infections (BSIs) in patients with prolonged chemotherapy-induced neutropenia. However, increasing fluoroquinolone resistance may decrease the effectiveness of this approach. METHODS: We assessed the prevalence of colonization with fluoroquinolone-resistant Enterobacterales (FQRE) among patients admitted for hematopoietic cell transplantation (HCT) from November 2016 to August 2019 and compared the risk of gram-negative BSI between FQRE-colonized and noncolonized patients. All patients received levofloxacin prophylaxis during neutropenia. Stool samples were collected upon admission for HCT and weekly thereafter until recovery from neutropenia, and underwent selective culture for FQRE. All isolates were identified and underwent antimicrobial susceptibility testing by broth microdilution. FQRE isolates also underwent whole-genome sequencing. RESULTS: Fifty-four of 234 (23%) patients were colonized with FQRE prior to HCT, including 30 of 119 (25%) allogeneic and 24 of 115 (21%) autologous HCT recipients. Recent antibacterial use was associated with FQRE colonization (P = .048). Ninety-one percent of colonizing FQRE isolates were Escherichia coli and 29% produced extended-spectrum ß-lactamases. Seventeen (31%) FQRE-colonized patients developed gram-negative BSI despite levofloxacin prophylaxis, compared to only 2 of 180 (1.1%) patients who were not colonized with FQRE on admission (P < .001). Of the 17 gram-negative BSIs in FQRE-colonized patients, 15 (88%) were caused by FQRE isolates that were genetically identical to the colonizing strain. CONCLUSIONS: Nearly one-third of HCT recipients with pretransplant FQRE colonization developed gram-negative BSI while receiving levofloxacin prophylaxis, and infections were typically caused by their colonizing strains. In contrast, levofloxacin prophylaxis was highly effective in patients not initially colonized with FQRE.

Comparison of Two High-Throughput Reverse Transcription-PCR Systems for the Detection of Severe Acute Respiratory Syndrome Coronavirus 2.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has emerged as the cause of a worldwide pandemic. Many commercial SARS-CoV-2 reverse transcription-PCR (RT-PCR) assays have received Emergency Use Authorization from the U.S. Food and Drug Administration. However, there are limited data describing their performance, in particular the performance of high-throughput SARS-CoV-2 RT-PCR systems. We analyzed the diagnostic performance of two high-throughput systems: cobas 6800 and Panther Fusion, and their associated RT-PCR assays, with a collection of 389 nasopharyngeal specimens. The overall agreement between the platforms was 96.4% (375/389). Cohen's kappa analysis rated the strength of agreement between the two platforms as "almost perfect" (κ = 0.922; standard error, 0.051). Furthermore, there was no significant difference between corresponding cycle threshold values generated on the two systems (P value = 0.88; Student's t test). Taken together, these data imply that the two platforms can be considered comparable in terms of their clinical performance. We believe that this information will be useful for those who have already adopted these platforms or are seeking to implement high-throughput RT-PCR testing to stem the SARS-CoV-2 pandemic.

Activity of Imipenem-Relebactam and Comparator Agents against Genetically Characterized Isolates of Carbapenem-Resistant Enterobacteriaceae.

Carbapenem-resistant Enterobacteriaceae (CRE) strains are an urgent public health threat. We evaluated the in vitro activities of 19 antimicrobial agents, including imipenem-relebactam, against (i) 106 CRE bloodstream isolates that primarily expressed Klebsiella pneumoniae carbapenemase (KPC) and (ii) 20 OXA-48-like-expressing CRE isolates. Ninety-five percent of CRE bloodstream isolates were susceptible to imipenem-relebactam. In contrast to their comparable activities against KPC-producing CRE strains, ceftazidime-avibactam was more active in vitro against OXA-48-like CRE strains than was imipenem-relebactam (90% susceptible versus 15% susceptible).

Strain Diversity of Pseudomonas fluorescens Group with Potential Blue Pigment Phenotype Isolated from Dairy Products.

The blue discoloration in Mozzarella cheese comes from bacterial spoilage due to contamination with Pseudomonas. Fourteen Pseudomonas fluorescens strains from international collections and 55 new isolates of dominant bacterial populations from spoiled fresh cheese samples were examined to assess genotypic and phenotypic strain diversity. Isolates were identified by 16S rRNA gene sequencing and tested for the production of the blue pigment at various temperatures on Mascarpone agar and in Mozzarella preserving fluid (the salty water in which the cheese is conserved, which becomes enriched by cheese minerals and peptides during storage). Pulsed-field gel electrophoresis analysis after treatment with the endonuclease SpeI separated the isolates into 42 genotypes at a similarity level of 80%. Based on the pulsotype clustering, 12 representative strains producing the blue discoloration were chosen for the multilocus sequence typing targeting the gyrB, glnS, ileS, nuoD, recA, rpoB, and rpoD genes. Four new sequence typing profiles were discovered, and the concatenated sequences of the investigated loci grouped the tested strains into the so-called ''blue branch'' of the P. fluorescens phylogenetic tree, confirming the linkage between pigment production and a specific genomic cluster. Growth temperature affected pigment production; the blue discoloration appeared at 4 and 14°C but not at 30°C. Similarly, the carbon source influenced the phenomenon; the blue phenotype was generated in the presence of glucose but not in the presence of galactose, sodium succinate, sodium citrate, or sodium lactate.