Systematic Analysis of Mobile Genetic Elements Mediating ß-Lactamase Gene Amplification in Noncarbapenemase-Producing Carbapenem-Resistant Enterobacterales Bloodstream Infections.

Noncarbapenemase-producing carbapenem-resistant Enterobacterales (non-CP-CRE) are increasingly recognized as important contributors to prevalent carbapenem-resistant Enterobacterales (CRE) infections. However, there is limited understanding of mechanisms underlying non-CP-CRE causing invasive disease. Long- and short-read whole-genome sequencing was used to elucidate carbapenem nonsusceptibility determinants in Enterobacterales bloodstream isolates at MD Anderson Cancer Center in Houston, Texas. We investigated carbapenem nonsusceptible Enterobacterales (CNSE) mechanisms (i.e., isolates with carbapenem intermediate resistance phenotypes or greater) through a combination of phylogenetic analysis, antimicrobial resistance gene detection/copy number quantification, porin assessment, and mobile genetic element (MGE) characterization. Most CNSE isolates sequenced were non-CP-CRE (41/79; 51.9%), whereas 25.3% (20/79) were Enterobacterales with intermediate susceptibility to carbapenems (CIE), and 22.8% (18/79) were carbapenemase-producing Enterobacterales (CPE). Statistically significant copy number variants (CNVs) of extended-spectrum ß-lactamase (ESBL) genes (Wilcoxon Test; P-value < 0.001) were present in both non-CP-CR E. coli (median CNV = 2.6×; n = 17) and K. pneumoniae (median CNV = 3.2×, n = 17). All non-CP-CR E. coli and K. pneumoniae had predicted reduced expression of at least one outer membrane porin gene (i.e., ompC/ompF or ompK36/ompK35). Completely resolved CNSE genomes revealed that IS26 and ISEcp1 structures harboring blaCTX-M variants along with other antimicrobial resistance elements were associated with gene amplification, occurring in mostly IncFIB/IncFII plasmid contexts. MGE-mediated ß-lactamase gene amplifications resulted in either tandem arrays, primarily mediated by IS26 translocatable units, or segmental duplication, typically due to ISEcp1 transposition units. Non-CP-CRE strains were the most common cause of CRE bacteremia with carbapenem nonsusceptibility driven by concurrent porin loss and MGE-mediated amplification of blaCTX-M genes. IMPORTANCE Carbapenem-resistant Enterobacterales (CRE) are considered urgent antimicrobial resistance (AMR) threats. The vast majority of CRE research has focused on carbapenemase-producing Enterobacterales (CPE) even though noncarbapenemase-producing CRE (non-CP-CRE) comprise 50% or more of isolates in some surveillance studies. Thus, carbapenem resistance mechanisms in non-CP-CRE remain poorly characterized. To address this problem, we applied a combination of short- and long-read sequencing technologies to a cohort of CRE bacteremia isolates and used these data to unravel complex mobile genetic element structures mediating ß-lactamase gene amplification. By generating complete genomes of 65 carbapenem nonsusceptible Enterobacterales (CNSE) covering a genetically diverse array of isolates, our findings both generate novel insights into how non-CP-CRE overcome carbapenem treatments and provide researchers scaffolds for characterization of their own non-CP-CRE isolates. Improved recognition of mechanisms driving development of non-CP-CRE could assist with design and implementation of future strategies to mitigate the impact of these increasingly recognized AMR pathogens.

Open-angle glaucoma secondary to blood clot in the Schlemm's canal following scleral buckle surgery and its treatment with tPA.

Obstruction of the episceral venous system can present with glaucoma. We present two patients who were referred to us for management of acute glaucoma with presumed episceral venous compression. The first patient had open-angle glaucoma with probable elevated episcleral venous pressure and blood in the Schlemm's canal, following a 360 degrees scleral buckle surgery. The second patient had open-angle glaucoma from delayed peribulbar hemorrhage following uncomplicated cataract surgery with blood in the Schlemm's canal. Both patients were successfully treated with intracameral injection with tissue plasminogen activator (tPA).

Accuracy of endovaginal sonography for the detection of fallopian tube blockage.

The patency of 814 fallopian tubes in 414 patients was evaluated by endovaginal sonography immediately prior to hysterosalpingography. In the 659 fallopian tubes that were normal with free spillage, endovaginal sonography did not reveal any tubal or peritubal abnormality (specificity 100%). Of the 64 fallopian tubes with definite hydrosalpinx on hysterosalpingography, only 22 were detected on endovaginal sonography (sensitivity 34%). Four of 57 (7%) fallopian tubes with definite proximal blockage on the hysterosalpingogram showed hydrosalpinx on the same side on endovaginal sonography, indicating the association of proximal and distal tubal blockages in a small group of patients with blocked fallopian tubes. This combination can only be detected by the addition of endovaginal sonography to hysterosalpingography. Ten of 11 (91%) hydrosalpinges in seven patients who underwent endovaginal sonography immediately after hysterosalpingography were detected by ultrasonography. Only two of these had been visible on pre-hysterosalpingography endovaginal sonograms. This would indicate that the poor sensitivity of endovaginal sonography for diagnosing hydrosalpinx is at least partly due to its lack of distention. We conclude that an abnormal endovaginal sonogram is highly predictive of the presence of a blocked tube, but endovaginal sonography has a poor sensitivity for the diagnosis of a hydrosalpinx detectable by hysterosalpingography. Endovaginal sonography would be useful to detect a combination of proximal and distal blockage in a subgroup of patients with tubal blockage.

The effect of iodoacetic acid on the electroretinogram and oscillatory potentials in rabbits.

It has been shown that a single injection of iodoacetic acid selectively (but temporarily) abolishes the b-wave of the electroretinogram. We examined whether such use of this chemical further substantiate our claim that the b-wave of the electroretinogram is a composite potential resulting from the summation (or integration) of faster retinal potentials, usually referred to as the oscillatory potentials. Full-field electroretinograms were recorded from adult New Zealand rabbits before and after a single, bolus injection of 15 mg/kg of buffered iodoacetic acid. Both the 1-1000 Hz electroretinogram and the 100-1000 Hz oscillatory potentials were recorded simultaneously. The oscillatory potentials considered in this study were those normally seen on the rising phase of the b-wave. Following the intravenous injection of iodoacetic acid, there was a progressive decrease in the amplitude and peak time of the b-wave. This observation also was reflected in the oscillatory potential recordings, in which the long-latency oscillatory potentials (3 and 4) progressively disappeared while oscillatory potential 2 remained. We believe that these findings further support our contention that the oscillatory potentials are major components of the b-wave.