Genetic Predictive Factors for Nonsusceptible Phenotypes and Multidrug Resistance in Expanded-Spectrum Cephalosporin-Resistant Uropathogenic Escherichia coli from a Multicenter Cohort: Insights into the Phenotypic and Genetic Basis of Coresistance.

Antimicrobial resistance in urinary tract infections (UTIs) is a major public health concern. This study aims to characterize the phenotypic and genetic basis of multidrug resistance (MDR) among expanded-spectrum cephalosporin-resistant (ESCR) uropathogenic Escherichia coli (UPEC) causing UTIs in California patient populations. Between February and October 2019, 577 ESCR UPEC isolates were collected from patients at 6 clinical laboratory sites across California. Lineage and antibiotic resistance genes were determined by analysis of whole-genome sequence data. The lineages ST131, ST1193, ST648, and ST69 were predominant, representing 46%, 5.5%, 4.5%, and 4.5% of the collection, respectively. Overall, 527 (91%) isolates had an expanded-spectrum ß-lactamase (ESBL) phenotype, with blaCTX-M-15, blaCTX-M-27, blaCTX-M-55, and blaCTX-M-14 being the most prevalent ESBL genes. In the 50 non-ESBL phenotype isolates, 40 (62%) contained blaCMY-2, which was the predominant plasmid-mediated AmpC (pAmpC) gene. Narrow-spectrum ß-lactamases, blaTEM-1B and blaOXA-1, were also found in 44.9% and 32.1% of isolates, respectively. Among ESCR UPEC isolates, isolates with an ESBL phenotype had a 1.7-times-greater likelihood of being MDR than non-ESBL phenotype isolates (P < 0.001). The cooccurrence of blaCTX-M-15, blaOXA-1, and aac(6')-Ib-cr within ESCR UPEC isolates was strongly correlated. Cooccurrence of blaCTX-M-15, blaOXA-1, and aac(6')-Ib-cr was associated with an increased risk of nonsusceptibility to piperacillin-tazobactam, cefepime, fluoroquinolones, and amikacin as well as MDR. Multivariate regression revealed the presence of blaCTX-M-55, blaTEM-1B, and the ST131 genotype as predictors of MDR. IMPORTANCE The rising incidence of resistance to expanded-spectrum cephalosporins among Escherichia coli strains, the most common cause of UTIs, is threatening our ability to successfully empirically treat these infections. ESCR E. coli strains are often MDR; therefore, UTI caused by these organisms often leads to treatment failure, increased length of hospital stay, and severe complications (D. G. Mark, Y.-Y. Hung, Z. Salim, N. J. Tarlton, et al., Ann Emerg Med 78:357-369, 2021, https://doi.org/10.1016/j.annemergmed.2021.01.003). Here, we performed an in-depth analysis of genetic factors of ESCR E. coli associated with coresistance and MDR. Such knowledge is critical to advance UTI diagnosis, treatment, and antibiotic stewardship.

Pleuritis and suppurative pneumonia associated with a hypermucoviscosity phenotype of Klebsiella pneumoniae in California sea lions (Zalophus californianus).

The aim of this study is to document the isolation of a hypermucoviscosity (HMV) phenotype of Klebsiella pneumoniae from 25 cases of suppurative pneumonia and pleuritis and two cases of abscesses in California sea lions (Zalophus californianus) from the central California coast, representing the first report of this zoonotic pathogen from the marine environment and only the second report in non-humans. Animals died 2h to 4 days after first being observed sick on beaches. Clinical signs varied from dyspnoea to coma. Gross post-mortem examination of 25 cases revealed fibrinous pleuritis, copious pus in the pleural cavity and suppurative bronchopneumonia. K. pneumoniae isolates obtained from lung and pleural swabs and the hepatic and subcuticular abscesses were highly mucoid on blood agar culture media and were positive to the "string test". Twenty-one of the 27 isolates were examined by PCR and all were positive for rmpA and K2wyz and negative for K1magA genes. Although pneumonia and pleuritis have previously commonly been observed in marine mammals, their association with pure cultures of a zoonotic bacteria, K. pneumoniae HMV phenotype, has not. This report provides further evidence of the role marine mammals play as sentinels of health risks to humans from coastal waters.

Recommendations for diagnosis of shiga toxin--producing Escherichia coli infections by clinical laboratories.

Shiga toxin--producing Escherichia coli (STEC) are a leading cause of bacterial enteric infections in the United States. Prompt, accurate diagnosis of STEC infection is important because appropriate treatment early in the course of infection might decrease the risk for serious complications such as renal damage and improve overall patient outcome. In addition, prompt laboratory identification of STEC strains is essential for detecting new and emerging serotypes, for effective and timely outbreak responses and control measures, and for monitoring trends in disease epidemiology. Guidelines for laboratory identification of STEC infections by clinical laboratories were published in 2006. This report provides comprehensive and detailed recommendations for STEC testing by clinical laboratories, including the recommendation that all stools submitted for routine testing from patients with acute community-acquired diarrhea (regardless of patient age, season of the year, or presence or absence of blood in the stool) be simultaneously cultured for E. coli O157:H7 (O157 STEC) and tested with an assay that detects Shiga toxins to detect non-O157 STEC. The report also includes detailed procedures for specimen selection, handling, and transport; a review of culture and nonculture tests for STEC detection; and clinical considerations and recommendations for management of patients with STEC infection. Improving the diagnostic accuracy of STEC infection by clinical laboratories should ensure prompt diagnosis and treatment of these infections in patients and increase detection of STEC outbreaks in the community.

Evaluation of commercial antisera for Salmonella serotyping.

We compared a set of commercial Salmonella somatic and flagellar serotyping antisera to in-house-prepared antisera from the Microbial Diseases Laboratory, California Department of Public Health, using 327 Salmonella enterica strains belonging to subgroups I, II, IIIa, IIIb, and IV. The sensitivities of Denka Seiken (Tokyo, Japan) somatic and flagellar antisera (using a tube agglutination assay) were 94.0% and 99.2%, respectively, and the specificity was 100% for both sets of sera. Polyvalent O and O1 antiserum sensitivity and specificity were >90%, with the exception of polyvalent O1 antiserum, for which sensitivity was 88.9%. When Denka Seiken flagellar antisera were used in a slide agglutination assay, the sensitivity and accuracy dropped to 88.9% and the specificity fell to 91%. Overall, Denka Seiken commercial antisera performed very well and, together with the comprehensive range of factors available, offer laboratories quality reagents suitable for serotyping strains of salmonellae.

Feasibility of reduction in use of the mouse bioassay: presence/absence screening for saxitoxin in frozen acidified mussel and oyster extracts from the coast of California with in vitro methods.

In the United States, the detection of paralytic shellfish poisoning (PSP) for regulatory purposes relies on the mouse bioassay (MBA). Using a saxitoxin presence/absence test could reduce animal usage significantly. Three in vitro methods, the RIDASCREEN Saxitoxin kit, MIST Alert, and a 5 h neuroblastoma assay, were evaluated in parallel with the MBA using 106 twice-frozen, acidified extracts from California-grown mussel and oyster tissues. For each assay, a cutoff point was established whereby data below or equal to that point were scored as negative and were assigned a score of zero. Data above the cutoff were considered positive and assigned a score of one. Pearson correlation coefficients were generated. The RIDASCREEN, MIST Alert, and neuroblastoma bioassay correlated to the MBA at 0.849, 0.853, and 0.832 when used for presence/absence detection. These data suggest that a reduction in MBA usage could be achieved in the surveillance of California-grown mussels and oysters for PSP-associated toxins. Correlation data between the in vitro assays, cost comparisons, and the potential for false negatives and false positives were examined. Implications of these methodologies in protecting public health are discussed.