Hospitalized patients with diarrhea: Rate of Clostridioides difficile infection underdiagnosis and drivers of clinical suspicion.

OBJECTIVES: Clostridioides difficile infection (CDI) represents a challenging issue, with an evolving epidemiology. Main objectives of our study were: to assess the frequency of diarrhea of overall etiology, including CDI, as a cause of hospital admission or occurring during hospital stay;- to determine the rate of underdiagnosis of community-acquired (CA-), health care associated (HCA)- and hospital onset (HO-) CDI, and explore factors associated with its clinical suspicion by physicians. METHODS: A prospective cohort study included all hospitalized patients with diarrhea at two acute-care hospitals. C. difficile (CD) tests were performed on every stool samples, irrespective of the treating physician request. Factors associated with the likelihood of CD test request by physicians were assessed. RESULTS: We enrolled 871 (6%) patients with diarrhea. CD test performed on all diarrheic stool samples was positive in 228 cases (26%); 37, 106, 85 cases of CA- (14%), HCA- (42%) and HO- diarrhea (24%), respectively. Treating physicians did not request CD test in 207 (24%) diarrhea cases. The rate of CDI underdiagnosis was 11% (24/228); it was higher in CA-CDI (27%, 10/37). Logistic regression analysis identified age >65 years (RR 1.1; 95 CI 1.06-1.2) and hospitalizations in the previous 3 months (RR 1.2; 95% CI 1.1-1.3) as independent factors associated with the likelihood of requesting the CD test by the physician. These risk factors differed by epidemiological classification of diarrhea and by hospital. CONCLUSIONS: Our study confirmed the relevance of CDI underdiagnosis and provided new insights in the factors underlying the lack of CDI clinical suspicion.

Molecular analysis of clinical isolates of ceftazidime-avibactam-resistant Klebsiella pneumoniae.

OBJECTIVES: To analyse the strains collected during a 1-year survey of ceftazidime-avibactam-resistant KPC-producing Klebsiella pneumoniae, in order to investigate the molecular mechanisms potentially responsible for their resistant phenotype. METHODS: Clinical KPC-producing K. pneumoniae isolates were collected from 31 patients in six different hospitals in Rome. For eight of the patients, an additional strain grown before the start of treatment was also available, bringing the total of isolates studied to 39. Antimicrobial susceptibility was determined by automated system, broth microdiluition and E-test as appropriate. In silico analysis of acquired resistance genes was achieved by whole-genome sequencing, while multilocus sequence typing and core genome multilocus sequence typing were employed for molecular typing. Mutations associated with ceftazidime-avibactam resistance were identified by Sanger sequencing of the blaKPC gene. Possible mutations in OmpK35 and OmpK36 outer membrane proteins were also investigated. RESULTS: Molecular analyses highlighted the circulation of the ST512, 101 and 307 high-risk clones; 26 of the 31 patients carried a mutated KPC variant, five had a wild-type KPC-3. Among the KPC variants detected, 11 were different mutations within the blaKPC-3 gene, four of which were novel mutational changes. CONCLUSIONS: Different mutations including single amino-acid substitutions, insertions or deletions within the blaKPC gene were found in 26/31 ceftazidime-avibactam-resistant KPC-producing K. pneumoniae strains belonging to high-risk clones circulating in Italy. Of note, in 14/31 cases the isolates displayed resistance to both ceftazidime-avibactam and carbapenems, raising concerns for the possible selection of a multidrug-resistant phenotype.

Ceftaroline Plus Ampicillin Against Gram-Positive Organisms: Results from E-Test Synergy Assays.

In an era of increasing drug resistance and limited numbers of antimicrobials in the drug production pipeline, healthcare-associated infections represent a growing public health threat. When therapeutic options are limited, clinicians often resort to using antimicrobial combinations that produce a synergistic effect on the target pathogen. Novel antibiotics are therefore welcome in the daily practice of medicine. For example, ceftaroline is a broad-spectrum cephalosporin active against a variety of bacteria, including methicillin-resistant Staphylococcus aureus, but with limited activity against enterococci, particularly Enterococcus faecium. In this study, we tested the efficacy of ceftaroline against clinical isolates of gram-positive bacteria (S. aureus, Enterococcus faecalis, and E. faecium) by the broth microdilution and E-test assays, and then evaluated the synergistic effect of ceftaroline and ampicillin using the E-test method. The time-kill assay was used to confirm the data on selected strains. This drug combination has been recently shown to be effective against E. faecalis and could offer the advantage of cost-effectiveness (compared to other synergistic associations) as well as good tolerability. The E-test was chosen because of its relative simplicity of use that makes it suitable for routine clinical laboratories as a quick tool to guide clinicians when confronted with difficult-to-treat infections that may require an empirical approach. Our results indicate the presence of a synergistic effect of ceftaroline and ampicillin on most of the strains used, especially E. faecium and E. faecalis. The fact that two of those Enterococcus strains were vancomycin resistant suggests that the possible use of this combination for combating the spread of vancomycin-resistant enterococci should be explored.