Non-Typhoidal Salmonellas (NTSs) are diffused worldwide. In Italy, more than 3500 cases are notified each year, but despite this, data about salmonellosis are scarce. Our multi-center, retrospective, descriptive study selected 252 patients with positive cultures for Salmonella spp. (feces 79.8%, blood 8.7%, feces and blood 7.5%), aiming to describe the epidemiological and clinical characteristics of this population. Bacteremic infections constituted 16.3% (41/252) of patients. Extreme ages (≤12 and ≥65 years old) accounted for 79.7%, but only elder ages were strongly associated with bacteremic infections (aOR 5.78). Invasive infections had a 7-fold higher mortality rate than non-invasive disease (9.8% vs. 1.4%, p = 0.013), with an overall rate of 2.8%. The two more represented serogroups were O:4 (52.8%) and O:9 (22.2%). The O:9 serogroup was strongly associated with a higher frequency of invasive infection (aOR 2.96, 95% CI 1.17–7.63). In particular, S. napoli, an emerging serovar in Europe, accounted for 31.7% of bacteremic infections and only 9.5% of non-bacteremic ones (p < 0.001). Antibiotic microbial resistance (AMR) observed a steep increasing trend and was detected in 60.4% of cases (122/202): amoxicillin/clavulanate, ampicillin, and gentamicin were most commonly involved (26.7%, 21.8%, 14.3%, respectively), while TMP/SMX, ciprofloxacin, and ceftriaxone were <10%. Resistance was, in general, less common in the O:9 serogroup, while amikacin resistance was significantly more common. Factors associated with an MDR Salmonella acquisition were time (OR 1.37 per year more), O:4 serogroup (OR 2.67), and being a woman (OR 2.11). The most frequent symptoms were diarrhea (90.5%) and fever (81.7%). In conclusion, our study highlights a high burden of NTS infections, leading to severe or fatal outcomes in frail patients. Furthermore, AMR shows an increasing trend with a concerning high prevalence of cephalosporine resistance compared to the rest of Europe.

We evaluated the prevalence of HIV-1 drug resistance in newly diagnosed individuals from 2017 to 2023, in Italy. Transmitted drug resistance (TDR) was evaluated by using the HIVdb algorithm (https://hivdb.stanford.edu/), through two different approaches: (1) by considering the complete list of mutations included for the genotypic susceptibility score and (2) by considering only major resistant mutations. Logistic regression analysis was used to estimate the association of TDR with the calendar year. We analysed 1188 drug-naive individuals diagnosed in Italy between 2017 and 2023 enrolled in the Antiviral Response Cohort Analysis database. Most of them (∼75 %) were males; their median (IQR) age was 40 (30-50) years. Non-B subtypes were found in 43.9 % of participants and significantly increased over time (from 44.2 % in 2017 to 54.8 % in 2023, P = 0.008). TDR prevalence was 29 %, driven by non-nucleoside reverse transcriptase inhibitor resistance (19.4 %). Rates of nucleoside reverse transcriptase inhibitors, protease inhibitors, and integrase strand transfer inhibitors resistance were 4.7 %, 4.4 %, and 5.1 %, respectively, with no significant temporal trends. When only major resistant mutations were considered, TDR prevalence was definitively lower (15.8 %), primarily driven by non-nucleoside reverse transcriptase inhibitor mutations (11.8 %). Rates of resistance for major nucleoside reverse transcriptase inhibitors, protease inhibitors, and integrase strand transfer inhibitors were 4.6 %, 1.7 % and 0.7 %, respectively. Resistance to two or more drug classes was rare (1.9 %). No association of major TDR within the calendar year was found, except for 2023 (AOR: 2.33 [1.14-4.74], P = 0.019). Over the period 2017-2023, the HIV-1 TDR appeared generally stable in Italy. However, the increased prevalence of major TDR in 2023 confirms the importance of continuous TDR surveillance in newly diagnosed individuals to inform clinical practice.

The clinical relevance of genotypic resistance testing (GRT) performed on viral DNA is still debated. Here, we investigate the role of archived resistance on the virological rebound (VR) after switching treatment. This retrospective study enrolled virologically suppressed people with HIV (PWH) included in the ARCA database with one proviral GRT performed in the 6 months prior to the switch to a modern regimen. Baseline genotypic susceptibility scores (GSS) from HIV-1 DNA GRT (DNA-GSS) and, for a subgroup, from historical plasma GRT (hRNA-GSS) were calculated based on the switch regimen. Survival analysis was used to assess the probability and predictors of VR. A total of 300 PWH were analysed; 23 % of them showed full or intermediate resistance (DNA-GSS <2). After the therapy switch, the overall probability of experiencing VR was 13.7 %, with PWH with DNA-GSS <2 showing a higher adjusted hazard risk of VR (aHR 2.15, 95 % CI, 1.08-4.27, P = 0.028). Shorter time under suppression preswitch was a negative predictor of VR (per 1-year increase, aHR 0.84 95 % CI, 0.75-0.93, P = 0.001). In the subgroup of PWH with historical plasma GRT (n = 129), hRNA-GSS was not associated with VR, while PWH with an intermediate or full resistance found in both DNA-GSS and hRNA-GSS had the highest probability of experiencing VR. Our findings evidence the role of archived resistance in predicting VR after switch therapy in suppressed PWH. Thus, proviral GRT could be a useful tool to optimise strategies for switching treatment, especially if paired with information on previous historical resistance and the duration under suppression.