f Infections caused by carbapenem-resistant KPC-producing Klebsiella pneumoniae are responsible for high rates of mortality and represent a major therapeutic challenge, especially when the isolates are also resistant to colistin. We used the checkerboard method to evaluate the synergistic activity of 10 antibiotic combinations against 13 colistin-resistant KPC-producing K. pneumoniae isolates (colistin MIC range of 8 to 128 mg/liter). Colistin plus rifampin was the only combination that demonstrated consistent synergistic bacteriostatic activity against 13/13 strains tested, reducing the colistin MIC below the susceptibility breakpoint (MIC < 2 mg/liter) in 7/13 strains at rifampin concentrations ranging from 4 to 16 mg/liter. Bactericidal synergistic activity was also documented for 8/13 tested strains. Other antimicrobial combinations with carbapenems, gentamicin, and tigecycline showed variously synergistic results. Colistin plus rifampin also exhibited bacteriostatic synergistic activity against 4/4 colistin-susceptible KPC-producing K. pneumoniae isolates (colistin MIC range of 0.5 to 2 mg/liter) and 4/4 ertapenem-resistant extended-spectrum beta-lactamase (ESBL)-producing K. pneumoniae isolates (ertapenem MIC range of 16 to 32 mg/liter). Collectively, our data suggest that colistin plus rifampin is the most consistently synergistic combination against KPC-producing K. pneumoniae isolates, including colistin-resistant strains. Colistin-rifampin combinations may have a role in the treatment of multidrug-resistant K. pneumoniae and may possibly slow the selection of heteroresistant subpopulations during colistin therapy.

IMPORTANCEConvalescent plasma (CP) has been generally unsuccessful in preventing worsening of respiratory failure or death in hospitalized patients with COVID-19 pneumonia. OBJECTIVE To evaluate the efficacy of CP plus standard therapy (ST) vs ST alone in preventing worsening respiratory failure or death in patients with COVID-19 pneumonia. DESIGN, SETTING, AND PARTICIPANTS This prospective, open-label, randomized clinical trial enrolled (1:1 ratio) hospitalized patients with COVID-19 pneumonia to receive CP plus ST or ST alone between July 15 and December 8, 2020, at 27 clinical sites in Italy. Hospitalized adults with COVID-19 pneumonia and a partial pressure of oxygen-to-fraction of inspired oxygen (PaO 2 /FiO 2 ) ratio between 350 and 200 mm Hg were eligible. INTERVENTIONS Patients in the experimental group received intravenous high-titer CP (Ն1:160, by microneutralization test) plus ST. The volume of infused CP was 200 mL given from 1 to a maximum of 3 infusions. Patients in the control group received ST, represented by remdesivir, glucocorticoids, and low-molecular weight heparin, according to the Agenzia Italiana del Farmaco recommendations. MAIN OUTCOMES AND MEASURESThe primary outcome was a composite of worsening respiratory failure (PaO 2 /FiO 2 ratio <150 mm Hg) or death within 30 days from randomization. RESULTSOf the 487 randomized patients (241 to CP plus ST; 246 to ST alone), 312 (64.1%) were men; the median (IQR) age was 64 (54.0-74.0) years. The modified intention-to-treat population included 473 patients. The primary end point occurred in 59 of 231 patients (25.5%) treated with CP and ST and in 67 of 239 patients (28.0%) who received ST (odds ratio, 0.88; 95% CI, 0.59-1.33; P = .54). Adverse events occurred more frequently in the CP group (12 of 241 [5.0%]) compared with the control group (4 of 246 [1.6%]; P = .04). CONCLUSIONS AND RELEVANCEIn patients with moderate to severe COVID-19 pneumonia, hightiter anti-SARS-CoV-2 CP did not reduce the progression to severe respiratory failure or death within 30 days. (continued) Key Points Question Is convalescent plasma useful in preventing worsening respiratory failure or death in patients with COVID-19 pneumonia? Findings In this randomized clinical trial of 487 patients with COVID-19 pneumonia and a partial pressure of arterial oxygen-to-fraction of inspired oxygen (PaO 2 /FiO 2 ) ratio between 350 and 200 mm Hg at enrollment, the rate of the primary clinical end point (need for mechanical ventilation, defined as PaO 2 /FiO 2 ratio <150 mm Hg, or death) was not significantly different between the convalescent plasma group and the control group. Meaning In this trial, convalescent plasma did not reduce the progression to severe respiratory failure or death within 30 days.

The aim of the study was to assess the microbiological activity and clinical efficacy of colistin and rifampin combination against multidrug-resistant (MDR) Pseudomonas aeruginosa infections. The antimicrobial activity of the colistin/rifampin combination was evaluated using the checkerboard and time-kill curve methods against different MDR P. aeruginosa strains. The combination of rifampin and colistin resulted fully (1 strain) or partially (5 strains) synergistic for 6/7 strains and minimum inhibitory concentrations (MICs) in combination were reduced to easily obtainable therapeutic levels. The time-kill curves showed that the combination was bactericidal against the strains tested. The clinical efficacy of the combination was tested in four patients with difficult-to treat infections (sepsis or pneumonia) caused by MDR P. aeruginosa. All infections were successfully treated. Our microbiological and clinical observations suggest that the addition of rifampin to colistin may result in a synergistic bactericidal combination that may be useful in patients with infections caused by MDR P. aeruginosa which are difficult to cure.

Introduction Different antivirals are available for the treatment of outpatients with COVID-19. Our aim was to describe a real-world experience of outpatient management of COVID-19 subjects at high risk of progression. Methods This prospective observational study conducted in the University Hospital of Pisa (January 2022–July 2022) included consecutive COVID-19 outpatients with at least one risk factor for disease progression. Patients received nirmatrelvir/ritonavir, molnupiravir, or 3-day remdesivir, according to the Italian Medicines Agency (AIFA) indications. All patients were followed up until 30 days from the first positive nasopharyngeal swab. The primary endpoint was a composite of death or hospitalization. Secondary endpoints were occurrence of adverse events and a negative test within 10 days from the first positive test. Multivariable analysis was performed to identify factors associated with death or hospitalization. Results Overall, 562 outpatients were included: 114 (20.3%) received molnupiravir, 252 (44.8%) nirmatrelvir/ritonavir, and 196 (34.9%) 3-day remdesivir. The composite endpoint occurred in 2.5% of patients and was more frequent in patients treated with remdesivir (5.1%) compared with molnupiravir (1.8%) or nirmatrelvir/ritonavir (0.8%, ANOVA among groups p = 0.012). On multivariable Cox regression analysis, presence of ≥ 3 comorbidities, hematological disease, gastrointestinal symptoms, and each-day increment from symptoms onset were factors associated with death or hospitalization, while antiviral treatment was not a predictor. Adverse events occurred more frequently in the nirmatrelvir/ritonavir group (49.2%). Nirmatrelvir/ritonavir compared with remdesivir was associated with a higher probability of having a negative test within 10 days from the first positive one. Conclusion Death or hospitalization did not differ among high-risk COVID-19 outpatients treated with currently available antivirals. Safety and time to a negative test differed among the three drugs. Supplementary Information The online version contains supplementary material available at 10.1007/s40121-022-00729-2.