Development and validation of a prediction model for severe respiratory failure in hospitalized patients with SARS-CoV-2 infection: a multicentre cohort study (PREDI-CO study).

OBJECTIVES: We aimed to develop and validate a risk score to predict severe respiratory failure (SRF) among patients hospitalized with coronavirus disease-2019 (COVID-19). METHODS: We performed a multicentre cohort study among hospitalized (>24 hours) patients diagnosed with COVID-19 from 22 February to 3 April 2020, at 11 Italian hospitals. Patients were divided into derivation and validation cohorts according to random sorting of hospitals. SRF was assessed from admission to hospital discharge and was defined as: Spo2 <93% with 100% Fio2, respiratory rate >30 breaths/min or respiratory distress. Multivariable logistic regression models were built to identify predictors of SRF, ß-coefficients were used to develop a risk score. Trial Registration NCT04316949. RESULTS: We analysed 1113 patients (644 derivation, 469 validation cohort). Mean (±SD) age was 65.7 (±15) years, 704 (63.3%) were male. SRF occurred in 189/644 (29%) and 187/469 (40%) patients in the derivation and validation cohorts, respectively. At multivariate analysis, risk factors for SRF in the derivation cohort assessed at hospitalization were age ≥70 years (OR 2.74; 95% CI 1.66-4.50), obesity (OR 4.62; 95% CI 2.78-7.70), body temperature ≥38°C (OR 1.73; 95% CI 1.30-2.29), respiratory rate ≥22 breaths/min (OR 3.75; 95% CI 2.01-7.01), lymphocytes ≤900 cells/mm3 (OR 2.69; 95% CI 1.60-4.51), creatinine ≥1 mg/dL (OR 2.38; 95% CI 1.59-3.56), C-reactive protein ≥10 mg/dL (OR 5.91; 95% CI 4.88-7.17) and lactate dehydrogenase ≥350 IU/L (OR 2.39; 95% CI 1.11-5.11). Assigning points to each variable, an individual risk score (PREDI-CO score) was obtained. Area under the receiver-operator curve was 0.89 (0.86-0.92). At a score of >3, sensitivity, specificity, and positive and negative predictive values were 71.6% (65%-79%), 89.1% (86%-92%), 74% (67%-80%) and 89% (85%-91%), respectively. PREDI-CO score showed similar prognostic ability in the validation cohort: area under the receiver-operator curve 0.85 (0.81-0.88). At a score of >3, sensitivity, specificity, and positive and negative predictive values were 80% (73%-85%), 76% (70%-81%), 69% (60%-74%) and 85% (80%-89%), respectively. CONCLUSION: PREDI-CO score can be useful to allocate resources and prioritize treatments during the COVID-19 pandemic.

Listeria monocytogenes meningitis in an immunocompromised patient.

This report describes a case of meningitis caused by Listeria monocytogenes in a stem cell transplant recipient on immunosuppressive therapy for cutaneous chronic graft-versus host disease. A 59-year-old woman had undergone allogeneic stem cell transplantation (from a matched unrelated donor) 13 months previously for chronic lymphocytic leukemia. She was on regular hematologic follow-up. Though her previous malignancy has been in remission, she was immunosuppressed due to the pharmacological treatment. We describe a meningitis caused by a typical food-borne pathogen, dangerous in patients with impaired cell-mediated immunity. Moreover the bacterium had a multidrug resistance, a rare characteristic in clinical listeriosis. Rapid diagnosis and treatment are key factors in these cases. We chose ampicillin and rifampicin that allowed a complete resolution of the clinical manifestations.

Pretreatment with the protegrin IB-367 affects Gram-positive biofilm and enhances the therapeutic efficacy of linezolid in animal models of central venous catheter infection.

BACKGROUND: Biofilms play an important role in the pathogenesis of several chronic infections and nosocomial infections related to indwelling medical devices. METHODS: To assess the efficacy of IB-367 and linezolid (LZD) in the treatment of central venous catheter (CVC) infections using the antibiotic-lock technique, in vitro and in vivo studies were performed. The in vitro antibiotic susceptibility assay for Staphylococcus aureus and Enterococcus faecalis biofilms developed on 96-well polystyrene tissue culture plates was performed to determine the activity of the compounds. Efficacy studies were performed in rat models of Gram-positive CVC infection. Silastic catheters were implanted into the superior cava of adult male Wistar rats. Twenty-four hours after implantation, the catheters were pretreated by filling with IB-367. Thirty minutes later, rats were challenged via the CVC with 1.0 x 10(6) CFU (colony forming units) of S aureus strain diffuse Smith and clinical isolate of slime-producing E faecalis. Administration of LZD into the CVC at a concentration equal to the minimum bacteriocidal concentration observed using adherent cells or at a much higher concentration (1024 microg/mL) began 24 hours later. RESULTS: Both for S aureus and E faecalis, the killing activities of LZD against adherent bacteria were at least 4-fold to 8-fold lower than that against freely growing cells. For both strains, in IB-367-pretreated wells, LZD strongly increases its activity. The in vivo studies showed that when CVCs were pretreated with IB-367, Gram-positive biofilm bacterial load was further decreased to 10(1) CFU/mL and bacteremia was not detected. CONCLUSIONS: IB-367 has potential as an adjunctive agent to LZD in the treatment of Gram-positive biofilm infections such as CVC infections.

In vitro activities of the lipopeptides palmitoyl (Pal)-Lys-Lys-NH(2) and Pal-Lys-Lys alone and in combination with antimicrobial agents against multiresistant gram-positive cocci.

The in vitro activities of the lipopeptides palmitoyl (Pal)-Lys-Lys-NH(2) and Pal-Lys-Lys against gram-positive cocci were investigated. Enterococci and streptococci demonstrated higher susceptibilities than staphylococci and Rhodococcus equi. A positive interaction was shown when the lipopeptides were combined with beta-lactams and vancomycin. These results suggest that lipopeptides are promising candidates for antimicrobial therapy for infections caused by gram-positive organisms.

The cathelicidin-derived tritrpticin enhances the efficacy of ertapenem in experimental rat models of septic shock.

Sepsis remains a serious clinical problem despite intense efforts to improve survival. In this study, the efficacy of ertapenem combined with the cathelicidin tritrpticin was investigated in two rat models of septic shock. Main outcome measures were bacterial growth in blood, peritoneum, spleen, liver, and mesenteric lymph nodes; endotoxin, interleukin 6, and tumor necrosis factor alpha concentrations in plasma; and lethality. Adult male Wistar rats were given (1) an intraperitoneal injection of 1 mg Escherichia coli serotype 0111:B4 LPS or (2) intra-abdominal sepsis induced via cecal ligation and puncture. For each model, all animals were randomized to receive intraperitoneally isotonic sodium chloride solution, 1 mg/kg tritrpticin, 15 mg/kg ertapenem, and 1 mg/kg tritrpticin combined with 15 mg/kg ertapenem. Each group included 20 animals. All compounds significantly reduced bacterial growth and lethality as compared with saline treatment. Treatment with tritrpticin resulted in significant decrease in plasma endotoxin and cytokine levels, whereas ertapenem exerted opposite effect. The combination between tritrpticin and ertapenem proved to be the most effective treatment in reducing all variables measured. In conclusion, tritrpticin enhances ertapenem efficacy in gram-negative septic shock rat models.

RNAIII-inhibiting peptide in combination with the cathelicidin BMAP-28 reduces lethality in mouse models of staphylococcal sepsis.

A mouse model of staphylococcal sepsis was used to evaluate the efficacy of RNAIII-inhibiting peptide (RIP) combined with the cathelicidin BMAP-28. Preliminary in vitro studies showed that both peptides, alone or combined, were able to inhibit the lipoteichoic acid-induced production of tumor necrosis factor alpha and nitric oxide by RAW 264.7 cells. For in vivo experiments, the main outcome measures were lethality, quantitative blood cultures, and detection of tumor necrosis factor alpha and interleukin 6 plasma levels. BALB/c mice were injected i.v. with 2.0 x 10(6) colony-forming units of live Staphylococcus aureus ATCC 25923 or with 5.0 x 10(8) heat-killed cells of the same strain. All animals were randomized to receive i.v. isotonic sodium chloride solution, 10-mg/kg RIP, alone or in combination with 2-mg/kg BMAP-28, 7-mg/kg imipenem, or 7-mg/kg vancomycin, immediately and at 6 hours after bacterial challenge. In in vivo experiments performed with live bacteria, all compounds reduced lethality rates and bacteremia when compared with controls. In general, combined-treated groups had significantly lower bacteremia when compared with single-treated groups. Lowest lethality rates and bacteremia were obtained when RIP was administered in combination with BMAP-28 or vancomycin. In the experiments performed using heat-killed organisms, only BMAP-28 demonstrated significant efficacy on lethality rates and cytokines plasma levels when compared with controls. RIP combined with BMAP-28 exhibited the highest efficacy on all main outcome measurements. These data were observed on both immediate and delayed treatments. These results highlight the capacity of RIP and BMAP-28 to reduce the septic effects of bacterial cell components and exotoxins, and suggest their potential use in the treatment of severe staphylococcus-associated sepsis.

In vitro activities of tritrpticin alone and in combination with other antimicrobial agents against Pseudomonas aeruginosa.

The in vitro activity of the cathelicidin tritrpticin was investigated against multidrug-resistant Pseudomonas aeruginosa. The isolates were susceptible to the peptide at concentrations of 0.50 to 8 mg/liter. Tritrpticin completely inhibits lipopolysaccharide procoagulant activity at a 10 microM concentration. Fractionary inhibitory concentration indexes (0.385, 0.312, and 0.458) demonstrated synergy between the peptide and beta-lactams.

Amphibian peptides prevent endotoxemia and bacterial translocation in bile duct-ligated rats.

OBJECTIVE: To investigate the efficacy of amphibian antimicrobial peptides in preventing bacterial translocation and neutralizing endotoxins in bile duct-ligated rats. DESIGN: Prospective, randomized, controlled animal study. SETTING: Research laboratory in a university hospital. SUBJECTS: Adult male Wistar rats. INTERVENTIONS: Adult male Wistar rats underwent sham operation or bile duct ligation (BDL). Eight groups were studied: sham operation with saline treatment, sham operation with 120 mg/kg tazobactam-piperacillin, sham operation with 2 mg/kg uperin 3.6, sham operation with 2 mg/kg magainin2, BDL with saline treatment, BDL with 120 mg/kg tazobactam-piperacillin, BDL with 2 mg/kg uperin 3.6, and BDL with 2 mg/kg magainin2. MEASUREMENTS AND MAIN RESULTS: Main outcome measures were: endotoxin and tumor necrosis factor-alpha concentrations in plasma and evidence of bacterial translocation in blood, peritoneum, liver, and mesenteric lymph nodes. Endotoxin and tumor necrosis factor-alpha plasma levels were significantly higher in BDL rats compared with sham-operated animals. All amphibian peptides achieved a significant reduction of plasma endotoxin and tumor necrosis factor-alpha concentration when compared with saline- and tazobactam-piperacillin-treated groups. On the other hand, both tazobactam-piperacillin and peptides significantly reduced bacterial growth compared with the control. Tazobactam-piperacillin and magainin2 exerted the maximal inhibition of bacterial growth. CONCLUSION: In conclusion, because of their multifunctional properties, amphibian peptides could be interesting compounds to inhibit bacterial translocation and endotoxin release in obstructive jaundice.

Pre-treatment of central venous catheters with the cathelicidin BMAP-28 enhances the efficacy of antistaphylococcal agents in the treatment of experimental catheter-related infection.

An in vitro antibiotic susceptibility assay for Staphylococcus aureus biofilms developed on 96-well polystyrene tissue culture plates was performed to elucidate the activity of the 27 residues cathelicidin peptide BMAP-28, quinupristin/dalfopristin (Q/D), linezolid, and vancomycin. Efficacy studies were performed in a rat model of staphylococcal CVC infection. Silastic catheters were implanted into the superior cava. Twenty-four hours after implantation the catheters were filled with BMAP-28. Thirty minutes later rats were challenged via the CVC with 1.0x10(6) CFU of S. aureus strain Smith diffuse. Administration of antibiotics into the CVC at a concentration equal to the MBC observed using adherent cells, or at a much higher concentration (1024 microg/mL) began 24 h later. The inhibition activities of all antibiotics against adherent bacteria were at least two-four-fold lower that against freely growing cells. When antibiotics were used in BMAP-28 pre-treated wells, they showed higher activities. The in vivo studies showed that when CVCs were pre-treated with BMAP-28 or with a high dose of antibiotics, biofilm bacterial load was reduced from 10(7) to 10(3) CFU/mL and bacteremia reduced from 10(3) to 10(1) CFU/mL. When CVCs were treated with both BMAP-28 and antibiotics, biofilm bacterial load was further decreased to 10(1) CFU/mL and bacteremia was not detected. These results suggest that CVC pre-treated with BMAP-28 represents an attractive choice for the treatment of device-related infections caused by staphylococci.

LL-37 protects rats against lethal sepsis caused by gram-negative bacteria.

We investigated the efficacy of LL-37, the C-terminal part of the only cathelicidin in humans identified to date (termed human cationic antimicrobial protein), in three experimental rat models of gram-negative sepsis. Adult male Wistar rats (i) were given an intraperitoneal injection of 1 mg Escherichia coli 0111:B4 LPS, (ii) were given 2 x 10(10) CFU of Escherichia coli ATCC 25922, or (iii) had intra-abdominal sepsis induced via cecal ligation and puncture. For each model, all animals were randomized to receive intravenously isotonic sodium chloride solution, 1-mg/kg LL-37, 1-mg/kg polymyxin B, 20-mg/kg imipenem, or 60-mg/kg piperacillin. Lethality; growth of bacteria in blood, peritoneum, spleen, liver, and mesenteric lymph nodes; and endotoxin and tumor necrosis factor alpha (TNF-alpha) concentrations in plasma were evaluated. All compounds reduced lethality compared to levels in controls. Endotoxin and TNF-alpha plasma levels were significantly higher in conventional antibiotic-treated rats than in LL-37- and polymyxin B-treated animals. All drugs tested significantly reduced bacterial growth compared to saline treatment. No statistically significant differences between LL-37 and polymyxin B were noted for antimicrobial and antiendotoxin activities. LL-37 and imipenem proved to be the most effective treatments in reducing all variables measured. Due to its multifunctional properties, LL-37 may become an important future consideration for the treatment of sepsis.

RNAIII-inhibiting peptide significantly reduces bacterial load and enhances the effect of antibiotics in the treatment of central venous catheter-associated Staphylococcus aureus infections.

BACKGROUND: Medical devices used in clinical practice are often associated with biofilm-associated staphylococcal infections. METHODS: An in vitro antibiotic susceptibility assay of Staphylococcus aureus biofilms using 96-well polystyrene tissue-culture plates was performed to test the effects of RNAIII-inhibiting peptide (RIP), ciprofloxacin, imipenem, and vancomycin. Efficacy studies were performed using a rat model of central venous catheter (CVC)-associated infection. Twenty-four hours after implantation, the catheters were filled with RIP (1 mg/mL). Thirty minutes later, rats were challenged, via the CVC, with 1.0 x 10(6) cfu of S. aureus strain Smith diffuse. The antibiotic-lock technique was begun 24 h later. RESULTS: Minimum inhibitory concentrations of antibiotics in biofilms were at least 4-fold higher than those against the freely growing planktonic cells. When they were first treated with RIP, the cells in biofilms became as susceptible to antibiotics as did planktonic cells. These data were confirmed by the in vivo studies. In particular, when CVCs were treated with both RIP and antibiotics, the biofilm bacterial load was further reduced to 1 x 10(1) cfu/mL, and bacteremia was not detected, suggesting that there was 100% elimination of bacteremia and a 6 log10 reduction in biofilm bacterial load. CONCLUSION: RIP significantly reduces bacterial load and enhances the effect of antibiotics in the treatment of CVC-associated S. aureus infections.

Citropin 1.1-treated central venous catheters improve the efficacy of hydrophobic antibiotics in the treatment of experimental staphylococcal catheter-related infection.

An in vitro antibiotic susceptibility assay for Staphylococcus aureus biofilms developed on 96-well polystyrene tissue culture plates was performed to elucidate the activity of citropin 1.1, rifampin and minocycline. Efficacy studies were performed in a rat model of staphylococcal CVC infection. Silastic catheters were implanted into the superior cava. Twenty-four hours after implantation the catheters were filled with citropin 1.1 (10 microg/mL). Thirty minutes later the rats were challenged via the CVC with 1.0 x 10(6) CFU of S. aureus strain Smith diffuse. Administration of antibiotics into the CVC (the antibiotic lock technique) began 24 h later. The study included: one control group (no CVC infection), one contaminated group that did not receive any antibiotic prophylaxis, one contaminated group that received citropin 1.1-treated CVC, two contaminated groups that received citropin 1.1-treated CVC plus rifampin and minocycline at concentrations equal to MBCs for adherent cells and 1024 microg/mL in a volume of 0.1 mL that filled the CVC and two contaminated groups that received rifampin or minocycline at the same concentrations. All catheters were explanted 7 days after implantation. Main outcome measures were: minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC), synergy studies, quantitative culture of the biofilm formed on the catheters and surrounding venous tissues, and quantitative peripheral blood cultures. MICs of conventional antibiotics against the bacteria in a biofilm were at least four-fold higher than against the freely growing planktonic cells. In contrast, when antibiotics were used on citropin 1.1 pre-treated cells they showed comparable activity against both biofilm and planktonic organisms. The in vivo studies show that when CVCs were pre-treated with citropin 1.1 or with a high dose of antibiotics, biofilm bacterial load was reduced from 10(7) to 10(3) CFU/mL and bacteremia reduced from 10(3) to 10(1) CFU/mL. When CVCs were treated both with citropin 1.1 and antibiotics, biofilm bacterial load was further reduced to 10(1) CFU/mL and bacteremia was not detected, suggesting 100% elimination of bacteremia and a log 6 reduction in biofilm load. Citropin 1.1 significantly reduces bacterial load and enhances the effect of hydrophobic antibiotics in the treatment of CVC-associated S. aureus infections.

In vitro activity of amphibian peptides alone and in combination with antimicrobial agents against multidrug-resistant pathogens isolated from surgical wound infection.

The in vitro activities of three amphibian peptides magainin II amide, citropin 1.1 and temporin A alone and in combination with eight clinically used antimicrobial agents (imipenem, ceftazidime, clarithromycin, vancomycin, amikacin, polymyxin E, ciprofloxacin and linezolid) were investigated against several multidrug-resistant Pseudomonas aeruginosa and Staphylococcus aureus strains isolated from surgical wound infections. Antimicrobial activities were measured by MIC, MBC and time-kill studies. P. aeruginosa strains were more susceptible to magainin II amide and less susceptible to temporin A. S. aureus isolates were highly susceptible to temporin A and citropin 1.1. The combination studies showed synergy between citropin 1.1 and clarithromycin. Magainin II amide and temporin A showed synergism with imipenem and ceftazidime. Finally, all peptides showed synergistic effects with polymyxin E. These results provide evidence for the potential use of these antimicrobial peptides in the topical or systemic treatment of surgical wound infections.

Temporin A alone and in combination with imipenem reduces lethality in a mouse model of staphylococcal sepsis.

BACKGROUND: Morbidity and mortality from staphylococcal toxic shock remain high, despite the availability of antibiotics to which the microorganism is sensitive. METHODS: In in vitro experiments, the ability of temporin A to inhibit lipoteichoic acid-induced production of tumor necrosis factor (TNF)- alpha and nitric oxide (NO) was determined. Also, mouse models of staphylococcal sepsis were used to evaluate the efficacy of temporin A alone and in combination with imipenem. BALB/c mice were injected intravenously with live Staphylococcus aureus or heat-killed cells and then received either isotonic sodium chloride solution, 2 mg/kg temporin A, 7 mg/kg imipenem, or 2 mg/kg temporin A in combination with 7 mg/kg imipenem immediately and 6 h after challenge. The main outcome measures were lethality rates, plasma bacterial counts, and plasma TNF- alpha and interleukin (IL)-6 levels. RESULTS: The in vitro experiments showed that temporin A did not cause TNF- alpha or NO release. In the in vivo experiments with live bacteria, both compounds reduced lethality rates and bacterial growth. Imipenem exhibited the highest efficacy. The combination-treated group had significantly lower bacterial counts than did the singly-treated groups and the lowest lethality rates. In the experiments with heat-killed cells, only temporin A demonstrated significant efficacy with respect to lethality and reduction of plasma TNF- alpha and IL-6 levels. DISCUSSION: This study shows that temporin A can reduce the stimulatory effects of bacterial cell components and suggests that it may be beneficial in the treatment of severe staphylococcal sepsis.

Comparative efficacies of quinupristin-dalfopristin, linezolid, vancomycin, and ciprofloxacin in treatment, using the antibiotic-lock technique, of experimental catheter-related infection due to Staphylococcus aureus.

We performed in vitro studies to elucidate the bactericidal activity of the antibiotics in an adherent-cell biofilm model. Efficacy studies were performed in a staphylococcal central venous catheter (CVC) infection rat model. Silastic catheters were implanted into the superior cava. Via the CVC the rats were challenged with 1.0 x 10(6) CFU of a live Staphylococcus aureus strain. Twenty-four hours later, the antibiotic-lock technique was started. All animals were randomized to receive daily isotonic sodium chloride solution, quinupristin-dalfopristin (Q/D), linezolid, vancomycin, or ciprofloxacin at the minimal bactericidal concentration (MBC) and at 1,024 microg/ml in a volume of 0.1 ml that filled the CVC. The main outcome measures were MICs and MBCs for both planktonic and adherent cells, quantitative culture of the catheters and surrounding venous tissues, and quantitative peripheral blood cultures. The killing activities of all antibiotics against the adherent bacteria were at least fourfold lower than those against freely growing cells, with the exception of Q/D, which showed comparable activities against both adherent and planktonic organisms. Overall, Q/D at 1,024 microg/ml produced the greatest reduction in the number of cells recovered from the catheters, while at the same concentration, Q/D and vancomycin demonstrated higher activities than ciprofloxacin or linezolid in reducing the number of organisms recovered from the blood cultures. This study points out that treatment outcome of device-related infections cannot be predicted by the results of a standard susceptibility test such as the MIC. Our findings suggest that the clinically used antibiotics cannot eradicate the CVC infection through the antibiotic-lock technique, even at a concentration of 1,024 microg/ml.

In vitro activity and killing effect of uperin 3.6 against gram-positive cocci isolated from immunocompromised patients.

The in vitro activity of uperin 3.6, alone or combined with six antibiotics, against gram-positive cocci, including Rhodococcus equi, methicillin-resistant staphylococci, and vancomycin-resistant enterococci, was investigated. All isolates were inhibited at concentrations of 1 to 16 mg/liter. Synergy was demonstrated when uperin 3.6 was combined with clarithromycin and doxycycline.

In vitro activity of MSI-78 alone and in combination with antibiotics against bacteria responsible for bloodstream infections in neutropenic patients.

MSI-78 is a 22 amino acid amphipathic peptide with potent antimicrobial activity against Gram-positive and Gram-negative organisms, including antibiotic-resistant strains. In this study, we assessed the in vitro activity of MSI-78 alone and in combination with eight clinically used antimicrobial agents against several strains of Pseudomonas aeruginosa, Staphylococcus aureus, Staphylococcus epidermidis and Escherichia coli isolated from blood of neutropenic febrile patients. Antimicrobial activity of MSI-78 was measured by minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), time-kill studies and checkerboard titration method. The Gram-negative isolates were susceptible to the peptide at concentrations in the range 0.50-16 mg/L, while staphylococci showed lower susceptibility. MSI-78 demonstrated a higher antimicrobial activity than colistin against Gram-negative organisms. The checkerboard titration method demonstrated synergy when the peptide was combined with beta-lactams. These results provide evidence for the potential use of MSI-78 in the management of severe infections in neutropenic patients.

In vitro activity of citropin 1.1 alone and in combination with clinically used antimicrobial agents against Rhodococcus equi.

OBJECTIVES: The aim of this study was to investigate the in vitro activity of citropin 1.1, an antimicrobial peptide derived from the Australian tree frog Litoria citropa, alone and in combination with ampicillin, ceftriaxone, doxycycline, netilmicin, ciprofloxacin, rifampicin, linezolid, vancomycin, clarithromycin and imipenem against 12 nosocomial isolates of Rhodococcus equi. METHODS: Antimicrobial activity of citropin 1.1 was measured by MIC, MBC, time-kill studies and chequerboard titration method. RESULTS: All isolates were inhibited at concentrations of citropin 1.1 between 2 and 8 mg/L. Combination studies demonstrated synergy only when the peptide was combined with clarithromycin, doxycycline and rifampicin. CONCLUSIONS: Our findings show that citropin 1.1 is active against R. equi and that its activity could be enhanced when it is combined with hydrophobic antibiotics.

In vitro activity and killing effect of citropin 1.1 against gram-positive pathogens causing skin and soft tissue infections.

The in vitro activity of citropin 1.1 against gram-positive cocci was measured by MIC, minimal bactericidal concentration, time-kill studies, and a checkerboard titration method. Streptococci and staphylococci were inhibited at concentrations between 1 and 16 mg/liter, respectively. Enterococci showed less susceptibility. Synergy was demonstrated when citropin 1.1 was combined with clarithromycin and doxycycline.