Virucidal and Immunostimulating Activities of Monogalactosyl Diacylglyceride from Coccomyxa sp. KJ, a Green Microalga, against Murine Norovirus and Feline Calicivirus.

Human noroviruses are the most common pathogens causing acute gastroenteritis and may lead to more severe illnesses among immunosuppressed people, including elderly and organ transplant recipients. To date, there are no safe and effective vaccines or antiviral agents for norovirus infections. In the present study, we aimed to demonstrate the antiviral activity of monogalactosyl diacylglyceride (MGDG) isolated from a microalga, Coccomyxa sp. KJ, against murine norovirus (MNV) and feline calicivirus (FCV), the surrogates for human norovirus. MGDG showed virucidal activities against these viruses in a dose- and time-dependent manner-MGDG at 100 µg/mL reduced the infectivity of MNV and FCV to approximately 10% after 60 min incubation. In the animal experiments of MNV infection, intraoral administration of MGDG (1 mg/day) exerted a therapeutic effect by suppressing viral shedding in the feces and produced high neutralizing antibody titers in sera and feces. When MGDG was orally administered to immunocompromised mice treated with 5-fluorouracil, the compound exhibited earlier stopping of viral shedding and higher neutralizing antibody titers of sera than those in the control mice administered with distilled water. Thus, MGDG may offer a new therapeutic and prophylactic alternative against norovirus infections.

Exopolysaccharide Produced by Plant-Derived Lactobacillus plantarum SN35N Exhibits Antiviral Activity.

A lactic acid bacterial strain, Lactobacillus plantarum SN35N, which has been isolated from the pear, secretes negatively charged acidic exopolysaccharide (EPS) to outside cells. We have previously found that the SN35N-derived acidic EPS inhibits the catalytic activity of hyaluronidase (EC 3.2.1.35) promoting inflammation. The aim of this study is to find other health benefits of EPS. EPS has been found to exhibit an inhibitory effect against the influenza virus (Alphainfluenzavirus Influenza A virus) and feline calicivirus (Vesivirus Feline calicivirus), which is recognized as a model of norovirus. Although more studies on the structure-function relationship of EPSs are needed, SN35N-derived EPS is a promising lead for developing not only anti-inflammatory agents, but also antiviral substances.

Strong alkaline electrolyzed water efficiently inactivates SARS-CoV-2, other viruses, and Gram-negative bacteria.

Air spaces and material surfaces in a pathogen-contaminated environment can often be a source of infection to humans, and disinfection has become a common intervention focused on reducing the contamination levels. In this study, we examined the efficacy of SAIW, a unique electrolyzed water with chlorine-free, high pH, high concentration of dissolved hydrogen, and low oxygen reduction potential, for the inactivation of several viruses and bacteria. Infectivity assays revealed that initial viral titers of enveloped and non-enveloped viruses, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), influenza A virus, herpes simplex virus type 1, human coronavirus, feline calicivirus, and canine parvovirus, were reduced by 2.9- to 5.5-log10 within 30 s of SAIW exposure. Similarly, the culturability of three Gram-negative bacteria (Escherichia coli, Salmonella, and Legionella) dropped down by 1.9- to 4.9-log10 within 30 s of SAIW treatment. Mechanistically, treatment with SAIW was found to significantly decrease the binding and subsequent entry efficiencies of SARS-CoV-2 on Vero cells. Finally, we showed that this chlorine-free electrolytic ion water had no acute inhalation toxicity in mice, demonstrating that SAIW holds promise for a safer antiviral and antibacterial disinfectant.

Icariin, Formononetin and Caffeic Acid Phenethyl Ester Inhibit Feline Calicivirus Replication In Vitro.

Cats infected with feline calicivirus (FCV) often display oral ulcers and inflammation of the upper respiratory tract, which can lead to death in severe cases. Antiviral therapy is one of the most effective ways to control FCV infection. Natural compounds in Chinese herbal medicines and medicinal plants provide abundant resources for research on antiviral drugs. In this study, we found that icariin (ICA), formononetin (FMN) and caffeic acid phenethyl ester (CPAE) show low cytotoxicity towards F81 cells, that the three natural compounds have apparent antiviral effects on FCV in vitro, and that they can inhibit different FCV strains. Then, we found that ICA and FMN mainly function in the early stage of FCV infection, while CAPE can function in both the early and late stages of FCV infection. Finally, we found that ICA has an antagonistic effect on FMN and CAPE in FCV infection, and FMN has a synergistic effect with CAPE against FCV infection. Our results showed that ICA, FMN and CAPE may be potential drug candidates for FCV-induced diseases.

Survival and Inactivation by Advanced Oxidative Process of Foodborne Viruses in Model Low-Moisture Foods.

Enteric viruses, such as human norovirus (NoV) and hepatitis A virus (HAV), are the major causes of foodborne illnesses worldwide. These viruses have low infectious dose, and may remain infectious for weeks in the environment and food. Limited information is available regarding viral survival and transmission in low-moisture foods (LMF). LMFs are generally considered as ready-to-eat products, which undergo no or minimal pathogen reduction steps. However, numerous foodborne viral outbreaks associated with LMFs have been reported in recent years. The objective of this study was to examine the survival of foodborne viruses in LMFs during 4-week storage at ambient temperature and to evaluate the efficacy of advanced oxidative process (AOP) treatment in the inactivation of these viruses. For this purpose, select LMFs such as pistachios, chocolate, and cereal were inoculated with HAV and the norovirus surrogates, murine norovirus (MNV) and feline calicivirus (FCV), then viral survival on these food matrices was measured over a four-week incubation at ambient temperature, by both plaque assay and droplet-digital RT-PCR (ddRT-PCR) using the modified ISO-15216 method as well as the magnetic bead assay for viral recovery. We observed an approximately 0.5 log reduction in viral genome copies, and 1 log reduction in viral infectivity for all three tested viruses following storage of select inoculated LMFs for 4 weeks. Therefore, the present study shows that the examined foodborne viruses can persist for a long time in LMFs. Next, we examined the inactivation efficacy of AOP treatment, which combines UV-C, ozone, and hydrogen peroxide vapor, and observed that while approximately 100% (4 log) inactivation can be achieved for FCV, and MNV in chocolate, the inactivation efficiency diminishes to approximately 90% (1 log) in pistachios and 70% (< 1 log) in cereal. AOP treatment could therefore be a good candidate for risk reduction of foodborne viruses from certain LMFs depending on the food matrix and surface of treatment.

Magnolia officinalis and Its Honokiol and Magnolol Constituents Inhibit Human Norovirus Surrogates.

Norovirus is a major cause of foodborne disease and nonbacterial gastroenteritis globally. This study evaluated the antiviral effects of Magnolia officinalis extract and its honokiol and magnolol constituents against human norovirus surrogates, murine norovirus (MNV) and feline calicivirus (FCV) in vitro, and in model food systems. Pretreatment or cotreatment of M. officinalis extract at 1 mg/mL reduced MNV and FCV titers by 0.6-1.8 log. Honokiol and magnolol, which are the major polyphenols in the extract, showed significant antiviral effects against MNV and FCV. The virus-infected cells that were treated with M. officinalis extract exhibited significantly increased glutathione levels (p < 0.05). The extract, honokiol, and magnolol revealed ferric ion-reducing and 2,2-diphenyl-1-picrylhydrazyl radical scavenging activities in a dose-dependent manner. Furthermore, MNV and FCV titers were reduced by >1.6 log or to undetectable levels in apple, orange, and plum juices and by 0.9 and 1.6 log in milk, respectively, when they were treated with the extract at 5 mg/mL. Therefore, the present study suggests that M. officinalis extract can be used as an antiviral food material to control norovirus foodborne diseases.

Feline calicivirus strain 2280 p30 antagonizes type I interferon-mediated antiviral innate immunity through directly degrading IFNAR1 mRNA.

Feline calicivirus (FCV) belongs to the Caliciviridae, which comprises small RNA viruses of both medical and veterinary importance. Once infection has occurred, FCV can persist in the cat population, but the molecular mechanism of how it escapes the innate immune response is still unknown. In this study, we found FCV strain 2280 to be relatively resistant to treatment with IFN-ß. FCV 2280 infection inhibited IFN-induced activation of the ISRE (Interferon-stimulated response element) promoter and transcription of ISGs (Interferon-stimulated genes). The mechanistic analysis showed that the expression of IFNAR1, but not IFNAR2, was markedly reduced in FCV 2280-infected cells by inducing the degradation of IFNAR1 mRNA, which inhibited the phosphorylation of downstream adaptors. Further, overexpression of the FCV 2280 nonstructural protein p30, but not p30 of the attenuated strain F9, downregulated the expression of IFNAR1 mRNA. His-p30 fusion proteins were produced in Escherichia coli and purified, and an in vitro digestion assay was performed. The results showed that 2280 His-p30 could directly degrade IFNAR1 RNA but not IFNAR2 RNA. Moreover, the 5'UTR of IFNAR1 mRNA renders it directly susceptible to cleavage by 2280 p30. Next, we constructed two chimeric viruses: rFCV 2280-F9 p30 and rFCV F9-2280 p30. Compared to infection with the parental virus, rFCV 2280-F9 p30 infection displayed attenuated activities in reducing the level of IFNAR1 and inhibiting the phosphorylation of STAT1 and STAT2, whereas rFCV F9-2280 p30 displayed enhanced activities. Animal experiments showed that the virulence of rFCV 2280-F9 p30 infection was attenuated but that the virulence of rFCV F9-2280 p30 was increased compared to that of the parental viruses. Collectively, these data show that FCV 2280 p30 could directly and selectively degrade IFNAR1 mRNA, thus blocking the type I interferon-induced activation of the JAK-STAT signalling pathway, which may contribute to the pathogenesis of FCV infection.

Assay validation and determination of in vitro binding of mefloquine to plasma proteins from clinically normal and FIP-affected cats.

The antimalarial agent mefloquine is currently being investigated for its potential to inhibit feline coronavirus and feline calicivirus infections. A simple, high pressure liquid chromatography assay was developed to detect mefloquine plasma concentrations in feline plasma. The assay's lower limit of quantification was 250 ng/mL. The mean ± standard deviation intra- and inter-day precision expressed as coefficients of variation were 6.83 ± 1.75 and 5.33 ± 1.37%, respectively, whereas intra- and inter-day accuracy expressed as a percentage of the bias were 11.40 ± 3.73 and 10.59 ± 3.88%, respectively. Accordingly, this validated assay should prove valuable for future in vivo clinical trials of mefloquine as an antiviral agent against feline coronavirus and feline calicivirus. However, the proportion of mefloquine binding to feline plasma proteins has not been reported. The proportion of drug bound to plasma protein binding is an important concept when developing drug dosing regimens. As cats with feline infectious peritonitis (FIP) demonstrate altered concentrations of plasma proteins, the proportion of mefloquine binding to plasma proteins in both clinically normal cats and FIP-affected cats was also investigated. An in vitro method using rapid equilibrium dialysis demonstrated that mefloquine was highly plasma protein bound in both populations (on average > 99%).

Antiviral effect of copper chloride on feline calicivirus and synergy with ribavirin in vitro.

BACKGROUND: Feline calicivirus (FCV) is a common and highly prevalent pathogen causing upper respiratory diseases in kittens and felines in recent years. Due to the substantial genetic variability of the viral genes, existing vaccines cannot provide complete protection. Therefore, research on FCV antiviral drugs has received much attention. RESULTS: In this study, we found that copper chloride had dose-dependent antiviral effects on FCV in F81 cells. We also found that the combination of copper chloride and ribavirin had a synergistic protective effect against FCV in F81 cells. In contrast, the combination of copper chloride and horse anti-FCV immunoglobulin F (ab')2 showed an antagonistic effect, likely because copper chloride has an effect on F (ab')2 immunoglobulin; however, further research is needed to clarify this supposition. CONCLUSIONS: In summary, we found that copper chloride had low cytotoxicity and significant antiviral effects on FCV in F81 cells, providing a new drug candidate for the prevention and treatment of FCV infection.

Saxifraga spinulosa-Derived Components Rapidly Inactivate Multiple Viruses Including SARS-CoV-2.

Novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), influenza A virus (IAV), and norovirus (NV) are highly contagious pathogens that threaten human health. Here we focused on the antiviral potential of the medicinal herb, Saxifraga spinulosa (SS). Water-soluble extracts of SS were prepared, and their virus-inactivating activity was evaluated against the human virus pathogens SARS-CoV-2 and IAV; we also examined virucidal activity against feline calicivirus and murine norovirus, which are surrogates for human NV. Among our findings, we found that SS-derived gallocatechin gallate compounds were capable of inactivating all viruses tested. Interestingly, a pyrogallol-enriched fraction (Fr 1C) inactivated all viruses more rapidly and effectively than did any of the component compounds used alone. We found that 25 µg/mL of Fr 1C inactivated >99.6% of SARS-CoV-2 within 10 s (reduction of ≥2.33 log10 TCID50/mL). Fr 1C resulted in the disruption of viral genomes and proteins as determined by gel electrophoresis, electron microscopy, and reverse transcription-PCR. Taken together, our results reveal the potential of Fr 1C for development as a novel antiviral disinfectant.

Nitazoxanide protects cats from feline calicivirus infection and acts synergistically with mizoribine in vitro.

Feline calicivirus (FCV) is a highly contagious pathogen that causes acute upper respiratory infections and oral disease in cats, thus seriously endangering feline health. Recently, there have been outbreaks of particularly virulent variant strains of FCV, which can cause both acute symptoms and fatal systemic disease. The discovery of effective antiviral agents to treat FCV infection is, therefore, gradually assuming increased importance. In this study, we showed that both nitazoxanide and mizoribine had antiviral activity in F81 cells infected with different strains of FCV and also demonstrated a synergistic effect between the two drugs. Experiments in cats challenged with FCV showed that nitazoxanide significantly reduced the clinical symptoms of FCV infection, reduced viral load in the trachea and lungs, and reduced viral shedding. Our results showed that nitazoxanide and mizoribine could potentially be used as therapeutic agents to treat FCV infection.

Inactivation of Non-Enveloped Viruses and Bacteria by an Electrically Charged Disinfectant Containing Meso-Structure Nanoparticles via Modification of the Genome.

INTRODUCTION: A previous study demonstrated the virucidal effect of an electrically charged disinfectant (CAC-717), which contains meso-structure nanoparticles, on enveloped viruses (influenza viruses). However, the effect of CAC-717 on other microorganisms and the mechanisms by which CAC-717 inactivates the microorganisms remain unclear. In this study, CAC-717 was further evaluated in terms of its biocidal and virucidal activity as well as its effect on bacterial and viral nucleic acids. METHODS: The inactivation effects of CAC-717 against various microorganisms [non-enveloped virus, feline calicivirus (FCV); bacteria, Salmonella enterica and Escherichia coli] were investigated by comparing the viral titer of the medium tissue culture infectious dose (TCID50) and the D value (estimated treatment time required to reduce the number of microorganisms by 90%). Furthermore, the effects of CAC-717 on viral and bacterial genomic RNA/DNA were examined using a polymerase chain reaction (PCR). RESULTS: Treatment of an equal volume of CAC-717 with cell lysate infected with a non-enveloped virus, feline calicivirus (FCV), reduced the TCID50. Viral titer dropped below the detection limit after 2 min of treatment. The D value of FCV was 0.256 min (average of multiple endpoint D values) and endpoint D value was 0.341 min. The D value for E. coli and S. enterica was 0.290 min and 0.080 min (average of multiple endpoint D values), respectively and the endpoint D value was 0.545 min and 0.054 min, respectively. In addition, PCR showed the inhibition of nucleic acid amplification of the RNA and DNA genome of FCV and bacteria, respectively. CONCLUSION: Our findings suggest that CAC-717 inactivates viruses and bacteria by modifying the viral and bacterial nucleic acids.

Radiosensitivity increase in FCV-F9 virus using combined treatments with natural antimicrobials and γ-irradiation.

AIMS: The objective was to evaluate the possible synergistic effect of cranberry juice (CJ) and commercial citrus extract (BS) against FCV-F9 viral titre in vitro in combination with γ-irradiation and to determinate the D10 values and radiosensitivity increase. METHODS AND RESULTS: Virus samples were treated with a formulation containing a mixture of BS or CJ. Results showed a D10 of 0·05, 0·42% and 1·34 kGy for the virus treated with the BS, the CJ and the irradiation alone respectively. Concentrations needed to reduce 6 log TCID50  ml-1 of viral titre were BS-0·3%, CJ-2·52% and 8·04 kGy. Irradiation combined with BS-0·01% and CJ-0·1% against FCV-F9 virus showed D10 values of 0·74 and 0·72 kGy, respectively, resulting in a viral radiosensitization of 1·28 and 1·50 for respective treatments. CONCLUSION: The higher viral radiosensitization observed after combining γ-irradiation with BS-0·01% and CJ-0·1% indicates that CJ and BS could be used as antiviral agents alone or in combination with γ-irradiation to prevent NoV outbreaks. SIGNIFICANCE AND IMPACT OF THE STUDY: Cranberry juice and BS could be used in hurdle approaches in combined treatment with γ-irradiation to assure food safety without a detrimental effect on nutritional value and maintain low processing cost.

Ìn situ inactivation of human norovirus GII.4 by cold plasma: Ethidium monoazide (EMA)-coupled RT-qPCR underestimates virus reduction and fecal material suppresses inactivation.

Cold atmospheric-gaseous plasma (CAP) is an emerging non-thermal technology for decontamination of foodborne bacterial and viral pathogens. We obtained a >5 log10 reduction in the titer (TCID50) of feline calicivirus (FCV) on stainless steel discs and Romaine lettuce leaves after 3 min wet exposure to air plasma generated by a two-dimensional array of integrated coaxial-microhollow dielectric barrier discharge (2D-AICM-DBD). However, when human norovirus (HuNoV GII.4) was treated for 5 min under the same conditions, ~2.6 log10 (>99.5%) reduction in genome copy number was observed as measured by ethidium monoazide-coupled RT-qPCR (EMA-RT-qPCR). To assess this discrepancy, we studied CAP's effect on FCV by the cell culture method and by the EMA-coupled RT-qPCR method. It was found that the molecular titration method (EMA-RT-qPCR) underestimates the level of virus reduction by CAP. Additionally, the fecal matter present in HuNoV samples partially suppressed virucidal activity of CAP. Assuming that the lower virus reduction measured by EMA-RT-qPCR method compared to cell culture method for FCV is the same as for HuNoV, we can conclude that FCV may be used as a surrogate for HuNoV to assess the virucidal effect of CAP. CAP is able to inactivate 3.5 Log10 units of HuNoV at low titers after 2 min of exposure.

Antiviral effect of sinefungin on in vitro growth of feline herpesvirus type 1.

Feline herpesvirus type 1 (FHV-1) causes a potentially fatal disease in cats. Through the use of virus inhibition and cytotoxicity assays, sinefungin, a nucleoside antibiotic, was assessed for its potential to inhibit the growth of FHV-1. Sinefungin inhibited in vitro growth of FHV-1 most significantly over other animal viruses, such as feline infectious peritonitis virus, equine herpesvirus, pseudorabies virus and feline calicivirus. Our results revealed that sinefungin specifically suppressed the replication of FHV-1 after its adsorption to the host feline kidney cells in a dose-dependent manner without obvious cytotoxicity to the host cells. This antibiotic can potentially offer a highly effective treatment for animals infected with FHV-1, providing alternative medication to currently available antiviral therapies.

In-Depth Characterization of Bioactive Extracts from Posidonia oceanica Waste Biomass.

Posidonia oceanica waste biomass has been valorised to produce extracts by means of different methodologies and their bioactive properties have been evaluated. Water-based extracts were produced using ultrasound-assisted and hot water methods and classified according to their ethanol-affinity (E1: ethanol soluble; E2: non-soluble). Moreover, a conventional protocol with organic solvents was applied, yielding E3 extracts. Compositional and structural characterization confirmed that while E1 and E3 extracts were mainly composed of minerals and lipids, respectively, E2 extracts were a mixture of minerals, proteins and carbohydrates. All the extracts showed remarkably high antioxidant capacity, which was not only related to phenolic compounds but also to the presence of proteins and polysaccharides. All E2 and E3 extracts inhibited the growth of several foodborne fungi, while only E3 extracts decreased substantially the infectivity of feline calicivirus and murine norovirus. These results show the potential of P. oceanica waste biomass for the production of bioactive extracts.

Cat flu: Broad spectrum polymeric antivirals.

Feline herpesvirus type 1 (FHV-1) and feline calicivirus (FCV) are considered as main causes of feline upper respiratory tract disease and the most common clinical manifestations include rhinotracheitis, conjunctivitis, and nasal/facial ulcerations. While the primary infection is relatively mild, secondary infections pose a threat to young or immunocompromised cats and may result in a fatal outcome. In this study, we made an effort to evaluate antiviral potency of poly(sodium 4-styrenesulfonates) (PSSNa) as potent FHV-1 and FCV inhibitors for topical use. Mechanistic studies showed that PSSNa exhibits a different mechanism of action depending on target species. While PSSNa acts directly on FHV-1 particles blocking their interaction with the host's cell and preventing the infection, the antiviral potency against FCV is based on inhibition at late stages of the viral replication cycle. Altogether, PSSNa polymers are promising drug candidates to be used in the treatment and prevention of the viral upper respiratory tract disease (URTD), regardless of the cause.

The Adenosine Analogue NITD008 has Potent Antiviral Activity against Human and Animal Caliciviruses.

The widespread nature of calicivirus infections globally has a substantial impact on the health and well-being of humans and animals alike. Currently, the only vaccines approved against caliciviruses are for feline and rabbit-specific members of this group, and thus there is a growing effort towards the development of broad-spectrum antivirals for calicivirus infections. In this study, we evaluated the antiviral activity of the adenosine analogue NITD008 in vitro using three calicivirus model systems namely; feline calicivirus (FCV), murine norovirus (MNV), and the human norovirus replicon. We show that the nucleoside analogue (NA), NITD008, has limited toxicity and inhibits calicivirus replication in all three model systems with EC50 values of 0.94 µM, 0.91 µM, and 0.21 µM for MNV, FCV, and the Norwalk replicon, respectively. NITD008 has a similar level of potency to the most well-studied NA 2'-C-methylcytidine in vitro. Significantly, we also show that continual NITD008 treatment effectively cleared the Norwalk replicon from cells and treatment with 5 µM NITD008 was sufficient to completely prevent rebound. Given the potency displayed by NITD008 against several caliciviruses, we propose that this compound should be interrogated further to assess its effectiveness in vivo. In summary, we have added a potent NA to the current suite of antiviral compounds and provide a NA scaffold that could be further modified for therapeutic use against calicivirus infections.

Key role of singlet oxygen and peroxynitrite in viral RNA damage during virucidal effect of plasma torch on feline calicivirus.

A dielectric barrier discharge (DBD) plasma torch has been used to evaluate the mechanism underlying inactivation of feline calicivirus (FCV) by plasma treatment. Plasma treatment of cell lysate infected with FCV F9 strain reduced the viral titer of the median tissue culture infectious dose (TCID50). The D value (treatment time required to lower the viral titer to 1/10) was 0.450 min, while the viral titer dropped below the detection limit within 2 min. FCV was not significantly inactivated by heat or UV applied at levels corresponding to those generated from the DBD plasma torch after 2 min (38.4 °C and 46.79 mJ/cm2 UV, respectively). However, TCID50 was reduced by 2.47 log after exposure to 4.62 mM ONOO-, corresponding to the concentration generated after 2 min of plasma treatment. Radical scavengers, including superoxide dismutase, dimethyl sulfoxide, and catalase, did not significantly affect viral titers; however, sodium azide, uric acid, and ascorbic acid, which are scavengers of 1O2 radicals, ONOO-, and peroxynitrous acid (ONOOH; produced from ONOO- under acidic conditions), respectively, significantly increased TCID50 and intact viral RNA. These findings suggest that ONOO- and 1O2 play an important role in FCV inactivation by attacking viral RNA during DBD plasma torch treatment.

In vitro efficacy of povidone iodine and hydroxyethyl cellulose, alone and in combination, against common feline ocular pathogens.

Infectious ocular disease, such as conjunctivitis, is common in cats and can be caused by several viruses and bacteria, either as a single infection or as co-infections. In this study, povidone-iodine (PVP-I), alone or compounded with hydroxyethyl cellulose (HEC), was investigated for its efficacy against these pathogens in vitro. Whilst PVP-I alone was effective at inhibiting feline herpesvirus type 1 (FHV-1), Chlamydia felis, and Mycoplasma felis, PVP-I with HEC exerted a synergistic inhibitory effect against FHV-1 and C. felis. In contrast, only minimal inhibition of feline calicivirus was observed. These results demonstrate that PVP-I, alone and in combination with HEC, is effective against some feline ocular pathogens when tested in cell lines in vitro. In vivo studies investigating the systemic safety, ocular tolerance, and clinical efficacy of this combination in cats would be necessary before it could be recommended as a therapy in affected cats.