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Journal: International journal of antimicrobial agents


Chloroquine and hydroxychloroquine have been found to be efficient on SARS-CoV-2, and reported to be efficient in Chinese COV-19 patients. We evaluate the role of hydroxychloroquine on respiratory viral loads.


The COVID-19 epidemic is believed to have started in late January 2020 in France. We report here a case of a patient hospitalized in December 2019 in our intensive care, of our hospital in the north of Paris, for hemoptysis with no etiological diagnosis and for which RT-PCR was performed retrospectively on the stored respiratory sample which confirmed the diagnosis of COVID-19 infection. Based on this result, it appears that the COVID-19 epidemic started much earlier.


Hydroxychloroquine (HCQ) has been largely used and investigated as therapy of COVID-19 across various settings, at total dose usually ranging from 2400 mg to 9600 mg. In Belgium, off-label use of low-dose HCQ (2400 mg in total over five days) was recommended for hospitalized patients with COVID-19.


Recently, a novel coronavirus (2019-nCoV), officially known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), emerged in China. Despite drastic containment measures, the spread of this virus is ongoing. SARS-CoV-2 is the aetiological agent of coronavirus disease 2019 (COVID-19) characterised by pulmonary infection in humans. The efforts of international health authorities have since focused on rapid diagnosis and isolation of patients as well as the search for therapies able to counter the most severe effects of the disease. In the absence of a known efficient therapy and because of the situation of a public-health emergency, it made sense to investigate the possible effect of chloroquine/hydroxychloroquine against SARS-CoV-2 since this molecule was previously described as a potent inhibitor of most coronaviruses, including SARS-CoV-1. Preliminary trials of chloroquine repurposing in the treatment of COVID-19 in China have been encouraging, leading to several new trials. Here we discuss the possible mechanisms of chloroquine interference with the SARS-CoV-2 replication cycle.


With ongoing global outbreak of coronavirus disease 2019 (COVID-19), management of exposure events is a concern. Long-term care hospitals (LTCHs) are especially vulnerable to cluster outbreaks, since it is difficult to find facilities and healthcare personnel for their separate isolation care in a large outbreak situation. Although several drugs have been proposed as treatment regimens, there are no data on the effectiveness and safety of post-exposure prophylaxis (PEP) for COVID-19. After a large COVID-19 exposure event in a LTCH in Korea, PEP using hydroxychloroquine (HCQ) was conducted to 211 persons including 189 patients and 22 careworkers, whose baseline polymerase chain reaction (PCR) tests for COVID-19 were negative. PEP was completed in 184 (97.4%) patients and 21 (95.5%) careworkers without serious adverse events. At the end of 14 days of quarantine, follow-up PCR tests were all negative. Based on our experience, further clinical studies would be conducted for COVID-19 PEP.


Interest of anti-infective agents in COVD-19 showed discrepant results. However, there is no evaluation about the impact in changes of practices on the prognosis over time.


SARS-CoV-2, the novel coronavirus from China, is spreading around the world, causing a huge reaction despite its current low incidence outside China and the Far East. Four common coronaviruses are in current circulation and cause millions of cases worldwide. This article compares the incidence and mortality rates of these four common coronaviruses with those of SARS-COV-2 in Organisation for Economic Co-operation and Development countries. It is concluded that the problem of SARS-CoV-2 is probably being overestimated, as 2.6 million people die of respiratory infections each year compared with less than 4000 deaths for SARS-CoV-2 at the time of writing.


The recent emergence of the novel pathogenic SARS-coronavirus 2 (SARS-CoV-2) is responsible for a global pandemic. In face of the health emergency, drug repositioning is the most reliable option to design an efficient therapy for infected patients without delay. The first step of the viral replication cycle, i.e. the attachment to the surface of respiratory cells mediated by the spike (S) viral protein, offers several potential therapeutic targets. The S protein uses the ACE-2 receptor for entry, but also sialic acids linked to host cell surface gangliosides. Using a combination of structural and molecular modeling approaches, we showed that chloroquine (CLQ), one of the drugs currently under investigation for SARS-CoV-2 treatment, binds sialic acids and gangliosides with high affinity. We identified a new type of ganglioside-binding domain at the tip of the N-terminal domain of the SARS-CoV-2 spike (S) protein. This domain (aa 111-158), which is fully conserved among clinical isolates worldwide, may improve the attachment of the virus to lipid rafts and facilitate the contact with the ACE-2 receptor. We showed that in presence of CLQ (or of the more active derivative hydroxychloroquine, CLQ-OH), the viral spike is no longer able to bind gangliosides. The identification of this new mechanism of action of CLQ and CLQ-OH supports the use of these repositioned drugs to cure SARS-CoV-2 infected patients and stop the pandemic. Our in silico approaches might also be used to assess the efficiency of a broad range of repositioned and/or innovative drug candidates before their clinical evaluation.


The aim of this study was to seek additional data on the antimicrobial susceptibility of Staphylococcus spp. after habituation to low levels of the topical antimicrobial agent tea tree (Melaleuca alternifolia) oil. Meticillin-susceptible Staphylococcus aureus (MSSA), meticillin-resistant S. aureus (MRSA) and coagulase-negative staphylococci (CoNS) were habituated to 0.075% tea tree oil for 3 days. Subsequently, the susceptibility of five isolates each of MSSA, MRSA and CoNS to fusidic acid, mupirocin, chloramphenicol, linezolid and vancomycin was determined by Etest, and susceptibility to tea tree oil, terpinen-4-ol, carvacrol and triclosan was determined by agar dilution. Following habituation to 0.075% tea tree oil, antimicrobial MICs differed between control and habituated isolates on 33 occasions (out of a possible 150), with MICs being higher in habituated isolates on 22 occasions. Using clinical breakpoint criteria, one MSSA isolate changed susceptibility category from vancomycin-susceptible (MIC=2μg/mL) to intermediate susceptibility (MIC=3μg/mL) after habituation in one of two replicates. For the non-antibiotic antimicrobial agents, MICs of habituated and control isolates differed on 12 occasions (out of a possible 120); 10 occasions in MRSA and 2 occasions in MSSA. MICs were higher for habituated isolates on five occasions. However, all the differences were one serial dilution only and were not regarded as significant. Habituation to sublethal concentrations of tea tree oil led to minor changes in MICs of antimicrobial agents, only one of which may have been clinically relevant. There is no evidence to suggest that tea tree oil induces resistance to antimicrobial agents.

Concepts: Microbiology, Staphylococcus aureus, Antibiotic resistance, Staphylococcus, Methicillin-resistant Staphylococcus aureus, Vancomycin, Antimicrobial, Tea tree oil


The emergence of SARS-coronavirus-2 (SARS-CoV-2) is responsible for a global pandemic disease referred to as coronavirus disease 19 (Covid-19). Hydroxychloroquine/azithromycin combination therapy is currently tested for curing Covid-19, with promising results. However, the molecular mechanism of action of this combination is not established yet. Using molecular dynamics (MD) simulations we show that both drugs act in synergy to prevent any close contact between the virus and the plasma membrane of host cells. We reveal unexpected molecular similarity between azithromycin and the sugar moiety of GM1, a lipid raft ganglioside acting as a host attachment cofactor for respiratory viruses. Due to this mimicry, azithromycin interacts with the ganglioside-binding domain of SARS-CoV-2 spike protein. This binding site shared by azithromycin and GM1 displays a conserved amino acid triad Q-134/F-135/N-137 located at the tip of the spike protein. We also show that hydroxychloroquine molecules can saturate virus attachment sites on gangliosides in the vicinity of the primary coronavirus receptor ACE-2. Taken together, these data show that azithromycin is directed against the virus, whereas hydroxychloroquine is directed against cellular attachment cofactors. We conclude that both drugs act as competitive inhibitors of SARS-CoV-2 attachment to the host cell membrane. This is consistent with a synergistic antiviral mechanism at the plasma membrane level, where the most efficient therapeutic intervention probably stands. This molecular mechanism may explain the beneficial effects of hydroxychloroquine/azithromycin combination therapy in patients with Covid-19. Incidentally, our data suggest that the conserved Q-134/F-135/N-137 triad could be considered as a target for vaccine strategies.