1. Introduction:
Severe Acute Respiratory Coronavirus 2 (SARS-CoV-2), a newly identified
coronavirus with size of 60–140 nm similar to SARS-CoV (approximately
80% similar), caused the most severe pandemic disorder of
21st century called COVID-19 (Lipsitch, Swerdlow, &
Finelli, 2020; Malik et al., 2020). SARS-CoV-2 attaches to Angiotensin
Converting Enzyme 2 (ACE2) receptor with 10–20 folds higher affinity
than SARS-CoV (X. Xu et al., 2020). Today, massive antibiotic therapy is
considered for some COVID-19 patients that result in more susceptibility
to subsequent infections (Mak, Chan, & Ng, 2020); one of the most
irritant complications is antibiotic-associated diarrhea (Wei et al.,
2020). In this situation, probiotics may be a reasonable choice; they
were defined as “Live microorganisms which when administered in
adequate amounts confer a health benefit to the host”
(Bahreini-Esfahani & Moravejolahkami, 2020). on the other hand,
Probiotics have shown useful effects on treatment and prevention of
viral infections (Mousa, 2017) due to the proven immunomodulatory
activity and ability to stimulate interferon production; gut–lung axis
explains the possible relations between respiratory disorders and gut
microbiome (Marsland, Trompette, & Gollwitzer, 2015).
Recently, some COVID-19 patients showed microbial dysbiosis with
decreased Lactobacillus and Bifidobacterium (K. Xu et al.,
2020). Several different probiotics, including Lactobacillus
acidophilus, Bifidobacterium and Saccharomyces boulardii , along
with minerals & vitamins were given to a COVID-19 case; this type of
nutritional support lowered the complication of massive antibiotic
therapy (Horowitz, Freeman, & Bruzzese, 2020). As well, COVID-19-like
symptoms disappeared after two days administration of oral probiotic in
a 9 years-old boy (Ji et al., 2020). Results of a case series consist of
62 SARS-CoV2 infected patients in Zhejiang province were interesting;
probiotics were administered as adjunct (X.-W. Xu et al., 2020). Other
reports showed significant effect of probiotics; Compared to patients
with non-severe disease, patients with severe disease had significantly
more frequency to receive probiotics tablets (87.5% vs 40.4%, p=0.037)
(Xiufeng Jiang et al., 2020). Results from another research suggested
concurrent use of probiotics in COVID-19 patients to decrease the risk
for Candida albicans (caused by prophylaxis with azithromycin)
(Block, 2020).
Up to April 2020, two clinical trials have been registered regarding the
probiotics supplementation in COVID-19 patients (Lythgoe & Middleton,
2020), however, more information is needed for designing research
protocols. We tried to summarize the possible relationships between
probiotics and viral infections especially SARS-CoV-2-related literature
in this systematic review.