RESUMEN
OBJECTIVETo investigate the dynamics of viral RNA, IgM, and IgG and their relationships in patients with SARS-CoV-2 pneumonia over an 8-week period. DESIGNRetrospective, observational case series. SETTINGWenzhou Sixth Peoples Hospital PARTICIPANTSThirty-three patients with laboratory confirmed SARS-CoV-2 pneumonia admitted to hospital. Data were collected from January 27 to April 10, 2020. MAIN OUTCOME MEASURESThroat swabs, sputum, stool, and blood samples were collected, and viral load was measured by reverse transcription PCR (RT-PCR). Specific IgM and IgG against spike protein (S), spike protein receptor binding domain (RBD), and nucleocapsid (N) were analyzed. RESULTSAt the early stages of symptom onset, SARS-CoV-2 viral load is higher in throat swabs and sputum, but lower in stool. The median (IQR) time of undetectable viral RNA in throat swab, sputum, and stool was 18.5 (13.25-22) days, 22 (18.5-27.5) days, and 17 (11.5-32) days, respectively. In sputum, 17 patients (51.5%) had undetectable viral RNA within 22 days (short persistence), and 16 (48.5%) had persistent viral RNA more than 22 days (long persistence). Three patients (9.1%) had a detectable relapse of viral RNA in sputum within two weeks of their discharge from the hospital. One patient had persistent viral RNA for 59 days or longer. The median (IQR) seroconversion time of anti-S IgM, anti-RBD IgM, and anti-N IgM was 10.5 (7.75-15.5) days, 14 (9-24) days, and 10 (7-14) days, respectively. The median (IQR) seroconversion time of anti-S IgG, anti-RBD IgG, and anti-N IgG was 10 (7.25-16.5) days, 13 (9-17) days, and 10 (7-14) days, respectively. By week 8 after symptom onset, IgM were negative in many of the previously positive patients, and IgG levels remained less than 50% of the peak levels in more than 20% of the patients. In about 40% of the patients, anti-RBD IgG levels were 4-times higher in convalescence than in acute phase. SARS-CoV-2 RNA coexisted with antibodies for more than 50 days. Anti-RBD IgM and IgG levels, including anti-RBD IgM levels at presentation and peak time, were significantly higher in viral RNA short persistence patients than in long persistence patients. CONCLUSIONThis study adds important new information about the features of viral load and antibody dynamics of SARS-CoV-2. It is clear from these results that the viral RNA persists in sputum and stool specimens for a relatively long time in many patients. Anti-RBD may also serve as a potential protective antibody against SARS-CoV-2 infection, as viral persistence appears to be related to anti-RBD levels. Earlier treatment intervention also appears to be a factor in viral persistence. WHAT IS ALREADY KNOWN ON THIS TOPICThere are several reports about the serum antibodies against SARS-CoV-2. However, most of them evaluate diagnostic accuracy. Only two articles report dynamics of SARS-CoV-2 viral RNA and antibodies with serial samples, but the observation periods are within 30 days. None of the studies investigate the profiles of SARS-CoV-2 viral load and antibodies in a long period. Three reports investigate profiles in respiratory samples, but there are no reports on the dynamics of the viral load in stool samples. WHAT THIS STUDY ADDSIn both sputum and stool, SARS-CoV-2 RNA persists for a long time. The anti-RBD antibodies may involve in the clearance of SARS-CoV-2 infection. After eight weeks from symptom onset, IgM were negative in many of the previously positive patients, and IgG levels remained less than 50% of the peak levels in more than 20% of the patients. In about 40% of the patients, anti-RBD IgG levels increased 4-time higher in convalescence than in acute phase. Long persistence of SARS-CoV-2 viral RNA in sputum and stool presents challenges for management of the infection. The IgM/IgG comb test is better than single IgM test as a supplement diagnostic tool. Anti-RBD may be a protective antibody, and is valuable for development of vaccines.
RESUMEN
Objective To investigate the species distribution and the difference of virulence gene spectra of Aeromonas isolated from intestinal tract and extraintestinal body fluid,and the correlation of their pathogenicity with infection sites.Methods A total of 156 Aeromonas strains isolated from the fecal specimens of patients with acute diarrhea and extraintestinal specimens were collected during May 2013 and September 2015.Eighteen virulence genes in these strains,including hlyA,aerA,act,alt,ast,aexT,ascV,aopP,ascF-G,gcat,tapA,fla,Ser,exu,ahyB,eprCAl,lip and laf,were detected by polymerase chain reaction(PCR).Last,the differences of virulence gene spectra between intestinal and extraintestinal Aeromonas were analyzed.Results Among 156 Aeromonas strains,79 were from fecal specimens,and 77 from extraintestinal specimens.Aeromonas caviae(A.caviae,51.9％) was the most common species in the intestinal strains,while Aeromonas hydrophila(A.hydrophila,48.1％) and A.caviae(39.0％) were the main pathogens in extraintestinal infections.The most prevalent virulence genes in intestinal and extraintestinal Aeromonas were gcat,act,fla,ahyB,exu and lip (＞ 45.57 ％),while aexT,aopP,ascF-G and ascV were less frequently detected (＜ 20.78％).The detection rates of gcat,ahyB,laf,ast,exu,lip,hlyA and aerA genes in intestinal Aeromonas were significantly lower than those in extraintestinal isolates (P ＜ 0.05).The detection rates of gcat,ahyB,exu,lip,eprCAl and hlyA genes in extraintestinal A.hydrophila were significantly higher than those in intestinal A.hydrophila (P ＜ 0.05).The detection rates of lip and hlyA genes in extraintestinal A.caviae were significantly higher than those in intestinal A.caviae (P ＜ 0.05),while that of aopP gene was just the reverse.There was no significant difference in the detection rates of virulence genes between intestinal and extraintestinal Aeromonas veronii.Conclusion There are significant differences in the species distribution and virulence genes of Aeromonas isolated from intestinal and extraintestinal specimens,indicating that clinicians should treat them differentially.