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Poteete O, Cox P, Ruffin F, Sutton G, Brinkac L, Clarke TH, Fouts DE, Fowler VG, Thaden JT. Serum susceptibility of Escherichia coli and its association with patient clinical outcomes. PLoS One 2024; 19:e0307968. [PMID: 39074102 DOI: 10.1371/journal.pone.0307968] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2024] [Accepted: 07/14/2024] [Indexed: 07/31/2024] Open
Abstract
The innate immune system eliminates bloodstream pathogens such as Escherichia coli in part through complement protein deposition and subsequent bacterial death (i.e., "serum killing"). Some E. coli strains have developed mechanisms to resist serum killing, though the extent of variation in serum killing among bloodstream infection (BSI) isolates and the clinical impact of this variation is not well understood. To address this issue, we developed a novel assay that uses flow cytometry to perform high throughput serum bactericidal assays (SBAs) with E. coli BSI isolates (n = 183) to define the proportion of surviving bacteria after exposure to serum. We further determined whether E. coli resistance to serum killing is associated with clinical outcomes (e.g., in-hospital attributable mortality, in-hospital total mortality, septic shock) and bacterial genotype in the corresponding patients with E. coli BSI. Our novel flow cytometry-based SBA performed similarly to a traditional SBA, though with significantly decreased hands-on bench work. Among E. coli BSI isolates, the mean proportion that survived exposure to 25% serum was 0.68 (Standard deviation 0.02, range 0.57-0.93). We did not identify associations between E. coli resistance to serum killing and clinical outcomes in our adjusted models. Together, this study describes a novel flow cytometry-based approach to the bacterial SBA that allowed for high-throughput testing of E. coli BSI isolates and identified high variability in resistance to serum killing among a large set of BSI isolates.
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Affiliation(s)
- Orianna Poteete
- Department of Medicine, Division of Infectious Diseases, Duke University School of Medicine, Durham, NC, United States of America
| | - Phillip Cox
- Department of Medicine, Division of Infectious Diseases, Duke University School of Medicine, Durham, NC, United States of America
| | - Felicia Ruffin
- Department of Medicine, Division of Infectious Diseases, Duke University School of Medicine, Durham, NC, United States of America
| | - Granger Sutton
- J. Craig Venter Institute, Rockville, MD, United States of America
| | - Lauren Brinkac
- J. Craig Venter Institute, Rockville, MD, United States of America
| | - Thomas H Clarke
- J. Craig Venter Institute, Rockville, MD, United States of America
| | - Derrick E Fouts
- J. Craig Venter Institute, Rockville, MD, United States of America
| | - Vance G Fowler
- Department of Medicine, Division of Infectious Diseases, Duke University School of Medicine, Durham, NC, United States of America
- Duke Clinical Research Institute, Durham, NC, United States of America
| | - Joshua T Thaden
- Department of Medicine, Division of Infectious Diseases, Duke University School of Medicine, Durham, NC, United States of America
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Barai L, Hasan MR, Haq JA, Ahsan CR. Salmonellacidal antibody response to Salmonella enterica serovar Typhi in enteric fever and after vaccination with Vi capsular polysaccharide. Int J Infect Dis 2022; 121:120-125. [PMID: 35568365 DOI: 10.1016/j.ijid.2022.05.022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2022] [Revised: 04/08/2022] [Accepted: 05/07/2022] [Indexed: 10/18/2022] Open
Abstract
OBJECTIVES Serum salmonellacidal (bactericidal) antibody could be used to detect functional capacity of antibody in patients with enteric fever and after typhoid vaccination. METHODS Salmonellacidal antibody response was measured by colorimetric serum salmonellacidal assay from 70 acute and 11 convalescence sera of patients infected with Salmonella Typhi and Paratyphi A and also from 15 control and 6 Vi capsular polysaccharide vaccinated volunteer's sera. RESULTS Sera from patients with typhoid and paratyphoid A showed significant (p < 0.05) levels of salmonellacidal antibody titer (549.9 ± 108.5 and 528.7 ± 187.3) compared with control (0.133 ± 0.1). Moreover, this titer increased significantly (p <0.05) in sera collected between 7 and 10 days and between 11 and 25 days of fever (titer 535.7 ± 119.2 and 794.6 ± 235.6) compared with sera collected from patients with fever for less than 7 days (136.4 ± 52.7). The mean titer significantly (p < 0.05) decreased to 5.5 ± 2.1 after 6-8 weeks onset of illness. Although, very low salmonellacidal titers (2.5 ± 1.5 and 2.3 ± 1.5) were detected after Vi CPS vaccine among the human volunteers, but mean titer was raised 15-fold from pre- to postvaccinated sera (0.166-2.5). CONCLUSION The serum salmonellacidal antibody by colorimetric salmonellacidal assay could be used to detect acute typhoidal cases and also to monitor immune response of typhoid vaccine.
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Affiliation(s)
- Lovely Barai
- Department of Microbiology, Bangladesh Institute of Research and Rehabilitation in Diabetes, Endocrine and Metabolic Disorders (BIRDEM), Dhaka, Bangladesh.
| | - Md Rokibul Hasan
- Department of Microbiology, Bangladesh Institute of Research and Rehabilitation in Diabetes, Endocrine and Metabolic Disorders (BIRDEM), Dhaka, Bangladesh
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Increasing the High Throughput of a Luminescence-Based Serum Bactericidal Assay (L-SBA). BIOTECH 2021; 10:biotech10030019. [PMID: 35822773 PMCID: PMC9245470 DOI: 10.3390/biotech10030019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Revised: 09/02/2021] [Accepted: 09/16/2021] [Indexed: 11/16/2022] Open
Abstract
Serum bactericidal assay (SBA) is the method to investigate in vitro complement-mediated bactericidal activity of sera raised upon vaccination. The assay is based on incubating the target bacteria and exogenous complement with sera at different dilutions and the result of the assay is represented by the sera dilution being able to kill 50% of bacteria present in the inoculum. The traditional readout of the assay is based on measurement of colony-forming units (CFU) obtained after plating different reaction mixes on agar. This readout is at low throughput and time consuming, even when automated counting is used. We previously described a novel assay with a luminescence readout (L-SBA) based on measurement of ATP released by live bacteria, which allowed to substantially increase the throughput as well as to reduce the time necessary to perform the assay when compared to traditional methods. Here we present a further improvement of the assay by moving from a 96-well to a 384-well format, which allowed us to further increase the throughput and substantially reduce costs while maintaining the high performance of the previously described L-SBA method. The method has been successfully applied to a variety of different pathogens.
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Toh ZQ, Higgins RA, Mazarakis N, Abbott E, Nathanielsz J, Balloch A, Mulholland K, Licciardi PV. Evaluating Functional Immunity Following Encapsulated Bacterial Infection and Vaccination. Vaccines (Basel) 2021; 9:677. [PMID: 34203030 PMCID: PMC8234458 DOI: 10.3390/vaccines9060677] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Revised: 06/16/2021] [Accepted: 06/16/2021] [Indexed: 11/19/2022] Open
Abstract
Encapsulated bacteria such as Streptococcus pneumoniae, Haemophilus influenzae type b and Neisseria meningitidis cause significant morbidity and mortality in young children despite the availability of vaccines. Highly specific antibodies are the primary mechanism of protection against invasive disease. Robust and standardised assays that measure functional antibodies are also necessary for vaccine evaluation and allow for the accurate comparison of data between clinical studies. This mini review describes the current state of functional antibody assays and their importance in measuring protective immunity.
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Affiliation(s)
- Zheng Quan Toh
- Murdoch Children’s Research Institute, Parkville, VIC 3052, Australia; (Z.Q.T.); (R.A.H.); (N.M.); (E.A.); (J.N.); (A.B.); (K.M.)
- Department of Paediatrics, The University of Melbourne, Parkville, VIC 3052, Australia
| | - Rachel A. Higgins
- Murdoch Children’s Research Institute, Parkville, VIC 3052, Australia; (Z.Q.T.); (R.A.H.); (N.M.); (E.A.); (J.N.); (A.B.); (K.M.)
| | - Nadia Mazarakis
- Murdoch Children’s Research Institute, Parkville, VIC 3052, Australia; (Z.Q.T.); (R.A.H.); (N.M.); (E.A.); (J.N.); (A.B.); (K.M.)
| | - Elysia Abbott
- Murdoch Children’s Research Institute, Parkville, VIC 3052, Australia; (Z.Q.T.); (R.A.H.); (N.M.); (E.A.); (J.N.); (A.B.); (K.M.)
| | - Jordan Nathanielsz
- Murdoch Children’s Research Institute, Parkville, VIC 3052, Australia; (Z.Q.T.); (R.A.H.); (N.M.); (E.A.); (J.N.); (A.B.); (K.M.)
| | - Anne Balloch
- Murdoch Children’s Research Institute, Parkville, VIC 3052, Australia; (Z.Q.T.); (R.A.H.); (N.M.); (E.A.); (J.N.); (A.B.); (K.M.)
| | - Kim Mulholland
- Murdoch Children’s Research Institute, Parkville, VIC 3052, Australia; (Z.Q.T.); (R.A.H.); (N.M.); (E.A.); (J.N.); (A.B.); (K.M.)
- Department of Paediatrics, The University of Melbourne, Parkville, VIC 3052, Australia
- London School of Hygiene and Tropical Medicine, University of London, London WC1E 7HT, UK
| | - Paul V. Licciardi
- Murdoch Children’s Research Institute, Parkville, VIC 3052, Australia; (Z.Q.T.); (R.A.H.); (N.M.); (E.A.); (J.N.); (A.B.); (K.M.)
- Department of Paediatrics, The University of Melbourne, Parkville, VIC 3052, Australia
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Antibody Binding and Complement-Mediated Killing of Invasive Haemophilus influenzae Isolates from Spain, Portugal, and the Netherlands. Infect Immun 2020; 88:IAI.00454-20. [PMID: 32719154 DOI: 10.1128/iai.00454-20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Accepted: 07/22/2020] [Indexed: 02/06/2023] Open
Abstract
Haemophilus influenzae is a Gram-negative bacterium that can be classified into typeable (types a through f) and nontypeable (NTHi) groups. This opportunistic pathogen asymptomatically colonizes the mucosal epithelium of the upper respiratory tract, from where it spreads to other neighboring regions, potentially leading to disease. Infection with NTHi can cause otitis media, sinusitis, conjunctivitis, exacerbations of chronic obstructive pulmonary disease, and pneumonia, but it is increasingly causing invasive disease, including bacteremia and meningitis. Invasive NTHi strains are more resistant to complement-mediated killing. However, the mechanisms of complement resistance have never been studied in large numbers of invasive NTHi strains. In this study, we determined the relationship between binding of IgG or IgM and the bacterial survival in normal human serum for 267 invasive H. influenzae strains from Spain, Portugal, and the Netherlands, of which the majority (200 [75%]) were NTHi. NTHi bacteria opsonized with high levels of IgM had the lowest survival in human serum. IgM binding to the bacterial surface, but not IgG binding, was shown to be associated with complement-mediated killing of NTHi strains. We conclude that evasion of IgM binding by NTHi strains increases survival in blood, thereby potentially contributing to their ability to cause severe invasive diseases.
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Necchi F, Saul A, Rondini S. Setup of luminescence-based serum bactericidal assay against Salmonella Paratyphi A. J Immunol Methods 2018; 461:117-121. [PMID: 29969587 DOI: 10.1016/j.jim.2018.06.025] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2018] [Revised: 06/10/2018] [Accepted: 06/29/2018] [Indexed: 10/28/2022]
Abstract
Increasing awareness of Salmonella Paratyphi A's contribution to enteric fever episodes throughout Asia has led to the development of new S. Paratyphi A vaccines. Assays are needed to measure functional antibodies elicited by the new vaccine candidates to assess their immunogenicity and potential protective capacities. Serum bactericidal assay (SBA) is the method of choice to measure functional antibody titers against various bacterial pathogens, but it is rarely been used for large dataset and clinical samples because it is time consuming and labor-intensive. Recently we developed a high-throughput luminescence-based SBA method, against different pathogens, including Salmonella Typhimurium and Enteritidis, Shigella flexneri serovars 2a and 3a, Shigella sonnei and Neisseria meningitidis. Here we further demonstrated the applicability of such method with invasive isolates of S. Paratyphi A to assess the complement-mediated antibody-dependent killing of both preclinical and clinical standard sera. As already found for other organisms, titers obtained by the luminescence-based SBA strongly correlated with those obtained by the conventional agar plate-based assay. The SBA assay described here is a useful tool for measuring functional antibodies elicited by Salmonella vaccines, with the potential of being applied to immunogenicity assessment in clinical trials.
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Affiliation(s)
- Francesca Necchi
- GSK Vaccines Institute for Global Health (GVGH) S.r.l., via Fiorentina 1, 53100 Siena, Italy.
| | - Allan Saul
- GSK Vaccines Institute for Global Health (GVGH) S.r.l., via Fiorentina 1, 53100 Siena, Italy
| | - Simona Rondini
- GSK Vaccines Institute for Global Health (GVGH) S.r.l., via Fiorentina 1, 53100 Siena, Italy
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