Impact of bacterial and viral coinfection in community-acquired pneumonia in adults

Factors associated with antibiotic resistance and survival analysis of severe pneumonia patients infected with Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa: A retrospective cohort study in Jakarta, Indonesia

Background

Antimicrobial resistance is one of the most significant challenges to global public health and the risk factors in severe pneumonia are constantly growing. Therefore, this study aimed to identify factors associated with antimicrobial resistance and conduct survival analysis of severe pneumonia patients with single and multiple pathogens in the National Referral Hospital, Jakarta, Indonesia.

Methods

A retrospective method was used, and secondary data were collected from severe pneumonia patients admitted to the intensive care unit at Cipto Mangunkusumo National Referral Hospital, Jakarta, Indonesia, from January 2016 to December 2022. Respiratory specimens were collected through bronchial washing. Furthermore, univariate and multivariate analyses were performed to analyze factors associated with antimicrobial resistance. Kaplan‒Meier survival curves were generated with the log-rank test to compare 30-day mortality between patients infected with single, dual, and multiple pathogens.

Results

The results showed that a total of 333 patients from 415 enrolled were analyzed. Klebsiella pneumoniae (35.4%), Acinetobacter baumannii (29.3%), and Pseudomonas aeruginosa (15.4%) were the most frequently isolated Gram-negative pathogens. Factors associated with resistance to aminoglycoside, carbapenem, and quinolone were sepsis, cerebrovascular disease, and ventilator-associated pneumonia, as indicated by p < 0.05. In addition, the Kaplan-Meier curves showed that multiple pathogens influenced the survival rate of severe pneumonia patients (p < 0.05).

Conclusions

Sepsis, cerebrovascular disease, and ventilator-associated pneumonia were associated with antimicrobial resistance in severe pneumonia patients. The survival rate of patients infected with multiple pathogens was low. This suggests the importance of further awareness regarding empirical antibiotic stewardship and mortality assessment in severe pneumonia patients.

Disease burden and macrolide resistance of Mycoplasma pneumoniae infection in adults in the Asia-Pacific region

OBJECTIVES

In the Asia-Pacific region, Mycoplasma pneumoniae (MP) could be a notable pathogen responsible for adult community-acquired pneumonia (CAP), with varying prevalence rates. This comprehensive review aimed to explore the epidemiology, clinical manifestations, macrolide resistance, and molecular characteristics of MP in adults across several countries in Asia.

METHODS

PubMed, Embase, and Google Scholar were searched for relevant articles from 2010-2023 based on the following keywords: adult and Mycoplasma pneumoniae.

RESULTS

The prevalence of MP in CAP patients in these countries ranged from 2.1% in Korea to 25.5% in Japan. Macrolide resistance was prominent, particularly in China, with rates ranging 26.9-100%. Clinical manifestations of MP infection included protean extrapulmonary manifestations, and complications such as rhabdomyolysis and thrombocytopenia. Molecular characteristics, especially the multiple locus variable-number tandem-repeat analysis type 4/5/7/2, remained predominant across various countries, emphasising the importance of ongoing surveillance.

CONCLUSIONS

This review highlights the urgent need for continued monitoring of MP infections, macrolide resistance, and molecular characteristics to inform effective prevention and treatment strategies in the Asia-Pacific region.

Comparison of Real-time Polymerase Chain Reaction and Culture for Targeting Pathogens in Pediatric Severe Community-Acquired Pneumonia

Objective

This study aims to determine the frequency of pathogen detection by real-time polymerase chain reaction (PCR), the frequency of pathogen isolation by culture; and compare the value of real-time PCR and culture of nasopharyngeal aspiration samples in patients with severe community-acquired pneumonia (sCAP).

Materials and Methods

It was a prospective and descriptive study. All pediatric patients diagnosed with sCAP were performed real-time PCR and culture of nasopharyngeal aspiration samples.

Results

A total of 336 patient samples were obtained from children with sCAP. Real-time PCR detected pathogens in 312 patients (92.9%), while culture isolated bacteria in 228 patients (67.9%). Coinfections were reported in 279 cases (83.0%) through real-time PCR. The frequency of agreement between culture and real-time PCR was quite high (P < .001).

Conclusion

Real-time PCR demonstrated more ability for detecting microorganisms than culture. This finding highlighted the value of real-time PCR for targeting pathogens in children with sCAP, particularly in cases involving complex pathogens or those requiring timely identification.

Enhancing pathogen description and antibiotic regimen selection in community-acquired pneumonia through RT-qPCR assays

Background

Adults with community-acquired pneumonia (CAP) in China suffer high morbidity. CAP is caused by a multitude of pathogens; however, pathogen-directed clinical symptoms are often lacking. Therefore, patients lacking an accurate microbiological diagnosis are administered with empirical antimicrobials.

Methods

We collected bronchoalveolar lavage fluid, as well as clinical and laboratory data from 650 adult patients with CAP admitted to three hospitals in Hubei, Sichuan, and Zhejiang provinces in China. Specimens were cultured and tested using real-time reverse transcription qPCR (RT-qPCR) assays for the presence of 42 respiratory bacteria and viruses. CAP was investigated with respect to regions, genders, and age and patterns of infections or co-infections. Employing clinical guidelines adapted for diagnosis, we assessed retrospectively the appropriate pathogen-directed therapy and compared it with the initial empirical therapies.

Results

Our study identified that 21.38% (139/650) of the patients were classified as having Severe CAP (S-CAP), with a higher prevalence among males, older adults, and during the warm season. Bacterial pathogens were detected in 35.53% (231/650) of cases. K. pneumoniae, H. influenzae, and S. aureus were the most prevalent bacteria across different demographics and regions. Viral pathogens were found in 48.76% (317/650) of patients Epstein-Barr, Human rhinovirus, and Cytomegalovirus were the most common viruses. Co-infections were present in 24.31% (158/650) of cases, with viral-bacterial co-infections being the most frequent. The RT-qPCR demonstrated significantly higher detection rates for key pathogens compared to standard culture methods. It showed potential in optimizing antimicrobial prescriptions by allowing for de-escalation in 18.30% (95/518) of patients, among which reducing the number of excessive antibiotics mainly comprised decreasing the use of 2nd or 3rd generation cephalosporins (5.79%, 30/518) and β-lactamase inhibitor combinations.

Conclusion

The study highlights the significant burden of S-CAP, particularly among specific demographics and seasons. The prevalence of bacterial and viral pathogens, along with the high rate of co-infections, emphasizes the need for comprehensive diagnostic approaches. The RT-qPCR assays emerge as a superior diagnostic tool, offering enhanced pathogen detection capabilities and facilitating more precise antimicrobial therapy. This could lead to improved patient outcomes and contribute to the rational use of antimicrobials, addressing the growing concern of antibiotic resistance.

Evaluation and clinical practice of pathogens and antimicrobial resistance genes of BioFire FilmArray Pneumonia panel in lower respiratory tract infections

BACKGROUND

Existing panels for lower respiratory tract infections (LRTIs) are slow and lack quantification of important pathogens and antimicrobial resistance, which are not solely responsible for their complex etiology and antibiotic resistance. BioFire FilmArray Pneumonia (PN) panels may provide rapid information on their etiology.

METHODS

The bronchoalveolar lavage fluid of 187 patients with LRTIs was simultaneously analyzed using a PN panel and cultivation, and the impact of the PN panel on clinical practice was assessed. The primary endpoint was to compare the consistency between the PN panel and conventional microbiology in terms of etiology and drug resistance, as well as to explore the clinical significance of the PN panel. The secondary endpoint was pathogen detection using the PN panel in patients with community-acquired pneumonia (CAP) or hospital-acquired pneumonia (HAP).

RESULTS

Fifty-seven patients with HAP and 130 with CAP were included. The most common pathogens of HAP were Acinetobacter baumannii and Klebsiella pneumoniae, with the most prevalent antimicrobial resistance (AMR) genes being CTX-M and KPC. For CAP, the most common pathogens were Haemophilus influenzae and Staphylococcus aureus, with the most frequent AMR genes being CTX-M and VIM. Compared with routine bacterial culture, the PN panel demonstrated an 85% combined positive percent agreement (PPA) and 92% negative percent agreement (NPA) for the qualitative identification of 13 bacterial targets. PN detection of bacteria with higher levels of semi-quantitative bacteria was associated with more positive bacterial cultures. Positive concordance between phenotypic resistance and the presence of corresponding AMR determinants was 85%, with 90% positive agreement between CTX-M-type extended-spectrum beta-lactamase gene type and phenotype and 100% agreement for mecA/C and MREJ. The clinical benefit of the PN panel increased by 25.97% compared with traditional cultural tests.

CONCLUSION

The bacterial pathogens and AMR identified by the PN panel were in good agreement with conventional cultivation, and the clinical benefit of the PN panel increased by 25.97% compared with traditional detection. Therefore, the PN panel is recommended for patients with CAP or HAP who require prompt pathogen diagnosis and resistance identification.

Impact of viral detection in patients with community-acquired pneumonia: An observational cohort study

PURPOSE

The presence of a respiratory virus in patients with community-acquired pneumonia (CAP) may have an impact on the bacterial etiology and clinical presentation. In this study we aimed to assess the role of viral infection in the bacterial etiology and outcomes of patients with CAP.

METHODS

We performed a retrospective study of all adults hospitalized with CAP between November 2017 and October 2018. Patients were classified according to the presence of viral infection. An unvaried and a multivaried analysis were performed to identify variables associated with viral infection and clinical outcomes.

RESULTS

Overall 590 patients were included. A microorganism was documented in 375 cases (63.5%). A viral infection was demonstrated in 118 (20%). The main pathogens were Streptococcus pneumoniae (35.8%), Staphylococcus aureus (2.9%) and influenza virus (10.8%). A trend to a higher rate of S. aureus (p=0.06) in patients with viral infection was observed. Patients with viral infection had more often bilateral consolidation patterns (17.8% vs 10.8%, p=0.04), respiratory failure (59.3% vs 42.8%, p=0.001), ICU admission (17.8% vs 7%, p=0.001) and invasive mechanical ventilation (9.3% vs 2.8%, p=0.003). Risk factors for respiratory failure were chronic lung disease, age >65 years, positive blood cultures and viral infection. Influenza, virus but no other respiratory viruses, was associated with respiratory failure (OR, 3.72; 95% CI, 2.06-6.73).

CONCLUSIONS

Our study reinforces the idea that co-viral infection has an impact in the clinical presentation of CAP causing a more severe clinical picture. This impact seems to be mainly due to influenza virus infection.

Clinical characteristics of severe influenza virus-associated pneumonia complicated with bacterial infection in children: a retrospective analysis

BACKGROUND

We aimed to investigate the clinical characteristics of severe influenza virus-associated pneumonia complicated with bacterial infection in children.

METHODS

We retrospectively analysed data concerning 64 paediatric patients with severe influenza virus-associated pneumonia who had been treated at our hospital. The patients were divided into observation (44 patients) and control (20 patients) groups, based on the presence or absence of concomitant bacterial infection, and clinical data were compared between the groups.

RESULTS

The mean age in the observation group was 2.71 ± 1.44 years, 42 (95.45%) were aged ≤ 5 years, and 18 (40.9%) had underlying diseases. The mean age in the control group was 4.05 ± 2.21 years, 13 (65%) were aged ≤ 5 years, and 3 (15%) had underlying diseases. There was a statistically significant difference in patient age and the proportion of patients with underlying diseases (P < 0.05). The observation group had higher duration of fever values, a higher number of patients with duration of fever ≥ 7 days, a higher incidence of gasping, and a higher incidence of seizures/consciousness disturbance, and the differences were statistically significant (P < 0.05). Secondary bacterial infections in the observation group were mainly due to gram-negative bacteria, with Haemophilus influenzae and Moraxella catarrhalis being the most common pathogens. The observation group had a higher proportion of patients treated in the paediatric intensive care unit and a longer hospital stay, and the differences were statistically significant (P < 0.05).

CONCLUSION

Severe influenza virus-associated pneumonia complicated with bacterial infection was more common in children aged ≤ 5 years. Younger patients with underlying diseases were more susceptible to bacterial infection (mainly due to gram-negative bacteria). The timely administration of neuraminidase inhibitors and antibiotics against susceptible bacteria is likely to help improve cure rates.

Impact of influenza virus infection on lung microbiome in adults with severe pneumonia

BACKGROUND

Bacterial and viral infections are commonly implicated in the development of pneumonia. We aimed to compare the diversity and composition of lung bacteria among severe pneumonia patients who were influenza virus positive (IFVP) and influenza virus negative (IFVN).

METHODS

Bronchoalveolar lavage fluid specimens were procured from patients diagnosed with severe pneumonia to investigate the microbiome utilizing 16S-rDNA sequencing. The alpha diversity of the microbiome was evaluated employing Chao1, Shannon, and Simpson indexes, while the beta diversity was assessed using principal component analysis and principal coordinate analysis. Linear discriminant analysis effect size (LEfSe) was employed to determine the taxonomic differences between the IFVP and IFVN groups.

RESULTS

A total of 84 patients with 42 in the IFVP group and 42 in the IFVN group were enrolled. Slightly higher indexes of Shannon and Simpson were observed in the IFVP group without statistically significant difference. The dominant bacterial genera were Streptococcus, Klebsiella, Escherichia-Shigella in the IFVN group and Acinetobacter, Streptococcus, Staphylococcus in the IFVP group. Streptococcus pneumoniae and Acinetobacter baumannii were the most abundant species in the IFVN and IFVP groups, respectively. LEfSe analysis indicated a greater abundance of Klebsiella in the IFVN group.

CONCLUSIONS

Individuals with severe pneumonia infected with IFV exhibit heightened susceptibility to certain bacteria, especially Acinetobacter baumannii, and the underlying mechanism of the interaction between IFV and Acinetobacter baumannii in the progression of pneumonia needs further investigation.

Fasting Plasma Glucose Levels at the Time of Admission Predict 90-Day Mortality in Patients with Viral Pneumonia. A Prospective Study

PURPOSE

To determine the effect of fasting plasma glucose (FPG) level at admission affects the 90-day mortality rate in patients with viral pneumonia.

METHODS

Two hundred fifty viral pneumonia patients were stratified into normal FPG (FPG<7.0 mmol/L), moderately-elevated FPG (FPG=7.0-14.0 mmol/L), and highly-elevated FPG groups (FPG≥14.0 mmol/L) according to the FPG level at the time of admission. The clinical characteristics, etiologies, and prognosis of different groups of patients were compared. Kaplan-Meier survival and Cox regression analyses were used to determine the relationship between the FPG level and 90-day all-cause mortality rate in patients with viral pneumonia.

RESULTS

Patients in the moderately- and highly-elevated FPG groups had a higher proportion of severe disease and mortality compared with the normal FPG group (P<0.001). Kaplan-Meier survival analysis showed a significant trend toward higher mortality and increased cumulative risk at 30, 60, and 90 d in patients with an FPG=7.0-14.0 mmol/L and an FPG≥14 mmol/L (χ²=51. 77, P<0.001). Multivariate Cox regression analysis revealed that compared with an FPG<7.0 mmol/L, FPG=7.0 and 14.0 mmol/L (HR: 9.236, 95% CI: 1.106-77.119, P=0.040) and FPG≥14.0 mmol/L (HR: 25.935, 95% CI: 2.586-246.213, P=0.005) were independent risk factors for predicting the 90-day mortality rate in viral pneumonia patients.

CONCLUSIONS

The higher the FPG level at admission in a patient with viral pneumonia, the higher the risk of all-cause mortality within 90 d.

Bacterial Co-Infections and Antimicrobial Resistance in Patients Hospitalized with Suspected or Confirmed COVID-19 Pneumonia in Kazakhstan

Our study was carried out to characterize respiratory tract microbiota in patients with “COVID-like pneumonia” in Kazakhstan and analyze differences between COVID-19 positive and negative groups. Sputum samples were collected from hospitalized patients, ≥18 years old, in the three cities in Kazakhstan with the highest COVID-19 burden in July 2020. Isolates were identified by MALDI-TOF MS. Susceptibility testing was performed by disk diffusion. We used SPSS 26 and MedCalc 19 for statistical analysis. Among 209 patients with pneumonia, the median age was 62 years and 55% were male. RT-PCR-confirmed SARS-CoV-2 cases were found in 40% of patients, and 46% had a bacterial co-infection. Co-infection was not associated with SARS-CoV-2 RT-PCR test results, but antibiotic use was. The most frequent bacteria were Klebsiella pneumoniae (23%), Escherichia coli (12%), and Acinetobacter baumannii (11%). Notably, 68% of Klebsiella pneumoniae had phenotypic evidence of extended-spectrum beta-lactamases in disk diffusion assays, 87% of Acinetobacter baumannii exhibited resistance to beta-lactams, and >50% of E. coli strains had evidence of ESBL production and 64% were resistant to fluoroquinolones. Patients with a bacterial co-infection had a higher proportion of severe disease than those without a co-infection. The results reinforce the importance of using appropriate targeted antibiotics and effective infection control practices to prevent the spread of resistant nosocomial infections.

Clinical characteristics and severity prediction score of Adenovirus pneumonia in immunocompetent adult

BACKGROUND

Compared with children and immunocompromised patients, Adenovirus pneumonia in immunocompetent adults is less common. Evaluation of the applicability of severity score in predicting intensive care unit (ICU) admission of Adenovirus pneumonia is limited.

METHODS

We retrospectively reviewed 50 Adenovirus pneumonia inpatients in Xiangtan Central Hospital from 2018 to 2020. Hospitalized patients with no pneumonia or immunosuppression were excluded. Clinical characteristics and chest image at the admission of all patients were collected. Severity scores, including Pneumonia severity index (PSI), CURB-65, SMART-COP, and PaO2/FiO2 combined lymphocyte were evaluated to compare the performance of ICU admission.

RESULTS

Fifty inpatients with Adenovirus pneumonia were selected, 27 (54%) non-ICU and 23 (46%) ICU. Most patients were men (40 [80.00%]). Age median was 46.0 (IQR 31.0-56.0). Patients who required ICU care (n = 23) were more likely to report dyspnea (13[56.52%] vs 6[22.22%]; P = 0.002) and have lower transcutaneous oxygen saturation ([90% (IQR, 90-96), 95% (IQR, 93-96)]; P = 0.032). 76% (38/50) of patients had bilateral parenchymal abnormalities, including 91.30% (21/23) of ICU patients and 62.96% (17/27) of non-ICU patients. 23 Adenovirus pneumonia patients had bacterial infections, 17 had other viruses, and 5 had fungi. Coinfection with virus was more common in non-ICU patients than ICU patients (13[48.15%]VS 4[17.39%], P = 0.024), while bacteria and fungi not. SMART-COP exhibited the best ICU admission evaluation performance in Adenovirus pneumonia patients (AUC = 0.873, p < 0.001) and distributed similar in coinfections and no coinfections (p = 0.26).

CONCLUSIONS

In summary, Adenovirus pneumonia is not uncommon in immunocompetent adult patients who are susceptible to coinfection with other etiological illnesses. The initial SMART-COP score is still a reliable and valuable predictor of ICU admission in non-immunocompromised adult inpatients with adenovirus pneumonia.

The Role of Biomarkers in Influenza and COVID-19 Community-Acquired Pneumonia in Adults

Pneumonia is a growing problem worldwide and remains an important cause of morbidity, hospitalizations, intensive care unit admission and mortality. Viruses are the causative agents in almost a fourth of cases of community-acquired pneumonia (CAP) in adults, with an important representation of influenza virus and SARS-CoV-2 pneumonia. Moreover, mixed viral and bacterial pneumonia is common and a risk factor for severity of disease. It is critical for clinicians the early identification of the pathogen causing infection to avoid inappropriate antibiotics, as well as to predict clinical outcomes. It has been extensively reported that biomarkers could be useful for these purposes. This review describe current evidence and provide recommendations about the use of biomarkers in influenza and SARS-CoV-2 pneumonia, focusing mainly on procalcitonin (PCT) and C-reactive protein (CRP). Evidence was based on a qualitative analysis of the available scientific literature (meta-analyses, randomized controlled trials, observational studies and clinical guidelines). Both PCT and CRP levels provide valuable information about the prognosis of influenza and SARS-CoV-2 pneumonia. Additionally, PCT levels, considered along with other clinical, radiological and laboratory data, are useful for early diagnosis of mixed viral and bacterial CAP, allowing the proper management of the disease and adequate antibiotics prescription. The authors propose a practical PCT algorithm for clinical decision-making to guide antibiotic initiation in cases of influenza and SARS-CoV-2 pneumonia. Further well-design studies are needed to validate PCT algorithm among these patients and to confirm whether other biomarkers are indeed useful as diagnostic or prognostic tools in viral pneumonia.

High incidence of the virus among respiratory pathogens in children with lower respiratory tract infection in northwestern China

Lower respiratory tract infection (LRTI) is one of the major reasons for childhood mortality that threaten the health of the public. We aimed to investigate the epidemiological pathogens and their infection analysis among children with LRTI. Sputum specimens were collected for polymerase chain reaction detection and microbiological tests to identify the viral infection and bacterial infection. The serological specimens were separated from venous blood using for Mycoplasma pneumoniae and Chlamydia pneumoniae detection. The virus was confirmed in 86.2% of the children. Human rhinovirus (38.3%), respiratory syncytial virus (32.1%), and parainfluenza virus type 3 (27.2%) were the most frequently identified pathogens. Patients with viral and bacterial coinfection showed younger age (p = 0.032), a higher proportion of wheezing rales (p = 0.032), three depressions sign (p = 0.028), and tachypnea (p = 0.038), and more likely associated with severe pneumonia (p = 0.035). Additionally, older children were more susceptible to viral-atypical bacterial coinfection (p = 0.032). Vomiting (p = 0.011) and fever (p = 0.003) were more likely to occur in children with viral-atypical bacterial coinfection. Attention should be paid to the virus infection of LRTI, as viral-bacterial coinfection and viral-atypical bacterial co-infection may have a detrimental impact on the gravity of LTRI.

Development and validation of a nomogram for predicting Mycoplasma pneumoniae pneumonia in adults

The study aimed to explore predictors of Mycoplasma pneumoniae pneumonia (MPP) in adults and develop a nomogram predictive model in order to identify high-risk patients early. We retrospectively analysed the clinical data of a total of 337 adult patients with community-acquired pneumonia (CAP) and divided them into MPP and non-MPP groups according to whether they were infected with MP. Univariate and multivariate logistic regression analyses were used to screen independent predictors of MPP in adults and to developed a nomogram model. Receiver operating characteristic (ROC) curve, calibration curve, concordance index (C-index), and decision curve analysis (DCA) were used for the validation of the evaluation model. Finally, the nomogram was further evaluated by internal verification. Age, body temperature, dry cough, dizziness, CRP and tree-in-bud sign were independent predictors of MPP in adults (P < 0.05). The nomogram showed high accuracy with C-index of 0.836 and well-fitted calibration curves in both the training and validation sets. The area under the receiver operating curve (AUROC) was 0.829 (95% CI 0.774-0.883) for the training set and 0.847 (95% CI 0.768-0.925) for the validation set. This nomogram prediction model can accurately predict the risk of MPP occurrence in adults, which helps clinicians identify high-risk patients at an early stage and make drug selection and clinical decisions.

A multicenter analysis of inpatient antibiotic use during the 2015-2019 influenza seasons in the United States: Untapped opportunities for antimicrobial stewardship

Outpatient antibiotic use increases during winter months, but information on temporal changes in inpatient antibiotic use in US hospitals is limited. The use of certain inpatient antibiotics, including extended-spectrum cephalosporins, macrolides, and tetracyclines, was strongly associated with influenza activity during the 2015-2019 viral respiratory seasons.

Streptococcus pneumoniae and Influenza A Virus Co-Infection Induces Altered Polyubiquitination in A549 Cells

Epithelial cells are an important line of defense within the lung. Disruption of the epithelial barrier by pathogens enables the systemic dissemination of bacteria or viruses within the host leading to severe diseases with fatal outcomes. Thus, the lung epithelium can be damaged by seasonal and pandemic influenza A viruses. Influenza A virus infection induced dysregulation of the immune system is beneficial for the dissemination of bacteria to the lower respiratory tract, causing bacterial and viral co-infection. Host cells regulate protein homeostasis and the response to different perturbances, for instance provoked by infections, by post translational modification of proteins. Aside from protein phosphorylation, ubiquitination of proteins is an essential regulatory tool in virtually every cellular process such as protein homeostasis, host immune response, cell morphology, and in clearing of cytosolic pathogens. Here, we analyzed the proteome and ubiquitinome of A549 alveolar lung epithelial cells in response to infection by either Streptococcus pneumoniae D39Δcps or influenza A virus H1N1 as well as bacterial and viral co-infection. Pneumococcal infection induced alterations in the ubiquitination of proteins involved in the organization of the actin cytoskeleton and Rho GTPases, but had minor effects on the abundance of host proteins. H1N1 infection results in an anti-viral state of A549 cells. Finally, co-infection resembled the imprints of both infecting pathogens with a minor increase in the observed alterations in protein and ubiquitination abundance.

Bacterial co-infections in community-acquired pneumonia caused by SARS-CoV-2, influenza virus and respiratory syncytial virus

Background

A mismatch between a widespread use of broad-spectrum antibiotic agents and a low prevalence of reported bacterial co-infections in patients with SARS-CoV-2 infections has been observed. Herein, we sought to characterize and compare bacterial co-infections at admission in hospitalized patients with SARS-CoV-2, influenza or respiratory syncytial virus (RSV) positive community-acquired pneumonia (CAP).

Methods

A retrospective cohort study of bacterial co-infections at admission in SARS-CoV-2, influenza or RSV-positive adult patients with CAP admitted to Karolinska University Hospital in Stockholm, Sweden, from year 2011 to 2020. The prevalence of bacterial co-infections was investigated and compared between the three virus groups. In each virus group, length of stay, ICU-admission and 30-day mortality was compared in patients with and without bacterial co-infection, adjusting for age, sex and co-morbidities. In the SARS-CoV-2 group, risk factors for bacterial co-infection, were assessed using logistic regression models and creation of two scoring systems based on disease severity, age, co-morbidities and inflammatory markers with assessment of concordance statistics.

Results

Compared to influenza and RSV, the bacterial co-infection testing frequency in SARS-CoV-2 was lower for all included test modalities. Four percent [46/1243 (95% CI 3–5)] of all SARS-CoV-2 patients had a bacterial co-infection at admission, whereas the proportion was 27% [209/775 (95% CI 24–30)] and 29% [69/242 (95% CI 23–35)] in influenza and RSV, respectively. S. pneumoniae and S. aureus constituted the most common bacterial findings for all three virus groups. Comparing SARS-CoV-2 positive patients with and without bacterial co-infection at admission, a relevant association could not be demonstrated nor excluded with regards to risk of ICU-admission (aHR 1.53, 95% CI 0.87–2.69) or 30-day mortality (aHR 1.28, 95% CI 0.66–2.46) in adjusted analyses. Bacterial co-infection was associated with increased inflammatory markers, but the diagnostic accuracy was not substantially different in a scoring system based on disease severity, age, co-morbidities and inflammatory parameters [C statistic 0.66 (95% CI 0.59–0.74)], compared to using disease severity, age and co-morbidities only [C statistic 0.63 (95% CI 0.56–0.70)].

Conclusions

The prevalence of bacterial co-infections was significantly lower in patients with community-acquired SARS-CoV-2 positive pneumonia as compared to influenza and RSV positive pneumonia.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-022-07089-9.

Antibiotic Resistance Patterns and Association with the Influenza Season in the United States: A Multicenter Evaluation Reveals Surprising Associations Between Influenza Season and Resistance in Gram-negative Pathogens

Background

Viral infections are often treated with empiric antibiotics due to suspected bacterial coinfections, leading to antibiotic overuse. We aimed to describe antibiotic resistance (ABR) trends and their association with the influenza season in ambulatory and inpatient settings in the United States.

Methods

We used the BD Insights Research Database to evaluate antibiotic susceptibility profiles in 30-day nonduplicate bacterial isolates collected from patients >17 years old at 257 US healthcare institutions from 2011 to 2019. We investigated ABR in Gram-positive (Staphylococcus aureus and Streptococcus pneumoniae) and Gram-negative (Enterobacterales [ENT], Pseudomonas aeruginosa [PSA], and Acinetobacter baumannii spp [ACB]) bacteria expressed as the proportion of isolates not susceptible ([NS], intermediate or resistant) and resistance per 100 admissions (inpatients only). Antibiotics included carbapenems (Carb), fluoroquinolones (FQ), macrolides, penicillin, extended-spectrum cephalosporins (ESC), and methicillin. Generalized estimating equations models were used to evaluate monthly trends in ABR outcomes and associations with community influenza rates.

Results

We identified 8 250 860 nonduplicate pathogens, including 154 841 Gram-negative Carb-NS, 1 502 796 Gram-negative FQ-NS, 498 012 methicillin-resistant S aureus (MRSA), and 44 131 NS S pneumoniae. All S pneumoniae rates per 100 admissions (macrolide-, penicillin-, and ESC-NS) were associated with influenza rates. Respiratory, but not nonrespiratory, MRSA was also associated with influenza. For Gram-negative pathogens, influenza rates were associated with the percentage of FQ-NS ENT, FQ-NS PSA, and Carb-NS ACB.

Conclusions

Our study showed expected increases in rates of ABR Gram-positive and identified small but surprising increases in ABR Gram-negative pathogens associated with influenza activity. These insights may help inform antimicrobial stewardship initiatives.

Frequency and Significance of Coinfection in Patients with COVID-19 at Hospital Admission

Objective Viral pneumonia is not rare in community-acquired pneumonia (CAP). Mixed or secondary pneumonia (coinfection) can be seen in viral pneumonia; however, its frequency in coronavirus disease 2019 (COVID-19) has only been investigated in a few studies of short duration, and its significance has not been fully elucidated. We investigated the frequency and significance of co-infection in patients with COVID-19 over a 1-year study period. Methods Coinfection was investigated via multiplex polymerase chain reaction (PCR), culture of respiratory samples, rapid diagnostic tests, and paired sera. We used logistic regression analysis to analyze the effect of coinfection on severity at admission and Cox proportional-hazards model analysis to analyze the effect of coinfection on need for high-flow nasal cannula, invasive mandatory ventilation use, and death, respectively. Patients We retrospectively investigated 298 patients who suffered CAP due to severe acute respiratory syndrome coronavirus-2 infection diagnosed by PCR and were admitted to our institution from February 2020 to January 2021. Results Primary viral pneumonia, and mixed viral and bacterial pneumonia, accounted for 90.3% and 9.7%, respectively, of COVID-19-associated CAP, with viral coinfection found in 30.5% of patients with primary viral pneumonia. Influenza virus was the most common (9.4%). Multivariable analysis showed coinfection not to be an independent factor of severity on admission, need for high-flow nasal cannula or invasive mandatory ventilation, and mortality. Conclusion Viral coinfection was common in COVID-19-associated CAP. Severity on admission, need for high-flow oxygen therapy or invasive mandatory ventilation, and mortality were not affected by coinfection.

Imaging of Pulmonary Superinfections and Co-Infections in COVID-19

New challenges in imaging and management of COVID-19 pneumonia emerge as the pandemic continues across the globe. These arise not only due to the COVID-19 pneumonia but also related to various superinfections and co-infections. Limited use of bronchoscopic and other aerosol generating procedures to obtain representative lower respiratory samples from these patient groups for accurate identification of organism, increases the responsibility of radiologists in suggesting the most likely cause of secondary infection. Imaging features of many of these infections overlap with features of COVID-19 pneumonia. In this review, we highlight imaging findings that can aid in the diagnosis of superinfections and co-infections in patients with COVID-19 pneumonia, and also help in predicting the likely causative organism.

Lung ultrasound may support internal medicine physicians in predicting the diagnosis, bacterial etiology and favorable outcome of community-acquired pneumonia

To assess the usefulness of lung ultrasound (LUS) for identifying community-acquired pneumonia (CAP) among adult patients with suspected lower respiratory tract infection (LRTI) and for discriminating between CAP with different cultural statuses, etiologies, and outcomes. LUS was performed at internal medicine ward admission. The performance of chest X-ray (CXR) and LUS in diagnosing CAP in 410 patients with suspected LRTI was determined. All possible positive results for pneumonia on LUS were condensed into pattern 1 (consolidation + / − alveolar-interstitial syndrome) and pattern 2 (alveolar-interstitial syndrome). The performance of LUS in predicting culture-positive status, bacterial etiology, and adverse outcomes of CAP was assessed in 315 patients. The area under the receiver operating characteristic curve for diagnosing CAP by LUS was significantly higher than for diagnosis CAP by CXR (0.93 and 0.71, respectively; p < 0.001). Pattern 1 predicted CAP with bacterial and mixed bacterial and viral etiologies with positive predictive values of 99% (95% CI, 94–100%) and 97% (95% CI, 81–99%), respectively. Pattern 2 ruled out mortality with a negative predictive value of 95% (95% CI, 86–98%), respectively. In this study, LUS was useful in predicting a diagnosis of CAP, the bacterial etiology of CAP, and favorable outcome in patients with CAP.

The microbiota-related coinfections in COVID-19 patients: a real challenge

BACKGROUND

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the cause of ongoing global pandemic of coronavirus disease 2019 (COVID-19), has infected millions of people around the world, especially the elderly and immunocompromised individuals. The infection transmission rate is considered more rapid than other deadly pandemics and severe epidemics encountered earlier, such as Ebola, Zika, Influenza, Marburg, SARS, and MERS. The public health situation therefore is really at a challenging crossroads.

MAIN BODY

The internal and external and resident microbiota community is crucial in human health and is essential for immune responses. This community tends to be altered due to pathogenic infections which would lead to severity of the disease as it progresses. Few of these resident microflora become negatively active during infectious diseases leading to coinfection, especially the opportunistic pathogens. Once such a condition sets in, it is difficult to diagnose, treat, and manage COVID-19 in a patient.

CONCLUSION

This review highlights the various reported possible coinfections that arise in COVID-19 patients vis-à-vis other serious pathological conditions. The local immunity in lungs, nasal passages, oral cavity, and salivary glands are involved with different aspects of COVID-19 transmission and pathology. Also, the role of adaptive immune system is discussed at the site of infection to control the infection along with the proinflammatory cytokine therapy.

[The use of a new semi-quantitative rapid test for procalcitonin in the diagnosis of multisegmental community-acquired pneumonia]

AIM

Evaluation of the possibilities of a new semi-quantitative rapid test for procalcitonin in the diagnosis of multisegmental community-acquired pneumonia.

MATERIALS AND METHODS

A one-stage comparative study involved 123 patients hospitalized in a hospital with a confirmed diagnosis of community-acquired pneumonia. The mean age of the patients was 49.521.0 (MSD) years. On the first day of hospitalization, all patients underwent a general clinical examination, chest x-ray, and a plasma procalcitonin level was determined using a semi-quantitative rapid test.

RESULTS

Indicators of a new semi-quantitative rapid test for procalcitonin of at least 2 ng/ml are directly related to laboratory and instrumental indicators reflecting the severity of community-acquired pneumonia, namely, the severity of respiratory failure (p=0.001), respiratory rate (p=0.001), and heart rate contractions (p=0.001), systolic blood pressure (p=0.025), oxygen saturation (p=0,001), erythrocyte sedimentation rate (p=0.021), fibrinogen (p=0.003) and high CRB-65 scores (p=0.001). They are also associated with multisegmental community-acquired pneumonia (2=4.7; p=0.030) and complications of this disease, such as hydrothorax (p=0.029) and death (2=22.1; p=0.001).

CONCLUSION

Using a new semi-quantitative rapid test for procalcitonin allows you to optimize the diagnosis of complications of community-acquired pneumonia and determine the high risk of multisegmental pneumonia.

Identification of pathogens from the upper respiratory tract of adult emergency department patients at high risk for influenza complications in a pre-Sars-CoV-2 environment

The emergence of SARS-CoV-2 and subsequent COVID-19 pandemic highlights the morbidity and potential disease severity caused by respiratory viruses. To elucidate pathogen prevalence, etiology of coinfections and URIs from symptomatic adult Emergency department patients in a pre-SARS-CoV-2 environment, we evaluated specimens from four geographically diverse Emergency departments in the United States from 2013-2014 utilizing ePlex RP RUO cartridges (Genmark Diagnostics). The overall positivity was 30.1% (241/799), with 6.6% (16/241) coinfections. Noninfluenza pathogens from most to least common were rhinovirus/enterovirus, coronavirus, human metapneumovirus and RSV, respectively. Broad differences in disease prevalence and pathogen distributions were observed across geographic regions; the site with the highest detection rate (for both mono and coinfections) demonstrated the greatest pathogen diversity. A variety of respiratory pathogens and geographic variations in disease prevalence and copathogen type were observed. Further research is required to evaluate the clinical relevance of these findings, especially considering the SARS-CoV-2 pandemic and related questions regarding SARS-CoV-2 disease severity and the presence of co-infections.

Viral respiratory infections: a cause of community-acquired pneumonia or a predisposing factor?

PURPOSE OF REVIEW

A cause for community-acquired pneumonia (CAP) is only identified in ∼50% of cases. Nasopharyngeal PCR panels contain more viruses than previously. The problem then becomes determining the relevance of the organisms identified rather than figuring out which virus is present. This review addresses how to distinguish between viral CAP and bacterial CAP, how viral CAP predisposes to bacterial CAP and some novel antiviral treatment being conducted.

RECENT FINDINGS

The pneumonia severity index has been studied in patients with viral CAP. There are new studies using biomarkers to help determine when antimicrobial treatment is needed in CAP patients, and there is still no consensus. Newer devices are being invented in an effort to separate upper from lower respiratory organisms to make test results more relevant. Several outcome studies in patients with viral CAP are reviewed.

SUMMARY

In addition to clinical correlation, using biomarkers can be useful to distinguish viral from bacterial CAP. Outcomes in patients with a co-infection are generally worse as a viral infection may predispose someone to a bacterial pneumonia. Influenza CAP treatment may be initially accompanied with antimicrobials until a patient's diagnosis is clear (∼48-72 h). Future research is being conducted for antiviral treatment more than for influenza.

Retrospective review analysis of COVID-19 patients co-infected with Mycoplasma pneumoniae

Introduction

Coronavirus disease 2019 (COVID-19) is an extremely infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The outbreak of this virus has resulted in significant morbidity and mortality throughout the world. We have seen an unprecedented spread of this virus, leading to extreme pressure on health-care services. Mycoplasma pneumoniae causes atypical bacterial pneumonia and is known to co-infect patients with viral pneumonias.

Methods

In this retrospective study, patients' data of 580 inpatients with confirmed SARS-CoV-2 infection were reviewed retrospectively over a 3-month period which included the the first peak of COVID-19 infections in the UK.

Results

Eight patients with COVID-19 and M. pneumoniae coinfection were identified - four males and four females. All patients were Caucasian, with an age range of 44-89 years. 37.5% of patients were hypertensive, whereas 25% had Type 2 diabetes mellitus. Dyspnea, cough, and pyrexia were found to be very common in these patients. Majority of the patients had abnormal C-reactive protein, lymphopenia, neutrophilia along with bilateral consolidation, and ground-glass opacities. Two patients required admission to intensive care, both of whom unfortunately died along with one patient receiving ward based care.

Conclusion

Our confirmed the presence of co-infection with M. pneumoniae and describes the clinical features, investigation results, clinical course, and outcomes for these patients. Further research is needed to review the role of procalcitonin in excluding bacterial co-infection and to assess the impact of co-infection of patients with COVID-19 on morbidity and mortality.

Lessons of the month: Co-infection with SARS-CoV-2 and influenza B virus in a patient with community-acquired pneumonia

Why we only infrequently detect or report two or more respiratory viruses co-infecting an adult host is poorly understood. We report a rare case where influenza B and SARS-CoV-2 caused viral pneumonia in a 74-year-old man diagnosed during the UK winter epidemic/pandemic for these organisms and discuss concepts of co-infection.

Influenza virus-mediated suppression of bronchial Chitinase-3-like 1 secretion promotes secondary pneumococcal infection

Infections of the lung are among the leading causes of death worldwide. Despite the preactivation of innate defense programs during viral infection, secondary bacterial infection substantially elevates morbidity and mortality rates. Particularly problematic are co-infections with influenza A virus (IAV) and the major bacterial pathogen Streptococcus pneumoniae. However, the molecular processes underlying the severe course of such co-infections are not fully understood. Previously, the absence of secreted glycoprotein Chitinase-3-like 1 (CHI3L1) was shown to increase pneumococcal replication in mice. We therefore hypothesized that an IAV preinfection decreases CHI3L1 levels to promote pneumococcal infection. Indeed, in an air-liquid interface model of primary human bronchial epithelial cells (hBECs), IAV preinfection interfered with apical but not basolateral CHI3L1 release. Confocal time-lapse microscopy revealed that the gradual loss of apical CHI3L1 localization during co-infection with influenza and S. pneumoniae coincided with the disappearance of goblet as well as ciliated cells and increased S. pneumoniae replication. Importantly, extracellular restoration of CHI3L1 levels using recombinant protein significantly reduced bacterial load in influenza preinfected bronchial models. Thus, recombinant CHI3L1 may provide a novel therapeutic means to lower morbidity and mortality associated with post-influenza pneumococcal infections.

Cascaded deep learning classifiers for computer-aided diagnosis of COVID-19 and pneumonia diseases in X-ray scans

Computer-aided diagnosis (CAD) systems are considered a powerful tool for physicians to support identification of the novel Coronavirus Disease 2019 (COVID-19) using medical imaging modalities. Therefore, this article proposes a new framework of cascaded deep learning classifiers to enhance the performance of these CAD systems for highly suspected COVID-19 and pneumonia diseases in X-ray images. Our proposed deep learning framework constitutes two major advancements as follows. First, complicated multi-label classification of X-ray images have been simplified using a series of binary classifiers for each tested case of the health status. That mimics the clinical situation to diagnose potential diseases for a patient. Second, the cascaded architecture of COVID-19 and pneumonia classifiers is flexible to use different fine-tuned deep learning models simultaneously, achieving the best performance of confirming infected cases. This study includes eleven pre-trained convolutional neural network models, such as Visual Geometry Group Network (VGG) and Residual Neural Network (ResNet). They have been successfully tested and evaluated on public X-ray image dataset for normal and three diseased cases. The results of proposed cascaded classifiers showed that VGG16, ResNet50V2, and Dense Neural Network (DenseNet169) models achieved the best detection accuracy of COVID-19, viral (Non-COVID-19) pneumonia, and bacterial pneumonia images, respectively. Furthermore, the performance of our cascaded deep learning classifiers is superior to other multi-label classification methods of COVID-19 and pneumonia diseases in previous studies. Therefore, the proposed deep learning framework presents a good option to be applied in the clinical routine to assist the diagnostic procedures of COVID-19 infection.

The microbial coinfection in COVID-19

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a novel β-coronavirus, is the main pathogenic agent of the rapidly spreading pneumonia called coronavirus disease 2019 (COVID-19). SARS-CoV-2 infects much more people, especially the elder population, around the world than other coronavirus, such as SARS-CoV and MERS-CoV, which is challenging current global public health system. Beyond the pathogenesis of SARS-CoV-2, microbial coinfection plays an important role in the occurrence and development of SARS-CoV-2 infection by raising the difficulties of diagnosis, treatment, prognosis of COVID-19, and even increasing the disease symptom and mortality. We summarize the coinfection of virus, bacteria and fungi with SARS-CoV-2, their effects on COVID-19, the reasons of coinfection, and the diagnosis to emphasize the importance of microbial coinfection in COVID-19. KEY POINTS: • Microbial coinfection is a nonnegligible factor in COVID-19. • Microbial coinfection exacerbates the processes of the occurrence, development and prognosis of COVID-19, and the difficulties of clinical diagnosis and treatment. • Different virus, bacteria, and fungi contributed to the coinfection with SARS-CoV-2.

Where is Chlamydophila pneumoniae pneumonia?

BACKGROUND

Molecular diagnostic methods have recently gained widespread use, and consequently, the importance of viral pathogens in community-acquired pneumonia (CAP) has undergone re-evaluation. Under these circumstances, the role of Chlamydophila pneumoniae as a pathogen that causes CAP also needs to be reviewed.

METHODS

We reviewed articles that contained data on the frequency of identification of C. pneumoniae pneumonia as a causative pathogen for CAP. The articles were identified by performing a search in PubMed with the keywords "community-acquired pneumonia" and "pathogen".

RESULTS

Sixty-three articles were identified. The reviewed articles demonstrated that the rates of identification of C. pneumoniae as the causative pathogen for CAP were significantly lower in assessments based on polymerase chain reaction (PCR) methods than in those based on serological methods. In some studies, it was possible to compare both serological and PCR methods directly using the same set of samples.

CONCLUSIONS

The use of PCR methods, including multiplex PCR assays, has revealed that C. pneumoniae may play a limited role as a pathogen for CAP.

Influenza sequelae: from immune modulation to persistent alveolitis

Acute influenza virus infections are a global public health concern accounting for millions of illnesses worldwide ranging from mild to severe with, at time, severe complications. Once an individual is infected, the immune system is triggered in response to the pathogen. This immune response can be beneficial ultimately leading to the clearance of the viral infection and establishment of immune memory mechanisms. However, it can be detrimental by increasing susceptibility to secondary bacterial infections and resulting in permanent changes to the lung architecture, in the form of fibrotic sequelae. Here, we review influenza associated bacterial super-infection, the formation of T-cell memory, and persistent lung injury resulting from influenza infection.

Multicenter Evaluation of the BioFire FilmArray Pneumonia/Pneumonia Plus Panel for Detection and Quantification of Agents of Lower Respiratory Tract Infection

The ability to provide timely identification of the causative agents of lower respiratory tract infections can promote better patient outcomes and support antimicrobial stewardship efforts. Current diagnostic testing options include culture, molecular testing, and antigen detection. These methods may require collection of various specimens, involve extensive sample treatment, and can suffer from low sensitivity and long turnaround times. This study assessed the performance of the BioFire FilmArray Pneumonia Panel (PN panel) and Pneumonia Plus Panel (PNplus panel), an FDA-cleared sample-to-answer assay that enables the detection of viruses, atypical bacteria, bacteria, and antimicrobial resistance marker genes from lower respiratory tract specimens (sputum and bronchoalveolar lavage [BAL] fluid). Semiquantitative results are also provided for the bacterial targets. This paper describes selected analytical and clinical studies that were conducted to evaluate performance of the panel for regulatory clearance. Prospectively collected respiratory specimens (846 BAL and 836 sputum specimens) evaluated with the PN panel were also tested by quantitative reference culture and molecular methods for comparison. The PN panel showed a sensitivity of 100% for 15/22 etiologic targets using BAL specimens and for 10/24 using sputum specimens. All other targets had sensitivities of ≥75% or were unable to be calculated due to low prevalence in the study population. Specificity for all targets was ≥87.2%, with many false-positive results compared to culture that were confirmed by alternative molecular methods. Appropriate adoption of this test could provide actionable diagnostic information that is anticipated to impact patient care and antimicrobial stewardship decisions.

Influenza and Bacterial Coinfection in Adults With Community-Acquired Pneumonia Admitted to Conventional Wards: Risk Factors, Clinical Features, and Outcomes

Background

Relevance of viral and bacterial coinfection (VBC) in non-intensive care unit (ICU) hospitalized adults with community-acquired pneumonia (CAP) is poorly characterized. We aim to determine risk factors, features, and outcomes of VBC-CAP in this setting.

Methods

This is a prospective cohort of adults admitted to conventional wards with CAP. Patients were divided into VBC-CAP, viral CAP (V-CAP), and bacterial CAP (B-CAP) groups. Independent risk and prognostic factors for VBC-CAP were identified.

Results

We documented 1123 episodes: 57 (5.1%) VBC-CAP, 98 (8.7%) V-CAP, and 968 (86.1%) B-CAP. Patients with VBC-CAP were younger than those with B-CAP (54 vs 71 years; P < .001). Chronic respiratory disease was more frequent in patients with VBC-CAP than in those with V-CAP (26.3% vs 14.3%%; P = .001). Among those with influenza (n = 153), the VBC-CAP group received empirical oseltamivir less often (56.1% vs 73.5%; P < .001). Patients with VBC-CAP also had more respiratory distress (21.1% VBC-CAP; 19.4% V-CAP, and 9.8% B-CAP; P < .001) and required ICU admission more often (31.6% VBC-CAP, 31.6% V-CAP, and 12.8% B-CAP; P < .001). The 30-day case-fatality rate was 3.5% in the VBC-CAP group, 3.1% in the V-CAP group, and 6.3% in the B-CAP group (P = .232). Furthermore, VBC-CAP was associated with severity criteria (odds ratio [OR], 5.219; P < .001) and lack of empirical oseltamivir therapy in influenza cases (OR, 0.401; P < .043).

Conclusions

Viral and bacterial coinfection-CAP involved younger patients with comorbidities and with poor influenza vaccination rate. Patients with VBC-CAP presented more respiratory complications and more often required ICU admission. Nevertheless, 30-day mortality rate was low and related either to severity criteria or to delayed initiation of oseltamivir therapy.

Type I interferons are important co-stimulatory signals during T cell receptor mediated human MAIT cell activation

Mucosal associated invariant T (MAIT) cells are abundant unconventional T cells that can be stimulated either via their TCR or by innate cytokines. The MAIT cell TCR recognises a pyrimidine ligand, derived from riboflavin synthesising bacteria, bound to MR1. In infection, bacteria not only provide the pyrimidine ligand but also co-stimulatory signals, such as TLR agonists, that can modulate TCR-mediated activation. Recently, type I interferons (T1-IFNs) have been identified as contributing to cytokine-mediated MAIT cell activation. However, it is unknown whether T1-IFNs also have a role during TCR-mediated MAIT cell activation. In this study, we investigated the co-stimulatory role of T1-IFNs during TCR-mediated activation of MAIT cells by the MR1 ligand 5-amino-6-d-ribitylaminouracil/methylglyoxal. We found that T1-IFNs were able to boost interferon-γ and granzyme B production in 5-amino-6-d-ribitylaminouracil/methylglyoxal-stimulated MAIT cells. Similarly, influenza virus-induced T1-IFNs enhanced TCR-mediated MAIT cell activation. An essential role of T1-IFNs in regulating MAIT cell activation by riboflavin synthesising bacteria was also demonstrated. The co-stimulatory role of T1-IFNs was also evident in liver-derived MAIT cells. T1-IFNs acted directly on MAIT cells to enhance their response to TCR stimulation. Overall, our findings establish an important immunomodulatory role of T1-IFNs during TCR-mediated MAIT cell activation.