Clinical profile and microbiological aetiology diagnosis in adult patients hospitalized with community-acquired pneumonia

Microbiology of Severe Community-Acquired Pneumonia and the Role of Rapid Molecular Techniques

The microbiology of severe community acquired pneumonia (SCAP) has implications on management, clinical outcomes and public health policy. Therefore, knowledge of the etiologies of SCAP and methods to identify these microorganisms is key. Bacteria including Streptococcus pneumoniae, Staphylococcus aureus and Enterobacteriaceae continue to be important causes of SCAP. Viruses remain the most commonly identified etiology of SCAP. Atypical organisms are also important etiologies of SCAP and are critical to identify for public health. With the increased number of immunocompromised individuals, less common pathogens may also be found as the causative agent of SCAP. Traditional diagnostic tests, including semi-quantitative respiratory cultures, blood cultures and urinary antigens continue to hold an important role in the evaluation of patients with SCAP. Many of the limitations of the aforementioned tests are addressed by rapid, molecular diagnostic tests. Molecular diagnostics utilize culture-independent technology to identify species-specific genetic sequences. These tests are often semi-automated and provide results within hours, which provides an opportunity for expedient antibiotic stewardship. The existing literature suggests molecular diagnostic techniques may improve antibiotic stewardship in CAP, and future research should investigate optimal methods for implementation of these assays into clinical practice.

Evaluation of the BioFire FilmArray Pneumonia Panel Plus to the Conventional Diagnostic Methods in Determining the Microbiological Etiology of Hospital-Acquired Pneumonia

Hospital-acquired pneumonia (HAP) is a substantial public health issue that is associated with high mortality rates and is complicated by an arsenal of microbial etiologies, expressing multidrug-resistant phenotypes, rendering relatively limited therapeutic options. BioFire FilmArray Pneumonia Panel plus (BFPP) is a simple multiplexed PCR system that integrates sample preparation, nucleic acid extraction, amplification, and analysis of microbial etiology, with a turnaround time of about one hour. In comparison to standard culture methods, BFPP is simpler, easier to perform, and can simultaneously detect the most common pathogens involved in lower respiratory tract infections (34 targets). Accordingly, we evaluated the diagnostic performance of the multiplexed BFPP for the rapid detection of 27 clinically relevant respiratory pathogens and 7 genetic markers among 50 HAP cases admitted to the intensive care unit (ICU), who submitted mini-bronchoalveolar (mBAL) specimens. In comparison to standard culture methods, BFPP showed an overall sensitivity of 100% [95% CI; 90-100] and overall specificity of 90% [95% CI; 87.4-92.5] among all the tested bacterial targets. BFPP identified 11 viral targets (22%) among the tested specimens. The BFPP semi-quantitative analysis showed a concordance rate of 47.4% among positive culture specimens. For the investigation of the antibiotic resistance genes, BFPP showed a positive percent agreement (PPA), a negative percent agreement (NPA), and an overall percent agreement (OPA), reaching 97% [95% CI; 90-100], 95% [95% CI; 91.5-97], and 95% [95% CI; 93-97], respectively, with standard antibiotic sensitivity testing. In conclusion, BFPP has the potential to enhance the rapid microbiological diagnosis of HAP cases, and could aid in tailoring appropriate antibiotic therapies.

Multiplex polymerase chain reaction detection of Streptococcus pneumoniae and Haemophilus influenzae and their antibiotic resistance in patients with community-acquired pneumonia from southwest Iran

BACKGROUND

This study aimed to evaluate the occurrence of Streptococcus pneumoniae and Haemophilus influenzae in sputum of patients with community-acquired pneumonia (CAP) using culture and multiplex polymerase chain reaction (M-PCR) methods and to survey the antibiotic resistance patterns of aforesaid isolates.

RESULT

In total, 23.9 % (n = 22/92) of sputum samples showed positive results in the culture method. S. pneumoniae and H. influenzae were isolated from 15 (16.3 %) and 7 (7.6%) samples, respectively. Using M-PCR, 44 (47.8 %) samples were positive for S. pneumoniae and H. influenzae. Of these, S. pneumoniae and H. influenzae were detected in 33 (35.8%) and 11 (11.9%) of the sputum samples, respectively. The sensitivity, specificity, and accuracy rates of PCR in detection of S. pneumoniae in comparison with culture method were 100, 76.6, and 83.6%, respectively. While, the sensitivity, specificity, and accuracy rates of PCR in detection of H. influenzae in comparison with culture method were 100, 95.3, and 95.8%, respectively. Out of 11 isolates of H. influenzae, two strains confirmed as H. influenzae type b (Hib) and 3 isolates were type f. However, 6 isolates were non-typable. The co-trimoxazole and amoxicillin/clavulanate were the less effective antibiotics against S. pneumonia and H. influenzae, respectively. Ceftriaxone with 13.3% resistance rates was the most effective antibiotic against S. pneumoniae, while, clarithromycin, ceftriaxone, and gentamicin with resistance rates of 28.6% for each one were the most effective chemicals against H. influenzae isolates.

CONCLUSION

In this study, the prevalence of S. pneumoniae was more than H. influenzae using culture and M-PCR methods. The M-PCR provided better efficiency in detecting the bacterial agents in CAP patients compared to culture method. This method can improve the early detection of pathogens contributed to CAP. The drug resistant S. pneumoniae and H. influenzae indicated the need to develop a codified monitoring program to prevent further spread of these strains.

Bacterial Membrane Vesicles in Pneumonia: From Mediators of Virulence to Innovative Vaccine Candidates

Pneumonia due to respiratory infection with most prominently bacteria, but also viruses, fungi, or parasites is the leading cause of death worldwide among all infectious disease in both adults and infants. The introduction of modern antibiotic treatment regimens and vaccine strategies has helped to lower the burden of bacterial pneumonia, yet due to the unavailability or refusal of vaccines and antimicrobials in parts of the global population, the rise of multidrug resistant pathogens, and high fatality rates even in patients treated with appropriate antibiotics pneumonia remains a global threat. As such, a better understanding of pathogen virulence on the one, and the development of innovative vaccine strategies on the other hand are once again in dire need in the perennial fight of men against microbes. Recent data show that the secretome of bacteria consists not only of soluble mediators of virulence but also to a significant proportion of extracellular vesicles—lipid bilayer-delimited particles that form integral mediators of intercellular communication. Extracellular vesicles are released from cells of all kinds of organisms, including both Gram-negative and Gram-positive bacteria in which case they are commonly termed outer membrane vesicles (OMVs) and membrane vesicles (MVs), respectively. (O)MVs can trigger inflammatory responses to specific pathogens including S. pneumonia, P. aeruginosa, and L. pneumophila and as such, mediate bacterial virulence in pneumonia by challenging the host respiratory epithelium and cellular and humoral immunity. In parallel, however, (O)MVs have recently emerged as auspicious vaccine candidates due to their natural antigenicity and favorable biochemical properties. First studies highlight the efficacy of such vaccines in animal models exposed to (O)MVs from B. pertussis, S. pneumoniae, A. baumannii, and K. pneumoniae. An advanced and balanced recognition of both the detrimental effects of (O)MVs and their immunogenic potential could pave the way to novel treatment strategies in pneumonia and effective preventive approaches.