Impact of rapid microbiological testing on the management of lower respiratory tract infection

Potential of Nanotechnology-based Formulations in Combating Pulmonary Infectious Diseases: A Current Scenario

BACKGROUND

Pulmonary microbial infection is mainly caused by microbes like atypical bacteria, viruses, and fungi, on both the upper and lower respiratory tracts. One of the demands of the present is the use of nanotechnology-based treatments to fight various lung infections.

AIM

The main aim of the study is to explore all pulmonary infectious diseases and to compare the advanced and novel treatment approaches with the conventional methods which are available to treat infections.

METHODS

This work sheds light on pulmonary infectious diseases with their conventional and present treatment approaches along with a focus on the advantageous roles of nano-based formulations. In the literature, it has been reported that the respiratory system is the key target of various infectious diseases which gives rise to various challenges in the treatment of pulmonary infections.

RESULTS

The present review article describes the global situation of pulmonary infections and the different strategies which are available for their management, along with their limitations. The article also highlights the advantages and different examples of nanoformulations currently combating the limitations of conventional therapies.

CONCLUSION

The content of the present article further reflects on the summary of recently published research and review works on pulmonary infections, conventional methods of treatment with their limitations, and the role of nano-based approaches to combat the existing infectious diseases which will jointly help the researchers to produce effective drug formulations with desired pharmacological activities.

Association between semi-quantitative microbial load and respiratory symptoms among Thai military recruits: a prospective cohort study

BACKGROUND

Multiplex real-time polymerase chain reaction assays have improved diagnostic sensitivity for a wide range of pathogens. However, co-detection of multiple agents and bacterial colonization make it difficult to distinguish between asymptomatic infection or illness aetiology. We assessed whether semi-quantitative microbial load data can differentiate between symptomatic and asymptomatic states for common respiratory pathogens.

METHODS

We obtained throat and nasal swab samples from military trainees at two Thai Army barracks. Specimens were collected at the start and end of 10-week training periods (non-acute samples), and from individuals who developed upper respiratory tract infection during training (acute samples). We analysed the samples using a commercial multiplex respiratory panel comprising 33 bacterial, viral and fungal targets. We used random effects tobit models to compare cycle threshold (Ct) value distributions from non-acute and acute samples.

RESULTS

We analysed 341 non-acute and 145 acute swab samples from 274 participants. Haemophilus influenzae type B was the most commonly detected microbe (77.4% of non-acute and 64.8% of acute samples). In acute samples, nine specific microbe pairs were detected more frequently than expected by chance. Regression models indicated significantly lower microbial load in non-acute relative to acute samples for H. influenzae non-type B, Streptococcus pneumoniae and rhinovirus, although it was not possible to identify a Ct-value threshold indicating causal etiology for any of these organisms.

CONCLUSIONS

Semi-quantitative measures of microbial concentration did not reliably differentiate between illness and asymptomatic colonization, suggesting that clinical symptoms may not always be directly related to microbial load for common respiratory infections.

Value of multiplex PCR to determine the bacterial and viral aetiology of pneumonia in school-age children

BACKGROUND

Conventional methods for the aetiological diagnosis of community-acquired pneumonia (CAP) are often insufficient owing to low sensitivity and the long wait for the results of culture and particularly serology, and it often these methods establish a diagnosis in only half of cases.

AIM

To evaluate the most common bacterial and viral agents in CAP using a fast responsive PCR method and investigate the relationship between clinical/laboratory features and aetiology, thereby contributing to empirical antibiotic selection and reduction of treatment failure.

METHODS

In children aged 4-15 years consecutively admitted with a diagnosis of CAP, the 10 most commonly detected bacterial and 12 most commonly detected viral agents were investigated by induced sputum using bacterial culture and multiplex PCR methods. Clinical and laboratory features were compared between bacterial and viral pneumonia.

RESULTS

In 78 patients, at least one virus was detected in 38 (48.7%) and at least one bacterium in 32 (41%). In addition, both bacteria and viruses were detected in 16 (20.5%) patients. Overall, the agent detection rate was 69.2%. The most common viruses were respiratory syncytial virus and influenza and the most frequently detected bacteria were S. pneumoniae and H. influenzae. PCR was superior to culture for bacterial isolation (41% vs 13%, respectively). Fever, wheezing and radiological features were not helpful in differentiating between bacterial and viral CAP. White blood cell count, CRP and ESR values were significantly higher in the bacterial/mixed aetiology group than in the viral aetiology group.

CONCLUSION

In CAP, multiplex PCR is highly reliable, superior in detecting multiple pathogens and rapidly identifies aetiological agents. Clinical features are poor for differentiation between bacterial and viral infections. The use of PCR methods allow physicians to provide more appropriate antimicrobial therapy, resulting in a better response to treatment, and it may be possible for use as a routine service if costs can be reduced.

Nanotechnological applications for the control of pulmonary infections

Pulmonary infections are the major global problem. According to the global burden of disease study, lower respiratory infections were ranked third among the leading causes of death after ischaemic heart disease and cerebrovascular disease. Despite the availability of treatment options and diagnostic methods, the severity of pulmonary infections is increasing due to the emergence of multiple drug resistance and lack of sensitivity in pathogenic microbes.

In this context, nanotechnology based treatment therapies have emerged as a promising approach to circumvent the limitations of conventional therapies and also manage the problem of drug resistance in pulmonary infections. The present chapter is focused on the global status of existing management strategies of pulmonary infections and their limitations. Moreover, the role of nanotechnology for the management of pulmonary infections with a special reference to different type of nanomaterials has also been discussed.

The role of multiplex PCR test in identification of bacterial pathogens in lower respiratory tract infections

Objectives: Lower respiratory tract infection is one of the most important causes of morbidity and mortality. However establishing a microbial diagnosis for patients with lower respiratory tract infection is still challenging and is often achieved in only half of cases by conventional methods. This study was designed to compare the fast responsive PCR method with the culture method in lower respiratory tract infections and to evaluate the reliability of multiplex PCR method.

Methods: One hundred ninety seven patients with the symptoms of acute lower respiratory tract infection, and diagnosed with community-acquired pneumonia, acute exacerbation of chronic obstructive pulmonary disease and exacerbations of bronchiectasis were included in the study. Both culture and PCR methods was performed for the isolation of most commonly seen bacteria, from sputum, nasopharyngeal swabs and bronchoalveolar lavage fluid samples.

Results: While at least one bacterial isolation was determined in 62 (31.5%) of all patients with culture method, this number increased to 125 (63.5%) with multiplex PCR. The bacteria most commonly identified by PCR were S. pneumoniae (32%) and H. influenzae (31%). There was a significant difference between PCR and culture in terms of multi-factor detection rates (p<0.005). Multiple bacteria were detected in only two cases in cultures; however, multiple pathogens were detected in 47 cases with PCR.

Conclusions: Conventional methods, such as culture and serology are not always adequate to detect the pathogens in lower respiratory tract. Real-time PCR assays proved highly sensitive and rapid. The prevalence of bacteria and multiple agent detected by real-time PCR compared with culture was substantially higher. Widespread use of PCR methods, by providing the immediate and appropriate ''agent specific antibiotic treatment'' of LRTI, will help reduce failure and contributes to a reduction in antibiotic resistance.

The increasing application of multiplex nucleic acid detection tests to the diagnosis of syndromic infections

On 14 January 2013, the US Food and Drug Administration (FDA) announced permission for a multiplex nucleic acid test, the xTAG® Gastrointestinal Pathogen Panel (GPP) (Luminex Corporation, USA), which simultaneously detects 11 common viral, bacterial and parasitic causes of infectious gastroenteritis, to be marketed in the USA. This announcement reflects the current move towards the development and commercialization of detection technologies based on nucleic acid amplification techniques for diagnosis of syndromic infections. We discuss the limitations and advantages of nucleic acid amplification techniques and the recent advances in Conformité Européene - in-vitro diagnostic (CE-IVD)-approved multiplex real-time PCR kits for the simultaneous detection of multiple targets within the clinical diagnostics market.

Microbiological diagnosis of community-acquired respiratory tract infections by nucleic acid detection

BACKGROUND

Microbiological diagnostic procedures have changed significantly over the last decade. Initially the implementation of the polymerase chain reaction (PCR) resulted in improved detection tests for microbes that were difficult or even impossible to detect by conventional methods such as culture and serology, especially in community-acquired respiratory tract infections (CA-RTI). A further improvement was the development of real-time PCR, which allows end point detection and quantification, and many diagnostic laboratories have now implemented this powerful method.

OBJECTIVE

At present, new performant and convenient molecular tests have emerged targeting in parallel many viruses and bacteria responsible for lower and/or upper respiratory tract infections. The range of test formats and microbial agents detected is evolving very quickly and the added value of these new tests needs to be studied in terms of better use of antibiotics, better patient management, duration of hospitalization and overall costs.

CONCLUSIONS

Molecular tools for a better microbial documentation of CA-RTI are now available. Controlled studies are now required to address the relevance issue of these new methods, such as, for example, the role of some newly detected respiratory viruses or of the microbial DNA load in a particular patient at a particular time. The future challenge for molecular diagnosis will be to become easy to handle, highly efficient and cost-effective, delivering rapid results with a direct impact on clinical management.

Minimally Invasive Diagnostic Strategy in Immunocompromised Patients with Pulmonary Infiltrates

Acute respiratory failure (ARF) is the main reason for ICU admission in patients with haematological malignancies. High mortality rates of up to 50% are reported in this situation, and mortality is highest when mechanical ventilation is needed. Rapid and accurate diagnostic methods are needed in these vulnerable patients to ensure the prompt initiation of effective treatment. However, the broad array of possible cause of ARF raises diagnostic challenges. In this review, we discuss the DIRECT strategy, which identifies the most plausible diagnosis in each patient based on the type of immune deficiency and clinical presentation. We will focus on non-invasive laboratory tests developed in recent years, discussing their sensitivity and specificity. We also discuss the usefulness in cancer patients with specific organ dysfunctions of biomarkers introduced over the past few years.

[Diagnostic strategy for acute respiratory failure in patients with haematological malignancy]

INTRODUCTION

About 15% of patients with haematological malignancy develop acute respiratory failure (ARF), necessitating admission to intensive care where their mortality is of the order of 50%.

STATE OF THE ART

The prognosis of these patients is not determined by the pathological characteristics of the malignancy but by the cause of the acute respiratory failure. In effect, the need to resort to mechanical ventilation in the presence of dysfunction of other organs dominates the prognosis. Even if the use of non-invasive ventilation in these patients has reduced the need for intubation and reduced the mortality, its prolonged use in the most severely affected patients prevents the optimal diagnostic and therapeutic management.

PERSPECTIVES

Fibreoptic bronchoscopy with broncho-alveolar lavage (BAL) is considered the cornerstone of aetiological diagnosis but its diagnostic effectiveness is poor, at best 50%, and this has led to increasing interest in high resolution CT scanning and regularly reawakens a transitory enthusiasm for surgical lung biopsy. Furthermore, in hypoxaemic patients, fibreoptic bronchoscopy with BAL may be the origin of the resort to mechanical ventilation, and thus increased mortality. The place of recently developed non-invasive tools is under evaluation. In effect, though the individual performance of diagnostic molecular techniques on sputum, blood, urine or naso- pharyngeal secretions has been established, the combination of these tools as an alternative to BAL has not yet been reported.

CONCLUSION

This review deals with acute respiratory failure in patients with haematological malignancy. It includes a review of the recent literature and considers the current controversies, in particular the risk-benefit balance of fibreoptic bronchoscopy with BAL in severely hypoxaemic patients.

Evaluation and improvement of real-time PCR assays targeting lytA, ply, and psaA genes for detection of pneumococcal DNA

The accurate diagnosis of pneumococcal disease has frequently been hampered not only by the difficulties in obtaining isolates of the organism from patient specimens but also by the misidentification of pneumococcus-like viridans group streptococci (P-LVS) as Streptococcus pneumoniae. This is especially critical when the specimen comes from the respiratory tract. In this study, three novel real-time PCR assays designed for the detection of specific sequence regions of the lytA, ply, and psaA genes were developed (lytA-CDC, ply-CDC, and psaA, respectively). These assays showed high sensitivity (<10 copies for lytA-CDC and ply-CDC and an approximately twofold less sensitivity for psaA). Two additional real-time PCR assays for lytA and ply described previously for pneumococcal DNA detection were also evaluated. A panel of isolates consisting of 67 S. pneumoniae isolates (44 different serotypes and 3 nonencapsulated S. pneumoniae isolates from conjunctivitis outbreaks) and 104 nonpneumococcal isolates was used. The 67 S. pneumoniae isolates were reactive in all five assays. The new real-time detection assays targeting the lytA and psaA genes were the most specific for the detection of isolates confirmed to be S. pneumoniae, with lytA-CDC showing the greatest specificity. Both ply PCRs were positive for all isolates of S. pseudopneumoniae, along with 13 other isolates of other P-LVS isolates confirmed to be non-S. pneumoniae by DNA-DNA reassociation. Thus, the use of the ply gene for the detection of pneumococci can lead to false-positive reactions in the presence of P-LVS. The five assays were applied to 15 culture-positive cerebrospinal fluid specimens with 100% sensitivity; and serum and ear fluid specimens were also evaluated. Both the lytA-CDC and psaA assays, particularly the lytA-CDC assay, have improved specificities compared with those of currently available assays and should therefore be considered the assays of choice for the detection of pneumococcal DNA, particularly when upper respiratory P-LVS might be present in the clinical specimen.

Naso- and oropharyngeal potential respiratory pathogens in adults with nonpneumonic lower respiratory tract infection

The objective of this prospective study was to determine positive isolation rates for potential respiratory pathogens (PRPs) in the naso- and oropharynx of adults hospitalized for nonpneumonic lower respiratory tract infection (NPLRTI), compared with patients with community-acquired pneumonia (CAP) and healthy controls. The study population was 315 non-chronic obstructive pulmonary disease adults hospitalized with febrile lower respiratory tract infection (158 NPLRTI and 157 CAP) and 450 control subjects. Each participant was sampled by oropharyngeal swab, nasopharyngeal swab, and nasopharyngeal washings that were tested by conventional bacteriologic methods to identify PRP. At least 1 of the samples was positive for at least 1 of the 3 PRP bacteria in 55 NPLRTI patients (35%) compared with 51 CAP patients (33%) (NS) and 100 controls (22%) (P = 0.003 compared with NPLRTI and P = 0.02 compared with CAP). Samples were positive for Streptococcus pneumoniae in 14 NPLRTI patients (9%) compared with 29 CAP patients (19%) (P = 0.02) and 16 controls (4%) (NPLRTI P = 0.015, CAP P < 0.0001). The corresponding rates for Haemophilus influenzae were 23 (15%), 16 (10%), and 60 (13%) (NS for all 3 comparisons), and for Moraxella catarrhalis, 28 (18%), 25 (16%), and 48 (11%), respectively (NPLRTI versus controls, P = 0.03, NS other comparisons). We conclude that the rate of positive naso/oropharyngeal isolates for at least 1 of the 3 PRP bacteria in NPLRTI patients is similar to the corresponding rates for CAP patients and is higher in both groups than in controls.

Role of cell culture for virus detection in the age of technology

Viral disease diagnosis has traditionally relied on the isolation of viral pathogens in cell cultures. Although this approach is often slow and requires considerable technical expertise, it has been regarded for decades as the "gold standard" for the laboratory diagnosis of viral disease. With the development of nonculture methods for the rapid detection of viral antigens and/or nucleic acids, the usefulness of viral culture has been questioned. This review describes advances in cell culture-based viral diagnostic products and techniques, including the use of newer cell culture formats, cryopreserved cell cultures, centrifugation-enhanced inoculation, precytopathogenic effect detection, cocultivated cell cultures, and transgenic cell lines. All of these contribute to more efficient and less technically demanding viral detection in cell culture. Although most laboratories combine various culture and nonculture approaches to optimize viral disease diagnosis, virus isolation in cell culture remains a useful approach, especially when a viable isolate is needed, if viable and nonviable virus must be differentiated, when infection is not characteristic of any single virus (i.e., when testing for only one virus is not sufficient), and when available culture-based methods can provide a result in a more timely fashion than molecular methods.

Diagnostic strategy in cancer patients with acute respiratory failure

OBJECTIVE

Nearly 15% of cancer patients experience acute respiratory failure (ARF) requiring admission to the intensive care unit, where their mortality is about 50%. This review focuses on ARF in cancer patients. The most recent literature is reviewed, and emphasis is placed on current controversies, most notably the risk/benefit ratio of fiberoptic bronchoscopy and BAL in patients with severe hypoxemia.

BACKGROUND

Fiberoptic bronchoscopy with bronchoalveolar lavage (BAL) is the cornerstone of the causal diagnosis. However, the low diagnostic yield of about 50%, related to the widespread use of broad-spectrum antimicrobial therapy in cancer patients, has generated interest in high-resolution computed tomography (HRCT) and primary surgical lung biopsy. In patients with hypoxemia, bronchoscopy and BAL may trigger a need for invasive mechanical ventilation, thus considerably decreasing the chances of survival.

DISCUSSION

The place for recently developed, effective, noninvasive diagnostic tools (tests on sputum, blood, urine, and nasopharyngeal aspirates) needs to be determined. The prognosis is not markedly influenced by cancer characteristics; it is determined chiefly by the cause of ARF, need for mechanical ventilation, and presence of other organ failures. Although noninvasive ventilation reduces the need for endotracheal intubation and diminishes mortality rate, its prolonged use in patients with severe disease may preclude optimal diagnostic and therapeutic management. The appropriateness of switching to endotracheal mechanical ventilation in patients who fail noninvasive ventilation warrants evaluation.

CONCLUSION

This review discusses risks and benefits from invasive and non invasive diagnostic and therapeutic strategies in critically ill cancer patients with acute respiratory failure. Avenues for research are also suggested in order to improve survival in these very high risk patients.