The incidence of Legionella pneumophila: a prospective study in a tertiary care hospital in India

Genetic Diversity of the Legionella pneumophila dotA Gene Detected on Surfaces of Respiratory Therapy Equipment

Legionellosis is a neglected disease due to the absence of well-defined clinical symptoms and difficulties in isolating the causal organism. Legionella spp. is known to colonize the lumen of respiratory therapy equipment(RTE) and evade conventional detection by entering the viable but non-culturable state. Monitoring these surfaces for Legionella pneumophila in addition to routine monitoring of water could aid in decreasing incidences of hospital-acquired infections by this pathogen. In this study swabs of different respiratory therapy equipment were tested for the presence of Legionella by conventional culture-based methods versus molecular detection of culture-independent template by polymerase chain reaction (PCR). Genetic diversity of the genes amplified were studied using bioinformatic tools. The dotA genes were genetically diverse indicating no clonality. This communication highlights that the persistence of virulence genes like dotA on abiotic surfaces can result in the mobilization of these genes to other species and give rise to virulent forms especially in a healthcare setting.

Legionella and Legionnaires' disease: Time to explore in India

Legionella pneumophila was first recognised as a fatal cause of pneumonia more than four decades ago, during the 1976-American Legion convention in Philadelphia, USA. Legionella spp. continue to cause disease outbreaks of public health significance, and at present, Legionnaires' disease (LD) has emerged as an important cause of community and hospital-acquired pneumonia. Parallel to this, the understanding of LD has also increased exponentially. However, the disease is likely to be underreported in many countries because of the dearth of common definitions, diagnostic tests and active surveillance systems. In this review, we outline the basic concepts of Legionella including clinical presentations, epidemiology, laboratory diagnosis and the status of LD in India. This article also summarises the progress of research related to Legionella in this country, identifying the research gaps and discussing priorities to explore this unexplored pathogen in India.

Multiplex polymerase chain reaction of genetic markers for detection of potentially pathogenic environmental Legionella pneumophila isolates

Background & objectives:

Genomic constitution of the bacterium Legionella pneumophila plays an important role in providing them a pathogenic potential. Here, we report the standardization and application of multiplex polymerase chain reaction (PCR) for the detection of molecular markers of pathogenic potential in L. pneumophila in hospital environment.

Methods:

Culture of the standard strains of L. pneumophila was performed in buffered charcoal-yeast extract agar with L-cysteine at pH 6.9. Primers were designed for multiplex PCR, and standardization for the detection of five markers annotated to L. pneumophila plasmid pLPP (11A2), lipopolysaccharide synthesis (19H4), CMP-N-acetylneuraminic acid synthetase (10B12), conjugative coupling factor (24B1) and hypothetical protein (8D6) was done. A total of 195 water samples and 200 swabs were collected from the hospital environment. The bacterium was isolated from the hospital environment by culture and confirmed by 16S rRNA gene PCR and restriction enzyme analysis. A total of 45 L. pneumophila isolates were studied using the standardized multiplex PCR.

Results:

The PCR was sensitive to detect 0.1 ng/μl DNA and specific for the two standard strains used in the study. Of the 45 hospital isolates tested, 11 isolates had four markers, 12 isolates had three markers, 10 isolates had two markers, nine isolates had one marker and three isolates had none of the markers. None of the isolates had all the five markers.

Interpretation & conclusions:

The findings of this study showed the presence of gene markers of pathogenic potential of the bacterium L. pneumophila. However, the genomic constitution of the environmental isolates should be correlated with clinical isolates to prove their pathogenic potential. Rapid diagnostic methods such as multiplex PCR reported here, for elucidating gene markers, could help in future epidemiological studies of bacterium L. pneumophila.

Environmental surveillance of Legionella pneumophila in distal water supplies of a hospital for early identification & prevention of hospital-acquired legionellosis

Background & objectives

Legionella pneumophila, a ubiquitous aquatic organism is found to be associated with the development of the community as well as hospital-acquired pneumonia. Diagnosing Legionella infection is difficult unless supplemented with, diagnostic laboratory testing and established evidence for its presence in the hospital environment. Hence, the present study was undertaken to screen the hospital water supplies for the presence of L. pneumophila to show its presence in the hospital environment further facilitating early diagnosis and prevention of hospital-acquired legionellosis.

Methods

Water samples and swabs from the inner side of the same water taps were collected from 30 distal water outlets present in patient care areas of a tertiary care hospital. The filtrate obtained from water samples as well as swabs were inoculated directly and after acid buffer treatment on plain and selective (with polymyxin B, cycloheximide and vancomycin) buffered charcoal yeast extract medium. The colonies grown were identified using standard methods and confirmed for L. pneumophila by latex agglutination test.

Results

About 6.66 per cent (2/30) distal water outlets sampled were found to be contaminated with L. pneumophila serotype 2-15. Isolation was better with swabs compared to water samples.

Interpretation & conclusions

The study showed the presence of L. pneumophila colonization of hospital water outlets at low levels. Periodic water sampling and active clinical surveillance in positive areas may be done to substantiate the evidence, to confirm or reject its role as a potential nosocomial pathogen in hospital environment.

Detection of Mycoplasma pneumoniae and Legionella pneumophila in Patients Having Community-Acquired Pneumonia: A Multicentric Study from New Delhi, India

Atypical pathogens including Mycoplasma pneumoniae and Legionella pneumophila are increasingly recognized as important causes of community-acquired pneumonia (CAP). Mycoplasma pneumoniae accounts for 20-40% of all CAP and L. pneumophila is responsible for 3-15% of cases. The paucity of data from India in this regard prompted us to conduct this prospective multicentric analysis to detect the prevalence of M. pneumoniae and L. pneumophila in our geographical region. A total of 453 patients with symptoms of pneumonia and 90 controls with no history of lower respiratory tract infections were included in the study. A duplex polymerase chain reaction (PCR) targeting 543 bp region of P1 adhesin gene of M. pneumoniae and 375 bp region of macrophage infectivity potentiator (mip) gene of L. pneumophila was standardized for simultaneous detection of these atypical pathogens. Respiratory secretions, blood, and urine samples were collected from each patient and control and were subjected to duplex PCR, culture and serology for M. pneumoniae and L. pneumophila. Urine samples were subjected for detecting L. pneumophila antigen. Among the 453 patients investigated for M. pneumoniae, 52 (11.4%) were positive for IgM antibodies, 17 were positive by culture, and seven tested positive by PCR (P1 gene). Similarly for L. pneumophila, 50 cases (11%) were serologically positive for IgM antibodies, one was positive by PCR (mip gene) and urine antigen detection. A total of eight samples were positive by duplex PCR for M. pneumoniae P1 gene (N = 7) and L. pneumophila mip gene (N = 1). Of the 90 controls, two samples (2.2%) showed IgM positivity, and 15 (16.7%) showed IgG positivity for M. pneumoniae. For L. pneumophila, three samples (3.3%) tested positive for IgM, and 12 (13.3%) tested positive for IgG antibodies. The study findings indicate the presence of M. pneumoniae and L. pneumophila in our geographical region, and a combination of laboratory approaches including PCR, culture, and serology is required for effective detection of these agents.

Application of real-time quantitative polymerase chain reaction assay to detect Legionella pneumophila in patients of community-acquired pneumonia in a tertiary care hospital

Legionella pneumophila is one of the important pathogen responsible for community -acquired pneumonia attributing for 1-5% of cases. Since early and accurate therapy reduces mortality, rapid and reliable diagnostic methods are needed. A total of 134 samples of blood, urine and respiratory tract fluids were collected. Blood was tested for IgG, IgM and IgA antibodies using commercially available kits. A total of 8 (6%) samples were found to be positive for L. pneumophila by quantitative reverse transcription polymerase chain reaction (qRT-PCR), compared to conventional PCR where 6 (4.4%) samples were positive. Serology was positive in a total of 32 (23%) cases though only 3 (2.2%) of the PCR-positive cases were positive by serology as well. These results suggest that real-time PCR can detect Legionella infection early in the course of the disease before serological response develops.

Legionella pneumophila infection associated with renal failure causing fatality in a known case of sarcoidosis

Legionella pneumophila infection may become fatal in immunocompromised state. We report here the first known fatal case from India due to Legionella pneumophila infection complicated by renal failure in a patient undergoing treatment for Sarcoidosis. Sarcoidosis is an idiopathic systemic inflammatory disease involving multiple organs. Urine antigen detection and polymerase chain reaction targeting 16S rRNA gene could help in rapid diagnosis of the infection and thereby start specific therapy. Clinical awareness along with availability of rapid diagnostic tests and institution of specific therapy may reduce morbidity and mortality associated with this infection especially in immunocompromised state.

The bacterial aetiology of adult community-acquired pneumonia in Asia: a systematic review

BACKGROUND

Community-acquired pneumonia (CAP) is a major cause of adult mortality in Asia. Appropriate empirical treatment depends on knowledge of the pathogens commonly responsible. However, assessing the aetiological significance of identified organisms is often difficult, particularly with sputum isolates that might represent contamination with oropharyngeal flora.

METHODS

A systematic review of all adult CAP aetiology studies from Asia, excluding the Middle East, published in English between 1 January 1990 and 1 March 2012 was conducted. Forty-eight studies reporting on 10 423 patients were included, representing data from China, India, Indonesia, Japan, Malaysia, The Philippines, Singapore, South Korea, Taiwan, Thailand and Vietnam. Data from large parts of Asia were unavailable and there was substantial heterogeneity in methodology.

RESULTS

As in western studies, Streptococcus pneumoniae, Mycoplasma pneumoniae, Chlamydophila pneumoniae, Legionella spp. and Haemophilus influenzae were all significant pathogens. However, compared with western studies, S. pneumoniae was of less relative importance. Gram-negative bacilli and Mycobacterium tuberculosis were more important, and in northeast Thailand Burkholderia pseudomallei was a major pathogen.

CONCLUSION

These data have major implications for diagnostic strategies and empirical treatment. Narrow-spectrum antibiotics targeting S. pneumoniae may be inappropriate in many Asian settings, and agents active against TB may lead to partial response and delayed TB diagnosis.