Document Type : Original Article
Authors
Department of Clinical & amp; Chemical Pathology, Faculty of Medicine, Sohag university, Sohag, Egypt
Abstract
Highlights
Conclusion
This study found that smokers, males, having CAP with an underlying COPD and presenting with non-productive cough, and GIT and neurological manifestation should be conside-red for Legionella infection. Whereas, patients hospitalized for more than 10 days, who acquired HAP should be suspected for Legionella until prove otherwise.
Keywords
Main Subjects
Introduction
In 1976, an outbreak of severe pneumonia among the participants of the American Legion Convention in Philadelphia led to the description of Legionnaires’ disease. The disease was found to be caused by a bacterial infection(1-3). The causative agent of Legionn-aires’ disease (LD) was named Legionella. This bacteria was found also to cause Pontiac fever(4). Legionella has been thus retrospect-tively recognized as the cause of Legionnaires’ disease outbreaks since 1947(1, 5).
Although L. pneumophila serogroup 1 is the commonest human pathogen of the genus Legionella; it is possible that, under favorable situations, the majority of other species and serotypes are also incriminated in Legionnaires’ disease due to their competency for cellular invasion and intracellular proliferation(6, 7).
Legionellae are aerobic, gram-negative, non-spore-forming bacteria. Legionella spp. are ubiquitous in freshwater habitats, including rivers, lakes, streams, ponds, hot springs, and subsurface waters, and are naturally part of microbial ecosystems. Around 56 distinct Legionella species are encompassing more than 70 serogroups, with nearly half of them have been isolated from clinical specimens, but all species are regarded as possible human pathogens(8-11).
Legionella bacteria are intracellular pathogens; so antimicrobial agents that achieve intra-cellular concentrations higher than the minimal inhibitory concentration (MIC) are effective for their treatment, especially macrolides and quinolones(12). The activities of levofloxacin and azithromycin are similar and both are considered the first-line therapy(13). Patients
with legionnaire disease who do not receive appropriate antibiotics can have bad prognosis and high mortality rate(14).
Legionellosis can be diagnosed with many modalities(15,16). Detection of Legionella in water sources could be used as a predicting risk factor for LD (17). However, it is important to bear several factors in mind. First, we need specific serological tests to diagnose Legionella infection. Second, it is important to escalate the discrepancy between the performances of a test in a research laboratory with what actually can be achieved in a clinical diagnostic laboratory. The substantial inter-laboratory difference has been documented for the ability to culture legionellae. Third, the good interpretation of the diagnostic tests needs a suitable "gold standard”, which is lacked in our situation, where sensitivity and specificity data vary with different comparison standards. Fourth, the utility of diagnostic tests is affected by local Legionella epidemiology. L. pneumophila serogroup 1 is the chief and the most common cause of legionellosis in many areas of the world. However, other species and serogroups are more important in some regions. For example, Legionella longbeachae is a major cause of legionellosis in Australia and New Zealand, where it is often associated with exposure to the potting mix. Infection with this species will not be detected by current urinary antigen tests and will be missed by laboratories that perform serological assays only for L. pneumophila (10, 18, 19).
Advancements in Legionella in vitro diagno-stics are often derived from the application of novel approaches to existing assays or through de novo development of innovative techno-logies. (mass spectrometry and realtime PCR-based TaqMan array cards) and emerging (immunomagnetic separation [IMS], isothermal nucleic acid amplification, high-resolution melt analysis, and wholegenome sequencing [WGS]) techniques that may enhance Legionella detection and characterization in various clinical settings(20, 21). However, data from the developing world
are still scarce(22). In Egypt, the magnitude of legionellosis is not well recognized. Additionally, the few previous studies carried out addressed only L. Pneumophila (23).
Aim of the study
To detect the prevalence of legionella among pneumonia patients in environmental water samples in Sohag University Hospital.
Patients and Methods
Subjects:
This study was conducted on the available number of newly diagnosed patients with pneumonia on environmental water samples taken from 10 water outlets over the period from December 2016 to December 2017 at Sohag University Hospital.
Methods:
The following were done to all subjects:
Ethical consideration:
This research was revised by the Scientific Ethical Committee of Sohag University Hospital. Informed written consent will be taken from all patients
Results
The present study was conducted on 100 subjects to determine the prevalence of Legionella among newly diagnosed pneumonia patients by full clinical examination & radio-logical & laboratory investigations who were attendants of outpatient clinic and inpatient departments of Sohag university hospital. They were 44 males (44%), 3 of them were positive for legionella culture and 56 females (56%), 2 of them were positive for legionella culture. Their age ranged from 26-85 years with mean value 58.04±11.51 years. Table 1 summarizes the demographic and clinical data of the study population.
In our study, we found that Cases with Legionella showed a significantly higher prevalence of neurological manifestations (100% compared to only 21% among Legionella negative cases); need more ICU admission and ventilatory support (100% for both among Legionella positive cases compared to only 49.5% and 51.6% among Legionella negative cases; respectively).
Also, we found that Legionella positive cases are more likely to be males and smokers, being cardiac, having more chest pain or GIT manifestations, higher degrees of dyspnea. However, all these factors showed non-significant differences between the two groups, mostly due to the limited number of legionella positive cases (only 5 cases).
Discussion
Studies about LD are rare in the developing world, and the problem of Legionella is undoubtedly underestimated. Few countries of the world consider LD a notifiable disease, and incidence of L. pneumophila and other species can be obtained, whereas, most other countries have rare data because of lack of diagnostics and surveillance systems. It is worth mentio-ning that the worldwide occurrence of Legionnaires’ disease is challenging to measure and attention should be taken in explanation of the surveillance figures (24, 25).
The diagnosis of Legionella infection can be done by many investigation arrays. Bacterial culture is considered the most specific means, but it is associated with a long time, low sensitivity and technical difficulty. Direct Fluorescent-Antibody (DFA) test is much more rapid than culture, but it has poor sensitivity. Radioimmunoassay, enzyme immunoassay, and latex agglutination can be used for detection of only L.pneumophila (serogroup 1) in urine with moderate sensitivity. Serologic methods are extremely sensitive, but these require a long time to detect seroconversion in patients(26, 27).
So in our study, we use urine culture on Buffered Charcoal Yeast Extract Agar (BCYE) & confirm its results using urine antigen latex agglutination test as a screening test to detect the prevalence of legionella among our pneumonia patients.
In the current study, the mean age of the study population showed no difference between LD positive cases and LD negative ones, which is not agreed on by many previous studies. The fact that we had only 5 LD positive cases may explain these different results.
Similar to many previous reports, our study showed that legionellosis was more common in smokers and male patients. Smoking as a risk factor for legionellosis was found in previous studies(28). Smoking raises the risk of legionellosis by 121% for each pack of cigarettes used up daily. This increased risk is due to the difficulty in eliminating the microorganism from the bronchial tree, due to the worsening of the respiratory mucosa and weakened cilia caused by tobacco smoking that facilitates entry into and subsequent invasion of the alveolar macrophages, depending on the individual’s immune rank (29, 30).
In the current study, diabetes did not seem to be a risk factor for legionellosis, it was in about 20% of cases with legionella only, whereas former studies showed that diabetes was detected in 23-41% of patients (31).
This study found that COPD was a potential risk factor for Legionnaires' disease, found in 3 out of the 5 positive Legionnaires' cases; which agrees with the study of Maniwa et al. who reported that 21% of patients with LD suffered from COPD (32).
In the current study, neurologic symptoms showed significantly higher prevalence and GIT manifestations showed higher but non-significant prevalence among LD cases; seen in 100% of the cases. These manifestations were previously reported in LD, with a prevalence of 50% and 20%; respectively (33).
Regarding ICU and ventilatory support need, our finding showed that 100 % of patients with legionellosis were admitted to ICU and needed ventilatory support, and both were significantly higher among LD positive cases compared to negative ones. This is comparable with other studies (28). This result can be attributed to older age (not seen in our study) and underlying co-morbidity of patients with legionella pneumonia which causes severe disease (34).
References
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