An epidemiological study concerning pneumococcal LRTI in rural parts of Bengal and influence of socioenvironmental parameters on it


Background: Lower respiratory tract infection (LRTI) is a major public health problem. One of the major agents causing community acquired pneumonia is Streptococcus pneumoniae, or pneumococcus. This study was aimed to correlate between socio-environmental parameters and incidence of LRTI (by s0 pneumoniae ) in rural parts of West Bengal. Materials and Methods: A house to house survey was made in a rural community and sputum samples were collected from persons having features of lower respiratory tract infection. The socio-environmental background of the patients were taken in detail. The pneumococci isolated from the samples were tested for antibiotic susceptibility. Results: Out of 947 samples collected, 70 (4.77%) were positive for S pneumoniae. 15.71% were found to be resistant to penicillin. Highest incidence was found to occur in summer months, and in persons living in narrow spaces and in houses polluted with smoke. Conclusion: Although a low percentage of pneumococci were found among the community acquired pneumonia in rural parts of Bengal, many of the strains showed resistance to penicillin and erythromycin. That is a thing for concern in itself. Better living conditions regarding household with proper smoke outlet facility would have a good impact in bringing down the incidence in this area, where people are already burdened with lack of proper facilities for living.

Keywords: LRTI, pneumococci, socioenvironmental parameters

How to cite this article:
Dopthapa YP, Banerjee D, Chakraborty B, Chakraborty B, Ghosh I, Halder D. An epidemiological study concerning pneumococcal LRTI in rural parts of Bengal and influence of socioenvironmental parameters on it. Ann Trop Med Public Health 2015;8:276-9
How to cite this URL:
Dopthapa YP, Banerjee D, Chakraborty B, Chakraborty B, Ghosh I, Halder D. An epidemiological study concerning pneumococcal LRTI in rural parts of Bengal and influence of socioenvironmental parameters on it. Ann Trop Med Public Health [serial online] 2015 [cited 2020 Dec 2];8:276-9. Available from:

Acute respiratory tract infection (ARTI) is considered to be one of the major public health problems and is a leading cause of morbidity and mortality in many developing countries. It is known that community-acquired respiratory tract infection (RTI) is one of the most common reasons for physician visits and antibiotic prescription. [1],[2] Lower RTI (LRTI) includes community-acquired pneumonia and acute exacerbation of chronic obstructive pulmonary disease (COPD). The World Health Organization (WHO) health statistics (2013) show that pneumonia accounts for a whopping 18% of the causes of death in children below 5 years of age. [3] According to WHO, “for every 100 respiratory infections, only 20% require antibiotic treatment – the remaining 80 infections most likely have a viral origin.” [3] Thus, antibacterial therapy should be avoided unless a bacterial cause has been confirmed or is deemed likely. The etiology of LRTI, thereby, plays a significant role in making decisions regarding the treatment. Streptococcus pneumoniae (S. pneumonia) is the most common cause of community-acquired RTI such as otitis media, sinusitis, and pneumonia. [1] Globally, pneumococcal diseases account for one-two million deaths annually in both extremes of age. [2]

Our main aim was to find out the incidence of this pathogen among LRTI cases who reside in rural parts of West Bengal, where the scarcity of money and medicine remains a scourge and poor living conditions prevail. We also wanted to find out the influence of different socioenvironmental parameters, if any, on the occurrence of this disease, and to check the antibiotic susceptibility patterns of the pneumococcal isolates found here.

Materials and Methods

Study area

The study was based on a house-to-house survey as well as patients attending the outpatient department (OPD) in a rural community of Budge Budge II block and LB Dutta Hospital of the block in the district of South 24 Parganas, West Bengal, India. There are 65 villages in the block with a total population of 190,000. Majority of the residents were engaged as daily wage laborers in the government or private sectors and lived in unhygienic and overcrowded conditions.

Sampling and sample size

The multistage random sampling technique was adopted in the study. Out of the 947 study subjects, 22%, i.e., 208 patients were selected from the OPD of LB Dutta Hospital. The rest of the patients, i.e., 739 were selected at the community level through the cluster sampling method. The visits were divided into four phases and in each visit, 10 study subjects from each cluster were selected. Starting in an unbiased manner, households were approached until the desired number of subjects was included/selected from each cluster.

Inclusion criteria

People of all age groups and from both the sexes suffering from acute RTI presented with sore throat, cough with expectoration fever, fast breathing, chest pain, breathing difficulty, and pneumonia for <7 days.

Exclusion criteria

Patients with dry cough due to URTI/tuberculosis (TB)/asthma/COPD/ARTI, patients with comorbidity of diabetes mellitus, patients with human immunodeficiency virus (HIV)/acquired immune deficiency syndrome (AIDS), patients getting steroid, patients with other immune compromised states, patients with any other chronic debilitating illness like congestive cardiac failure (CCF), etc., and the patients receiving antibiotics were excluded from the study.

Data collection

A household list was prepared with the help of accredited social health activist (ASHA) volunteers. Demographic, socioeconomic as well as environmental data, obtained by interviewing the head of each household, were recorded on that structured pro forma. Data were collected for a period of 1 year from September 2012 to August 2013, thus covering all the seasons, i.e., autumn (September to November), winter (December to February), summer (March to May), and rainy (June to August).

Collection and transport of samples

Sputum samples were collected in a disposable, wide-mouthed, screw-capped plastic container. The patient was instructed to spit the coughed material directly into the opened container without spilling over the rim. The cap of the container was screwed up tightly. A thick portion of the sputum was taken in a cotton swab from the container and put into Amies transport medium (M651-500G. HiMedia, Mumbai-400 086, India). The specimen was then taken into the vaccine box at room temperature and transported to the laboratory within 2-3 h.

Laboratory investigation

The samples were processed on the same day. The sputum samples were selected to be cultured by Gram staining [following the rejection criteria of sputum ≥10 squamous epithelial cells (SECs)/ low power field (LPF) and/or acceptance of the specimen if polymorphonuclear leukocyte (PMN): SEC = 10:1] (Lynne S. Garcia. “Clinical Microbiology Procedures Handbook” – Volume 1, 3rd Edition, page The selected sputum samples were homogenized by shaking with sterile water and glass beads for 20-30 min and inoculated in sheep blood agar, chocolate agar (with 5-10% CO 2 ), and MacConkey agar, and after overnight incubation at 37΀C, identification of the organism was done by its colony character, and by hemolysis, Gram stain morphology, and standard biochemical tests.

Identification of microorganisms

Microorganisms were identified by standard methods and antimicrobial susceptibility testing was performed using disk diffusion by Kirby-Bauer method (Bauer et al. 1966) in the same reference laboratory.

Identification of pathogens of S. pneumoniae

Gram stain identification: Gram-positive elongated cocci in pairs or in short chain

Culture media: Blood agar or chocolate agar

Colony: On a blood agar plate, colonies of S. pneumoniae appeared as small, grey, moist (sometimes mucoidal) colonies and characteristically produced a zone of alpha-hemolysis. When the culture aged 24-48 h, the colonies became flattened and the central portion became depressed.

S. pneumoniae was identified by using Gram stain from the colony, catalase (negative), and optochin tests [optochin susceptible (≥14 mm in diameter) with bile (10% sodium deoxycholate) solubility positive].

Antimicrobial susceptibility testing was performed using disk diffusion by Kirby-Bauer method [interpreted as per Clinical and Laboratory Standards Institute (CLSI) guidelines], which corroborates the finding of Etest for penicillin and erythromycin.


Of the 947 samples collected from patients having acute RTI on the day of the visit, 70 (4.77%) were culture positive for S. pneumoniae, 140 (9.54%) for Klebsiella, 71 (4.83%) for Staphylococcus aureus, 83 (5.74%) for  Moraxella More Details, 6 (0.4%) for Haemophilus influenzae) 9 (0.6%) for Enterococcous, 8 (0.67%) for Pseudomonas, 2 (0.13%) for Acinetobacter, 2 (0.13%) for  E.coli, and 1 (.06%) group B Streptococcus. The study population had complaints of RTI.


Regarding the housing conditions of the community, 50.36% were living in brick houses and separate kitchen facilities were available to 46.25% of the study population. Most families lived in overcrowded homes, with an average of 2.5 persons per room. Households with environmental factors present, e.g., indoor air pollution arising from the usage of chullah for cooking purpose and from a tobacco smoker being present in the family, exhibited a significantly higher incidence of pneumococcal infection (P < 0.01). Interestingly enough, overcrowding by itself did not show any relation to the incidence of RTI by S. pneumoniae as maximum number of pneumococcal RTI patients enjoyed an average of >4.65 m 2 area per person, the highest area parameter found in the study group selected.

Similarly, the maximum number of pneumococcal cases was in persons living in brick houses rather than the ones living in soil-made houses or unfinished brick houses. Having a toilet had no significance either.

On the contrary, as expected, persons living in narrow spaces showed a higher incidence of pneumococcal RTI (and LRTI due to other pathogens also) than those living in open airy rooms. Having a kitchen within the living room especially had a direct bearing on the disease, particularly when the indigenous method of cooking/chullah was used. Tobacco smoking in the house was also associated with higher incidence of the disease. Hence, a narrow, non-airy space with insufficient outlet for smoke, whether from the kitchen or from tobacco smoking seems to be the important socioenvironmental factor in the epidemiology of this disease [Table 1].

Table 1: Socio-environmental data of the study population

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The incidence of pneumococcal RTI among males was 55.71% and among females 44.28%. So, there was no significant difference in the incidence between males and females.

The most serious infections of S. pneumoniae occur in children who are less than 3 years and in adults who are over 65 years. [4],[5] In our study, the incidence of pneumococcal RTI varied according to age, being higher among the 0-18 years age group [Table 2].

Table 2: Age group wise distribution of LRTI cases caused by S pneumoniae

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The incidence of pneumococcal infection was highest in the summer months in our study. However, other studies have depicted a definite peak in pneumococcal disease incidence in the winter months. These studies were from developed countries, where a possible major risk factor for catching pneumococcal LRTI is a dip in mercury. In our country, especially in the area we took up for survey, the winter months are pleasant while the summer months are dusty with high levels of pollution, possibly leading to our finding of an increase in the incidence of the disease in the hot, sultry months of the year [Table 3].

Table 3: Seasonal variation over one year study period

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A major concern about S. pneumoniae is the emergence of antimicrobial resistance, especially to penicillin. [6],[7],[8] Recent studies by the Centre for Disease Control and Prevention (CDC) National Surveillance System indicated a decreased susceptibility pattern to penicillin ranging 15-35%. Apart from showing resistance to penicillin and cephalosporin, pneumococcal coresistance to several other antimicrobial agents, including macrolides, sulfonamides, and tetracyclines, have been reported. [9],[10],[11],[12] In an international study published in 2004, macrolide resistance was the highest in Asia (51.7%). We found a 15.71% resistance to penicillin and 20% resistance to erythromycin in our study [Table 4].

Table 4: Antibiotic resistance pattern of isolated Streptococcous pneumoniae

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Our study in the rural parts of Bengal showed a 4.77% incidence of pneumococcal LRTI. The younger age group (0-18 years) was found to bear the maximum brunt. The definite environmental risk factors were found to be indoor air pollution (by smoke) and living in narrow spaces. Interestingly, the incidence of the infection, as found by us, was highest during the summer months, in clear contrast to other studies in which the incidence peaked in winter. Although a low percentage of pneumococci were found in community-acquired pneumonia in the rural parts of Bengal, many of the strains showed resistance to penicillin and erythromycin. That is a matter of concern in itself. Better living conditions regarding household with proper smoke outlet facility would have a good impact in bringing down the incidence in this area, where people are already burdened with the lack of proper facilities for living.


We thank the Indian Council of Medical Research (ICMR) for funding and other support to carry out this project.

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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/1755-6783.162671


[Table 1], [Table 2], [Table 3], [Table 4]

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