Laboratory records of patients admitted from 2006 through 2012 at R.L. Jalappa hospital, Kolar, Karnataka, were searched for the isolation of Streptococcus pneumoniae (S. pneumoniae) from samples received at the microbiology laboratory such as sputum, blood, pleural fluid, cerebrospinal fluid, peritoneal fluid, pus, conjunctival and ear swabs. All the samples processed were considered for the study. Ethical clearance from the Institutional Ethics committee was obtained before the start of the study. Identification of S. pneumoniae was done by standard methods [7] and antibiotic sensitivity pattern was determined by Kirby-Bauer disc diffusion method using the following antibiotic discs obtained from Hi-Media, Mumbai: Penicillin-G (10 units), Erythromycin (15 mcg), Chloramphenicol (30 mcg), Vancomycin (30 mcg), Linezolid (30 mcg), Tetracycline (30 mcg), Ciprofloxacin (5 mcg), Gentamicin (10 mcg) and Cotrimoxazole (25 mcg). Clinical details of patients from whom S.pneumoniae was isolated, was obtained by reviewing hospital records. The data is presented as frequencies, in tables with percentages, and in the bar chart.

During the period of study, pneumococci were isolated from 34 patients. Twenty one (61.76%) were children and 13(38.24%) were adults. Twenty five (73.5%) were males and 9(26.5%) were females. The different clinical syndromes in which pneumococcus was isolated is presented in [Table/Fig-1]. Both in adults and children, pneumonia and meningitis were the most common conditions from which pneumococcal isolations were made. However, conditions such as primary bacteraemia, conjunctivitis, otitis media and cellulitis were also associated with pneumococcal isolations, but this was only among children.

[Table/Fig-1]:

Clinical conditions coused by S. pneumoniae in different age groups

The isolation rate of pneumococci from different samples is presented in [Table/Fig-2]. S. pneumoniae was isolated from 34 of a total of 37,070 samples. This accounted for an isolation rate of 0.092%. The isolation rate of pneumococci in different samples varied widely from 0.012% to 10% depending upon the type of sample. Among the 34 isolates of pneumococci,14(41.17%) were from body fluids (9 from pleural fluid and 5 from CSF). There were 9(26.47%) isolates from blood: 6(66.66%) of them were obtained from patients who had concurrent pneumonia (secondary bacteraemia) and 3(33.33%) of them from patients with no particular foci of infection (primary bacteraemia). Most of the patients were treated with β-lactam and aminoglycoside antibiotics. The information on the outcome of illness was available only in 20 patients. Out of 20 patients, 18(90%) patients recovered completely after treatment with appropriate antibiotics and 2 (10%) patients expired; one of them died of meningitis and the other of septicaemia.

Antibiogram of the isolates of pneumococci is presented in [Table/Fig-3]. All the isolates (100%) were sensitive to penicillin, erythromycin, chloramphenicol, vancomycin and linezolid. Sensitivity to gentamicin, ciprofloxacin and tetracycline varied from 79.4% to 88.2%. Only 50% of the isolates were sensitive to cotrimoxazole.

Preponderance of a single pattern of resistance was not noticed. Resistance to gentamicin, ciprofloxacin, tetracycline, or cotrimoxazole, was observed among the isolates singly or in combination throughout the study period. However, isolates sensitive to all the antibiotics tested were also encountered throughout the study period. An isolate which was resistant to all the 4 antibiotics: gentamicin, ciprofloxacin, tetracycline and cotrimoxazole, was encountered for the first time in the year 2012.

In this retrospective analysis of pneumococcal infections, as proven by isolation of pneumococci that occurred over aperiod of seven years at a rural tertiary care hospital at Kolar, Karnataka (in southern India), we found that over the years, S. pneumoniae was isolated from 0.092% of the specimens from patients suspected of pneumococcal infections. This means, there were nine pneumococcal isolations for every 10,000 relevant samples processed. The isolation rate from clinical specimens is a reflection of incidence of the disease. This isolation rate is less when compared to other studies in India. A multicentre study from India reported an isolation rate of 2.5% [2]. Another study exclusively conducted among children admitted to hospitals at Bangalore, India, documented an isolation rate of 1.14% [8]. Prior administration of antibiotics is known to reduce the isolation rate of pneumococci [9]. This factor might also have influenced our isolation rate. We could not assess the impact of prior antibiotic administration on the isolation rate, as history of prior antibiotic administration was not consistently recorded in the case sheets. Antigen detection methods will increase the detection rate; however antibiotic sensitivity pattern cannot be determined.

Pneumococcal infections are more common in children and our data also supports this observation [10]. Pneumococci colonize and establish themselves as commensals in the upper respiratory tract of children. When predisposing factors are found, the organisms overgrow and cause conditions such as sinusitis, conjunctivitis and otitis media. The organisms become blood borne when there is a loss of integrity in the mucous membrane of the upper respiratory tract and may cause meningitis and other clinical syndromes which are more common in children [1]. Pneumococcal bacteraemia can be primary or secondary being associated with pneumonia or other focal lesions in the body [1,7]. In our study, 9 patients had bacteraemia. Among them, 3 had primary bacteraemia and 6 were secondary bacteraemic cases.

All the isolates of pneumococci (100%) in our study were sensitive to penicillin, erythromycin, chloramphenicol, vancomycin and linezolid. Resistance to penicillin among pneumococci isolated in India appears to be low; it has been reported to vary between 1 to12% according to different studies [6,11–13]. This contrasts with the situation in neighbouring Southeast Asian countries and Srilanka where the resistance to penicillin is as high as 40 to 70% among the isolates [14]. The low prevalence of penicillin resistance among pneumococci in India is thought to be due to the absence of dissemination of penicillin resistant clones [15]. Our isolates tested were from a rural population and this could explain the high susceptibility to penicillin. However, as we have not determined the minimum inhibitory concentration (MIC) to penicillin, we might have missed the organisms with intermediate resistance to penicillin [2]. As India presents a unique situation with respect to resistance to penicillin, vigilance is required; the spread of the resistant clones from neighbouring countries may pose therapeutic difficulties in treating the patients.

Other studies from India have also recorded low prevalence of pneumococcal resistance to erythromycin and chloramphenicol similar to our observations [6,11,12]. We found that 50% of our isolates were resistant to cotrimoxazole, 20% were resistant to gentamicin, 15% to ciprofloxacin and 12% to tetracycline. Similar prevalence of resistance to these antibiotics has been reported in other studies in India [2,6].

In the recent years, there has been considerable effort in preventing invasive pneumococcal infections using polyvalent pneumococcal vaccines. A conjugate pneumococcal vaccine with a cocktail of antigens from 13 serotypes of pneumococci is available in India [16] and is indicated for use among children, elderly and patients with special risk. We may hope that the burden of invasive pneumococcal infections will be drastically reduced with active vaccination.

The present study from a hospital situated in a rural area of Karnataka shows that pneumococcal infections are relatively less common. Over a period of seven years, 34 isolations of pneumococci were made from patients’ samples. Infections were more common among children than adults. All the strains isolated were sensitive to penicillin as well as to erythromycin, chloramphenicol, vancomycin and linezolid. The resistance pattern to gentamicin, ciprofloxacin and cotrimoxazole were similar to that reported from other studies in India.