Year :
2011
| Month :
April
| Volume :
5
| Issue :
2
| Page :
240 - 241
Full Version
The Prevalence Of Moraxella Catarrhalis
In Lower Respiratory Tract Infections
Published: April 1, 2011 | DOI: https://doi.org/10.7860/JCDR/2011/.1285
ANITA K .B,FASEELA T.S,
NEVILLE FERNANDEZ,CHAITHRA S MALLI,
SRIKARA MALLYA
Dept of Microbiology, AJ Institute of Medical Sciences, Mangalore,
Karnataka, India
Correspondence Address :
Anita.K.B, Nandanvan, Near KUSHE School, Attavara, Mangalore,
Karnataka, India -575001
E-mail id: anitakasargod@yahoo.com, Phone: +91 9945354173
Abstract
The recognition of Moraxella catarrhalis as an important human respiratory tract pathogen, together with the increasing prevalence of beta lactamase producing strains, has generated much interest in this bacterium. The aim of the present study was to know the prevalence of respiratory tract infections which were caused due to Moraxella catarrhalis, to compare its isolation rates with the common respiratory pathogens and to study its antibiotic susceptibility pattern. Sputum samples were collected from 1402 adult patients with lower respiratory tract infections. The specimens were subjected to gram staining, culturing and antibiotic sensitivity testing. The isolates were identified by their appearance on gram staining and their colony characteristics and their biochemical tests.
The β - lactamse assay ANITA K .B,. FASEELA T S, NEVILLE FERNANDEZ, CHAITHRA S MALLI, SRIKARA MALLYA and antibiotic susceptibility testing were done. A total of 137 Moraxella catarrhalis strains were isolated from 1402 sputum samples (9.8%). The isolation rate of Moraxella catarrhalis alone was 10.2%. The isolation with H. influenzae was 10.9% and with S. pneumoniae, it was 4.16%. The isolation along with both H. influenzae and S. pneumoniae was 30.6%. The antibiotic sensitivity pattern showed only 14% sensitivity to Penicillin, but the sensitivity to Amoxyclav was 100%. There was more than 90% sensitivity to both cefotaxime and ceftriaxone. The sensitivity to erythromycin was 84%, while it was 95% to both tetracycline and chloramphenicol. β -lactamase production was detected in 86% of the isolates.
Keywords
MORAXELLA CATARRHALIS, RESPIRATORY PATHOGEN
Introduction
Respiratory diseases range in severity from common cold to life threatening illnesses such as Pneumonia. Depending on the part of the respiratory tract which is involved, the infections can be classified as rhinitis, pharyngitis, laryngitis, tracheitis, bronchitis and pneumonia. The aetiological agents which are implicated inrespiratory tract infections could be viral, bacterial, protozoal or fungal. Moraxella catarrhalis was once considered as a nonpathogenic commensal of the upper respiratory tract (2), (7). Now, it is considered as the third commonest pathogen of the respiratory tract after Streptococcus pneumoniae and Hemophilus influenzae (1), (3), (8), (12), (13), (16), (18), (19), (20). Because this organism rarely causes bacteraemia and empyema, the diagnosis is usually based on the findings from the expectorated sputum (4).
Material and Methods
A total of 1402 adult cases with lower respiratory tract infections, with multiple risk factors, were studied. Because Moraxella catarrhalis rarely causes bacteraemia or empyema, the diagnosis is usually based on the findings from the expectorated sputum (4). Sputum samples were taken as the specimens. Only those sputum samples with less than 10 epithelial cells and more than 25 polymorphonuclear leucocytes / low power field were studied (12). A gram stained sputum sample which shows a predominance of gram negative diplococci is highly predictive of the presence of Moraxella catarrhalis (23). In the absence of reliable and clinically useful serological tests, the gram staining of sputum remains the corner stone of the diagnosis. Indeed, this is the single most useful diagnostic test which can be used in establishing the lower respiratory tract infections which are caused by Moraxella catarrhalis (5), (23). The specimens were subjected to gram staining, culturing and antibiotic sensitivity testing. The culturing was done on 5% sheep blood agar and chocolate agar. The isolates were identified by their appearance on gram staining and by their colony characteristics and their biochemical tests. The β - lactamse assay was done by the iodometric method and antibiotic susceptibility testing was done by the Kirby Bauer disc diffusion method.
Results
A total of 137 Moraxella catarrhalis strains were isolated from 1402sputum samples (9.8%). Out of the 1402 samples, 801 isolates were of H. infuenzae and S. pneumoniae (57.1%) and 464 isolates were of other pathogens (33.1%) (Table/Fig 1).
The isolation rate of Moraxella catarrhalis alone was 10.2%. The isolation with H. influenzae was 10.9% and with S. pneumoniae, it was 4.16%. The isolation along with both H. influenzae and S. pneumoniae was 30.6% (Table/Fig 2).
The incidence of M.catarrhalis was 68% in patients of ages above 50 years. The study of the antibiotic sensitivity pattern showed only 14% sensitivity to Penicillin, but it showed 100% sensitivity to Amoxyclav. There was more than 90% sensitivity to both cefotaxime and ceftriaxone. The sensitivity to erythromycin was 84%, while it was 95% to both tetracycline and chloramphenicol. β -lactamase production was detected in 86% of the isolates.
Discussion
Moraxella catarrhalis which was for long considered as a commensal, has of late gained importance as a pathogen which causesrespiratory disease, especially lower respiratory tract infections in adults. Although the cexacerbation of chronic bronchitis is the commonest manifestation of the infection with Moraxella catarrhalis, pneumonia may also occur (10). More recently, it has been recognized as a nosocomial respiratory tract pathogen (14), (15). Evidence to prove the pathogenecity of Moraxella catarrhalis includes its presence as the predominant organism in the gram staining of the sputum of patients with chronic obstructive pulmonary disease. In the absence of reliable and clinically useful serological tests, the gram staining of sputum remains the corner stone of diagnosis. Indeed, this is the single most useful diagnostic test which can be used in establishing the lower respiratory tract infections which are caused by Moraxella catarrhalis (5), (23). The clinical improvement on treatment with appropriate antibiotics in patients with suspected moraxella infections and presence of specific antibodies in the sera of patients with Moraxella catarrhalis infection are the other evidences to prove the pathogenecity of M. catarrhalis. In our study, we isolated Moraxella catarrhalis from 137 patients. Pure growth of Moraxella catarrhalis was seen in 10.2% of the specimens and a majority of the isolates were found in association with S. pneumoniae and H. influenzae (30.6%).
The antibiotic sensitivity patterns showed a high level of resistance to Penicillin. This is because of a rapid increase in the prevalence of the β- lactamase producing strains of Moraxella. In our study, 86% isolates were β- lactamase producers as was seen in several studies across the world (21), (22), (24). The β- lactamase activity of M. catarrhalis is inhibited by β- lactam inhibitors like clavulanic acid and salbactum (23). This is reflected in the fact that our isolates were 100% sensitive to the amoxycillin -clavunilic acid combination. Antimicrobial susceptibility among community acquired respiratory tract infections in the respiratory surveillance programme study showed a more or less similar study pattern (19), (20) It has been demonstrated in vitro, that M. catarrhalis BRO enzymes can confer protection from β - lactam antibiotics to other co-existing respiratory pathogens residing in the host. This phenomenon which is referred to as the ‘indirect pathogenicity’ of M catarrhalis, may lead to antibiotic failure when treating a mixed infection containing both susceptible bacteria and resistant M. catarrhalis strains (6), (8), (9), (10), (12), (17), (23) . All these factors put together, with a great increase in the proportion of strains which produce β – lactamase, makes it necessary for the incidence of M. catarrhalis to be reported when seen both in isolation and when it is coexisting with other pathogens. This will help in prescribing the appropriate antibiotics and will also help in combating the infections by other pathogens, which may otherwise be protected by β- lactamase which is produced by M. catarrhalis.
Conclusion
Moraxella catarrhalis is finally being recognized as an important cause of human disease. It is a significant cause of respiratory tract infections in adults with underlying lung disease. The emergence of antibiotic resistance in M. catarrhalis suggests that the incidence of these infections may continue to rise.
Reference
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