| Abstract|| |
Background: Moraxella catarrhalis is gaining significance as a pathogen over few decades because of increased rate of isolation in respiratory specimens and due to emergence of multidrug resistant strains. Therefore, appropriate antimicrobial agents are required for eradication and prevention of spread of the organism. Material and Methods: -The study was conducted over 1-year period inpatients of lower respiratory tract infections (L.R.T.I.) in P.G.I.M.S. Rohtak (Haryana) . Assessment of clinical significance of M.catarrhalis was ascertained on the basis of preformed criteria. Results: A total of 63 clinically significant M. catarrhalis were isolated from a tertiary care hospital. The isolates showed maximum resistance to cotrimoxazole (82.5%), pencillin (77.7%), and ampicillin (71.4%) while susceptibility was maximum to cefotaxime (87.3%) followed by tetracycline (85.7%) ciprofloxacin (84.1%), erythromycin (80.9%) amikacin (79.3%), gentamycin (77.7%), and cefazolin (76.2%). Multidrug resistance to >3 antimicrobials was seen in 22 (34.9%) of cases. Conclusions: Predominant or pure growth of M.catarrhalis in throat swabs from cases of L.R.T.I. should be reported and treated by microbiologist and clinician respectively. Antibiotic therapy should be decided based on sensitivity report for rapid respose and recovery of patients.
Keywords: Moraxella catarrhalis , opportunistic pathogens, respiratory pathogens
|How to cite this article:|
Gupta N, Arora S, Kundra S. Moraxella catarrhalis as a respiratory pathogen. Indian J Pathol Microbiol 2011;54:769-71
| Introduction|| |
Moraxella More Details catarrhalis (Branhamella catarrhalis) , an aerobic gram negative diplococcus is frequently found as a commensal of upper respiratory tract.  But over the last -two to three decades the bacterium has emerged as a genuine pathogen and is now considered as important cause of upper respiratory tract infections in otherwise healthy children and elderly people and lower respiratory tract infections particularly in patients with chronic obstructive pulmonary disease (COPD).  Studies have shown that M. catarrhalis binds to the major basement membrane glycoprotein that is thickened in airways of smokers. M. catarrhalis is currently recognized as the third most frequent cause of acute otitis media and acute sinusitis in young children. ,, M. catarrhalis along with Haemophilus influenzae has been recognized as important cause of community acquired respiratory infections including community acquired pneumonia, acute exacerbation of chronic bronchitis, acute sinusitis, and acute otitis media. 
Recently, increased isolation as well as rise in the drug resistant strains of M. catarrhalis has renewed our interest to assess the role of M. catarrhalis in respiratory-tract infections and its antibiotic profile which is absolutely essential for determining effective therapy.
| Materials and Methods|| |
All the patients presenting during the 1-year period with one or more clinical findings suggestive of respiratory tract infection such as wheezing, stridor, rales or crackles, tachypnea, thoracic retractions, or decreased breath sounds constituted the study group. Early morning samples were plated on 5% sheep blood agar and MacConkey medium. The isolated M. catarrhalis were identified by gram stain, colony morphology, lack of pigmentation of colony on blood agar, oxidase production, failure to produce acid from glucose, maltose, lactose, and sucrose, growth at 22°C on nutrient agar and finally reduction of nitrate to nitrite. 
Assessment of pathogenic significance of isolates of M. catarrhalis was based on four predetermined criteria (1) clinical examination of respiratory infection based on history, examination, and chest X-ray, (2) isolation of M. catarrhalis as the sole potential pathogen, (3) Absence of antibiotic treatment in the previous two weeks, and (4) subsequent clinical response to an antibiotic to which the isolate was sensitive. Isolates were considered to be of pathogenic significance when all four criteria were satisfied.
| Results|| |
A total of 63 M. catarrhalis of pathogenic significance were isolated in pure growth. Out of 63 cases 49 (77.7%) were males and 14 (22.2%) females [Table 1]. The isolates showed maximum resistance to cotrimoxazole (82.5%), penicillin (77.7%), and ampicillin (71.4%) while susceptibility was maximum to cefotaxime (87.3%) followed by tetracycline (85.7%) ciprofloxacin (84.1%), erythromycin (80.9%) amikacin (79.3%), gentamycin (77.7%), and cefazolin (76.2%) [Table 2].
Multidrug resistance to >3 antimicrobials was seen in 22 (34.9%) of cases [Table 3].
| Discussion|| |
Clinical interest in M. catarrhalis is recently recognized, still majority of laboratories do not report M. catarrhalis as a pathogen, especially when a well-recognized pathogen (e.g., Streptococcus pneumoniae or H. influenzae) is present in the clinical specimen. In addition, the isolation of M. catarrhalis from sputum is complicated by the presence of nonpathogenic Neisseria More Detailse.  It is extremely important to realize that the M. catarrhalis carriage rate in children is high (up to 75%). ,, In contrast, the carriage rate of M. catarrhalis in healthy adults is very low (about 1% to 3%).  Interestingly, nasopharyngeal carriage rates are significantly higher in winter and autumn than in spring and summer. 
M. catarrhalis is now considered an important pathogen in respiratory tract infections, both in children and in adults with underlying COPD. Local factors such as mucociliary clearance, aerodynamics, alveolar macrophage activity, complement-mediated killing, and surfactant activity play an important role in host defense against oropharyngeal pathogens.  In COPD patients, local host defense against respiratory pathogens is relatively poor, and since M. catarrhalis is not a normal inhabitant of the upper respiratory tract in adults infections caused by M. catarrhalis are frequent in these patients.  Similarly in our study >50% of clinically significant Moraxellae was isolated from more than 50 years age group.
In our study, out of 63 patients from which M. catarrhalis was isolated 77.7% were males and 22.25% were females. Others, have reported that in respiratory tract infections 60% of M. catarrhalis were isolated from males and 40% from females. 
In our study, resistance to penicillin was 77.7%. This penicillin resistance is due to two types of ß-lactamases: The BRO-1 and BRO- 2 types. Both are membrane associated, and they differ by only a single amino acid. These enzymes are encoded by chromosomal genes and these genes can be relatively easily transferred from cell to cell by conjugation. , These ß-Lactamases from M. catarrhalis not only protects the bacteria, but also inactivate penicillin therapy of concomitant infections by serious airway pathogens such as S. pneumoniae and/or nontypeable H. influenzae.,,, Recent studies from Australia, Europe, and the United States have reported ß-lactamase production in over 90% of isolates. ,,,,,,
In our study, we only focused on pure isolates; however, in clinical microbiology practice it is important to realize that an additional important organism can also be isolated in about 40% to 50% of sputum cultures like S. pneumoniae or H. influenzae. ,,,[ 28] It is important to define the role of M. catarrhalis in such mixed infections, particularly with respect to the adequate management of patients with specific antibiotic therapy.
In our study, resistance to cotrimoxazole is 82.5%, which practically excludes it as therapeutic option; on the other hand sensitivity to tetracycline seems to be good (85.7%). However, because of frequent side effects and various other options available like cephalosporins, macrolides and fluoroquinolones, tetyracyclines are rarely used. In our study resistance to ciprofloxacin is 16.8% while others have reported 0-1% resistance. , Overall, in our study 34.9% M. catarrhalis are multidrug resistant as shown in [Table 3], which indeed warrants reporting clinically significant M. catarrhalis. Therefore, we emphasize the ignorance of M. catarrhalis as a pathogen in respiratory tract and advice laboratories and clinicians to recognize report and treat it appropriately with antibiotics based on sensitivity to avoid therapeutic failure and serious consequences.
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Deputy Director, Zoonosis Divison, National Center for Disease Control (NCDC), 22 Shamnath Marg, Delhi
Source of Support: None, Conflict of Interest: None
[Table 1], [Table 2], [Table 3]