Introduction:
Moraxella catarrhalis is a gram-negative diplococcus, formerly known as Neisseria catarrhalis or Branhamella catarrhalis that is found in the human upper respiratory tract as normal flora.(1) It colonizes the respiratory tract of a small proportion of adult and larger proportion of children. The genus Moraxella also includes the normal human microflora of the genital tract.(2)
Over the past decade, Moraxella catarrhalis has emerged as an important human pathogen.(3) It is now accepted as the third commonest pathogen of the respiratory tract after Streptococcus pneumoniae and Haemophilus influenzae.(4-5) It is the most common pathogen isolated in childhood acute maxillary sinusitis and acute otitis media. In adults, M. catarrhalis is the second cause after non-typeable Hemophilus influenzae that accounts for 10% of bacterial-mediated exacerbation in patients with chronic obstructive pulmonary disease (COPD). In immuno-compromised hosts, the bacterium can cause a variety of severe infections including pneumonia, endocarditis, septicemia, and meningitis. In addition, hospital outbreaks of respiratory disease due to M.
catarrhalis have been described, now establishing the bacterium as a nosocomial pathogen. Viral damage to respiratory tract epithelium may also promote invasion by Moraxella catarrhalis.(6-7)
Its contribution to the total disease burden brought about by otitis media will increase in the near future, because the routine use of pneumococcal conjugate vaccines is associated with an increase in nasopharyngeal colonization rates and episodes of otitis media caused by Moraxella catarrhalis and other organisms.(8) The emergence of Moraxella catarrhalis as a pathogen together with increasing prevalence of ß-lactamase producing strains has renewed the interest in these bacterial species. The availability of new antimicrobial agents and the evolution of bacterial resistance mechanisms have contributed to changes in the epidemiology and the treatment regimens of infections caused by M. Catarrhalis.(9-10) Hence this study was aimed at determining the prevalence and antibiotic resistance pattern of Moraxella catarrhalis as a pathogen in respiratory tract infections of cancer patients.
Materials and Methods
Study design and setting
This retrospective study (March 2017- April 2018) was conducted in the Division of Microbiology Malabar cancer centre, Thalassery, Kannur. Patients of all age groups, suspected of RTI recorded in microbiology registers were included in the study. The study was approved by Institutional Review Board (IRB), MCC. A total of 355 respiratory samples data were analysed, out of which 100 respiratory samples data showing meaningful growth were taken for the study. Laboratory data showing Respiratory tract infections with predominantly gram-negative diplococci and heavy growth of M. catarrhalis in culture in the absence of other respiratory pathogens were included for the study.
The isolates were identified by gram staining method and conventional biochemical methods. Antibiotic susceptibility testing was done by Kirby-Bauer disc diffusion technique. To differentiate Moraxella from other Gram negative cocci, special biochemical test like Catalase, Nitrate reduction, Oxidase, Sugar Fermentation, DNase, Rapid Carbohydrate utilization, Hydrolysis of Tributyrin were performed.
Result
Out of the total 100 meaningful respiratory samples, 124 respiratory pathogen were isolated. Among 124 isolates 19 (15.3%) were Moraxella catarrhalis. Other bacterial isolates were as follows: Pseudomonas aeruginosa 17 (13.7%), Klebsiella pneumoniae 17 (13.7%), Escherichia coli 14 (11.2%), Acinetobacter baumanii 10(8.0%), Streptococcus spp 10 (8.0%), Staphylococcus spp 9 (7.2%), Candida albicans 8 (6.4%), Staphylococcus aureus 7 (5.6%) and others 13 (10.4%) (Table 1).
| Table 1: Profile of Respiratory Pathogens isolated (N=124) |
| Bacterial isolate |
Number (%) |
Klebsiella pneumoniae |
17 (13.7%) |
Staphylococcus aureus |
7 (5.6%) |
Pseudomonas aeruginosa |
17 (13.7%) |
Streptococcus spp. |
10 (8.06%) |
Acinetobacter baumanni |
10 (8.06%) |
Escherichia coli |
14 (11.29%) |
Candida albicans |
8 (6.45%) |
Moraxella catarrhalis. |
19 (15.3%) |
Staphylococcus spp |
9 (7.25%) |
Others |
13 (10.48%) |
The rate of isolation of M. catarrhalis was more in males 60.7%, compared with females showing 39.3%. The differences noted in the distribution of pathogens among the sexes were significant. Moraxella infection were predominately seen in elderly age group (>60 years old) (Table 2).
| Table 2: Age wise distribution of patients with Moraxella catarrhalis (N=19) |
| Age |
Number of patient |
0-10 |
0 |
11-20 |
0 |
21-30 |
0 |
31-40 |
1 (5.2%) |
41-50 |
2 (10.5%) |
51-60 |
3 (15.78%) |
>60 |
13 (68.4%) |
In our study, the susceptibility pattern of M. catarrhalis showed that all the isolates were more susceptible to Amoxycillin-clavulanic acid (57.8%), followed by Chloramphenicol (50.1%) [Table 3.]
| Table 3: Antibiotic sensitivity pattern of Moraxella catarrhalis (N=19) |
Antibiotic |
Sensitive (n %) |
Resistant (n %) |
Amoxyclav |
11 (57.8%) |
8 (42.2%) |
Ceftazidime |
5 (26.3%) |
14 (73.7%) |
Ampicilin |
7 (36.8%) |
12 (63.2%) |
Co-trimaxazole |
7 (36.8%) |
12 (63.2%) |
Chloramphenicol |
10 (50.1%) |
9 (47.4%) |
Cefixime |
10 (52.6%) |
9 (47.4%) |
Levofloxacin |
6 (31.6%) |
13 (68.4%) |
| Table 4: Underlying pulmonary pathology in patients with Moraxella infection (N=19) |
| Pulmonary pathology |
Number (%) |
COPD |
2 (10.5%) |
Pulmonary tuberculosis |
4 (21.0%) |
Lung carcinoma |
9 (47.3%) |
Bronchiectasis |
2 (10.5%) |
Pneumonia |
2 (10.5%) |
Pulmonary causes for Moraxella infections in this study were COPD 2 (10.5%), old pulmonary tuberculosis 4 (21.0%), carcinoma of lung 9 (47.3%), Bronchiectasis 2 (10.5%), and Pneumonia 2 (10.5%) (Table 4). History of smoking was present in 11 (57.9%) patients. Other co- morbidities were diabetes mellitus, hypertension etc.
Discussion
Global increase in the prevalence of Moraxella catarrhalis has drawn our attention to this commensal of upper respiratory tract as an important cause of respiratory infections for last 20–30 years, because it was indistinguishable from commensal Neisseria by gram stain and also difficult to distinguish by colony morphology. In the present study the isolation rate of Moraxella catarrhalis is 15.3%. This finding correlates with the study of Tamang et al.(9)
The emergence of M. catarrhalis as a pathogen, together with the increasing prevalence of ß-lactamase producing strains, has renewed interest in this bacterial species. The underlying risk factors which were associated with M. catarrhalis infections were studied. Age was a critical determinant of the pathogenic significance of the isolates of M. catarrhalis. With advancing age, the pathological significance of the isolates becomes greater. Studies have shown that the elderly are at an increased risk of respiratory tract infections which are caused by M. catarrhalis when compared to the young adults.
In our study the rate of isolation of Moraxella from Lung carcinoma was 47.3%. Different studies have proved the age of the patient as a critical determinant of the pathogenic significance of the isolate (7), current study also denotes that the incidence of M. catarrhalis was maximum in patients above 60 yrs of age. Among 19 (15.3%) isolates of Moraxella catarrhalis, 60.7% were from males and 39.3% from female patients. Previous studies had implicated Haemophilus influenzae, Staphylococcus aureus, Streptococcus pneumoniae, Klebsiella pneumoniae, and Streptococcus pyogenes as the main common bacterial pathogens for RTIs.(2,3) Our findings were in harmony with these studies, in terms of Pseudomonas aeruginosa 17 (13.7%), Klebsiella pneumoniae 17 (13.7%), Escherichia coli 14 (11.2%), Acinetobacter baumanii 10(8.0%), Streptococcus spp 10 (8.0%), Staphylococcus spp 9 (7.2%), Candida albicans 8 (6.4%), Staphylococcus aureus 7 (5.6%) and others 13 (10.4%).
Most important factor being considered is the increase in production of beta-lactamase in Moraxella catarrhalis. A European study done in 2002 showed that 98% of specimens produced beta-lactamase. Many treatment failures with Ampicillin or Amoxicillin are due to the production of this enzyme. In our study 63.1% of isolates were resistance to Ampicillin. However they were sensitive to Amoxicillin clavulanic acid (57%) followed by Chloramphenicol (50%). This data indicates that the antibiotic susceptibility of Moraxella catarrhalis is similar to other recent studies.(10) Amin et. al, found that the most active antibiotic for Moraxella catarrhalis were Amoxycillin-clavulanate, Ceftriaxone, and Levofloxacin (100%) and the least active was Ampicillin.(10) Ahmad et. al, reported Ampicillin resistance in 66.7% strains of Moraxella catarrhalis, they however found all the strains to be sensitive to amoxycillin-clavulanate.(7)
When we observe the sensitivity and resistance pattern, the highest resistance was already anticipated for Ampicillin, but observing resistance with similar percentage to azithromycin and Levofloxacin is alarming. With more definite results, we need to review the drug susceptibility in our region, hence prescribing the more sensitive drug at an earlier phase of infection and improving the outcome of our patients.
Conclusion
Moraxella catarrhalis has now been rediscovered as a pathogen. In terms of clinical significance, it clearly comes third in the respiratory tract after Streptococcus pneurnoniae and Haemophilus influenza. Respiratory tract infection in patients with immuno- compromised nature is the best known example of its clinical impact, but the potential of the organism to cause nosocomial infection is less well recognized.
Despite the limited number of isolates used in the study, minimal antibacterial resistance was present. Keeping in mind the increasing prevalence of patient being infected with Moraxella catarrhalis in our region, a larger scale research should be conducted to evaluate resistance pattern of Moraxella catarrhalis. In view of the ß-lactamase- positivity rate observed in our study, antibiotic such as amoxicillin are not appropriate for treatment if this organism is considered to be the cause of infection. Continued surveillance of antimicrobial susceptibility pattern and application of control measures against further transmission are required to decrease the emergence of the resistant strains.
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