Moraxella Catarrhalis Respiratory Infection in Adults
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MORAXELLA CATARRHALIS RESPIRATORY INFECTION IN ADULTS N K Chin, G Kumarasinghe, T K Lim ABSTRACT Moraxella catarrhalis (MC) is an upper respiratory tract commensal which may also be pathogenic. In this report we examined the clinical features, microbiology and therapeutic response in 30 consecutive adult patients with pneumonia who had MC isolated in the sputum. The mean age was 66 years with an equal sex ratio. Most patients gave a history of cigarette smoking (77%) and had underlying pulmonary diseases (73%). Dyspnea and productive cough were the most common complaints (87%). Fever was a manifestation in 60% of patients. Chest X-ray features of pneumonia were noted in 78% of patients while leucocytosis (>II,000/mm3) was evident in 70%. While all isolates were susceptible to tetracycline, 70% were resistant to penicillin/ampicillin by in -vitro testing. Three patients died, two from their underlying illnesses and one front myocardial infarct. We believe that MC isolated in sputum cultures from symptomatic adults with underlying respiratory diseases should be treated as a pathogen. The short term prognosis is good. Keywords : Moraxella catarrhalis, respiratory infection. SINGAPORE MED .1 1993; Vol 34: 409-411 INTRODUCTION biology laboratory, National University Hospital. Only spu- Moraxella catarrhalis (MC), a gram -negative diplococci, was tum specimens with > 25 white blood cells and < 25 epithelial first described in 1896. It was initially known as Micrococcus cells per low power field on microscopic examination were or Neisseria catarrhalis and was considered to be a harmless studiedttl. All sputum samples were then inoculated onto both upper respiratory tract commensalft, but subsequently gained blood and chocolate agar plates and incubated overnight at recognition as an important pathogen. It was renamed 37°C under aerobic conditions with added 5% CO2. Pure or Branhamella catarrhalis in the 1970s, and in 1990, Moraxella predominant growth of MC was considered to be significant. catarrhalis"[. The features used for its identification in our laboratory are It is the third most common pathogen following Ilemophilus listed in Table I19í. Antibiotic susceptibility testing was per- injluenzae and Streptococcus pneumoniae in causing adult lower formed by the Kirby -Bauer disc diffusion technique" respiratory tract infection°, childhood sinusitis and otitis me- Case -notes were then traced from the Medical Record Of- lts capacity to produce beta-lactamase, first noted in fice, and patients with definite pneumonia were identified. 1977, may cause penicillin resistance in mixed infection by The definition of pneumonia was taken to be the presence of protecting other pathogens usually susceptible to beta-lactam any two of the following features: chest X-ray (CXR) infil- antibiotics. Being a non -fastidious organism, it can survive in trates, leucocytosis (> 11,000/mm3), cough productive of pu- dried sputum for up to 27 days, therefore making nosocomial rulent sputum or fever. The following patient data were col- spread possible. The short-term mortality in some patient pop- lected: name, sex, age, smoking history, underlying lung ulation may be as high as 45%tQ7i. condition(s), underlying systemic disease(s), presenting com- In this report, we examined the clinical features, microbi- plaints, relevant clinical findings, CXR appearance, total white ology and therapeutic response in 30 patients with acute lower cell and differential count, sputum and blood culture results respiratory tract infections who had MC isolated in their sputa. and antibiotic sensitivity, treatment given and response, and the eventual outcome. MATERIALS AND METHOD Pneumonia was considered to be community -acquired if Consecutive patients with sputum cultures that grew MC be- there were no hospital admissions in the previous 3 weeks and tween March 1989 to April 1991 were traced from the micro - nosocomial if it developed after 3 or more days of hospital stay. Patients less than 12 years of age were excluded from the study. Department of Medicine National University Hospital RESULTS Lower Kent Ridge Road During the two-year period, there were 30 adult patients with Singapore 0511 significant growth of MC from their sputa and clinical evi - N K Chin, MBBS, M Med (Int Med) Registrar Table I - Laboratory characteristics used in the identification of M. catarrhalis T K Lint, MBBS, M Med ant Med), DAMS Assoc. Professor Colonial morphology non -pigmented, opaque. smooth, Department of Microbiology does not adhere to agar National University Hospital Growth on Nutrient agar positive G Kumarasinghe. MBBS (Ceylon), MRC Path (UK) Gram -stain Gram negative diplococci Consultant Microbiologist Oxidase positive Correspondence to : Dr T K Lim Dcoxyribonuclease (DNAase) positive Pulmonary and Critical Care Medicine University of Michigan Medical Center Nitrate reduction test positive 3916 Traubman, Ann Arbor Sugar fermentation test with Michigan glucose, maltose, lactose States United of America and sucrose negative 409 Fig I - Age distribution of the 30 patients with M. Fig 2 - In -vitro antibiotic susceptibility testing of M. eatarrhalis pneumonia. catarrhati.s isolated front 30 sputum samples. 12 60 70% 10- 60 z 4- 40 - 20 - rn CI) rn rn rn rn M V N CO I CO O O O O O O Age (yrs) CO N CO n CO dente of pneumonia. The sex distribution was equal. Most of them were elderly (77% were > 60 years old), with a mean E age of 66 years (range 33-84 years) (Fig 1). There were 87% Chinese and 13% Malays. Most of them (77%) were current or ex -smokers. to he an upper respiratory tract commensal. However, with Most of the patients (73%) had some form of underlying better characterisation of the organism (Table I) and greater pulmonary diseases, consisting of chronic obstructive pulmo- awareness of its pathogenicity, more cases have been described nary disease (COPD), bronchial asthma, bronchiectasis, recently. Hager et al presented the findings in 6 cases of MC bronchogenic carcinoma (CA), previous pulmonary tuberculo- pneumonia and reviewed the literature describing 429 case sis (PTB) and pulmonary fibrosis, in various combinations. from 26 studies of MC bronchopulmonary infections in 1987u'í. Some of them had co -existing systemic illness as well. Of the In a large series of 42 cases of MC pneumonia described by remaining eight patients without underlying lung problems, Paul et al in 1990(6), an increase in the number of cases in the six had either hypertension, diabetes mellitus, ischaemic heart last few years was noted. There was a higher rate of malnutri- disease, chronic renal failure, rheumatic heart disease or CA tion among the patients who were elderly and they and a esophagus; four of them also smoked cigarettes. higher mortality rate. Our data are very similar to theirs in that The incidence of community -acquired pneumonia was 83%. our patients were also elderly, frequently with underlying lung The most common presenting complaint was cough produc- or systemic diseases. These patients had clinical evidence of tive of sputum (87%), followed by progressively increased pneumonia, with cough productive of purulent sputum and shortness of breath. Eighteen patients were febrile on admis- progressively worsening dyspnea, sometimes associated with sion. fever. The most common presentation of MC pneumonia was Of the 26 patients who had CXR done, 58% showed evi- hence an infective exacerbation of chronic obstructive pulmo- dence of bronchopneumonia, 20% definite lobar pneumonia, nary disease or bronchiectasis. Increased morbidity and mor- 22% with features consistent with underlying COPD, PTB tality rates were related to the underlying illness and old age. with fibrocalcific changes or pulmonary fibrosis. Total white Chest X-ray changes are non-specific, which may he lobar cell count was raised to more than 11,000 x 105/L in 70% of or bronchopneumonic, sometimes reflecting changes consist- patients (mean 13,300 x 10ó/L), with polymorph predominance.+ ent with underlying long-standing cardio-pulmonary disease. Seventeen patients who had blood cultures taken showed no Infective infiltrates, if present, are non-cavitatory1óií. bacteremia. None of the seventeen patients who had blood cultures In -vitro antibiotic testing demonstrated that 70% of the performed had bacteria isolated from the blood. This is proba- MC isolates were resistant to the penicillin group, 13% were bly a reflection of the mildness of MC pneumonia and con- resistant to co-trimoxazole, 13% resistant to cephalexin, 3% to trasts with gram -negative pneumoniae which are often associ- erythromycin but none to tetracycline (Fig 2). We did not test ated with bacteraemiau'í. This observation confirms our earli- for the production of beta-lactamase. er experience with bacteraemic sepsis in which MC was not Sixteen patients were treated with ampicillin/penicillin, of identified in 200 positive blood cultures"Jt. Total white counts whom 9(56%) responded. The seven non -responders were sub (TWC) are usually mildly to moderately elevated, with sequently given erythromycin or intravenous (i/v) cephalosporin polymorph predominance. In this study, the mean TWC was with good results. Twelve patients responded to their first -line 13,300 x 106/L; only two patients had a TWC of more than antibiotics : ten were given i/v ceftriaxone, one co-trimoxazole 21,000 x 106/L. One-third of the patients had normal TWC and one ciprofloxacin. Two patients did not receive any treat- despite clinical evidence of infection. ment, one recovered