Lower Respiratory Bacterial Infections

1. Lower respiratory bacterial infectionsaetiology, diagnosis Dr.T.V.Rao MD Dr.T.V.Rao MD

2. Upper respiratory system Nose, pharynx, associated structures Purpose: to take in, warm and moisten air Most common site of infections Lower respiratory system Larynx, trachea, bronchi, alveoli Purpose: ventilation, gas exchange Respiratory system environment is diverse Dr.T.V.Rao MD

3. Anatomy of the respiratory system (and sites of infection) Dr.T.V.Rao MD

4. Acute Infection: Fever, chills Back pain, myalgias, arthralgias Headache, malaise, chills Nausea, vomiting Chest Infection: Cough Chest pain Rales, wheezing, noisy chest Characteristic changes on chest x-rays Increasing respiratory distress, may require mechanical ventilation Clinical Presentation: Lower respiratory Tract Infection Dr.T.V.Rao MD

5. Pneumonia is the sixth leading cause of death in US Increasing numbers of patients at risk Ageing population Increase in patients with immunocompromising conditions Lower Respiratory Tract InfectionsEpidemiology

6. Diagnosis depends on clinical presentation and age too • Most of these cases diagnosis depends on clinical presentation and minimum laboratory and radiologic investigations may be needed most of these cases recovered smoothly with appropriate management unless an underlying lung pathological or systemic disease may worsen the condition or continue with chronicity appropriate follow-up of these patients in OPC is appreciated especially after discharge from hospital Dr.T.V.Rao MD

7. LOWER RESPIRATORY TRACT • Infections of the lower respiratory tract are the leading cause of cause of mortality world wide. Streptococcus pneumoniae is the leading bacterial agent of community acquired pneumonia along with Haemophilus influenzaand Moraxella catarrhalis Dr.T.V.Rao MD

8. Pneumococcus a significant pathogen • Pneumococcus is the most common bacterial pathogen causing febrile pneumonia in children and adults • The clinical syndromeis characteristic and distinctive : acute onset of high, spiking fever, with chills, cough, and sputum production Dr.T.V.Rao MD

9. Categories of Lower Respiratory Tract Infections • Acute bronchitis • Community acquired pneumonia • Hospital acquired pneumonia • Pneumonia in the immunocompromised host Dr.T.V.Rao MD

10. Community Acquired PneumoniaEtiologic Agents Dr.T.V.Rao MD Carroll KC. 2002. J Clin Microbiol 40:3115-3120. Sharp SE, et.al. Cumitech 2003

11. Specimen collection: • The patient should be standing, If possible or sitting upright in bed. • He or she should take deep breath to full the lungs, and empty then in one breath, coughing as hard and as deeply as possible. • Sputum brought up should be spit into screw capped container. • Visually inspect the specimen. • Tighten the cap of the container and send immediately to lab. Dr.T.V.Rao MD

12. Sputum collection • Sputum of less than 2ml should not be processed unless obviously purulent • Only 1 sputum per 24hr .submitted • Some scoring system should be used to reject specimen that re oral contamination. Dr.T.V.Rao MD

13. Transportation in <2 hr is recommended with refrigeration if delays anticipated. Handle all samples using universal precautions. Perform Gram stain and plant specimen as soon as possible Transportation of sputum Dr.T.V.Rao MD

14. Induced sputum Patients who are unable to produce sputum may be assisted by respiratory therapy technician. Aerosol induced specimen are collected by allowing the patient to breath aerosolized droplets of a solution of 15% sodium chloride and 10% glycerin for approximately 10 minute obtaining such specimen may avoid the need for a more invasive procedures ,such as bronchoscopy or needle aspiration, in many cases. Dr.T.V.Rao MD

15. Microscopic examination of Gram-stained smear Acceptable <1% of cells present are squamous epithelial cells Unacceptable >1% of cells present are squamous epithelial cells Bronchoalveolar Lavage (BAL) Specimen Acceptability Thorpe JE et. al. 1987. Bronchoalveolar lavage for diagnosing acute bacterial pneumonia. J. Infect. Dis. 155:855-861 Dr.T.V.Rao MD

16. Sputum collected under supervision of nurse or resident Samples were processed immediately Screened for epithelial cells Screened for predominant morphotype (> 75% of the organisms seen) Sputum planted to blood agar, chocolate agar and MacConkey agar Strictly defined clinical and diagnostic parameters Methods of collection is important.. Dr.T.V.Rao MD

17. Microscopic Examination • Prepare a gram stain smear for all lower respiratory tract specimens to determine the presence of oropharyngeal contamination (indicated by squamous epithelial cells) and lower respiratory tract secretions (indicated by WBCs) as well as to identity the most likely pathogens (Indicated by the predominant organisms associated with WBCs). Dr.T.V.Rao MD

18. Good quality specimens Quantify number and types of inflammatory cells Note presence of bronchial epithelial cells Concentrate on areas with WBCs when looking for organisms Determine if there is a predominant organism (> 10 per oil immersion field) Semiquantitate and report organism with descriptive If no predominant organism is present, report “mixed gram positive and gram negative flora” Sputum Gram Stain Dr.T.V.Rao MD

19. Proponents Demonstration of predominant morphotype on Gram stain guides therapy Accuracy is good when strict criteria are used Cheap, so why not? Antagonists Poor specimen collection Intralaboratory variability (Gram stain interpretation) Low sensitivity and specificity Empiric treatment guidelines Do much dependence ??? Sputum Gram Stain is helpful - yes Dr.T.V.Rao MD

20. Overall sensitivity and specificity for pneumococcal pneumonia: 57% and 97% Overall sensitivity and specificity for H. influenza pneumonia: 82 % and 99% Gram stain gave presumptive diagnosis in 80% of patients who had a good specimen submitted > 95% of patients in whom a predominant morphotype was seen on Gram stain received monotherapy Studies prove ... Dr.T.V.Rao MD

21. Be as descriptive as possible Moderate neutrophils Moderate Gram positive diplococcic suggestive of Streptococcus pneumoniae Few bacteria suggestive of oral flora Keep report short—avoid line listing of all morphotypes present Report gram staining with caution Dr.T.V.Rao MD

22. Squamous Epithelial Cells • If no squamous epithelial cell are found, report “ No epithelial cells seen” • If only a few epithelial cells are found report “ Few epithelial cells seen” • If abundant epithelial cells seen, indicating oropharyngeal contamination, such specimens are graded as unsatisfactory sample. Dr.T.V.Rao MD

23. Reporting the presence of leucocytes: • If no WBC are found report “No WBCs seen” • If WBCs are present in any amount state as few, moderate or numerous WBCs seen. Dr.T.V.Rao MD

24. INTERPRETATION OF GRAM STAIN: • None Few Moderate Numerous Squamous epithelial cells/ LPF*0 1-9 10-24 >25 • Neutrophils/LPF* 0 1-9 10-24 >25 Dr.T.V.Rao MD

25. Gram staining – reporting microbial observations • Type / Number of organisms / HPF** • Gram-positive cocci • Gram-negative cocci • Gram-negative rods • Gram-positive rods • PF*: (low power field) x 10 (examine 10-20 fields) • HPF**: (high power field) oil immersion Dr.T.V.Rao MD

26. Processing specimens for culture • Process specimens in biological safety cabinet, as aerosol can result in laboratory-squired respiratory infections. • Process all specimens as rapidly as possible, especially specimen from emergency department, and inpatients. Select the most purulent or most blood-tinged portion of the specimen. Significant growth above the cutoff should be reported; however if more than one pathogen is isolated than it is suggestive of oropharyngeal contamination and clinical correlation should be done before reporting the samples. Dr.T.V.Rao MD

27. Choosing culture Media: • Sheep Blood Agar • MacConkey agar • Chocolate agar Dr.T.V.Rao MD

28. Routine culture • Most of the commonly sought etiologic agents of lower respiratory tract infection will isolated on routinely used media : 5% sheep blood agar ,MacConkey agar for isolation and differentiation of gram-negative bacilli ,and chocolate agar for Neisseria spp and Haemophilus . Dr.T.V.Rao MD

29. Because of contaminating oral flora ,sputum specimens, specimens obtained by bronchial washing, and lavage tracheostomy, or endotracheal tube aspirates are not inoculated to enriched broth or incubated anaerobically. Only specimens obtained by percutaneous aspiration (including trans tracheal aspiration )and by protected bronchial brush are suitable for anaerobic culture: he latter must be done quantitatively for proper interpretation. Contamination with oral flora interferes results Dr.T.V.Rao MD

30. Sputum specimens from patients known to have cystic fibrosis should be inoculated to selective agar ,such as manitol salt agar for recovery of S .aureus and selective horse blood-bacitracin ,incubated anaerobically and aerobically ,for recovery of H,influenzae that may be obscured by the mucoid P,aeroginosa on routine media. Culturing specimens from cystic fibrosis Dr.T.V.Rao MD

31. Identify and perform susceptibility testing on 2-3 potential pathogens seen as predominant on Gram stain Alpha strep—rule out S. pneumoniae Yeast—rule out Cryptococcus neoformans only S. aureus, Gram negative bacilli < normal flora, quantify and limit ID; no susceptibility Add comment that organism not predominant on stain ID mould, Mycobacteria or Nocardia spp. Modified from Sharp SE, et. Al. 2003. Cumitech 7B. ASM Press. Sputum and Endotracheal SuctionCulture Evaluation Dr.T.V.Rao MD

32. Dilution Method Quantify each morphotype present and express as CFU/ml Calibrated Loop Method Quantify each morphotype present and express as log10 colony count ranges Thresholds for significance PSB > 103 CFU/ml BAL > 104 CFU/ml Baselski and Wunderink. 1994. ClinMicro Rev 7:547 Interpretation of Quantitative PSB/BAL Dr.T.V.Rao MD

33. Examine for and always report. • Streptococcus pyogenes • Group B streptococci in pediatric population • Francisella tularensis • Bordetella spp., especially Bordetella bronchiseptica • Yersinia pestis • Nocardia spp. • Bacillus anthracis • Cryptococcus neoformans • Molds, not considered saprophytic contaminants • Neisseria gonorrhoeae Dr.T.V.Rao MD

34. Always report, but do not make an effort to find low numbers, unless they are seen in the smear. • Streptococcus pneumoniae • Haemophilus influenzareport beta-lactamase Dr.T.V.Rao MD

35. Report if present in significant amounts, even if not predominant • 1 Moraxella catarrhalis • 2 Neisseria meningitides • Report the following for nosocomial infections: • 3. Pseudomonas aeruginosa • 4. Stenotrophomonas maltophilia • 5. Acinotobacter spp. • 6. Burkholderia spp. Dr.T.V.Rao MD

36. Report if present in significant amount and if it is the predominant organism in the culture, particularly if suggests infection with morphology consistent with isolate. • Staphylococcus aureus • Beta-hemolytic streptococcus B (adults), C, or G • Single morphotype of gram-negative rod (especially Klebsiella pneumoniae) • Fastidious gram-negative rods; usually report beta-lactamase • Corynebacterium spp. if urea positive or from ICU • Rhodococcus equi in immunocompromised patients Dr.T.V.Rao MD

37. Empiric therapy for outpatients Macrolide or tetracycline Hospitalized patients with CAP 2 sets of pre-treatment blood cultures Pleural fluid Gram stain/culture when appropriate Studies for Legionella, Mtb, fungi in select patients Sputum Gram stain/culture only if resistant or unusual pathogen is suspected Avoid extensive testing ATS. 2001. Am J Respir Crit Care Med 163: 1730-1754. ATS GuidelinesDiagnostic Tests for CAP Dr.T.V.Rao MD

38. Criteria for rejecting samples Mismatch of information on the label and the request Inappropriate transport temperature Excessive delay in transportation Inappropriate transport medium • specimen received in a fixative • dry specimen • sample with questionable relevance Insufficient quantity Leakage Dr.T.V.Rao MD

39. Immunocompromised PatientsSuggested BAL Protocol • Aerobic Gram stain quantitative bacterial culture • Fungal stain and culture • Mycobacterial stain and culture • Viral culture/Respiratory DFA • Pneumocystis DFA • Legionella culture Dr.T.V.Rao MD

40. Many other causes of Pneumonia with Acute Respiratory Disease & Fever S.Pneumoniae Legionella TB SARS RICIN toxin Staphylococcal Enterotoxin B Plague Tularemia

41. Respiratory system can host a variety of microbes Normal flora in “restricted areas” Susceptibility depends on age, immune system Some organisms are adept at evading immune system Damage generally due to cytotoxicity and inflammation Vaccines are available for some organisms Summary Dr.T.V.Rao MD

42. HBV1 Childhood Immunizations can reduce respiratory infections – follow the schedules Birth 1m 2m 3m 4m 6m 12m 15m 18m 4-6y 11-12y HBV3 HBV2 DTP DTP DTP DTP Hib Hib Hib Hib Polio Polio Polio MMR MMR or MMR Varicella Varicella

43. Do remember • The culture of lower respiratory specimens may result in more unnecessary microbiologic effort than any other type of specimen.”Raymond C Bartlett Dr.T.V.Rao MD

44. Programme created by Dr.T.V.Rao MD for Medical and Health Workers in the Developing World • Email • doctortvrao@gmail.com Dr.T.V.Rao MD