Bacteria Na Hindi Ka Iiwanan.docx

Bacteria Involved in Respiratory Infections Dr. Bungay

OS 213 Trans A07 Exam 1 03/13/2019

 Microorganisms of the normal flora may aid the host (by competing more effectively than pathogens or by producing nutrients the host can use)  Found in upper respiratory tract; the lower respiratory tract (small bronchi, alveoli) is usually sterile, because: o Particles the size of bacteria does not readily reach it  It is protected by alveolar macrophages

OUTLINE I. Facts on Respiratory Infections II. Normal Flora and common Pathogens A. Normal Flora B. Common Pathogens III. Streptococcus pneumoniae IV. Streptococcus pyogenes

B. COMMON PATHOGENS Table 2. Common pathogens of the respiratory tract.

DISEASE Objectives:  Discuss selected bacterial respiratory infections based on o Epidemiology o Pathogenesis o Clinical manifestations o Characteristics of the pathogen  Identify the most common methods used in diagnosis

Common cold

Dental caries Oral Thrush

I. FACTS ON RESPIRATORY INFECTIONS

Trench mouth

 Adults get colds about 2-4 times a year  Respiratory infections can be caused by viruses, bacteria or fungi, even parasites (paragonimiasis) o Most common are viruses (rhinoviruses, RSV for younger age groups)  Respiratory infections can be prevented by immunization, adequate nutrition, and addressing environmental factors  A growing number of infections – such as pneumonia and TB, are becoming harder to treat as the antibiotics used to treat them become less effective (antibiotic resistance)

Stomatitis Pharyngitis Otitis media Otitis externa Sinusitis Epiglotitis Whooping cough

II. NORMAL FLORA AND COMMON PATHOGENS

Bronchitis

 Majority of normal flora (commensals) are gram positive, but others are gram negative (i.e. Neisseria sp.) and others are fungal (Candida albicans) Table 1. Normal oral and upper respiratory tract flora

COMMON RESIDENTS (>50%)         

Oral streptococcus Neisseria spp. Corynebacteria Bacteroides sp. Anaerobic cocci Fusiform bacteria Candida albicans Streptococcus mutans Hemophilus influenza

OCCASIONAL/ TRANSIENT RESIDENTS (<10%) – FOUND IN CARRIERS  Streptococcus pyogenes  Streptococcus pneumoniae  Neisseria meningitides UNCOMMON RESIDENTS (<1%) – IF FOUND, PATIENT IS SICK!  Corynebacterium diphtheriae  Klebsiella pneumoniae  Pseudomonas spp. (attacks the eyes  Escherichia coli (found in most parts in the body. 90% of UTI is caused by this.)

A. NORMAL FLORA  Two (2) main functions that play a role in maintaining the healthy state of the host: o Competes with pathogenic organisms for potential attachment sites o Produces substances (toxins or acids) which are bactericidal  The normal microbial flora is relatively stable, with specific genera populating various body regions during particular periods in an individual’s life

Bronchiolitis

COMMON PATHOGENS Rhinoviruses (most common cause of URTI), Coronaviruses, Adenoviruses, Echoviruses, Coxsackie A and B; M. pneumonia, C. pneumonia S. mutans C. albicans Treponema vincentii, Fusobacterium fusiforme Herpes simplex virus Adenovirus, HSV, Coxsackie viruses, S. pyogenes, C. diptheriae S. pneumoniae, H. influenzae, M. catarrhalis P. aeruginosa S. pneumoniae, H. influenzae H. influenza Bordetella pertussis Viruses (Parainfluenza, Influenza, RSV) AND atypical microbes (Mycoplasma pneumoniae, Chlamydia pneumoniae) Respiratory syncytial viruses

 A patient with respiratory symptoms should NOT immediately be given antibiotics. o If viral, drink lots of water only.  The most common causes of respiratory infections are viral; they resolve by themselves within 1-2 days.  The genus Streptococcus includes three of the most important pathogens of humans: o Pneumococcus (S. pneumoniae): a leading cause of both pneumonia and meningitis (all ages) o Group A streptococcus (S. pyogenes): causes “strep throat”, which can lead to scarlet fever, rheumatic fever and rheumatic heart disease o Group B streptococcus (S. agalactiae): most common cause of newborn sepsis

III. STREPTOCOCCUS PNEUMONIAE A. GENERAL FEATURES    

Gram (+), non-motile, encapsulated diplococci Lancet shaped, in pairs Fastidious Common cause of respiratory infections

B. PATHOGENESIS  Found in nasopharynx  Sensitive to environmental agents  Two ways a person becomes infected: o Endogenous - carriers; due to impaired immune system o Exogenous - droplet transmission; most common

Trans Group 4: Angobung, Aquino, Arabis, Awitan

OS 213

Bacteria Involved in Respiratory Infections C. VIRULENCE FACTORS

 Capsule (most important virulence factor) o Antiphagocytic and antigenic o 85 capsular serotypes o Component incorporated into anti-capsular pneumococcal vaccines  Autolysin o Peptidoglycan hydrolase o Responsible for release of intracellular virulence factor  Pneumolysin o Attacks mammalian cells, causing lysis

D. CLINICAL SIGNIFICANCE  Acute bacterial pneumonia - invasive o Most common among pediatric (<5 years old), geriatric age groups, immunocompromised patients  Otitis media – upper respiratory infection o Due to contiguous spread from the nasopharynx through the Eustachian tube o More common in children since the Eustachian tube is more horizontal as compared to adults  Bacteremia / sepsis  Meningitis o among children and immunocompromised patients

Figure 3. Quellung test to identify S. pneumoniae. Antibody to capsular antigen causes capsular swelling.

 Gram stains and microbiological cultures are the mainstays of

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E. LABORATORY DIAGNOSIS

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diagnostic tests, but are positive in fewer than 50% of cases of pneumococcal pneumonia. For bacteremic pneumococcal pneumonia in adults, sputum Gram stain and cultures had sensitivities of 80% and 93%, respectively, provided an adequate specimen was produced prior to therapy. Blood Agar Plate culturing is used for laboratory diagnosis for S. pneumoniae where in α-hemolytic (partial), green colony growth is characteristic. Gram staining is also employed in lab diagnosis wherein Gram (+), purple diplococci or streptococci are expected. Quellung Test (not usually done): o Quellung is the German word for "swelling" of capsule – describes the microscopic appearance of pneumococcal or other bacterial capsules after their polysaccharide antigen has combined with a specific antibody. The antibody usually comes from a bit of serum taken from an immunized laboratory animal. As a result of this combination, and precipitation of the large, complex molecule formed, the capsule appears to swell, because of increased surface tension, and its outlines become clearly demarcated. (+) Optochin test: Zone of inhibition around the P disc is 14 mm in diameter indicating pneumococci

F. TREATMENT

Figure 1. Laboratory diagnosis of S. pneumoniae. Organism should be: (1) αhemolytic on blood agar plate (BAP) with 5% CO2(2) Gram positive diplococci (3) Sensitive to Optochin and positive in bile solubility test(4) Positive on Quellung test

 Primarily by antibiotics o Focus on inhibiting the cell wall. o Penicillins are no longer effective due to resistance due to alteration of penicillin-binding protein (PBP) o First-line drug: Amoxicillin/Co-amoxiclav o 3rd generation Cephalosporin and Vancomycin can also be used  Currently exploring the area of herbal medicine. Video on Antibiotic Resistance: youtube.com/watch?v=qBdYnRhdWcQ

G. PREVENTION

Figure 2. Examples of laboratory methods to diagnose S.pneumoniae: (A) αhemolysis on BAP, (B) Gram positive diplococci, (C) Swelling of capsule on Quellung test

Trans Group 4: Angobung, Aquino, Arabis, Awitan

 The most important thing to do to control S. pneumoniae is prevention by vaccination: o Pure polysaccharide vaccine (PPV): Polyvalent antipneumococcal capsular polysaccharide  23 different serotypes  Accounts for 90% of invasive strains  Only effective for 2 y.o. and above  But T-independent antigen doesn’t stimulate production of memory cells  protection wanes with time (about 5 years)  Should be done every 5 years  If given more than 2 times, the third dose will not have an effect  Used for more expansive serovar protection in addition to the conjugated vaccine when indicated: advanced age, splenectomy, HIV/AIDS, lymphoma, myeloma, alcoholism, diabetes  Does not stimulate memory immune response; all are primary response

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OS 213

Bacteria Involved in Respiratory Infections  SPE B (cysteine protease) o Cytolytic toxins and other exoenzymes  Streptolysin O  Damages cells resulting in release of lysosomal enzymes and degranulation  Strongly antigenic – Ask for an ASO titer as diagnostic for RF/RHD ■ Non-suppurative sequelae - RHF  ASO titer – most commonly used; serologic tests  Streptolysin S  Lyses erythrocytes, leukocytes and platelets  Streptokinase  Catalyzes conversion of plasminogen to plasmin  Streptodornases  C5a peptidases  Hyaluronidase

o Pneumoccocal conjugated vaccine (PCV)  Prevnar (13 strains) / Synflovix (10 strains)  Conjugated vaccine – aided by carrier protein to activate T cells  Indicated for use in infants <2 years of age (may immunize in at least 6 weeks old, but very expensive)  Recommendation (even for adults): Prevnar, then if indicated, 23 strains given after a year (dapat lifetime immunity na ito)

IV. STREPTOCOCCUS PYOGENES A. GENERAL FEATURES  Gram (+), nonmotile cocci, occurring in long chains  Causes strep throat / pharyngitis o Sore throat most common etiology - viral  Group A, β-hemolytic streptococcus (GABHS) o S. pyogenes is the most virulent o Can invade intact skin or mucous membrane o Low inoculum can cause infection o Nasopharyngeal carriage is common – carrier of other infection o Common cause of infection in neonates

B. PATHOGENESIS

D. CLINICAL SIGNIFICANCE  Acute pharyngitis or pharyngotonsillitis o Most common type of S. pyogenes infection o Pus/Purulent inflammation of the posterior oropharynx and tonsillar area o In children, tonsillitis often misdiagnosed because children have naturally hypertrophied tonsils!

Figure 5. Acute pharyngitis or pharyngotonsillitis. Note the white inflammatory plaques / exudates on the enlarged tonsils.

 Non-infectious sequelae: 2-3 weeks post-strep throat or skin

     Figure 4. Droplet transmission leading to streptococcal pharyngitis.

C. VIRULENCE FACTORS  Capsule o Composed of hyaluronic acid o Inhibits phagocytosis and for adhering to respiratory epithelial cells  Cell wall o Fimbriae  Contains M protein, which are highly antigenic and give variability  Glomeruli – acute glomeruli nephritis  Cross-react with the proteins of the heart valves -RHF  N-terminal has antiphagocytic activity  Lipoteichoic acid for adherence and antigenicity o C – carbohydrate  Rhamnose and N-acetylglucosamine  Basis of Lancefield criteria o Protein F (Fibronectin-binding protein)  Mediates adherence of bacteria on epithelia  Extracellular products o Streptococcal pyrogenic exotoxins (SPE)  SPE A and C (carried by bacteriophage)

Trans Group 4: Angobung, Aquino, Arabis, Awitan

infection, can have any of the ff. sequelae: o Acute rheumatic fever – increased risk in strep throat o Acute glomerulonephritis – impetigo, sore throat Cellulitis (hard to differentiate from S. aureus) Impetigo – can be caused by either staph and strep Erysipelas Puerperal sepsis: exogenous/endogenous transmission Invasive Group A streptococcal disease o Deep local invasion with or without necrosis o Necrotizing fasciitis / myositis o Toxic shock-like syndrome, fever, hypotension with multiple organ injury and rash

Figure 6. Erysipelas (left) and necrotizing fasciitis (right)

E. LABORATORY DIAGNOSIS  Throat swab, pus, lesion samples, sputum, blood or CSF.  Culture on Blood Agar Plate (BAP) o Small, opalescent colonies o β-hemolytic (complete hemolysis) o Sensitive to Bacitracin o Precipitin reaction (thin lines): Group A C-carbohydrate o Serologic test: Anti-Streptolysin O (ASO) Test and antiDnaseB titer are more specific for S. pyogenes

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OS 213

Bacteria Involved in Respiratory Infections

o CAMP test negative  CAMP Test – used to identify Group A β-hemolytic streptococci (S. pyogenes) which are not able to produce CAMP factor, thus, are not able to enlarge the zone of hemolysis of S. aureus. Group B strep are able to produce CAMP factor, and are thus positive for CAMP test.  Antigen detection tests o Kits for rapid determination from throat swabs  Uses enzymatic or chemical methods  EIA or agglutination tests  Completed minutes to hours o 60-90% sensitive o 98-99% specific o Sensitivity and specificity. Good kit can get antigen from the bacteria. True positives and negativeshighly sensitive test  Serologic tests o Rise in titer can be estimated o Antibodies include ASO in respiratory disease, anti-DNAse and antihyaluronidase in skin infections, antistreptokinase, anti-M type-specific antibodies

 Currently no vaccine for S. pyogenes  Prophylactic antibiotics for rheumatic fever END OF TRANS

Figure 7. Examples of laboratory methods to diagnose S. pyogenes. (A) Gram positive cocci occurring in chains under light microscope; (B) β-hemolysis on BAP (C) Sensitive to Bacitracin test.

Nice to know: Alpha hemolytic = partial hemolysis Gamma hemolytic = no hemolysis

F. TREATMENT  Drainage and debridement  Antibiotics: Penicillin and macrolides (erythromycin, clarithromycin, azithromycin) o Macrolides are only given if patient is allergic to penicillin; it is not a first line drug

G. PREVENTION  Rapid detection and eradication, hygienic measures

Trans Group 4: Angobung, Aquino, Arabis, Awitan

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