Chapter 22 Respiratory System infections Introduction Rebecca Lancefield graduate of Wesley and later Columbia Studied groups of surface antigens on strep on b hemolytic species Anatomy and Physiology Enormous variety of diseases from minor to fatal Upper respiratory head and neck o generally not life threatening but frequent o otitis ear infection can be ecternal or internal o nasal cavity nasopharynx and pharynx colonized by numerous bacteria of many classes aerobes anaerobes pharyngitic throat infection sinusitis and mastiodis infection of the air passages in the skull rhinitis nose infection o conjunctiva eye eyelid membranes usually no bacteria Tonsils lymphoid organs organisms swept into the nasolacrimal duct tear duct and nasopharynx o Inflammation due to tonsillitis causes enlargement of the adenoid or tonsils interfere with the draining of eustachain tubes causing ear infection These tubes equalized pressure in the middle ear and drain mucous secretions Lower respiratory chest o Normally sterile o more serious can be life threatening o particularly in the immuno compromised o laryngitis bronchitis pneumonitis results in infection of the alveoli if pus and fluid is pneumonia o pneumonia pertussis tuberculosis Muscociliary escalator Normal Microbiota Nasal cavity nasopharynx alpha and non hemolytic strep and dipheriods and pharynx are the only structures that are lined with all types of bacteria The eye is normally sterile due to lysozyme secretions with every blink Nasopharynx has opportunistic bacteria Bacterial Infections of The Upper Respiratory System Strep Throat o Symptoms most patients recover uneventfully in about a week many don t have symptoms at all difficulty swallowing swollen tonsils fever red throat with pus patches enlarged tender lymph nodes in neck not typical red eyes runny nose cough viral pharyngitis o Causative Agent Streptococcus pyogenes Gram positive coccus in variable chains hemolytic complete hemolysis of RBC a k a group A streptococcus due to Lancefield Group A carbohydrate in cell wall basis for rapid pyogenes species identification using antibodies or DNA test probes o Streptococcal pathogenesis Streptococcus pyogenes arsenal of virulence factors Has many superantigens that cause fleshing eating disease tissue damage and strep shock C5a peptidase Inhibits attraction of phagocytes by destroying c5a Hyaluronic and capsule M Protien Inhibits phagocytosis aids in penetration of epithetlium Interferes with phagocytosis by causing breakdown of C3b opsonin Protien F Responsible for attachment to host cells Protien G Streptococcul pyrogenic exotoxins SPE o Lyse leukocytes and erthrocytes Tissue degrading enzymes Interferes with phagocytosis by binding Fc segment of IgG Spuperantigens responsible for scarlet fever toxic shock etc Streptolysin O and S o Enchance spread of bacteria by breaking down DNA proteins blood clots tissue hyaluronic acid Scarlet Fever o Erythrogenic toxin o o Complications of Strep Throat rash due to the SPE systemic erythrogenic toxin red skin rash strawberry tongue in acute phase of strep throat scarlet fever sequelae complications days to months later 1 acute glomerulonephritis o abrupt fever fluid retention bloody urine o kidney damage due to inflammation from presence of immune complexes in the glomeruli 2 acute rheumatic fever 3 weeks later o behavior changes uncontrolled body movements o often damage to heart valves leakage heart failure in later life o susceptibility to subacute bacterial endocarditis when damaged valves are infected with normal micrbiota o Epidemiology o Streptococcal Pharyngitis Only humans because reacts specially with a human clotting factor Prevention No vaccine available o genome sequence of S pyogenes may reveal new epitopes Adequate ventilation Avoid crowds A sore throat with fever should be cultured for prompt treatment o to avoid complications Treatment Confirmed strep throat treated with 10 days of penicillin or erythromycin o Eliminates organisms in 90 of cases Diphtheria o Symptoms mild sore throat slight fever fatigue and malaise and often dramatic neck swelling bull neck whitish membrane forms on tonsils or in nasal cavity heart and kidney failure can follow o Causative Agent variably shaped arranged in palasades Corynebacterium diphtheriae Gram positive non spore forming certain strains make diphtheria toxin o Diptheria toxin tox gene provided by a bacteriophage lysogenic conversion phage integrates the C diptheriae chromosome forms a lysogen Toxin production from the tox gene is controlled by iron Fe concentration when Fe binds tox repressor protein toxin production is repressed turned off when available Fe is low Fe dissociates from tox repressor and toxin genes is expressed turned on o Pathogenesis C diptheriae cells not very invasive exotoxin bloodstream damage to heart nerves and kidneys Diphtheria toxin A B type exotoxin inactive protein cut into A and B chains B binds host cell membrane and A B enters by endocytosis free A chain becomes active enzyme inactivates EF2 stops protein synthesis in host cells enzyme re used inactivates large population of cells explains potency of diptheria toxin o Epidemiology Humans are primary reservoir present in chronic skin infections like cutaneous dipheria Spread by air acquired through inhalation Sources of infection include Carriers who recovered from infection Asymptomatic cases Contaminated fomites inanimate objects People with active disease o Prevention DPT trivalent vaccine diptheria pertussis tetanus antibodies to diptheria toxoid neutralize the toxin vaccination often neglected Immunity wanes after childhood booster immunization every 10 years o Treatment Effectiveness depends on early antiserum treatment Delay in treatment may be fatal Antibiotics penicillin and erythromycin eliminate C diptheriae but Even with antibiotic therapy 1 in 10 patients die transmission of disease stopped but no effect on absorbed toxin Sinus Earache and eye infections o Pinkeye Symptoms increased tears and redness swollen eyelids sensitivity to bright light large amounts of pus o Symptoms Sinusitis pain and pressure generally localized to involved sinus tenderness over sinus headache significant malaise o Symptoms Otitis media middle ear infection severe ear pain most common in young children mild fever may be absent vomiting often when ear pain peaks often ear drum ruptures trapped fluid drains via external ear canal o Causative Agents most commonly for