Dalia Kamal Eldien Mohammed

 Respiratory tract infections (RTIs) are any infection of the sinuses, throat or lungs.  They're usually caused by viruses, but they can also be caused by bacteria.  Respiratory tract infections classified in to:  Upper respiratory tract infections, which affect the nose, sinuses and throat  Lower respiratory tract infections, which affect the airways and lungs

Common upper respiratory tract infections include:  Common cold (mild viral infection of the nose, throat, sinuses and upper airways. It can cause a blocked nose followed by a runny nose, sneezing, a sore throat and a cough)  Tonsillitis (infection of the tonsils and tissues at the back of the throat)  Sinusitis (infection of the sinuses)  Laryngitis (infection of the larynx, or voice box)  A cough is the most common symptom of an upper RTI. Other symptoms include headaches, a stuffy or runny nose, a sore throat, sneezing and muscle aches.

Common lower RTIs include:  Flu (this can affect either the upper or lower respiratory tract)  Bronchitis (infection of the airways)  Pneumonia (infection of the lungs)  Bronchiolitis (an infection of the small airways that affects babies and children younger than two years)  Tuberculosis (persistent bacterial infection of the lungs)  The main symptom of a lower RTI is also a cough, although it is usually more severe and may bring up phlegm and mucus. Other possible symptoms are a tight feeling in the chest, increased rate of breathing,breathlessness and wheezing.

 Lower respiratory tract infections are quite common in the general population, occurring with increased frequency in older individuals and those with chronic diseases or compromised immune function.  Etiologic diagnosis of the responsible pathogen is made by culture of respiratory tract secretions(sputum) or by isolation of a compatible organism from blood cultures.  Common infection of the lower respiratory tract is pneumonia

Classification of pneumonia Pneumonia are classified to : A- Community acquired pneumonia common causes Streptococcus pneumoniae& Mycoplasma pneumoniae B- Hospital acquired pneumonia common causes Pseudomonas aeruginosa, Legionella pneumophila &Staphylococcus aureus

 bacterial sputum culture is ordered when a health practitioner suspects that someone has a bacterial infection of the lungs or airways, such as bacterial pneumonia. This may show as changes in the lungs as seen on a chest x-ray.  Symptoms of pneumonia may include:  Cough  Fever, chills  Muscle aches  Fatigue  Trouble breathing  Chest pain  Confusion  Sometimes a sputum culture may be ordered after treatment of an infection, to verify its efficacy.

Possible pathogens Gram positive Gram negative  Streptococcus pneumoniae Haemophilus influenzae  Staphylococcus aureus Klebsiella pneumoniae  Streptococcus pyogenes Pseudomonas aeruginosa Proteus species Yersina pestis Moraxella catarrhalis  Also Mycobacterium tuberculosis, Mycoplasma pneumoniae, and Legionella pneumophila.

 S. pneumoniae and H. influenzae are the commonest causes of acute respiratory tract infections in tropical countries.  S. aureus, S. pyogenes, and H. influenzae are often secondary invaders in patients with influenza virus pneumonia.  M. pneumoniae causes primary atypical pneumonia.  Fungi include Histoplasma capsulatum, Aspergillus species, Candida albicans, Cryptococcus neoformans, and Nocardia

 The presence of normal upper respiratory tract flora should be expected in sputum culture. Normal respiratory flora include:  Neisseria catarrhalis  Candida albicans  Diphtheroids  alpha-hemolytic streptococci  and some staphylococci.

 The specimen is sputum (is a thick fluid produced in the lungs and in the airways leading to the lungs). And blood for culture and serology  Sputum as it is being collected passes through the pharynx and the mouth. It therefore becomes contaminated with small numbers of commensal organisms  Give the patient a clean (need not be sterile), dry, wide-necked, leak-proof container, and request him or her to cough deeply to produce a sputum specimen.  If their is delaying use transport media – Amies or Stuart

How to Prepare the patient for the Test  Drinking a lot of water and other fluids at the night before the test, this may make it easier to cough up the sputum.  No food for one to two hours prior to expectoration  Rinsing the mouth by water prior to expectoration  Do not use mouthwash before collecting a sputum sample  Obtaining the specimen prior to antibiotic treatment

Macroscopical exam: Describe whether the sputum is:  Purulent: Green-looking, mostly pus  Mucopurulent: Green-looking with pus and mucus  Mucoid: Mostly mucus  Mucosalivary: Mucus with a small amount of saliva

Microscopical exam:  Gram stain, examine the smear for pus cells and predominant bacteria  Giemsa stained preparation when histoplasmosis is suspected  Giemsa or Wayson stained preparation when pneumonic plague is suspected Antigen detection  If the antisera are available

Culture the specimen  To obtain as pure a culture as possible of a respiratory pathogen it is necessary to reduce the number of commensals by Wash a purulent part of the sputum in about5 ml of sterile physiological saline. Inoculate in following media:-  Blood agar supports the growth of Gram positive cocci and most Gram negative rods, and is especially useful for evaluation of the colony morphology and hemolysis of streptococci.  Chocolate agar permits recovery of Haemophilus influenzae and other fastidious organisms that may grow less well on blood agar.  McConkey agar is selective for Gram negative bacteria and allows further classification into lactose ferment or non lactose ferment organisms.

 Incubate the blood agar & McConkey agar aerobically and the chocolate agar plate in a carbon dioxide enriched atmosphere  In blood agar apply Optochin discs in the well (????). Colonial morphology Gram stain Biochemical test Antimicrobial sensitivity test

A man 58 years of age, women 45 years old and her son, presenting to hospital with radiographic evidence of pneumonia and complaining of a 24-hour history of fever, chills, Muscle aches and cough, the doctor ask them to do sputum culture, proceed to identify the causative agents of each patient

 Susceptibility tests should be performed only when the amount of cultural growth of a pathogen is significant.  Strains of S. pneumoniae should be tested on blood agar for susceptibility to penicillin, tetracycline, and erythromycin.  Penicillin-resistant isolates of Streptococcus penumoniae have been noted with increasing frequency, and have been clinically significant in patients with pneumonia.Because of this, disk diffusion susceptibility testing with a 1ug oxacillin is recommended as a screening test on all S. pneumoniae isolates from sputum a zone size less than 20 mm indicates reduced susceptibility.  H. influenzae strains should be tested for betalactamase production  and susceptibility to ampicillin, tetracycline, and co-trimoxazole.  Ampicillin and amoxicillin are broad-spectrum penicillin, active against Gram positive bacteria (including enterococci) H. influenzae, and many coliforms.  Flucloxacillin and cloxacillin are used to treat beta-lactamase (penicillinase) producing