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Unformatted text preview: Case 35 Streptococcus pneumoniae A 45-year-old male with a known history of alcohol abuse presented at the Emergency Room with a 1-day history of fevers, shaking chills, and productive cough. He stated that he was coughing up blood-tinged sputum that had a rusty appearance. The patient also remarked that he had some left-sided chest pain that was worse when he breathed in or coughed ( pleuritic pain ) and some dyspnea (shortness of breath). He denied any significant past medical history, and was not taking any medications. He reported a 20-pack per-year history of smoking, and drinking at least one six- pack of beer per day. On physical exam he was a well-developed male in moderate distress. His temperature was 40 C, pulse 110 beats per minute, blood pressure 140/80 mmHg, respiratory rate 24, and O 2 saturation 90% on room air. His lung examination revealed decreased breath sounds and dullness to percussion in the left lower lung base. There were some rales and egophony present. A sputum sample and blood were collected and a chest X-ray was ordered. The results of the investigations were as follows. Laboratory findings: WBC 18 000, 80% PMNs, 10% bands, 10% lymphocytes. Chest X-ray: dense consolidation and air bronchograms in the left lower lobe (Figure 1). Sputum Gram stain: gram-positive, bullet-shaped diplococci and inflammatory cells (Figure 2). Blood cultures at 24 hours revealed gram-positive diplococci. (Figure 3). Figure 1. AP chest X-ray shows pneumonia of the left lower lobe with early consolidation . This disease is caused by the bacterium Streptococcus pneumoniae . The alveoli (the air sacs of the lungs, too small to be seen) become blocked with pus, forcing air out and causing the lung to solidify. Symptoms include coughing and chest pain. Figure 2. Gram stain of S. pneumoniae in sputum: note the bullet-shaped diplococci. Figure 3. Gram stain of S. pneumoniae from blood culture broth showing gram-positive bullet- shaped diplococci. Lydyard, Peter; Cole, Michael; Holton, John; Irving, Will; Porakishvili, Nino; Venkatesan, Pradhib; Ward, Kate, Jan 01, 201 Garland Science, Hoboken, ISBN: 9780203856871 1. What is the causative agent, how does it enter the body and how does it spread a) within the body and b) from person to person? Causative agent The patient is infected with Streptococcus pneumoniae , frequently termed the pneumococcus. S. pneumoniae is one of the main causes of respiratory tract infections worldwide, killing over 1 million individuals, mostly children, every year. Pneumococcal infection is the sixth leading cause of disease in the US and is responsible for about 6 million cases of otitis media , about 200 000 hospitalizations from pneumonia and invasive disease, and at least 40000 deaths annually, which are more deaths than acute infection with any other bacteria. S. pneumoniae is a gram-positive, catalase-negative diplococcus. The bacterial cells are bullet- or lancet-shaped when observed by Grams stain (Figure 3). The catalase test is used to distinguishobserved by Grams stain (Figure 3)....
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