A patient has presented in hospital with difficulty breathing, chest pain, fever

Question

A patient has presented in hospital with difficulty breathing, chest pain, fever, and a cough. The treating physician believes the patient has pneumonia. The patient is a 60-year old male who had recently been in the hospital for an leukemia, severely affecting his immune system. The hospital has been particularly hard hit with nosocomial infections lately and the physician is keen to identify this ASAP. The two main culprits of the recent nosocomial outbreaks were Pseudomonas aeruginosa and Acinetobacter baumanii, both of which cause a pneumonia-like illness and significantly affect immunocompromised patients. A final possibility would be the more common, community-acquired Streptococcus pneumoniae, which causes similar symptoms. a. What is the first experiment you would perform to distinguish between these potential infections? i. Describe the methods of this experiment in detail. ii. What result would you see for each of these infections in

Explanation / Answer

A nosocomial infection, also known as a hospital-acquired infection or HAI, is an infection whose development is favored by a hospital environment, such as one acquired by a patient during a hospital visit or one developing among hospital staff. Such infections include fungal and bacterial infections and are aggravated by the reduced resistance of individual patients. Many HAI are difficult to fight against with antibiotics and antibiotic resistance is spreading among Gram-negative bacteria that can infect people outside the hospital

Acinetobacter baumanii is a non-fermenting, Gram-negative, aerobic coccobacillus found extensively in natural environments that has emerged as one of the most troublesome pathogens for health care institutions globally. This microorganism is characterized by the rapid development of resistance to the majority of antimicrobials, including aminoglycosides, fluoroquinolones, and carbapenems .. In addition from its resistance profile, A. baumanii shows the ability to survive for prolonged periods throughout a hospital environment, thus potentiating its ability for nosocomial spread. As reported by reviews dating back to the 1970s, hospital acquired pneumonia is still the most common infection caused by this organism. However, more recently, infections involving the central nervous system, skin and soft tissue, and bone have emerged as highly problematic for certain institutions

Patients with pneumonia may present with chest discomfort, cough (productive or nonproductive paroxysmal cough), rigors (patients with typical pneumonia) or chills (patients with interstitial pneumonia), shortness of breath, and fever. Physical examination may reveal increases in respiratory rate and heart rate and dullness to percussion over affected regions of the lungs and rales.

Chest radiographs showing new consolidations or infiltrates are definitive in helping to establish a diagnosis of pneumonia. When alveolar sacs fill with inflammatory cells and fluid, the chest radiograph will show consolidated well-defined densities that are unilateral (inhalation or aspiration pneumonia), bilateral (hematogenous spread to lungs), localized, or uniform. When a chest radiograph shows inflammation and thickening of the alveolar septa that surround the alveoli, rather than a filling of the alveolar sacs with inflammatory material, the diagnosis is more likely to be an atypical (interstitial) pneumonia.

Some organisms form abscesses in the lung (e.g., Staphylococcus aureus, Enterobacteriaceae, Pseudomonas aeruginosa, and anaerobic organisms) and in such cases, a chest radiograph is useful in revealing abscess formation. If present, certain classic radiologic patterns may be of diagnostic value; for example,

Patient with VAP

Diagnosis of these patients can be difficult because:

There is still much debate concerning how to determine if a mechanically ventilated patient has VAP. There are now two approaches: the quantitative culture approach and the clinical approach.

Quantitative culture approach tries to discriminate between bacterial colonization and true bacterial infection by determining the bacterial burden. The respiratory tree can be sampled at various points; endotracheal aspirates and bronchoscopy. A quantitative endotracheal aspirate would be positive for bacterial colonization if the colony forming units (CFU) were less than 106 CFU/ml. If greater than 106 CFU/ml then the patient would have a VAP. If a bronchoscope was used to get a protected brush specimen to sample further down in the lungs then a CFU less than 103 CFU/ml would indicate the patient is only colonized. However, if the CFU from the protect brush specimen were greater than 103 CFU/ml then the patient has VAP. One important point to remember is that these samples should be obtained BEFORE antibiotic therapy has begun. If not false negative samples are more likely. The cultures can then also be used to identify the pathogen and determine its sensitivity to antimicrobial agents.

Clinical approach uses a Clinical Pulmonary Infection Score (CPIS) to determine if a patient is more likely to have VAP. The clinical criteria used are weighted and added together to produce a final score. A maximum score is 12 when the tracheal aspirate data arrives. A score of 6 or greater indicates the patient has VAP. Clinical criteria used are fever, leukocytosis, oxygenation, chest radiograph, and tracheal aspirates. It is not important for you to memorize this scoring procedure for the exam!

Some medical facilities utilize both approaches for diagnosis of VAP. The clinical approach is used to quickly determine if a protected brush specimen should be used to do quantitative cultures.

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