Bacterial Pneumonia


Article Author:
Saud Bin Abdul Sattar


Article Editor:
Sandeep Sharma


Editors In Chief:
Ron Feller
Grant Goold
Kyle Cohen


Managing Editors:
Avais Raja
Orawan Chaigasame
Carrie Smith
Abdul Waheed
Khalid Alsayouri
Frank Smeeks
Kristina Soman-Faulkner
Radia Jamil
Patrick Le
Sobhan Daneshfar
Anoosh Zafar Gondal
Saad Nazir
William Gossman
Pritesh Sheth
Hassam Zulfiqar
Navid Mahabadi
Steve Bhimji
John Shell
Matthew Varacallo
Heba Mahdy
Ahmad Malik
Mark Pellegrini
James Hughes
Beata Beatty
Nazia Sadiq
Hajira Basit
Phillip Hynes
Tehmina Warsi


Updated:
2/11/2019 8:56:52 PM

Introduction

The word "pneumonia" originates from the ancient Greek word "pneumon" which means "lung," so the word "penumonia" becomes "lung disease." Medically it is an inflammation of one or both lung's parenchyma that is more often but not always caused by infections. The many causes of pneumonia include bacteria, viruses, fungi, and parasites. This article is about bacterial causes of pneumonia as it is the major cause of mortality and morbidity by pneumonia. According to the new classification of pneumonia, there are four categories: community-acquired (CAP), hospital-acquired (HAP), healthcare-associated (HCAP) and ventilator-associated pneumonia (VAP). [1][2][3]

Types of Bacterial Pneumonia

  • CAP: The acute infection of lung tissue in a patient who has acquired it from the community.
  • HAP: The acute infection of lung tissue that develops 48 hours or longer after the hospitalization of a non-intubated patient.
  • VAP: A type of nosocomial infection of lung tissue that usually develops 48 hours or longer after intubation for mechanical ventilation.
  • HCAP: The acute infection of lung tissue acquired from healthcare facilities such as nursing homes, dialysis centres, and outpatient clinics or a patient with hospitalization within the past 3 months (previously included in HAP but becomes a separate category after some cases presenting as outpatients with pneumonia have been found to be infected with multidrug-resistant (MDR) pathogens previously associated with HAP).

Some articles include both HAP and VAP under the category of HCAP, so defining HCAP is problematic and controversial.

Etiology

Etiology of community-acquired pneumonia is an extensive list of agents that include bacteria, viruses, fungi, and parasites, but this article is about bacterial pneumonia and its causes. Bacteria have classically been categorized into two divisions on the basis of etiology, "typical" and "atypical" organisms. Typical organisms can be cultured on standard media or seen on Gram stain, but "atypical" organisms do not have such properties. [4]

  • Typical pneumonia refers to pneumonia caused by Streptococcus  pneumoniae, Haemophilus influenzae, S. aureus, Group A streptococci, Moraxella catarrhalis, anaerobes and aerobic gram-negative bacteria.
  • Atypical pneumonia is mostly caused by Legionella spp, Mycoplasma pneumoniae, Chlamydia pneumoniae, and C. psittaci.

The most common causes of community-acquired pneumonia (CAP) is S. pneumoniae followed by Klebsiella pneumoniae, Haemophilus influenzae, and Pseudomonas aeruginosa. The most common causes of HCAP and HAP are MRSA (methicillin-resistant Staphylococcus aureus) and Pseudomonas aeruginosa respectively. The causative agents of VAP include both multi-drug resistant (MDR) agents (e.g., S. pneumoniae, other Strep spp, H. influenzae and MSSA) and non-MDR (e.g., P. aeruginosa, methicillin-resistant Staphylococcus aureus, Acinetobacter spp. and antibiotic-resistant Enterobacteriaceae) bacterial pathogens.

Epidemiology

The incidence of CAP in the United States is more than 5 million per year; 80% of these new cases are treated as outpatients with the mortality rate of less than 1%, and 20% are treated as inpatients with the mortality rate of 12% to 40%. The incidence of CAP varies among different genders; for example, it is more common in males and African Americans than females and other Americans. The incidence rates are higher at extremes of age distribution range; the adult rate is usually 5.15 to 7.06 cases per 1000 persons per year, but in the population of age less than 4 years and greater than 60 years, the rate is more than 12 cases per 1000 persons. In 2005, influenza and pneumonia combined was the eighth most common cause of death in the United States and the seventh Most common cause of death in Canada. The mortality rate also is variable among different regions at  7.3% for the United States and Canada, 9.1% for Europe, and 13.3% for Latin America.[5][6]

Pathophysiology

The lower respiratory tract is not sterile, it always is exposed to environmental pathogens. Invasion and propagation of the above-mentioned bacteria into lung parenchyma at alveolar level causes bacterial pneumonia, and the body's inflammatory response against it causes the clinical syndrome of pneumonia. To prevent this proliferation of microorganisms there are a number of host defenses working together in lungs such as mechanical (e.g., hair in nostrils and mucus on nasopharynx and oropharynx) and chemical (e.g., proteins produced by alveolar epithelial cells like surfactant protein A and D, which have the intrinsic property of opsonizing bacteria). Another component of the pulmonary defense system is made up of immune cells such as alveolar macrophages, which work to engulf and kill proliferating bacteria, but once bacteria overcome the capacity of host defenses, they start proliferation. In this setting, the alveolar macrophages kickoff the inflammatory response to strengthen the lower respiratory tract defenses. This inflammatory response is the main culprit of clinical manifestation of bacterial pneumonia. Cytokines are released in response to the inflammatory reaction and cause the constitutional symptoms, for example, IL-1 (interleukin-1) and TNF (tumor necrosis factor) causes fever. Chemokine-like IL-8 (interleukin-8) and colony-stimulating factors like G-CSF (granulocyte colony-stimulating factor) promote chemotaxis and neutrophils maturation respectively, resulting in leukocytosis on serological lab and purulent secretions. These cytokines are responsible for the leakage of the alveolar-capillary membrane at the site of inflammation, causing a decrease in compliance and shortness of breath. Sometimes even erythrocytes cross this barrier and result in hemoptysis.[7][8][9]

Histopathology

Pathologically, lobar pneumonia is the acute exudative inflammation of a lung lobe. It has the following four advanced stages if left untreated:

  1. Congestion: In this stage, pulmonary parenchyma is not fully consolidated, and microscopically, the alveoli have serous exudates, pathogens, few neutrophils, and macrophages.
  2. Red hepatization: Here the lobe is now consolidated, firm, and liver-like. Microscopically, there is an addition of fibrin along with serous exudate, pathogens, neutrophils, and macrophages. The capillaries are congested, and the alveolar walls are thickened.
  3. Gray hepatization: The lobe is still liver-like in consistency but gray in color due to suppurative and exudative filled alveoli.
  4. Resolution: After a week, it starts resolving as lymphatic drainage or a productive cough clear the exudate.

History and Physical

The history findings of bacterial pneumonia may vary from indolent to fulminant. Clinical manifestation includes both constitutional findings and findings due to damage to the lung and related tissue. The following are major history findings:

  • Fever with tachycardia and/or chills and sweats.
  • The cough may be either nonproductive or productive with mucoid, purulent or blood-tinged sputum.
  • Pleuritic chest pain, if the pleura is involved.
  • Shortness of breath with normal daily routine work.
  • Other symptoms include fatigue, headache, myalgia, and arthralgia.

Physical findings also vary from patient to patient and mainly depend on the severity of lung consolidation and existence or nonexistence of pleural effusion. The following are major clinical findings:

  • Increased respiratory rate.
  • Percussion sounds vary from flat to dull.
  • Tactile fremitus.
  • Crackles, rales, and bronchial breath sounds are heard on auscultation.

Confusion manifests earlier in older patients. A critically ill patient may present with sepsis or multi-organ failure.

Evaluation

The approach to evaluate and diagnose pneumonia depends on different modalities but primarily it is like a tripod stand which has 3 legs which are summed up as:

  • Clinical Evaluation: It includes taking a careful patient history and performing a thorough physical examination to judge the clinical signs and symptoms mentioned above.
  • Laboratory Evaluation: This includes lab values such as complete blood count with differentials, inflammatory biomarkers like ESR and C-reactive protein, blood cultures, sputum analysis or Gram staining and/or urine antigen testing or polymerase chain reaction for nucleic acid detection of certain bacteria.
  • Radiological Evaluation:  It includes chest x-ray as an initial imaging test and the finding of pulmonary infiltrates on plain film is considered as a gold standard for diagnosis when the lab and clinical features are supportive.[10][2]

Treatment / Management

In all patients with bacterial pneumonia, empirical therapy should be started as soon as possible. The first step in treatment is a risk assessment to know whether the patient should be treated in an outpatient or inpatient setting. Cardiopulmonary conditions, age, and severity of symptoms affect risk for bacterial pneumonia, especially CAP.[11][12][13]

An expanded CURB-65 or CURB-65 pneumonia severity score can be used for risk quantification. It includes C = Confusion, U = Uremia (BUN greater than 20 mg/dL), R = Respiratory rate (greater than 30 per min), B = B.P (BP less than 90/60 mmHg) and age greater than 65 years. One point is scored for each previously mentioned risk factor. If the total of the score is 2 or more than 2, it indicates hospital admission. If the total is 4 or more than 4, it indicates ICU admission. Recommended therapy for different settings are as follows:

  • Outpatient Setting: For patients having comorbid conditions ( e.g., diabetes, malignancy, etc.) the regimen is "fluoroquinolone" or "beta-lactams + macrolide." For patients with no comorbid conditions, we can use "macrolide" or "doxycycline" empirically. Testing is usually not performed as the empiric regimen is almost always successful.
  • Inpatient Setting (non-ICU): Recommended therapy is fluoroquinolone or macrolide + beta-lactam.
  • Inpatient setting (ICU): Recommended therapy is beta-lactam + macrolide or beta-lactam + fluoroquinolone.

After getting a culture-positive lab result, therapies should be directed to the culture-specific pathogen.

The patient also can benefit from smoking cessation counseling and influenza and pneumococcal vaccination.

All patients treated at home should be scheduled for a follow-up visit within 2 days to assess any complication of pneumonia.

Differential Diagnosis

Differential Diagnosis in Children

  • Asthma or reactive airway disease
  • Bronchiolitis
  • Croup
  • Respiratory distress syndrome

Differential Diagnosis in Adults

  • Acute and chronic bronchitis
  • Aspiration of a foreign body
  • Asthma
  • Atelectasis
  • Bronchiectasis
  • Bronchiolitis
  • Chronic obstructive pulmonary disease
  • Fungal
  • Lung abscess
  • Pneumocystis jiroveci pneumonia
  • Respiratory failure
  • Viral

Prognosis

Prognosis of pneumonia depends on many factors including age, comorbidities, and hospital setting (inpatient or outpatient). Patients older than 60 years or younger than 4 years of age have a relatively poorer prognosis than young adults. Antibiotic resistance, very concerning due to the enhancement of antibiotic regimens, and infectious diseases, especially those like bacterial pneumonia, can be easily cured.

Complications

The most common complications of bacterial pneumonia are respiratory failure, sepsis, multiorgan failure, coagulopathy, and exacerbation of preexisting comorbidities. Three distinct complications are metastatic infections, lung abscess, and complicated pleural effusion.

Enhancing Healthcare Team Outcomes

The management of a pneumonia is multidisciplinary. Besides the administration of antibiotics, these patients often require chest physical therapy, a dietary consult, physical therapy to help regain muscle mass and a dental consult. The key is to educate the patient on discontinuation of smoking and abstaining from alcohol. Further, patients should be encouraged to get the appropriate influenza and pneumococcal vaccines. Finally, it is important to educate the patient on compliance with antibiotics if they want a complete resolution of the infectious process.[13][14] (Level V)

Outcomes

In healthy people, the outcome after a bacterial pneumonia is excellent. However, in people with advanced age, lung disease, immunosuppression, infection with aggressive gram-negative organisms (Klebsiella) and other comorbidities, the outcomes are usually poor. When a pneumonia is left untreated, it carries a mortality in excess of 25%. Pneumonia can also lead to extensive lung damage and lead to residual impairment in lung function. Other reported complications of pneumonia that occur in 1-5% of patients include lung abscess, empyema, and bronchiectasis.[15][16] (Level V)


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Bacterial Pneumonia - Questions

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How many polymorphonuclear cells must be present per low power field for a sputum specimen to be adequate for a pneumonia diagnosis?



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Which of the following cell types accumulates earliest in response to Streptococcal pneumonia?



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Which of the following medications is a bronchodilator and may be prescribed, along with other medications, to treat pneumonia?



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An older patient with a chronic obstructive pulmonary disease has developed pneumonia. Haemophilus influenzae is the causative organism. The patient is allergic to penicillin. Which of the following could be used for treatment?



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A heavy smoker in the ER is complaining of generalized fatigue. He claims that he is always out of breath and has no more energy. His only medications are bronchodilators, which he rarely uses. Auscultation reveals enhanced resonance of voice sounds in his left chest. What is the most likely diagnosis?



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A 51-year-old alcoholic is seen in the ER with complaints of a fever, chills, night sweats and anorexia. He says he has had productive thick sputum for the past 2 days and has a persistent cough. He describes his sputum as red jelly like and viscous. He has a WBC of 18 and a left shift. The rest of the exam is unremarkable. Chest x-ray reveals a possible consolidation. What organism is most likely causing this infection?



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An elderly female is admitted to the ICU with fevers and chills. Two days ago she developed flu like symptoms and a productive cough with thick blood tinged sputum. The intern on the team describes the sputum as currant jelly like. She may have a pneumonia caused by which organism?



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An elderly female goes to the intensive care unit with fevers and chills. She reports that two days ago, she developed flu-like symptoms. She has a productive cough with thick blood-tinged sputum. The intern on the team describes the sputum as currant jelly-like. She may have pneumonia. Which of the following caused it?



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A four-day-old term male infant with unremarkable pregnancy and birth develops tachypnea with 72 breaths per minute, jaundice, and poor feeding. The cardiac exam is normal. Pulmonary exam shows crackles. Which of the following is the most likely diagnosis?



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Which of the following cell types accumulates earliest in response to pneumococcal pneumonia?



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A patient with low-grade fever, general malaise, and no appetite is found to have dullness to percussion over the right lower lobe. Vocal fremitus is increased over the same area. He most likely has which of the following conditions?



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Which of the following is the least likely finding in a patient with pneumonia?



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In most patients without any comorbid conditions, the treatment of outpatient Streptococcus pneumoniae is which of the following?



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Who is at highest risk for developing pneumonia?



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Which of the following is not a typical complication of pneumonia?



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Who is not at increased risk for developing pneumonia?



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A 32-year-old HIV positive male presents with rapid onset of productive cough, low grade fever, and pleuritic chest pain. His last CD4 count was 400, and he reports that prior to this illness he has been compliant with HAART. What findings are you likely to see on chest x-ray?



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A 66-year-old male presents with a severe productive cough of 5 days duration along with chills, malaise, and fatigue. He has a prior history of well-controlled hypertension and hyperlipidemia. The physical exam is unremarkable. He has a temperature of 38.7 C but the other vital signs are normal. A chest x-ray reveals a dense right lower lobe infiltrate. What would be the best first course of action?



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In general, pneumonia treatment regimens do not include which of the following?



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Which of the following is a likely cause of lobar pneumonia in a diabetic patient?



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A patient with increased tactile fremitus may have which condition?



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Which cell type is the first to accumulate in a patient with pneumococcal pneumonia?



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Which of the following statements is true regarding invasive pneumococcal disease?



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A 20-month-old male has had a cough, runny nose, watery eyes, and decreased appetite for 5 days. He now has an abrupt onset, high-grade fever. The exam shows a fever, abdominal distention, grunting, intercostal retractions, rhonchi in the right lung, and dullness to percussion. The chest radiograph shows a left lower lobe infiltrate. Which of the following is the most likely infectious organism?



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A 75-year-old male is diagnosed with multilobar pneumonia and is intubated in the emergency department. A ventilator is placed on assist control mode with respiratory rate of 22, tidal volume of 6 ml/kg, FIO2 of 1 L/min, and PEEP of 10 cmH2O. An arterial blood gas shows pH=7.21, PCO2=34 mmHg, and PO2=56 mmHg. Which of the following is the most likely cause of the continued hypoxemia?



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Which of the following features is most likely in chest x-ray of a patient with a positive culture for S. pneumoniae?



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Which of the following pneumonia-causing organisms is seen more commonly in alcoholics?



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An 80-year-old female has a temperature of 101 F, is lethargic, and complains of a sore throat, cough, headache, and general malaise. She states that she was diagnosed with the common cold a few days ago. An exam reveals tachypnea and a pulse oximetry of 90% at room air. She has diminished breath sounds in her right lung base. What is the most likely diagnosis?



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Which of following organisms is not a common cause of lobar pneumonia?



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Which of following diseases is most likely caused by bacteria?



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A 69-year-old patient is in the emergency department after being found lethargic in a nursing home. A quick chest x-ray reveals lobar pneumonia. Which of the following would be most suggestive of severe pneumonia?



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A 67-year-old female came to the emergency department with a history of fall and a broken hip. She underwent hip replacement surgery. On the second postoperative day, extubation was attempted but not tolerated, thus reintubated. On the fourth postoperative day, she developed high-grade fever, dyspnea, and tachycardia. Her chest x-ray shows left lower lobe infiltrate. Her procalcitonin level is high along with elevated C-reactive protein. What will Gram staining of her sputum most likely show?



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A 40-year-old male complains of a dry cough from one week. He came back from vacation ten days ago. The cough is constant and associated with chest pain from the past week. He reports confusion, diarrhea and abdominal pain from the past one day. His chest x-ray shows pulmonary infiltrates on both lung lobes. His sputum gram stain shows only neutrophils without any pathogen. What is the most likely disease?



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A 78-year-old female came in the emergency with confusion and high-grade fever. After her urine and blood specimens sent to the laboratory, her blood pressure drops to 89/60 mmHg. Suddenly she becomes out of breath with respiratory rate of 28/min. providers are considering acute respiratory distress syndrome as followed by sepsis and pneumonia. They ordered chest x-ray and oxygen therapy but they also wanted to start an empiric therapy for pneumonia. Which of the following is the most likely recommended therapy for her?



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A senior man living in an assisted living facility came to the emergency department with cough and fever. He is diagnosed with pneumonia. Blood and sputum specimens were sent for laboratory testing. Empiric therapy started at that time. Now the sputum culture is back and positive with P. aeruginosa. Now therapy should be changed from previous empiric therapy to which of the following?



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A 17-year-old boy complains of dry cough form 1 week. The cough is persistent, indolent and associated with mild fever. His chest x-ray shows bilateral pulmonary infiltrates. What is the most common cause of this type of pneumonia in a young male?



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Bacterial Pneumonia - References

References

Leung AK,Hon KL,Leong KF,Sergi CM, Measles: a disease often forgotten but not gone. Hong Kong medical journal = Xianggang yi xue za zhi. 2018 Sep 24     [PubMed]
Grief SN,Loza JK, Guidelines for the Evaluation and Treatment of Pneumonia. Primary care. 2018 Sep     [PubMed]
Ashurst JV,Dawson A, Pneumonia, Klebsiella null. 2018 Jan     [PubMed]
Calik S,Ari A,Bilgir O,Cetintepe T,Yis R,Sonmez U,Tosun S, The relationship between mortality and microbiological parameters in febrile neutropenic patients with hematological malignancies. Saudi medical journal. 2018 Sep     [PubMed]
Shin EJ,Kim Y,Jeong JY,Jung YM,Lee MH,Chung EH, The changes of prevalence and etiology of pediatric pneumonia from National Emergency Department Information System in Korea, between 2007 and 2014. Korean journal of pediatrics. 2018 Sep     [PubMed]
Lat I,Daley MJ,Shewale A,Pangrazzi MH,Hammond D,Olsen KM, A Multicenter, Prospective, Observational Study to Determine Predictive Factors for Multidrug-Resistant Pneumonia in Critically Ill Adults: The DEFINE Study. Pharmacotherapy. 2018 Aug 12     [PubMed]
Søndergaard MJ,Friis MB,Hansen DS,Jørgensen IM, Clinical manifestations in infants and children with Mycoplasma pneumoniae infection. PloS one. 2018     [PubMed]
Karakuzu Z,Iscimen R,Akalin H,Kelebek Girgin N,Kahveci F,Sinirtas M, Prognostic Risk Factors in Ventilator-Associated Pneumonia. Medical science monitor : international medical journal of experimental and clinical research. 2018 Mar 5     [PubMed]
Phillips-Houlbracq M,Ricard JD,Foucrier A,Yoder-Himes D,Gaudry S,Bex J,Messika J,Margetis D,Chatel J,Dobrindt U,Denamur E,Roux D, Pathophysiology of Escherichia coli pneumonia: Respective contribution of pathogenicity islands to virulence. International journal of medical microbiology : IJMM. 2018 Mar     [PubMed]
Franquet T, Imaging of Community-acquired Pneumonia. Journal of thoracic imaging. 2018 Sep     [PubMed]
Ayede AI,Kirolos A,Fowobaje KR,Williams LJ,Bakare AA,Oyewole OB,Olorunfemi OB,Kuna O,Iwuala NT,Oguntoye A,Kusoro SO,Okunlola ME,Qazi SA,Nair H,Falade AG,Campbell H, A prospective validation study in South-West Nigeria on caregiver report of childhood pneumonia and antibiotic treatment using Demographic and Health Survey (DHS) and Multiple Indicator Cluster Survey (MICS) questions. Journal of global health. 2018 Dec     [PubMed]
Hanretty AM,Gallagher JC, Shortened Courses of Antibiotics for Bacterial Infections: A Systematic Review of Randomized Controlled Trials. Pharmacotherapy. 2018 Jun     [PubMed]
Julián-Jiménez A,Adán Valero I,Beteta López A,Cano Martín LM,Fernández Rodríguez O,Rubio Díaz R,Sepúlveda Berrocal MA,González Del Castillo J,Candel González FJ, [Recommendations for the care of patients with community-acquired pneumonia in the Emergency Department]. Revista espanola de quimioterapia : publicacion oficial de la Sociedad Espanola de Quimioterapia. 2018 Apr     [PubMed]
Coon ER,Maloney CG,Shen MW, Antibiotic and Diagnostic Discordance Between ED Physicians and Hospitalists for Pediatric Respiratory Illness. Hospital pediatrics. 2015 Mar     [PubMed]
Bickenbach J,Schöneis D,Marx G,Marx N,Lemmen S,Dreher M, Impact of multidrug-resistant bacteria on outcome in patients with prolonged weaning. BMC pulmonary medicine. 2018 Aug 20     [PubMed]
Luan Y,Sun Y,Duan S,Zhao P,Bao Z, Pathogenic bacterial profile and drug resistance analysis of community-acquired pneumonia in older outpatients with fever. The Journal of international medical research. 2018 Jan 1     [PubMed]

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