Multidrug-Resistant Pathogens of Pneumonia: Analytical Essay

Chapter 1. Introduction

1.1 Background

Acute Respiratory Infections (ARTIs) in infants and young children, mostly under 5 is one of the most distinct and dominant causes of mortality worldwide. Evidently, a significant portion of these casualties are caused by pneumonia which is a lower respiratory tract infection. According to a recent estimation, approximately 2 million children die every year globally (Levine, Foundation, & Dinleyici, 2010) on account of this detrimental condition and that is almost 19% of total children mortality rate. Nevertheless, this enumeration is more protrusive for Sub-Saharan Africa and South Asia (Nga Tong, BA, 2013)

Figure 1: Global Distribution of cause-specific mortality in children. (Ranganathan & Sonnappa, 2009)

Pneumonia generally occurs in lungs and it is basically the inflammation of lungs sac due to infection. A person having pneumonia suffer from relentless chest pain while breathing or coughing and the fluid or pus build up in alveoli of lungs causes some complications including limitations in oxygen intake which originates shortness of breath followed by fever, chills, and fatigue. However, more severe and life threatening conditions include sepsis, empyema, and pleural effusion or para-pneumonic effusion.

1.2 Types of Pneumonia Infection

Pneumonia is primarily categorized either as community or nosocomial pneumonia. The community-acquired pneumonia is the most common one and it generally occurs in the non-hospital patients. On the other hand, nosocomial infection is contracted by hospitalized patients in healthcare settings which involves ‘Hospital Acquired Pneumonia (HAP)’ and ‘Ventilator acquired pneumonia (VAP)’. Pneumonia is also classified based on the affected area and the way through which the inflammation occurs. These usually comprises of – bronchopneumonia (develops in bronchi), lobar pneumonia (emanates intra-alveolar space), interstitial pneumonia (permeate interstitial tissue in alveoli), lipoid pneumonia (augmentation of fat or lipid particles into the lungs), and aspiration pneumonia (due to insufflating toxic substances). Notably, a broad range of microbes including virus, bacteria, and fungi are held accountable for varying types of pneumonia and on this ground pneumonia are of three types- bacterial, viral, and fungal pneumonia.

1.2.1 General Classification

The most common classification of Pneumonia is based on exposure to pathogens which involves Community-acquired Pneumonia (CAP) and Nosocomial (Arshad, Fasanya, Cheema, & Singh, 2016).

1.2.1.1 Community-Acquired Pneumonia

CAP is infection of pulmonary parenchyma and commonly occurs in patients not residing in hospital facility. It is the most prevailing form of pneumonia and incurred from community. A current assessment shows that every 40 out of 1000 cases of pneumonia infection is caused by CAP (America, America, & McIntosh, 2002) Patients develops CAP mostly because of bacterial infection. However, some atypical pathogens also give rise to CAP.

Table 1. Microbial Pathogens Responsible for CAP

Microbial agents/

Cause

Prevalence (%)

North American Studies

Prevalence (%)

British Thoracic Society Studies

Bacteria

Streptococcus pneumoniae

Haemophilus influenzae

Staphylococcus aureus

Gram-negative bacilli

Klebsiella Pneumoniae

Miscellaneous

20–60

3–10

3–5

3–10

15-20

3–5

60–75

4–5

1–5

Rare

—

—

Atypical agents

Legionella

Mycoplasma pneumoniae

Chlamydia pneumonia

Chlamydia trachomatis

Chlamydia psittaci

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Coxiella brunette

10–20

2–8

1–6

4–6

—

2–5

5–18

—

Viruses

Ureplasma urealyticum

Pnumocistic carinii

Herpes Simplex virus

Hantavirus

Rhinovirus

Adenovirus

Haemophilus influenza type B

Respiratory syncytial virus

2-15

8-16

Aspiration

6-10

—

Collected from: (New, Journal, & Medicine, 1995) & (America et al., 2002)

1.2.1.2 Nosocomial Pneumonia

Nosocomial pneumonia infection on the other hand is caused by residence in long term care hospital facility. Patients generally get contracted by nosocomial infection within 48-72 hours after being admitted. Nosocomial pneumonia infection are of two types – Ventilator-Associated Pneumonia (VAP) and Hospital Acquired/ Healthcare-Associated Pneumonia (HAP) and both the types are generally caused by bacteria.

1.2.1.2.1 Ventilator Acquired Pneumonia

VAP- the patients admitted into the Intensive Care Unit (ICU) are at great risk for acquiring VAP. Depending on the ICU setting, etiology varies from patients to patients. Nonetheless, demographics shows that almost 28% patients receiving Mechanical Ventilation (MV) or any other respiratory support including endotracheal intubation and nasogastric tubes are contracted with VAP frequently (Asensio et al., 2000), (Chastre & Fagon, 2002).

1.2.1.2.2 Hospital-Acquired Pneumonia

HAP is the highest leading cause of death among the other nosocomial infections – Urinary Tract Infection (UTI), Surgical Site Infection (SSI), Blood Stream Infection (BSI), etc. (Gaynes & Edwards, n.d.). Several factors are associated with HAP, including, invasive medical or surgical procedures, peripheral venous catheterization, single-room stay of patients of multiple pathological conditions, roll boards, contact with healthcare workers, etc. (Asensio et al., 2000),(Gaynes & Edwards, nd.), (Lautenbach et al., 2001).

1.2.2 Anatomical Classification

Considering the location of infection, pneumonia is subdivided into three categories- lobar pneumonia, bronchopneumonia, and interstitial pneumonia.

1.2.2.1 Lobar Pneumonia

Lobar Pneumonia is characterized by accumulation of exudates in the intra-alveolar space, especially in one distinct lobe. It is also recognized as non-segmental pneumonia or focal non-segmental pneumonia. Most probable causative agent of lobar pneumonia is Streptococcus pneumonia known otherwise as pneumococcus. In lobar pneumonia we can see fluid-filled spaces that move from alveoli to alveoli until it occupies the whole lobe essentially. Therefore, it starts distally and spreads throughout the lobe. The progression of lobar pneumonia occurs in four stages- first congestion- which is alveolar edema followed by bacterial proliferation, then red hepatization- inflation of hemorrhagic exudates, grey hepatization- that is the accretion of suppurative alveolar exudates containing fibrin and finally resolution which is the processing of residual exudates. Severe complications of this class of pneumonia includes bacteremia and multi-organ infection.(Urinary & Dis-, 1930)

1.2.2.2 Bronchopneumonia

The term bronchopneumonia is generally used for the pneumonia infection that is significantly located in bronchi. It can infect in patches throughout the respiratory tract. Here, the congestion begins proximally from bronchioles and move toward the alveoli. Due to the pathophysiological similarities of bronchopneumonia with the lobar pneumonia, it is often leads to misdiagnosis or significant error in treatment plan. (Adolescence, 1933)

1.2.2.3 Interstitial Pneumonia

Interstitial pneumonia is characterized by progressive scarring in lungs. It permeates interstitial tissue in alveoli. The symptoms of infection includes fibrosis and inflammation. It is also termed as ‘cryptogenic fibrosing alveolitis’ (Turner-Warwick, Burrows, & Johnson, 1980). Interstitial pneumonia is only diagnosed when more acute disease supervenes and bring the patient to medical attention.(Inoue et al., 2003)

1.2.3 Etiological classification

Etiologically pneumonia is classified into – bacterial, viral and fungal pneumonia depending on the causative agents. However, the bacterial infections are more prevalent.

1.2.3.1 Bacterial Pneumonia

In bacterial pneumonia, bacteria causes the lung’s air sacs to become inflate and filled with pus, fluid and cellular debris. Bacterial pneumonia can be both mild and serious and it can eventually lead to total respiratory failure and even death. The severity of this type of pneumonia depends on the strength of the bacteria and how quickly the patient is diagnosed and treated. A cough with thick yellow, green or blood tinged mucus, severe chest pain along with fever can be the primary symptoms suggestive to bacterial infection (Virkki et al., 2002)

Streptococcus pnemoniae, Staphylococcus aureus, Mycobacterium tuberculosis, Haemophilus influnzae (type B) and Klebsiella pneumoniae are some of the common bacterial causative agents. (America et al., 2002)

Figure 2. Invading bacteria rate. Collected from:(Jones, 2010)

1.2.3.2 Viral Pneumonia

According to a recent study about 200 million cases of viral pneumonia occur every year. (Ruuskanen, Lahti, Jennings, & Murdoch, 2011). Viral pneumonia as suggested by the name is caused by virus. It occurs mostly on the immuno-compromised patients. Viral pneumonia is induced by rhinovirus, adenovirus, parainfluenza viruses1,2,3, influenza virus (A and B) and respiratory syncytial virus mostly (America et al., 2002). However, some other significant agents includes-

• Human meta-pneumovirus
• Human bocavirus
• Coronavirus types 229E, OC43, NL63, HKU1, SARS
• Enteroviruses
• Varicella-zoster virus
• Hantavirus
• Parechoviruses
• Epstein-Barr virus
• Human herpesvirus 6 and 7
• Herpes simplex virus
• Mimivirus
• Cytomegalovirus
• Measles etc. (Ruuskanen et al., 2011)

1.2.3.3 Fungal Pneumonia

Fungal pneumonia is mediated by fungus. In individuals with a normal immune system, fungi are a rare cause of pneumonia and often it’s regional. It is induced by Cryptococcus, Histoplasma, and coccidioides predominantly.

1.3 Clinical Symptoms and risk factors of Pneumonia

Usually the symptoms of pneumonia includes cough with or without bloody sputum which is the colored mucus. Again, as lungs are filled with exudates due to fluid buildup, oxygen intake by the lungs become significantly lower which ultimately causes dyspnea-shortness of breath followed by chest pain. Also, often there are systematic symptoms including fever and fatigue. Some generalized and well known risk factors of pneumonia are- being hospitalized, having a history of smoking and also, use of proton pump inhibitors has been recently associated with development of pneumonia (Gulmez et al., 2007). Additionally, having pulmonary diagnosis such as COPD (Chronic Obstructive Pulmonary Disorder) is a big risk factor. Impaired immune system, alcohol abuse, IV drug use and some neurological injuries also have great impact.

1.4 [Diagnosis of Pneumonia

Entrenched upon the symptoms, general diagnosis of pneumonia is usually done. Typical ways of diagnosing are- chest x-ray, differential diagnosis, having an ultrasound of lungs, microbiological diagnosis through blood culture etc. The most trivial form diagnosis is the chest x-ray and a usual chest x-ray of bronchopneumonia typically shows patchy areas that are spread out throughout the lungs. In atypical or interstitial pneumonia the pattern is also often spread throughout the lungs. However, in this case, it is often concentrated in the perihilar region of lungs and looks reticular, meaning there will be more line shaped opacities visible in a chest x-ray. In a lobar pneumonia, the fluid is localized to a single lobe or a set of lobes. Another way to detect lobar pneumonia, though, is to look for dullness to percussion which suggests that there is a lung consolidation. There is also tactile vocal fremitus which is when you feel more vibrations from a patient’s chest after they repeat certain phrases which is because sound travels better through the fluid filled consolidate tissue than air-filled healthy tissues. Late inspiratory crackles can also be heard along with bronchial breath sounds, bronchophony, and egophony.

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