Pneumonia means inflammation of the lung tissue (parenchyma). This inflammation can be caused by infections that is invasion of tissue by germs or by other means such as foreign bodies including aspiration of food particles, medicines, iodizing radiations, allergic reactions etc. infections can be various organisms (germs) which include viruses, bacteria or others like fungi, protozoa, worms etc. the reason doctors try to differentiate between these is because, if we can pin-point the organism, we can direct our treatment better, i.e. use the right medicine for the right bug.

Cause

Commonly the causative organisms are either bacteria or viruses. Both organisms usually tend to produce very similar symptoms. In individual cases, it may not be possible to differentiate this clinically. In the large majority of cases vigorous searching for the organism might not also be necessary. This is because; the treatment strategy will probably be the same by the time the answer is obtained.

Signs and Symptoms

In differentiating viral and bacterial pneumonia we may find that in viral pneumonia, the rise in temperature (fever) is generally lower than bacterial pneumonia. Bacterial pneumonia is older children tends to start typically with sudden onset of a shaking chill, followed by high fever, cough and chest pain. In adolescents and older children, this can be accompanied by intermittent drowsiness, bluish discolouration around mouth (perioval cyanosis), a dry hacking cough and a tendency to withhold (splinting) breathing excursions on the affected side. Occasionally delirium and anxiety are more obvious than in a viral pneumonia. Gastro-intestinal disturbances are also commoner in bacterial causes.

Most of the other features like a preceding runny nose and/or cough, fast breathing, lack of appetite etc. are present in both. It is also inadvisable to try to clinically differentiate in an infant or a young child.

Diagnosis

Investigations, like blood and other tests including culture and serology may help differentiate these two common pathogens (germs). A basic blood count and estimation of CRP or C-Reactive Protein (Procalcitonin in Western countries are fast becoming popular) can indicate early in the disease process which is the most likely causative group. But, interestingly, viral pneumonias can lead to secondary bacterial infection. Therefore, a repeat of these basic tests may be sometimes necessary in cases suspected to be viral in origin.

Given the above explanation, you may have already figured out that there may not be a straightforward answer to this. However, two basic rules apply. Hospitalization depends on the presenting condition of the patient (in other words, depending on the severity of symptoms) and their likelihood of becoming serious. Causative factor may also be a major determinant. For example, in radiation pneumonia, rapid deterioration is expected and hospitalization may be prudent

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Management

In communities with a high percentage of penicillin-resistant pneumococcus (as ours), for mildly ill children who may not need hospitalization, a high dose of amoxicillin, in childrennot allergic to penicillin group of medicines, may suffice. Alternatives include cefuroxime axetil or amoxycillin/clavulonic acid combinations. In allergic group, a macrolide like azithromycin is appropriate. For school-aged children, where another bug called Mycoplasma pneumonae occurs in significant proportion, azithromycin should be used as the antimicrobial of choice.

Adequate coverage and completion of antimicrobial course is extremely important to avoid developing resistance to these otherwise very effective medicines. The world seems to be running out of choices of medicines to effectively treat these otherwise potentially fatal diseases, thanks to wide spread unscrupulous and inappropriate use of these medicines by, say, going to your local medicine shop to seek advice from the shop-keeper! Doctors and all other conscientious citizens should engage in educating general public about the dangers of such practices. Time seems to be running out unless we can get a grip of this situation.

Prevention

Pneumonia is a disease process whereas immunizations (vaccinations) are usually against specific organisms. For example, there can be no immunization against fever, but many important organisms causing fever can be immunized against e.g. measles, chicken pox, diphtheria, tetanus etc. Two of the most common organisms that are notorious to cause pneumonia have vaccines against them. While vaccines against Haemophilus influenzae B [Hib] is highly effective against all sorts of diseases caused by this organism (most notably meningitis) including Hib pneumonia, vaccines against Pneumococcus pneumonae [Pneumococcalvaccines] are highly effective only against some strains (sub-types) of pneumococcus.  The former is universally available in Bangladesh and is part of the WHO led Universal Immunization Programme in full swing with excellent

preventative effect on the paediatric population, the later is yet to be available widely.

There are two types of pneumococcal vaccine, pneumococcal polysaccharide vaccine and pneumococcal conjugate vaccine. The first pneumococcal polysaccharide vaccine was licensed in the United States in 1977. In 1983, an improved pneumococcal polysaccharide vaccine was licensed, containing purified protein from 23 types of pneumococcal bacteria (the old formulation contained 14 types). This pneumococcal polysaccharide vaccine is commonly known as PPV23 or PPV. The PPV vaccine is licensed for use in adults and persons with certain risk factors who are over two years of age. The pneumococcal conjugate vaccine was licensed in the USA in early 2000. It is licensed for use in preventing pneumococcal disease in infants and toddlers (six weeks to five years of age). It is commonly known as PCV7 or PCV. Both pneumococcal vaccines are made from inactivated (killed) bacteria. The pneumococcal polysaccharide vaccine (PPV) contains long chains of polysaccharide (sugar) molecules that make up the surface capsule of the bacteria. The 23 types of pneumococci that are included cause 88% of invasive pneumococcal disease.

The pneumococcal conjugate vaccine (PCV) includes purified capsular polysaccharide of seven types of the bacteria "conjugated" (or joined) to a harmless variety of diphtheria toxin. The seven types of purified bacteria included account for 86% of bacteremia, 83% of meningitis, and 65% of acute otitis media (ear infection) among children less than six years of age in the United States.

The polysaccharide vaccine (PPV) can be given as a shot in the muscle or the fatty tissue of the arm or leg. The conjugate vaccine (PCV) is given as a shot in the muscle. Other hygienic measures are essential and have partial preventative effect, which I will be dealing in the next answer below.

Compiled by: Farhana Islam

MD, Canada