Infectious diseases

INFECTION AND INFECTIOUS DISEASE 

INFECTIOUS AGENTS 

The world is full of microorganism ,the vast majority of which are harmless to man and many of which are essential to life .Some of these organism live on or within human hosts: most of these form part of our normal flora and are benign passenger or symbiotes.A minority ,however ,ar pathogenic ,causing illness or even death to their host .It is thses viruses ,bacteria , protozoa ,and worms which are responsible for the infectious disease.

Infection remains the main cause of morbidity and mortality in man ,particularly in underdeveloped areas where it is associated with poverty and overcrowding .In the developed world increasing prosperity ,universal immunization and antibiotics have reduced the prevalence of infectious disease .However ,antibiotic -resistant strains of bacteria as well as viruses and ' new ' diseases such as human immunodeficiency virus ( HIV ) infection and variant Creutzfeldt-jakob disease ( vCJD) have emerged .Increased global mobility has aided the spread of infectious disease and allowed previously localized pathogens to establish themselves world-wide .Deteriorating social conditions in the inner city areas of our major conurbations have facilitated the resurgence of tuberculosis and other infection.Changes in farming and food-processing methods have controlled to an increase in the incidence of food and water-borne disease.

In the developing world successes such as the eradication of smallpox have been balance or outweighed by the new plagues.Infectious cause nearly 25% of all human deaths .Two billion people -one third of the world's population-are infected with tuberculosis ,250-300 million people catch malaria every year ,and 200 million are  infected with schistosomiasis .Infections are often multiple and there is synergy both between different infections ,and between infection and other factors such as malnutrition.Many of the infectious diseases affecting developing countries are preventable or treatable ,but continue to thrive owing to lack of money and political will.

INFECTIOUS AGENTS

The causative agents of infectious diseases can be divided into four groups.

Prions  are the most recently-recognized and the simplest infectious agents ,consisting of a single protein molecule.They contain no nucleic acid and therefore no genetic information : their ability to propagate within a host relies on inducing the conversion of endogenous protein into prion protein.

viruses  contain both protein and nucleic acid and so carry the genetic information for their own reproduction.However ,they lack the apparatus to replicate autonomously ,relying instead on "hijacking " the cellular machinary of the host .They are smalll ( usually less than 200 nanametres in diameter ) and each virus possesses only one species of nucleic acid ( either RNA or DNA ).

Bacteria  are usually though not always ,larger than viruses .Unlike the latter they have both DNA and RNA , with the genome encoded by DNA ,They are enclosed by a cell membrane ,and even bacteria which have adopted an intracellular existence remain enclosed within their own cell wall. Bacteria are capable of fully autonomous reproduction ,and the majority are not  dependent on host cells.

Eukaryotes are the most sophisticated infectious organism ,displaying sub-cellular compartmentalization .Different cellular functions are restricted to specific organelles ,e.g photosynthesis takes place in the choloroplast ,DNA transcription in the nucleus and respiration in the mitochondria ,Eukaryotic pathogens include unicellular protozoa ,fungi ( which can be unicellular or filamentous ) ,and multicellular parasite worms.

Other higher classes ,notably the insects and the arachnids ,also contain species which can parasitize man and cause disease .

       

Infection

INFECTION AND INFECTIOUS DISEASE

ORGANISM INTERACTION AND SOURCES OF INFECTION

HOST / ORGANISM INTERACTIONS

Each of us is colonized with huge numbers of micro-organism ( bacteria plus viruses ,fungi , protozoa , and worms ) with which we coexist .The relationship with some of these organism is symbolic ,in which both partners benefit ,while others are commensals , living on the host without causing harm .Infection and illness may be due to these normally harmless commensals and symbiotes evading the body's defences and  penetrating into abnormal sites.Alternatively ,disease may be caused by exposure to exogenous pathogenic organism which are not part of our normal flora.



The symptoms and signs of infection are a result of the interaction between host and pathogen .in some cases ,such as the early stages of influenza ,symptoms are almost entirely due to killing of host cells by the invading organism .Usually ,however ,the harmful effects of infection are due to a combination of direct microbial pathogenicity ,and the body's response to infection .In meningococcal septicemia ,for example ,much of the tissue damage is caused by cytokines released in an attempt to fight the bacteria .In a few instances , such as chronic South American trypanosomiasis ( Chaga's disease ) ,mortality is almost entirely immunological ,with the parasite itself having little effect once the inflammatory process has been triggered .



SOURCES OF INFECTION

The endogenous skin and bowel commensals can cause disease in the host ,either because they have been transferred to an inappropriate site ( e.g bowel coliforms causing urinary tract infection ) ,or because host immunity has been attenuated ( e.g candidiasis in an immune compromised host ) .Many infections are acquired from other people ,who may be symptomatic themselves or be asymptomatic carriers .Some bacteria ,like the meningococcus ,are common transient commensals ,but cause invasive disease in a small minority of those colonized .Infection with other organisms ,such as the hepatitis B virus ,can be followed in some cases by an asymptomatic but potentially infectious carrier state.



Zoonoses are infections that can be trasmitted from wild or domestic animals to man .Infections can be acquired in a number of ways : direct contact with the animal ,ingestion of meat or animal products , contact with animal urine or faeces ,aerosol inhalation ,via an arthropod vector ,or by inoculation of saliva in a bite person to person .



Most microorganisms do not have a vertebrate or arthropod host but are free-living in the environment . The vast majority of these environmental organisms are non-pathogenic ,but a few can cause human disease.Person to person transmission of these infections is rare .Some parasites may have a stage of their life cycle which is environmental ( for example the free-living larval stage of Strongyloides stercoralis and the hookworms ) even though the adult worm requires a vertebrate host.Other pathogens can survive for periods in water or soil and may be transmitted from host to host via this route ,these should not be confused with true environmental organisms.



World -wide mortality from infectious disease such as :

• Acute lower respiratory infections
• HIV/AIDS.
• Diarrheal disease.
• Tuberculosis.
• Malaria.
• Measels.
• Tetanus.
• Whooping cough.
• Meningitis.
• Leishmaniasis.

Lower respiratory infections

In the health  the lower respiratory tract is normally sterile owing to a highly efficient defence system and lower respiratory tract is frequently compromised by smoking

LOWER RESPIRATORY TRACT INFECTIONS 

Lower respiratory infections cause disease in the air sacs and the infection that results is called pneumonia. This part of the paper will address the various types of pneumonia (eg, generally, chronic interstitial pneumonia and fungal) and agents that cause them.

Acute respiratory infections are a public health problem of constant and widespread. Cause a greater burden of disease in the world that infection with human immunodeficiency virus, malaria, cancer or heart attacks.In  United States, causing more diseases and deaths than any other disease, and there was little change in mortality from respiratory tract infection for more than five decades.1 2 the results of an acute lower respiratory tract depends on the virulence of the organism and response of inflammation in the lung.

Changes in the characteristics of the aging population and the swelling numbers of immunocompromised patients with conditions increased the number of people in danger. A wide selection of new pathogens also provides challenges for the microbiology laboratory. Overtreatment of uncomplicated acute bronchitis, which is largely due to viruses, has led to unprecedented levels of multidrug resistance among invasive pathogens such as Streptococcous pneumoniae. Guidelines for a rational approach to evaluation and treatment of patients with acute bronchitis have been published recently in an attempt to reduce misuse of antibiotics and an attempt to prevent further increases in resistance rates. The role of the laboratory are very limited.

PNEUMONIA 

Pneumonia. It comes in a variety of situations and treatment should vary depending on the situation. It is classified as community or hospital acquired, depending on where the patient contracted the infection. Sometimes it is fatal in older people or those who are immunocompromised. The most common treatment is antibiotics and vary in their side effects and effectiveness. Pneumonia is the leading cause of death among children under five years. The most common cause of pneumonia is a bacterial pneumonia, Streptococcus pneumoniae accounts for two thirds of bacteremic pneumonia.

A dangerous type of lung infection with a mortality of about 25%. For optimal management of a pneumonia patient, the following assessment - pneumonia severity (including whether to treat as home, hospital or intensive care), identification of the bacteria, the analgesia for chest pain, need for supplemental oxygen, physical therapy, hydration, bronchodilators and possible complications of emphysema or lung abscess.

Community respiratory infections appropriate use of fluoroquinolones is a therapeutic option. These have been shown to be targeted in vitro and typical and atypical pathogens of interest. newer fluoroquinolones (eg moxifloxacin or gatifloxacin) have extended the activities Gram + ve, and once a day and, consequently, the potential first-line treatment of lower respiratory tract infections. However, clinical response is the best indicator of effectiveness of moxifloxacin or gatifloxacin, and have proved effective against community-acquired respiratory tract infections clinically.

Health information - Isosporiasis

NFECTIOUS NON - INFLAMMATORY DIARRHEAS

ISOSPORIASIS

Isosporiasis is a disease caused by protozoan Isospora Belli. Organism to infect the lining of the small intestine and can cause severe diarrhea and malabsorption (inability to absorb nutrients). Isospora beautiful spread in the faeces. Food or water contaminated by animal droppings can do this organism, it is also possible that oral-anal sex can spread the infection. Sometimes it occurs can be traced isosporiasis water contaminated by faeces. Isosporiasis is not common in the United States is more common in tropical areas of the world and in places where water contamination is a problem. isosporiasis United States is the first AIDS-defining illness in approximately 0.2% of AIDS.

CLINICAL MANIFESTATIONS

The infection causes severe diarrhea, not the blood and abdominal cramps that can last for weeks and the result of malabsorption and weight loss. In immunocompromised patients and in infants and children, diarrhea can be severe. Eosinophilia may be present (otherwise other protozoal infections).

DIAGNOSIS

Large oocyst detection in stool by modified acid-fast staining .


TREATMENT

Isosporiasis effective treatment is a combination of two drugs: trimethoprim and sulfamethoxazole (TMP-SMX, Bactrim, Septra). Treatment isosporiasis two double-strength tablets of TMP-SMX twice daily. The alternative is the double strength tablet three times daily. TMP-SMX therapy usually continues for 2-4 weeks. Patients who are intolerant to SMX, drug pyrimethamine (Daraprim), together with folinic acid can be implemented. This combination of drugs used per month.

To help control diarrhea, perhaps in combination with antibiotic treatment, a number of anti-diarrhea medication may be taken. And because the diarrhea is the direct result of intestinal inflammation caused by infection, certain drugs non-steroidal anti-inflammatory drugs (NSAIDs) help, such as ibuprofen. Another drug, has proven to significantly reduce diarrhea due to its anti-inflammatory drug, thalidomide (Thalomid). Women taking this drug should avoid becoming pregnant Thalidomide can cause severe birth defects.

PREVENTION

The most effective way to prevent isosporiasis is to eliminate its sources, mainly foods potentially contaminated human feces. This is particularly true for HIV positive people with weakened immune systems rave tion in the tropics and subtropics where water and food may be contaminated. Drink bottled water and ensure that food is cooked properly, can help reduce the risk of any rave isosporiasis tion in the tropics and subtropics.