Infections of the Blood and Lymphatic System. Cause - normal flora of the mouth and skin (e.g., streptococci and Staphylococcus epidermidis )
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Predisposing factors include congenital defects of the heart and diseases such as Rheumatic fever. Usually the valves are affected. Symptoms include fatigue and slight fever. The disease progresses slowly.
Dx - blood cultures in some, but some rare organisms are harder to identify
Tx - antibiotics
Prevention - prophylactic antibiotics (e.g., for oral surgery), sterile technique when using IV cathetersSubacute Bacterial Endocarditis
This infection is more severe and progresses more rapidly than does subacute bacterial endocarditis. The bacteria are more virulent and drug addiction is a predisposing factor.
Dx- blood cultures
Tx - antibioticsAcute Endocarditis
Cause - a variety of bacteria including Gram- and Gram + organisms as well as some fungi
Septicemia is an infection of the blood and is very serious. For example, the mortality rate for septicemia cause by Gram - bacteria is 30- 50%. The infection usually originates elsewhere (e.g., a boil or pneumonia). Symptoms include violent chills, fever, anxiety, lymphangitis (fig. 23.2), and rapid breathing. Septic shock is a life threatening condition characterized by low blood pressure and blood vessel collapse. Mortality rates are 50-70% and about 35,000 deaths occur in the U.S. each year from septicemia.
Dx - blood cultures
Tx – antibiotics and managing blood pressure
Prevention - avoid contamination of the blood and care to avoid contamination of patients who have invasive procedures.
Cause - Francisella tularensis
This zoonosis is also called rabbit fever but it occurs in several other mammals and arthropod vectors. There are 150-200 cases/year. The bacterium is one of the most infectious and a tech can become infected when culturing the organism. The symptoms vary but may include: skin lesions, swollen lymph nodes, diarrhea, cv or pulmonary disease. Mortality varies but can be up to 30% (for the pneumonic form).
Dx - culture on special media by experienced personnel in special facilities, and antibodies
Tx – antibiotics
Prevention - vaccination for high risk (although it does not always provide immunity), avoiding insect vectors, and care when skinning rabbits
Cause - Yersinia pestis
Plague exists naturally in many nonhuman animals (endemic in rodent populations in 15 of the states of the US). In the US there are a few (2-40) cases per year. It was responsible for the death of 35 million Europeans. Persons at highest risk in the US are vets, campers, backpackers, and people living near woodlands and forests. Manifestations include bubonic plague where the bacteria multiply in a flea bite, causing the formation of a bubo (a hard painful nodule) followed by chills, fever, headache, nausea, malaise, weakness, and tenderness of the bubo. This may progress to septicemic plague causing DIC, circulatory stagnation, subcutaneous hemorrhage, and gangrene (causing darkening of the skin, hence the name Black Death). Pneumonic plague is highly contagious. Untreated mortality rate from 50-60%. Pneumonic plague has a mortality rate of almost 100% even with treatment.
Dx – fluorescent antiboidy tests, stained smears
Tx - antibiotics ASAP, quarantine
Prevention - avoid fleas and a temporary vaccine for high risks
Although puerperal sepsis (AKA childbed fever) is now rare due to aseptic practices during childbirth, occasionally outbreaks do occur. In the past, this disease resulted in a relatively high mortality in post partum women. Symptoms include chills, fever, pelvic distention, and discharge (bloody) from the vagina
Dx – blood cultures
Tx – antibiotics
Prevention - aseptic conditions during childbirthPuerperal Fever (AKA Puerperal sepsis or childbed fever)
Neonatal sepsis and meningitis occurs with a high mortality (~ 50%). Symptoms include: fever, respiratory distress, and lethargy.
Dx – mothers can be tested prior to birth
Prevention- treat mother before or during birth, prophylactic antibiotics for infantGroup B Streptococcal disease
Cause- Bacillus anthracis
Anthrax can occur in three forms: (1) cutaneous anthrax is the most common and the least serious with an untreated mortality rate of 10-20%, the incubation time is 2-5 days and the disease results in a lesion at the portal of entry (23.7). (2) Respiratory anthrax is almost always fatal with or without treatment. The initial symptoms are similar to many mild respiratory infections and consequently sepsis occurs resulting in death (3) Intestinal anthrax is a very serious disease with the mortality rate between 25 and 50%. The symptoms are similar to food poisoning. It can spread resulting in sepsis.
Dx- blood culture, Gram stain of lesion, serology and DNA testing
Tx- antibiotics, for respiratory early and long term
Prevention- vaccination of humans and livestock, wearing respirators, dust-free environments.
Symptoms: fever, sore throat, and enlargement of the spleen and lymph nodes of the neck. Complications include: myocarditis, meningitis, hepatitis, or paralysis. Spread by saliva. Fatality does not usually occur in otherwise healthy individuals. Burkitt’s Lymphoma and Nasopharyngeal carcinoma are complications that occur mostly in certain geographic areas. Chronic fatigue syndrome may be related to EBV.
Dx - serology
Tx - usually not needed
Prevention - avoid other people’s salivaInfectious mononucleosis or the Kissing Disease
Cause - Plasmodium vivax, P. falciparium, P. malariae, and P. ovale
Malaria is one of the most significant diseases worldwide. The vector is the Anopheles mosquito. Mortality is about 1-3 million per year and 41% of humans live in areas where these organisms are endemic. The symptoms reoccur and coincide with the simultaneous rupture of rbcs and include: bouts of chills, fever, and sweating with complications such as anemia, enlargement of the spleen, liver, and kidneys, pulmonary failure and CNS and GI involvement. Morbidity is 300-500 million infected worldwide and currently a child dies every 20 seconds from malaria.
Dx - presence of the parasites in the blood, serological tests
Tx - antiparasitic medicine (Chloroquine)
Prevention - vector control, a vaccine is being studied, lower doses of anti-parasitic medicine
Usually a subclinical disease occurs that is most likely thought to be another disease. But, pregnant women can pass the parasite to the fetus causing severe birth defects, stillbirth, and miscarriage. It also can cause a fatal condition in immunocompromised individuals.
Dx- finding the parasite in blood, CSF, or tissue, or indirect immunofluorescence tests
Tx- Pyrimethamine and trisulfapyridine
Prevention- avoiding cats and their feces while pregnant or if immunocompromised, as well as avoiding raw meat.
Girl with hydrocephalus due to congenital toxoplasmosis.Toxoplasmosis
Normal flora of the upper respiratory system is diverse and includes organisms that are potential pathogens (e.g., Streptococcus pnuemoniae and Staphylococcus aureus). In addition, diphtheroids, micrococci and viridians streptococci are part of the normal flora.
Other parts of the upper respiratory system can also become infected (larynx or epiglottis). Streptococcal pharyngitis or strep throat makes up about 10% of the cases of pharyngitis.
Causative organism of Strep throat - Streptococcus pyogenes (Group A beta hemolytic streptococci)
Strep throat is a common throat infection characterized by a red throat, pus pockets, enlarged lymph nodes, and fever. Usually it is self-limiting. The major problem associated with these infections involves the serious sequelae that sometimes follow: Scarlet fever, Acute glomerulonephritis, & Rheumatic fever.
Diagnosis - serology, culture and isolation
Treatment – antibiotics (penicillin or erythromycin) for a full ten days.
Prevention - avoiding overcrowded conditions, adequate ventilation, prophylactic antibody treatment for
Causative organism- Corynebacterium diphtheriae
Diphtheria begins (localized infection) with a mild sore throat, fever, fatigue, and swelling of the throat. A pseudomembrane made up of the bacterium, damaged epithelial cells, fibrin, and blood cells forms in the throat that may cause asphyxiation. A systemic toxemia follows that is caused by the production of diphtherotoxin. Symptoms include: cardiovascular complications, paralysis, and if untreated death. Mortality is about 10% (ranging from 3.5%-22% depending on age, severity, and promptness of treatment). Humans are the primary reservoirs and the disease is spread by close contact with skin crusts shed by carriers or sick people, droplet nuclei or fomites.
Diagnosis - Culture and isolation on special media
Treatment – Antitoxin (an antiserum against the toxin), and antibiotics
Prevention - vaccination
Otitis media (middle ear infections) are caused also by organisms such as Streptococcus pneumoniae, S. pyogenes, and Haemophilus influenzae and can also lead to meningitis. Otitis media is responsible for 30 million doctor visits per year.
Bronchitis is an infection of the bronchi or bronchioles. About 15% of the human population has chronic bronchitis related to genetics, environmental conditions (e.g., exposure to dust), and smoking. Species of bacteria that cause bronchitis include: S. pneumoniae, Mycoplasma pneumoniae, Haemophilus, Moraxella, streptococci, and staphylococci.Other infections that arise from nasopharygneal infections
Causative organisms include Orthomyxoviruses, paramyxoviruses, coronaviruses, adenoviruses, enteroviruses, but 30-50% are caused by the 100 or more types of rhinoviruses.
Colds are very common and are self-limited (result in the loss of about 200 million work and school days/year). A cold is characterized by a scratchy throat, nasal discharge, headache and cough after a 2-4 day incubation. Symptoms last for about a week.
Diagnosis - not done, rule out bacterial infections sometimes
Treatment - for symptoms
Prevention - handwashing, careful disposal of infected tissues, avoidance of people with colds, and keeping hands away from the face.
Causative organisms - Streptococcus pneumoniae (> 60% of adult cases requiring hospitalization), also Klebsiella pneumoniae and Mycoplasma pneumoniae (walking pneumonia which is usually mild).
These organisms are inhaled and cause symptoms such as chills, high fever, cough, chest pain, and production of sputum (for Kp infections, also delirium). Classification of the disease is based on the site of infection: lobar (affecting one of the major lobes), or bronchial which begins in the bronchi and spreads throughout the lungs into the alveoli. Pneumonia is spread by droplets and carriers. Alcoholism is a predisposing factor for Kp infections but other immunocompromised individuals are also at risk. With S. pneumoniae, complications are septicemia, endocarditis, and meningitis. The overall mortality is 5% with antibiotics, 30% without except for K. pneumoniae, with mortality of 50-80% without treatment. Overall there are about 2 million cases of pneumonia/year in the US and 40,000-70,000 deaths. Deaths from pneumonia are the most for any infectious disease in the U.S.
Diagnosis - Gram stain, culture and isolation, X-ray of lungs
Treatment – antibiotics
Prevention – vaccination, avoiding crowds.
Causative agent - Bordetella pertussis
Whooping cough is a severe life threatening infection in young children (milder in older children and adults). The initial phase (catarrhal) is characterized by nasal drainage, sneezing and occasional coughing. The later phase (paroxysmsal) is characterized by recurrent, persistent cough followed by a “whoop” sound. The paroxysmsal stage also is characterized by the production of strong, sticky ropelike strings of mucus that cause the violent coughing. The closure of airways is what causes hypoxia and possibly death (especially in infants). A final convalescent stage occurs that can last up to six weeks or longer and is characterized by milder coughing and secondary infections. The toxins produced by this organism kill the epithelial cells of the respiratory system. Worldwide it causes 300,000-500,000 deaths per year and there are about 2,000-6,000 cases in the US each year. Whooping cough is transmitted by droplets (inhaled) and thus is easily acquired.
Diagnosis - Fluorescent antibody techniques, culture on a special medium, and serology
Treatment - early antibiotics and antitoxin, and supportive therapies e.g., suctioning.
Prevention - vaccination
Causative organism - Mycobacterium tuberculosis
Healthy people are generally resistant. The stages are: 1o that is subclinical and characterized by slight fever, chronic cough, weight loss, and night sweats. During this stage an inflammatory process resulting in the formation of tubercles (localized accumulations of bacteria and inflammatory cells). This stage may be followed by a latent period. The 2o stage (or reactivated TB) is characterized by violent coughing, greenish or bloody sputum, low-grade fever, anorexia, weight loss, fatigue, night sweats and chest pain. Finally a disseminated form may occur when the disease spreads to the other organs. This organism is spread by inhalation. World wide about 1/3 of the population is infected (maybe as many as 10 million in the US), also there are about 10 million new cases per year, and there are about three million deaths annually. The WHO declared this pandemic a global emergency in 1993.
Diagnosis - acid-fast staining, culture and isolation, skin test , X-ray, DNA probes
Treatment - cocktail of antibiotics (long term therapy required)
Prevention - a vaccine is available (not in the US) treatment of latent cases.
Causative organism - Legionella pneumophila
This disease is characterized by headache, malaise, fever, chills, cough, fluid in the lungs, chest pain and in 1/4 of the cases diarrhea, abdominal pain and vomiting. Death results from shock and kidney failure. It is transmitted by breathing in the organisms from the environment (not from other people). The immunocompromised and smokers are more at risk (actually males over 50 years of age). There is a 15% mortality due to respiratory failure
Diagnosis – culture and urine antigen test
Treatment – antibiotics
Prevention - avoiding water aerosols from contaminated sources and cleaning of these cooling systems etc.
Causative agent – orthomyxoviruses
This disease is characterized by headache, fever, muscle pain, and cough. It is spread by person to person aerosols. Pandemics occur and some have high mortality (1918 Swine flu pandemic). In the US there are 10,000-40,000 deaths annually, many due to secondary infections). Associated conditions: Reye’s syndrome and Guillain-Barre.
Diagnosis - symptoms, serology, and culture in chick eggs
Treatment – symptoms
Prevention - vaccines and avoiding overcrowding or others with the flu
Causative agent - a virus of the family Bunyaviridae
This starts as a flu-like illness but rapidly progresses to respiratory failure and death (about 60% mortality). It is spread by the urine and feces of deer mice and other rodents.
Diagnosis - serology
Treatment - symptoms
Prevention - avoiding rodents and their droppings (do not create aerosols by sweeping)
Flu-like illness in those who develop symptoms. It is restricted in geographical area because people get it from breathing in the fungus from the environment (not from other people). The majority of people recover spontaneously within a month., but in some it becomes a TB like illness and in some it becomes systemic (with a 50% mortality with treatment).
DX - microscopic exam for presence of fungi, skin tests, and serology
TX - anti-fungal drugs
Prevention - dust control (do not breath in fungal spores)
Causative organism - Histoplasma capsulatum
This disease is variable. The morbidity is 500,000/ year with a low mortality. In general it is characterized by a flu-like illness that is self-limiting. In a few a serious systemic infection occurs which leads to hepatosplenomegaly, anemia, and circulatory collapse.
DX - microscopic exam, skin testing (limited value) and serology
TX - antifungal drugs
Prevention - avoiding aerosols in chicken coops and bat caves