By I. Kippler. Shippensburg University of Pennsylvania. 2018.

Etiology purchase 50 mg minocycline amex antimicrobial or antimicrobial, transmission and pathogenesis 527 taependymal meninges adjacent to the subarachnoid space order 50mg minocycline free shipping bacteria at 8 degrees, and, occasionally, to the apical posterior areas of the lungs. In addition, chemotactic factors released by the macrophages attract circulating monocytes to the infection site, leading to their differentiation into mature macrophages with increased capacity to ingest and kill free bacteria (Correa 1997, Starke 1996, Vallejo 1994). Due to the fact that myco- bacteria are not able to grow under the adverse conditions of the extracellular envi- ronment, most infections are controlled by the host immune system. However, the initial pulmonary infection site, which is denominated “primary complex or Ghon focus” and its adjacent lymph nodes, sometimes reach sufficient size to develop necrosis and calcification demonstrable by radiographs (Feja 2005, Schluger 1994). It is generally associ- ated with close contact with cattle, and is variable from one country to another and even from region to region inside the same country (see Chapter 8). This situation oc- curs when repetitive or constant contact with the infectious source - generally fam- 528 Tuberculosis in Children ily members - takes place. Therefore, when a child is diagnosed, a search should be performed for an adult case with a high bacillary load in the respiratory tract (Alet 1986). On the other hand, older children may become infected from an external source, such as schoolmates, team leaders or young adults outside the home. The presence of extensive pulmonary lesions, such as cavities, is the most impor- tant individual human factor in determining the infectious power, since these le- sions are associated not only with an important concentration of oxygen that allows active bacillary multiplication, but also with a rapid pathway to the external envi- ronment. The amount of bacilli released into the atmosphere under these conditions is enough to produce the transmission from person to person (Correa 1997, Schluger 1994). The degree of pulmonary involvement is another important factor, since the exten- sion of the lesions is related to the bacillary load, the intensity and frequency of coughing, and the number of cavities that may propagate these bacilli. Rarely, non- pulmonary localization of the disease with high infectious power, such as the la- ryngeal form, becomes an infectious source. In this case, simple actions such as talking can cause the elimination of an important amount of mycobacteria (Correa 1997). Socioeconomic factors as well as the overcrowded living places in urban areas increase the risk of infection allowing larger contacts with infected persons. The concentration of bacilli depends on ventilation of the surroundings and expo- sure to ultraviolet light. From a public health point of view, these stages have absolutely different transmission implications and epidemiologic consequences. Household is the most frequent setting for exposure although several places that allow a close con- tact with potentially contagious adults such as school, day care centers and other th environments become occasional exposure places. During the 18 century, the “familial hypothesis” raised by the occurrence of familial clustering, dominated medical thinking. In adults, the dis- tinction between infection and disease becomes less difficult because the latter may 530 Tuberculosis in Children be the result of dormant bacilli acquired during a past infection. In children, the distinction may not be so clear because the disease more often progresses from an initial or primary infection. Asymptomatic presentations are more common among school-age children (80-90 %) than in infants less than one year old (40-50 %) (Correa 1997, Vallejo 1996). Erythema nodosum is a toxic allergic erythema with nodular lesions in the skin or under it, 2 to 3 cm large. These lesions are spontaneously painful and very painful under pressure, and are usually located bilaterally in feet and legs. The erythema nodosum is usually accompanied by pharyngitis, fever and joint inflam- mation and is more frequent in girls over six years. Phlyctenular conjunctivitis is an allergic keratoconjunctivitis characterized by the presence of small vesicles that usually evolve to ulcers and resolve without scars.

The degree of competitive inhibition cannot be decreased by increasing the concentration of the substrate minocycline 50 mg with mastercard antibiotics penicillin allergy. Based on their relationship to their host generic minocycline 50mg visa bacteria 1710, microorganisms classifed as saprophytes (free living microbes that subsist on dead or decaying organic matter, mostly found in soil). Parasites (establish themselves and multiply in hosts (it may be pathogens - disease producing) or commensals (without causing any damage to the host-normal fora). Secondary infection : When new parasite sets up an infection in a host whose resistance is lowered by a preexisting infectious disease. Cross infection : When a patient already suffering from a disease a new infection is set up from another host or another external source. Latent infection : Some parasites, following infection, may remain in the tissues in a latent or hidden form, multiply and producing clinical disease when the host resistance is lowered. It may also occur by i) Inhalation of pathogen (Infuenza) ii) Ingestion of food or drinks contaminated by pathogens iii) Inoculation directly into the tissues of the host (Tetanus spores). Infectious disease may be localized ( superfcial or deep-seated) or generalized (spreading through tissue spaces and circulation). However, it can be Endemic (when a small number of cases occur constantly among the population of a community eg: Typhoid), Epidemic (The disease fares up and large number of cases develop with in a community with in a short time. Based on the structure and shape three major group of bacteria namely, Bacillus (cylindrical forms), Coccus (spherical forms) and Spiral. Humans and animals have abundant normal fora (microbes) that usually do not produce disease under normal healthy condition. The pathogenesis of bacterial infection includes initiation of the infectious process and mechanisms that lead to the development of signs and symptoms of disease. The virion consists of nucleic acid surrounded by a protein coat called capsid which protects the nucleic acid from deleterious environment and to introduce viral genome into the host cells by adsorbing readily to the cell surface. They may be sporadic like Mumps, endemic like Infectious hepatitis, epidemic like Dengue fever or pandemic like Infuenza. Depending on the clinical outcome, Viral infections can be classifed as unapparent (sub clinical) or apparent (clinical or overt) infections. Depending on the cell morphology fungi can be divided into four classes - i) Yeasts : Unicellular fungi which occur as spherical and reproduce by simple budding ii) Yeast like fungi : Grow partly as yeast and partly as elongated cells resembling hyphae form a pseudo mycelium iii) Moulds : True mycelia and they are reproduced by the formation of different types of spores. Superfcial mycoses are of two types - surface infections (only on dead layers of skin) and cutaneous infections (cornifed layer). Infectious diseases are caused by foreign substances like fungi, bacteria, virus or parasite, when they enter in to the human body. Though the disease by such pathogen affects the body for a shorter duration, the person may survive after loosing functions of some of the organ (eg. The immune system provides such freedom enjoyed by an individual, in order to keep them free from diseases. Immune system keep memory about the pathogens and when the same pathogen reenters a better immune response is produced. Recognition and destruction of the mutant cells that can become cancerous and this is known as Immunosurveillance. Normally, Immune system does not produce antibodies against its own body tissues (self antigens), called as Immune tolerance or Self recognization. Depending on the nature of response towards the pathogen, Immune system is broadly classifed into Natural and Acquired immunity. They developed from the bone marrow stem cells and give rise to two families of white blood cells namely the Myeloid cells (named after bone marrow) and the Lymphoid cells, which take their name from the lymphatic system. The lymphoid cells include T and B lymphocytes which get their maturation in different lymphoid organs. B-cell maturation begins in the liver (fetal) and continues within the bone marrow as maturation progresses (adult) and T cells complete their maturation in the thymus.

Chromatolysis may be followed by regrowth of the axon from the point of damage discount 50 mg minocycline amex common antibiotics used for sinus infection, a phenomenon more often seen in the peripheral than in the central nervous system purchase 50mg minocycline free shipping treatment for dogs cold. In neuronal storage diseases, excessive amounts of lipids, carbohydrates, glycosaminoglycans, or glycoproteins accumulate within neurons, enlarging and distorting the normal geometry of the cell body and proximal processes. These are usually seen in the context of inherited disorders of lipid or glycosaminoglycan catabolism (eg. Some reflect the focal storage of metabolites, some the presence of viral proteins or nucleoproteins, and some the abnormal accumulation of structural proteins (eg. Lipofuscin is an insoluble mix of proteins, lipids, and minerals that accumulates in neurons and astrocytes during the normal aging process. Neuronophagia is the phagocytosis of degenerating neurons, usually by macrophages. This is commonly seen after hypoxic or ischemic insults or during viral infections. Dying back degeneration, a degeneration of the most distal axon, followed by the progressive loss of more and more proximal regions, is often seen in toxic peripheral neuropathies. Demyelination refers to the primary loss of myelin with relative preservation of the axon (eg. Spheroids contain mixtures of lysosomes, mitochondria, neurofilaments, and other cytoplasmic constituents. Slowing or cessation of axoplasmic transport at sites of damage presumably account for spheroids. This is seen in many types of mental retardation, including congenital hypothyroidism (cretinism). Atrophy is a reduction in the volume and surface area of dendritic branches, commonly seen in neurodegenerative diseases. Neuritic plaques are collections of degenerating axons and dendrites, mixed with microglia and astrocytes and associated with the extracellular deposition of amyloid (beta-amyloid, see lecture on Neurodegenerative diseases). Status spongiosis refers to a spongy state of the neuropil, the formation of fine to medium sized vacuoles representing swollen neuronal and astrocytic processes. This change is typical of transmissible spongiform encephalopathies, such as Creutzfeldt- Jacob disease. They contact blood vessels, pial surfaces, and enfold synapses in their functions to maintain the concentration of ions, neurotransmitters, and other metabolites within normal levels in the extracellular space. Astrocytes undergo hypertrophy (enlargement) and hyperplasia (proliferation) in response to a great many pathological processes, including hypoxic-ischemic damage and trauma. Astrocytes develop abundant pink cytoplasm, either due to imbibing plasma proteins and fluid in the short-term (when the blood-brain-barrier is broken) or filling up with intermediate filaments (in long-term scarring). The descriptive term of reactive, hypertrophic or gemistocytic is often used to describe this change. They are thought to be related to the hyperammonemia of hepatic failure (see notes on Metabolic diseases). Corpora amylacea are spherical accumulations of polyglucosan (branched-chain glucose polymers), which increase in numbers with age, particularly in a subventricular and subpial locations, and in glial scars. Neoplasia: Astrocytomas represent a common form of brain tumor (see notes on neoplasia) 5. Note that oligodendrocytes or progenitors of oligodendrocytes are able to remyelinate demyelinated axons, and thus help to repair demyelinated lesions.

The connective tissue of the sutures allows for continued growth of the skull bones as the brain enlarges during childhood growth proven minocycline 50mg antibiotic resistance epidemiology. The second mechanism for bone development in the skull produces the facial bones and floor of the brain case purchase minocycline 50mg amex bacteria candida. However, these cells differentiate into cartilage cells, which produce a hyaline cartilage model of the future bone. As this cartilage model grows, it is gradually converted into bone through the process of endochondral ossification. This is a slow process and the cartilage is not completely converted to bone until the skull achieves its full adult size. At birth, the brain case and orbits of the skull are disproportionally large compared to the bones of the jaws and lower face. This reflects the relative underdevelopment of the maxilla and mandible, which lack teeth, and the small sizes of the paranasal sinuses and nasal cavity. During early childhood, the mastoid process enlarges, the two halves of the mandible and frontal bone fuse together to form single bones, and the paranasal sinuses enlarge. At the time of birth, the facial bones are small and underdeveloped, and the mastoid process has not yet formed. Development of the Vertebral Column and Thoracic cage Development of the vertebrae begins with the accumulation of mesenchyme cells from each sclerotome around the notochord. These cells differentiate into a hyaline cartilage model for each vertebra, which then grow and eventually ossify into bone through the process of endochondral ossification. However, small areas of notochord tissue persist between the adjacent vertebrae and this contributes to the formation of each intervertebral disc. The ribs initially develop as part of the cartilage model for each vertebra, but in the thorax region, the rib portion separates from the vertebra by the eighth week. The cartilage model of the rib then ossifies, except for the anterior portion, which remains as the costal cartilage. The sternum initially forms as paired hyaline cartilage models on either side of the anterior midline, beginning during the fifth week of development. Eventually, the two halves of the cartilaginous sternum fuse together along the midline and then ossify into bone. The manubrium and body of the sternum are converted into bone first, with the xiphoid process remaining as cartilage until late in life. What are the two mechanisms by which the bones of the body are formed and which bones are formed by each mechanism? This error in the normal developmental process results in abnormal growth of the skull and deformity of the head. It is produced either by defects in the ossification process of the skull bones or failure of the brain to properly enlarge. It is a relatively common condition, occurring in approximately 1:2000 births, with males being more commonly affected. Primary craniosynostosis involves the early fusion of one cranial suture, whereas complex craniosynostosis results from the premature fusion of several sutures. The early fusion of a suture in primary craniosynostosis prevents any additional enlargement of the cranial bones and skull along this line. Continued growth of the brain and skull is therefore diverted to other areas of the head, causing an abnormal enlargement of these regions.