Routes of infection

Fig. 4.1 Routes of infection and spread of transmission of disease. CNS, central nervous system.

Two major advantages stem from the use of live vaccines. Firstly, the immunization mimics a natural infection such that only a single exposure is required to render an individual immune. Secondly, the exposure may be mediated through the natural route of infection (e.g. oral) thereby stimulating an immime response that is appropriate to a particular disease (e.g. secretory antibody as primary defence against poliomyelitis virus in the gut). 

Disadvantages associated with the use of live vaccines are also apparent. Live attenuated vaccines, administered through the natural route of infection, will be replicated in the patient and could be transmitted to others, ff attenuation is lost during this replicative process then irrfectiorrs rrtight result (see poliomyelitis, below). A second, major disadvantage of live vaccines is that the course of their action might be affected by the infeetion and immunological status of the patient. 

Osteomyelitis is most often classified by route of infection and duration of disease. 

Staphylococcus aureus is the predominant pathogen seen in all types of osteomyelitis. However, the spectrum of potential causative pathogens varies with patient-specific risk factors and route of infection. 

O The most common route of infection for endemic fungi is via the respiratory tract, where conidia aerosolized from contaminated soil are inhaled into the lung. 

Conidia Propagating form (spores) of filamentous fungi that are released into soil and air currents. Inhalation of spores is the most common route of infections for endemic fungi and invasive molds. 

The exact mechanism of bacterial infection of the prostate is not well understood. The possible routes of infection include ascending infection of the urethra, reflux of infected urine into prostatic ducts, invasion by rectal bacteria through direct extension or lymphatic spread, and by hematogenous spread. 

Bacteria sensitive to CAMP-mediated killing exhibit attenuated virulence in the host, while CAMP resistance confers an in vivo survival advantage (Groisman et al., 1992 Gunn et al., 2000 Rosenberger et al., 2004 Tamayo et al., 2005). Since many types of CAMPs are localized along common routes of infection, Salmonella and... 

Both ECV and PDV are infectious for susceptible cultured lepidopteran cells. However, the ECV is much more highly infectious when compart on a physical particle infectious particle ratio. For natural routes of infection in the insect, the viral occlusion and the PDV is far more highly infectious than ECVQJL). The occluded baculoviruses, therefore, have a biphasic life cycle the PDV and viral occlusion are the most efficient viral forms for natural infection of the insect, and the ECV form is the most efficient for secondary infection of tissues in the insect and cells in culture. The polyhedrin gene is not essential for cell culture infection. 

The frequency of fulminant hepatitis B (s. pp 376, 416, 421) is about 1%, yet it is clearly higher in an infection with HBV mutants and above all in a superinfection with HDV Fulminant hepatitis B may be due to a combination of several unfavourable factors such as pre- or coexisting liver disease, coinfection with HDV (approx. 50%), virus load, virulence and route of infection (e.g. intravenous drug addicts), hormonal strain, additional infections, haemodialysis and inadequate (too fast, too... 

Hepatobiliary organ mycosis may be caused by several fungal species, whereby the Candida species by far outnumber the others. With the exception of Candida sp. and Mucor sp., all hepatotoxic fungi have an airborne route of infection, (s. tab. 26.2)... 

Mostly attenuated organisms are being used as live virus vaccines however, in some instances, even virulent organisms could be used, provided they are not administered via the natural route of infection. For example, human adenovirus types 4 and 7 may cause acute respiratory infections in humans when administered via the oronasal route but provide protection when given orally in enteric-coated capsules. ... 

A number of advantages associated with live vaccines are that 1) they are cheap to produce because the inoculum dose is relatively less 2) they require fewer inoculations 3) they do not require adjuvants 4) they elicit both humoral and cell-mediated immune responses and 5) they can be inoculated by the natural route of infection. Some of the disadvantages associated with live vaccines are that 1) they are usually less stable than inactivated vaccines and may require refrigeration for storage 2) some of these vaccines under certain situations may revert to virulent form in the host and thereby lead to clinical disease 3) they may not be recommended for immunosuppressed, immature, older, or pregnant hosts 4) they may have a low level of residual virulence and 5) they may be contaminated with other adventitious organisms. 

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