SEPSIS AND SYSTEMIC INFECTIONSCZhhVg6]bZY!BVjgZZc9Vlhdc!8]g^hHb^i]:YLddY *(
but an inflammatory reaction, trichomoniasis vaginitis, may result in a frothy
cream-colored discharge.
A number of arthropods may be sexually transmitted. These include crab lice
and the scabies mite (Figure 2.14(A)).
3.7 Sepsis and Systemic Infections
A relatively small number of pathogens are able to enter the body in the
lymphatic or circulatory systems and produce a generalized or systemic
infection involving numerous body organs: brain, bone marrow, kidneys, liver,
lungs and spleen. Local skin infections, such as with Streptococcus pyogenes
orStaphylococcus aureus or infections of the GIT or urogenital system with
Enterobacteriaceae can unfortunately progress to acute generalized infections
within only a few days, given appropriate conditions. For example, Streptococcus
pyogenes or Staphylococcus aureus secrete toxins called superantigens
(Chapters 2 and 4 ) that stimulate the release of cytokines from immune cells and
produce an excessive inflammatory response called systemic inflammatory
response syndrome (SIRS) consisting of four characteristic stages. In stage I,
respiration, heart rate and body temperature all increase. The leukocyte count
may be increased or decreased. Stage II refers to the presence of the organism
in the blood of the patient; this is called sepsis. Normally less than 50% of
cases can be identified. Stage II may be cured intrinsically by the immune
system or extrinsically by the administration of antibiotics. If unsuccessful,
the condition progresses to stage III: serious sepsis or multiorgan dysfunction
syndrome (MODS) characterized by lactic acidosis, falling blood pressure,
hypoxia and oliguria. If clinical measures fail to stabilize the patient, then
stage IV, septic shock, develops with irreversible organ failure and the death
of the patient in most cases.
In contrast to the possible acute developments of localized infections,
generalized infections may have incubation times of up to three weeks.
A classical example of such a systemic infection is typhoid fever caused by
Salmonella typhi (Figure 3.22). The pathogen may be ingested and can enter
the body through the tonsils in the throat and Peyer’s patches in the gut. The
bacterium is distributed to various organs in the lymph and blood, infects
Figure 3.21 Electron micrograph ofTrichomonas vaginalis.Courtesy of Dr A. Curry, Manchester
Royal Infirmary, UK.
Figure 3.22 Light micrograph of Salmonella
typhi.Courtesy of Public Health Image Library,
Centers for Disease Control and Prevention, USA.