Infection antimicrobial regimen selection

While selection of antimicrobial therapy may be a major consideration in treating infectious diseases, it may not be the only therapeutic intervention. Other important therapies may include adequate hydration, ventilatory support, and other supportive medications. In addition, antimicrobials are unlikely to be effective if the process or source that leads to the infection is not controlled. Source control refers to this process and may involve removal of prosthetic materials such as catheters and infected tissue or drainage of an abscess. Source-control considerations should be a fundamental component of any infectious diseases treatment. It is also important to recognize that there may be many different antimicrobial regimens that may cure the patient. While the following therapy sections... 

Figure 66-4 provides an overview of patient- and antimicrobial agent-specific factors to consider when selecting an antimicrobial regimen. It further delineates monitoring of therapy and actions to take depending on the patients response to therapy. The duration of therapy depends on patient response and type of infection being treated. 

Aggressive, early antimicrobial therapy is critical in the management of septic patients. The regimen selected should be based on the suspected site of infection, likely pathogens, and the local antibiotic susceptibility patterns, whether the organism was acquired from the community or a hospital, and the patient s immune status. 

A systematic approach to the selection and evaluation of an antimicrobial regimen is shown in Table 35-1. An empiric antimicrobial regimen is begun before the offending organism is identified and sometimes prior to the documentation of the presence of infection, while a definitive regimen is instituted when the causative organism is known. 

If symptoms do not improve, the patient should be evaluated for persistent infection. There are many reasons for poor patient outcome with intraabdominal infection improper antimicrobial selection is only one. The patient maybe immunocompromised, which decreases the likelihood of successful outcome with any regimen. It is impossible for antimicrobials to compensate for a nonfunctioning immune system. There may be surgical reasons for poor patient outcome. Failure to identify all intraabdominal foci of infection or leaks from a GI anastomosis may cause continued intraabdominal infection. Even when intraabdominal infection is controlled, accompanying organ system failure, most often renal or respiratory, may lead to patient demise. 

Table 42-4 presents recommended and alternative regimens for selected situations. These are general guidelines, not rules, because there are many factors that cannot be incorporated into such a table. Guidelines for initial antimicrobial treatment of specific intraabdominal infections are presented in Table 42-5. 

Prophylaxis of infections in HSCT patients is in many ways similar to that used in other neutropenic patients. Selective decontamination with oral antimicrobials is used commonly considerations are the same as those discussed previously. Although some studies have shown decreased rates of bacteremia and other bacterial infections after HSCT, overall mortality rates were not reduced. The routine use of prophylactic antibiotics in HSCT therefore is still controversial. Fluoroquinolones have become the most frequently used agents, often combined with another agent (e.g., macrolides or rifampin) for enhanced gram-positive activity. These regimens usually are begun... 

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