Empiric antimicrobial

Select empirical antimicrobial therapy based on spectrum-of-activity considerations that provide a measured response proportional to the severity of illness. Provide a rationale for why a measured response in antimicrobial selection is appropriate. 

Many areas of the human body are colonized with bacteria— this is known as normal flora. Infections often arise from one s own normal flora (also called an endogenous infection). Endogenous infection may occur when there are alterations in the normal flora (e.g., recent antimicrobial use may allow for overgrowth of other normal flora) or disruption of host defenses (e.g., a break or entry in the skin). Knowing what organisms reside where can help to guide empirical antimicrobial therapy (Fig. 66-1). In addition, it is beneficial to know what anatomic sites are normally sterile. These include the cerebrospinal fluid, blood, and urine. 

The patient was admitted to the hospital with a presumptive diagnosis of health care-associated pneumonia (based on the recent hospitalization). He received intravenous hydration with normal saline, 5 L oxygen via face mask, an insulin infusion to control his glucose, and empirical antimicrobial therapy with piperacillin-tazobactam 2.25 g intravenously every 6 hours and vancomycin 1 g intravenously every 24 hours. All other medications are continued with the exception of the diabetes medications. 

Modify empirical antimicrobial regimens based on laboratory data and other diagnostic criteria. 

Empirical antimicrobial therapy should be modified on the basis of laboratory data and clinical response. 

Empiric antimicrobial therapyb + Dexamethasone6 Empiric antimicrobial therapy6 + Dexamethasone0... 

Determine if the patient can undergo an immediate LP or if the LP should be delayed until a CNS mass lesion can be ruled out. If the LP is delayed, blood cultures should be drawn and appropriate empirical antimicrobial therapy initiated immediately. 

Based on patient-specific data, local resistance patterns, and other relevant data, design an appropriate empirical antimicrobial regimen directed at the most likely pathogens empirical regimens should consist of high-dose intravenous cidal therapy. 

Design an appropriate empirical antimicrobial regimen based on patient-specific data for an individual with community-acquired pneumonia, aspiration pneumonia, and ventilator-... 

The severity of a patient s infection, based on the PEDIS scale, guides the selection of empirical antimicrobial therapy. While most patients with grade 2 diabetic foot infections can be treated as outpatients with oral antimicrobial agents, all grade 4 and many grade 3 infections require hospitalization, stabilization of the patient, and broad-spectrum IV antibiotic therapy.31... 

Based on culture and susceptibility data (if available), are there any changes that need to be made from your initial empiric antimicrobial selection (i.e., resistance to the regimen initially selected) ... 

Empiric antimicrobial therapy should target likely causative pathogen(s) based on patient-specific risk factors and route of infection. However, therapy should be modified based on culture and sensitivity data. 

TABLE 96-5. Dosing Guidelines for Empirical Antimicrobial Agents in Febrile Neutropenia... 

Empiric antimicrobial therapy Antimicrobial therapy given prior to the availability of microbiologic culture results. 

Adachi JA, Ostrosky-Zeichner L, DuPont HL, Ericsson CD Empirical antimicrobial therapy for traveler s diarrhea. Clin Infect Dis 2000 31 1079-1083. 

Empiric antimicrobial therapy should be instituted as soon as possible to eradicate the causative organism (Table 36-2). Antimicrobial therapy should last at least 48 to 72 hours or until the diagnosis of bacterial meningitis can be ruled out. Continued therapy should be based on the assessment of clinical improvement, cultures, and susceptibility testing results. Once a pathogen is identified, antibiotic therapy should be tailored to the specific pathogen. 

An empiric antimicrobial regimen should be started as soon as the presence of intraabdominal infection is suspected on the basis of likely pathogens. 

TABLE 43-6 1 Empirical Antimicrobial Therapy for Pneumonia in Adults ... 

Definitive therapy should be based on results of appropriately collected cultures and sensitivities, as well as clinical response to empiric antimicrobial agents. 

Selection of empiric antimicrobial therapy should be based on the most likely organisms. The most common organisms for acute exacerbation of COPD are Haemophilus influenzae, Moraxella catarrhalis, Streptococcus pneumoniae, and H. parainfluenzae. 

Antimicrobial agents are frequently used before the pathogen responsible for a particular illness or the susceptibility to a particular antimicrobial agent is known. This use of antimicrobial agents is called empiric (or presumptive) therapy and is based on experience with a particular clinical entity. The usual justification for empiric therapy is the hope that early intervention will improve the outcome in the best cases, this has been established by placebo-controlled, double-blind prospective clinical trials. For example, treatment of febrile episodes in neutropenic cancer patients with empiric antimicrobial therapy has been demonstrated to have impressive morbidity and mortality benefits even though the specific bacterial agent responsible for fever is determined for only a minority of such episodes. 

Table 51-1 Empiric Antimicrobial Therapy Based on Microbiologic Etiology. ...

These extended case studies complement the basic information presented in Chapters 1 to 40. They reinforce basic principles of pharmacology, such as the role of patient factors in empiric antimicrobial therapy Most of the cases provide clinical information obtained from a single patient some cases describe a composite of typical features derived from several patients. These cases illustrate simple pharmacologic principles, such as consideration of kidney function in drug dosing—concepts useful in answering examination questions, and in the clinics. 

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. 

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