Anti-infective chemoprophylaxis implies the administration of antimicrobial drugs to prevent infection. In a broader sense, it also includes the use of antimicrobial drugs soon after the acquisition of pathogenic microorganisms (eg, after compound fracture) but before the development of signs of infection.

Useful chemoprophylaxis is limited to the action of a specific drug on a specific organism. An effort to prevent all types of microorganisms in the environment from establishing themselves only selects the most drug-resistant organ isms as the cause of a subsequent infection. In all proposed uses of prophylactic antimicrobials, the risk of the patient’s acquiring an infection must be weighed against the toxicity, cost, inconvenience, and enhanced risk of superinfection resulting from the prophylactic drug.

Prophylaxis in Persons of Normal Susceptibility Exposed to a Specific Pathogen

 In this category, a specific drug is administered to prevent one specific infection. Particular examples are the injection of benzathine penicillin G intramuscularly once every 3 to 4 weeks to prevent reinfection with group A hemolytic streptococci in rheumatic patients; prevention of meningitis by eradicating the meningococcal carrier state with rifampin or ciprofloxacin; prevention of syphilis by the injection of benzathine penicillin G; prevention of plague pneumonia by oral administration of tetracycline in persons exposed to infectious droplets; prevention of leptospirosis with oral administration of doxycycline in a hyperendemic environment; and prevention of malaria in travelers to endemic areas of the world with various agents such as Malarone.

Early treatment of an asymptomatic infection is sometimes called prophylaxis. Thus, administration of INH, 6–10 mg/kg/day (maximum, 300 mg/day) orally for 6 months, to an asymptomatic person who converts from a negative to a positive tuberculin skin test result may prevent later clinically active tuberculosis.

Prophylaxis in Persons of Increased Susceptibility

 Certain anatomic or functional abnormalities predispose to serious infections. It may be feasible to prevent or abort such infections by giving a specific drug for short periods. Some important examples are listed here.

 A. Heart Disease

Persons with heart valve abnormalities or with prosthetic heart valves are unusually susceptible to implantation of microorganisms circulating in the bloodstream. Thus, infective endocarditis can sometimes be prevented if the proper drug can be used during periods of bacteremia. Large numbers of viridans streptococci are pushed into the circulation during dental procedures and operations on the mouth or throat. At such times, the increased risk warrants the use of a prophylactic antimicrobial drug aimed at viridans streptococci. For example, amoxicillin taken orally before the procedure and 2 hours later can be effective. Persons allergic to penicillin can take a macrolide or clindamycin orally. Recommendations for prophylaxis following non-dental procedures vary depending upon the type of valvular abnormality. For example, prophylaxis is no longer recommended following gastrointestinal or genitourinary procedures in patients with rheumatic valvular disease but may still be indicated in patients with congenital heart disease or those patients with prosthetic material. The reader is referred to the latest American Heart Association guidelines (www.heart.org) for the most current recommendations.

B. Respiratory Tract Disease

 Trimethoprim–sulfamethoxazole orally or pentamidine by aerosol is used for prophylaxis for pneumocystis pneumonia in AIDS patients.

C. Recurrent Urinary Tract Infection

For certain women who are subject to frequently recur ring urinary tract infections, the oral intake either daily or three times weekly of nitrofurantoin or trimethoprim sulfamethoxazole can markedly reduce the frequency of symptomatic recurrences over long periods.

Certain women tend to develop symptoms of cystitis after sexual intercourse. The ingestion of a single dose of antimicrobial drug ( eg, nitrofurantoin or trimethoprim–sulfamethoxazole) can prevent postcoital cystitis by early inhibition of growth of bacteria moved from the introitus into the proximal urethra or bladder during intercourse.

D. Opportunistic Infections in Severe Granulocytopenia

 Immunocompromised patients receiving organ transplants or antineoplastic chemotherapy often develop profound leukopenia. When the neutrophil count falls below 1000/μL, they become unusually susceptible to opportunistic infections, most often Gram-negative sepsis. Such persons are sometimes given a fluoroquinolone, a cephalosporin, or a drug combination (eg, vancomycin, gentamicin, and cephalosporin) directed at the most prevalent opportunists at the earliest sign—or even without clinical evidence—of infection. This is continued for several days until the granulocyte count rises again. Several studies suggest that there is benefit from empiric therapy. Two clinical cases—liver and bone marrow transplants—presented in Chapter 48 illustrate the infections that occur in these patients and the antimicrobials used for prophylaxis and treatment.

Prophylaxis in Surgery

A major portion of all antimicrobial drugs used in hospitals is used on surgical services with the stated intent of prophylaxis.

Several general features of surgical prophylaxis merit consideration:

1. The benefit of prophylactic antimicrobial agents for clean surgery has been established.

2. The type of antimicrobial agent that is chosen depends upon several factors: type of surgery and the knowledge of the endogenous microbiota; types of pathogens causing wound infections and their resistance patterns in a particular institution; patient allergies; penetration of the agent at the surgical site; cost and other considerations.

3. Cephalosporins, most commonly cefazolin, are the preferred agents.

4. The goal with administration of prophylactic agents is to ensure adequate tissue levels of the drug during the entire operative procedure. This may require redosing during long procedures (see list of recommendations for agents and dosing schedules in Bratzler et al).

5. The initial dose of systemic prophylactic antibiotic should be given within 60 minutes of the incision or within 120 minutes if vancomycin or a fluoroquinolone is used.

 6. Prolonged administration of antimicrobial drugs tends to alter the normal microbiota of organ systems, suppressing the susceptible microorganisms and favoring the implantation of drug-resistant ones. Thus, antimicrobial prophylaxis should usually continue for no more than 24 hours after the procedure and ideally should be given only intraoperatively.

7. Systemic levels of antimicrobial drugs usually do not prevent wound infection, pneumonia, or urinary tract infection if physiologic abnormalities or foreign bodies are present.

Topical antimicrobials for prophylaxis (eg, intravenous catheter site, closed urinary drainage, within a surgical wound, and acrylic bone cement) have limited usefulness.

Studies have demonstrated increased morbidity and mortality with S. aureus postsurgical wound infections, particularly if the infection is caused by MRSA. Many hospitals perform presurgical nares surveillance screening for MRSA using either culture or nucleic acid amplification. Patients who are found to be colonized are treated with mupirocin ointment to the nares for 3–5 days along with chlorhexidine for bathing in an attempt to eliminate colonization before the procedure. Some investigators advocate the addition of vancomycin to a cephalosporin for intraoperative prophylaxis in patients known to be MRSA carriers.

Disinfectants

 Disinfectants and antiseptics differ from systemically active antimicrobials in that they possess little selective toxicity. They are toxic not only for microbial pathogens but for host cells as well. Therefore, they can be used only to inactivate microorganisms in the inanimate environment or, to a limited extent, on skin surfaces. They cannot be administered systemically.

The antimicrobial action of disinfectants is determined by concentration, time, and temperature, and the evaluation of their effect may be complex. A few examples of disinfectants that are used in medicine or public health are listed in Table 1.

Table1. Chemical Disinfectants, Antiseptics, and Topical Antimicrobial Agents

اخر الاخبار

اخبار العتبة العباسية المقدسة

وزارة التعليم العالي تكرم جامعة العميد لحصولها على جائزة المكتبة الأكاديمية المتميزة

جمعية العميد تناقش استعداداتها لانطلاق فعاليات المؤتمر العلمي الرابع لإحياء تراث أمير المؤمنين (عليه السلام)

أكاديمية التطوير الإداري تواصل برنامج الخطة الخمسينية لعدد من ملاكات العتبة العباسية المقدسة

المجمع العلمي يواصل تقديم دورته التطويرية لعدد من الملاكات التربوية في الديوانية

المزيد

الآخبار الصحية

الرياضة وحدها لا تكفي.. كيف يؤثر الجلوس الطويل على الصحة؟

دراسة: بدائل السكر ليست آمنة على الكبد

تفاحة قبل النوم.. عادة بسيطة مفيدة أم خطر على الصحة؟

احذر مشاركتها مع الآخرين.. 3 أدوات شائعة قد تنقل أمراض خطيرة

المزيد

الآخبار التكنلوجية

الهنغاري لاسلو كراسناهوركاي يفوز بجائزة نوبل للآداب 2025

رسميا.. إعلان الفائز بجائزة نوبل للسلام لعام 2025

باحثون: تشات جي بي تي ونماذج الذكاء الاصطناعي يمكن "تسميمها"

عالمان في الأعصاب يرفعان دعوى قضائية ضد شركة آبل

المزيد

مواضيع ذات صلة

Drug–Pathogen Relationships

Measurement of Antimicrobial Activity

Clinical Implications of Drug Resistance

Origin of drug resistance

Resistance to Sulfonamide

Control of Antibiotics Overuse

International Distribution of Antibiotics: A Scandinavian Example

Rediscovery of Penicillin by a Basic Scientific Approach

Penicillin: the First Antibiotic

Sulfonamide: the First Antibacterial Agent Acting Selectively

Drug elimination

Drug distribution