Antibiotics as defense against biological warfare
Antibiotics are therapeutic agents that combat bacterial infections and play a vital role in public health, particularly in the context of biological warfare. They are designed to kill or inhibit the growth of specific bacteria, thereby mitigating the effects of various infectious diseases. In light of increasing threats of bioterrorism, law enforcement and health agencies are exploring the strategic use of antibiotics to counteract potential biological attacks involving harmful microorganisms.
There are several types of antibiotics, classified by their chemical structures and modes of action, with some targeting bacterial cell wall synthesis and others inhibiting protein synthesis. This diversity allows for both narrow- and broad-spectrum treatments based on the infection's specifics. Antibiotics are often used empirically—before the precise bacterial agent is identified—to provide timely intervention and prevent disease progression.
Prophylactic use of antibiotics, as exemplified during the anthrax incidents in 2001, can be crucial in protecting populations from bioweapons. The Centers for Disease Control and Prevention (CDC) emphasizes the importance of preparedness in the event of a bioterrorism attack, advocating for public awareness regarding the availability of antibiotics. This proactive approach to antibiotic use underlines their importance as a defense mechanism against the threats posed by biological warfare.
Antibiotics as defense against biological warfare
DEFINITION: Therapeutic agents that kill infectious microorganisms.
SIGNIFICANCE: Antibiotics kill certain types of bacteria that cause diseases without severely hurting the patients; they can thus abate the progression of some diseases and extensively reduce the effects of those diseases on human populations. Because of increasing threats of terrorism in the modern world, law-enforcement agencies are interested in the effective use of antibiotics for blunting the potential threat of microorganisms as biological weapons.
Microbial infections cause illnesses that diminish the quality of life and productivity and can eventually cause death. Effective early treatment can reverse the progression of some diseases, decrease the convalescence time, and potentially prevent the spread of infection from one person to another. Treatment can also check the onset of particular undesirable aftereffects caused by some diseases. Antibiotics are the first-line treatments against infectious diseases.
Classification
Most antibiotics are derived from compounds made by various microorganisms to kill competing bacteria. Many antibiotics, however, are completely synthetic in their composition, even though their chemical structures are variations of naturally produced antibiotics.
Antibiotics are classified according to their chemical structures, and drugs with similar chemical structures are classified in a common group. The largest group of antibiotics, the beta-lactams, consists of the penicillins (such as ampicillin, amoxicillin, and carbenicillin), cephalosporins (such as cephalexin, ceflaclor, and ceftizoxime), monobactams (aztreonam), and carbapenems (such as imipenem and meropenem). Other antibiotic groups include the macrolide antibiotics (such as erythromycin, clarithromycin, and azithromycin), tetracyclines (such as doxycycline and minocycline), aminoglycosides (such as streptomycin, kanamycin, tobramycin, and neomycin), sulfanilamides (such as sulfadiazine, sulfamethoxazole, and sulfamethizole), trimethoprim (similar to sulfanilamides but does not contain sulfur atoms), fluoroquinolones (such as ciprofloxacin, levofloxacin, moxifloxacin, and norfloxacin), and glycopeptide antibiotics (vancomycin).
Several antibiotic groups consist of only one drug; these include bacitracin, clindamycin, chloramphenicol, cycloserine, and fosfomycin. Streptogramin A and dalfopristin are given as a combination, and these drugs are the only members of the streptogramin group. The oxazolidinones group contains only one member, linezolid. A handful of antibiotics called antimycobacterials are specifically used to treat tuberculosis: isoniazid, ethambutol, pyrazinamide, and rifampin.
Mode of Action
Several chemically unrelated groups of antibiotics can target similar biochemical processes in bacterial cells. The abilities of distinct antibiotics to kill particular bacterial species vary extensively. Some antibiotics can kill only a few bacterial species (narrow-range antibiotics), whereas others can eradicate many different types of bacteria (broad-spectrum antibiotics).
Several antibiotics inhibit bacterial protein synthesis, which quickly kills bacterial cells. The protein synthesis-inhibiting antibiotics include the macrolides, tetracyclines, aminoglycosides, clindamycin, streptogramins, oxazolidinones, and chloramphenicol. Clindamycin is used to treat infections with anaerobic bacteria, and streptogramins and oxazolidinones are used for infections that resist other antibiotic treatments.
Many antibiotics inhibit the synthesis of the bacterial cell wall, which surrounds the bacterium and protects it. Without their cell wall, bacterial cells succumb to the host’s immune system. Antibiotics that inhibit bacterial cell wall synthesis include the beta-lactams, glycopeptides, bacitracin, cycloserine, and fosfomycin.
Some antibiotics interfere with the synthesis of essential molecules. Folic acid is an exceedingly vital cofactor for bacterial metabolism, and without it, bacteria die. The sulfanilamides, trimethoprim, and the drug dapsone (used to fight Hansen’s disease, or leprosy) obstruct the synthesis of folic acid. The fluoroquinolones inhibit bacterial (deoxyribonucleic acid) replication.
Of the antituberculosis drugs, rifampin inhibits gene expression, and isoniazid and ethanbutol hamper the synthesis of the waxy cell wall of Mycobacterium tuberculosis, the bacterial agent that causes tuberculosis. Pyrazinamide inhibits the synthesis of fatty acids, which are used for the construction of biological membranes.
Clinical Use
Antibiotic treatment can have great benefits even when the exact causative agent of a disease is unknown. Antibiotics, thus, are usually used before the microorganism responsible for the illness is defined. However, because continuous exposure of bacteria to antibiotics allows the evolution of bacteria that are resistant to antibiotics, the overuse of these drugs is ill-advised, and judicious use of antibiotics is the rule. For example, given that more than 90 percent of sinus and upper-respiratory infections are caused by viruses rather than by bacteria, immediate prescription of antibiotics for such conditions is unwarranted.
Prescribing healthcare professionals use a protocol known as empirical antimicrobial therapy (EAT) to guide their choices of antibiotics. Using EAT, the prescribing professional attempts to identify the bacterium most likely responsible for the illness through collection of a medical history, physical examination, and laboratory analyses of infected tissues. Because certain bacterial species have a tendency to infect certain organs, specific antibiotics are typically recommended for particular infections. Typically, certain drugs are considered to be the first choice for particular infections, and alternative drugs are used if the first-choice drugs fail to achieve the desired results. For example, the bacterial organisms Streptococcus pneumoniae, Moraxella catarrhalis, and Haemophilus influenzae cause the vast majority of middle-ear infections (otitis media), so the first-choice treatment for these infections is amoxicillin or a combination of trimethoprin and sulfamethoxazole (in a one-to-five ratio); the second-choice treatment is amoxicillin in combination with clavulanate or cefurxime axetil.
Antibiotics and Forensics
The presence of antibiotics in bodily fluids or tissue samples obtained after death usually indicates the presence of an infection in the deceased. The techniques for detecting antibiotics or their breakdown products in postmortem tissues exploit the unique chemical structure of each antibiotic. Cephalosporins, for example, are detected in postmortem tissues by means of high-performance liquid chromatography (HPLC), which separates compounds according to their differing rates of movement through a porous support material.
The prescription of antibiotics to prevent an impending infection is called antibiotic prophylaxis. In one example of the use of antibiotic prophylaxis, ciprofloxacin was given to approximately ten thousand people who had potentially been exposed to Bacillus anthracis, the causative agent of anthrax, as the result of bioterrorism attacks in New York City, Washington, DC, and Boca Raton, Florida, in the fall of 2001. This step probably saved many lives. In 2024, the Centers for Disease Control and Prevention (CDC) announced that the federal government and health agencies are preparing for an anthrax emergency. They believe that if a bioterrorist attack is launched, the terrorists would use anthrax because it is easy to make and can be released quietly. In the event of an anthrax attack, the CDC advised the public to pay attention to announcements online and on television so they know where they can get antibiotics. The aggressive prophylactic use of antibiotics may thwart a bioterrorism attack.
Bibliography
"Bioterrorism and Anthrax: The Threat." Centers for Disease Control and Prevention (CDC), 10 May 2024, www.cdc.gov/anthrax/bioterrorism/index.html. Accessed 13 Aug. 2024.
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Walsh, Christopher. Antibiotics: Actions, Origins, Resistance. Washington: ASM, 2003. Print.