Principles for Prescribing Antiinfectives

http://evolve.elsevier.com/Edmunds/NP/

This chapter discusses general treatment principles applicable to most infections, with an emphasis on those of bacterial origin. Although these general guidelines cover the most common first-line primary care drugs, many exceptions are made to these recommendations. Remember to consider each patient with an infection as an individual case. Patterns of resistance change constantly and guidelines for treatment are updated at least yearly. Although these recommendations were the most current on publication, do not fail to consult the newest information from state and federal sources. The emphasis in this unit is on typical oral treatment for common primary care problems. The only exception is the use of single IM injections primarily for the treatment of sexually transmitted diseases. The first nine antiinfective chapters are focused on bacteria. Viruses and protozoa are discussed in Chapter 69; fungi are discussed in Chapter 67.

The taxonomy of bacteria is undergoing changes that reflect the new body of information about the genetic components of bacteria. See Table 57-1 for information on bacteria that are important pathogens. Bacteria are one-cell organisms with a primitive nucleus and rigid cell walls that are porous and permeable to substances of low molecular weight. Gram-negative bacteria have a more complex cell wall than gram-positive bacteria. Bacteria are called gram negative or positive according to the results of laboratory Gram stains. The difference in their cell walls is an important factor in the ability of an antibiotic to penetrate the cell walls of bacteria and kill the bacteria. Another variable that is important in decision making is whether bacteria are aerobic or anaerobic (i.e., whether or not they need oxygen). This trait will determine where in the body the organism will grow best and potentially cause infection. This information is important when one is selecting appropriate antimicrobial therapy in the absence of culture results.

TABLE 57-1

Important Pathogens

	Morphology	Aerobe vs. Anaerobe	Organism	Most Important Pathogen	Disease Caused
BACTERIA
Gram positive	Cocci		Staphylococcus	S. aureus	Skin and soft tissue infective endocarditis Osteomyelitis, bacteremia, toxic shock syndrome
			Streptococcus	S. pyogenes group A β-hemolytic (GABH)	Pharyngitis/rheumatic fever Impetigo Endocarditis
			Enterococcus Pneumococcus	E. faecalis S. pneumoniae	Wound, UTI, endocarditis Pneumonia Meningitis
	Rods	Anaerobe	Bacillus Actinomyces	B. anthracis A. israelii A. haemolyticum	Anthrax Cervicofacial Pharyngitis
		Aerobe Anaerobe	Corynebacterium Listeria Clostridium	C. diphtheriae L. monocytogenes C. perfringens C. difficile C. tetani	Diphtheria Listeriosis Gas gangrene Enteritis Tetanus
		Aerobe		C. botulinum	Botulism
Gram negative	Cocci		Neisseria	N. gonorrhoeae	Gonorrhea
		Aerobe		N. meningitidis	Meningitis
			Moraxella	M. catarrhalis	Otitis media, sinusitis,
		Aerobe			pneumonia
	Bacilli		Pseudomonas	P. aeruginosa	Bacteremia
ENTEROBACTERIA			Escherichia Shigella Salmonella	E. coli S. dysenteriae S. typhi S. enteritidis	Gastroenteritis Shigellosis dysentery Typhoid fever Gastroenteritis
			Klebsiella Proteus	K. pneumoniae P. mirabilis P. vulgaris	UTI, various UTI, various UTI, various
			Yersinia Enterobacter Serratia Citrobacter Morganella	Y. pestis E. cloacae S. marcescens C. freundii M. morganii	Plague
			Vibrio Helicobacter	V. cholerae H. pylori	Cholera Gastritis, PUD
	Small bacilli		Haemophilus	H. influenzae	Sinusitis, otitis, bronchitis, pneumonia
			Bordetella Pasteurella	B. pertussis P. tularensis P. multocida	Whooping cough Tularemia Animal bite infections
			Campylobacter Gardnerella Legionella	C. jejuni G. vaginalis L. pneumophila	Gastroenteritis Vaginitis Legionnaire’s pneumonia
		Aerobe	Nocardia	N. asteroides	Pulmonary endocarditis, systemic infection
		Anaerobe	Bacteroides	B. fragilis
			Prevotella (formerly Bacteroides)	P. melaninogenica	URIs
Acid fast			Mycobacterium	M. tuberculosis M. avium M. leprae	Tuberculosis Bronchitis, etc Leprosy
Mycoplasma			Mycoplasma Ureaplasma	M. pneumoniae M. hominis M. urealyticum	Atypical pneumonia
Spirochetes			Treponema	T. pallidum T. pallidum sub	Syphilis Yaws
			Borrelia	B. burgdorferi	Lyme disease
Rickettsia			Rickettsia	R. rickettsii	Rocky Mountain spotted fever, typhus
PROTOZOA			Chlamydia (closely related to Gram bacteria)	C. trachomatis C. psittaci C. pneumoniae	Lymphogranuloma venereum, urethritis, and cervicitis Psittacosis Pneumonia
		Flagellate	Trichomonas Entamoeba Cryptosporidium (spore forming) Giardia (cyst forming) Leishmania Plasmodium	T. vaginalis E. histolytica C. parvum G. lamblia Many species P. falciparum P. vivax P. malariae P. ovale	Trichomonas vaginitis Amebiasis colitis Diarrhea Diarrhea Skin lesions Malaria Malaria Malaria Malaria
			Toxoplasma	T. gondii	Toxoplasmosis
HELMINTHIC	Trematode Cestode Nematode				Schistosomiasis Anisakiasis
			Ascaris	A. lumbricoides	Ascariasis Enterobiasis
			Trichinella	T. spiralis	Trichinosis