Understanding the ANTIMICROBIAL PROCESS Richard Wills, The increasing number of antibiotic resistant strains of bacteria and rising number of hospital acquired (nosocomial) infections continue to stress the importance of sterile technique. MD, MBA, ACSM, ACSM, MBA, MD, Approximately two million US patients each year in acute care facilities suffer from nosocomial infections, costing approximately $3.5 billion.According to the Centers for Disease Control’s Hospital Bobbie Hevner-Willey, Neal Hunter, Neal Hunter, Bobbie Hevner-Willey, Infections Program approximately one-third of nosocomial infections can be prevented through the use of well-organized infection control programs, but only 6 percent to 9 percent are actually prevented.1 Patients acquire infections through airborne contaminants, ineffective hand-washing agents or technique, ineffective sterilization or disinfection procedures, length of hospital stay, and crowding in ICUs.2,3 The patient’s own suppressed immune system, malnutrition or history of illness may contribute to susceptibility, CMA as well as the level of bacterial resistance to treatment.3 JUNE 2000 The Surgical Technologist 11 183 JUNE 2000 CATEGORY 1 urgical site infection (SSI) is the second most Golgi apparatus, lysosomes) within the cytoplasm common nosocomial infection (behind urinary are encased by the cell wall of the organism.8 tract infections). The primary cause of SSI is the There are three classifications of pathogenic patient’s own endogenous flora, but other microorganisms: sources include airborne contaminants or Type 1, Acellular, consists of prions, viroids, exogenous flora from the surgical team and con­ and viruses. These are the smallest organisms taminated or improperly sterilized instrumenta­ able to demonstrate pathogenic potential (Figure tion. Environmental sources—such as unsterile 1).12 Viruses are obligated intracellular parasites medications, contaminated antiseptic solutions that depend entirely upon the host cells’ synthet­ or wound dressings, and improper cleaning/ ic machinery for reproduction and energy pro­ decontamination of anesthesia equipment, IV duction. They contain either DNA or RNA. DNA lines or fluids—also pose risks.2 viruses frequently mature in the host cell’s nucle­ The purpose of this article is to help the surgical us, while RNA viruses mature in the cytoplasm. technologist understand types of pathogenic Type 2, Unicellular, are divided into prokary­ microorganisms, the environment in which they otic cells (chlamydiae, mycoplasmas, bacteria) thrive, and the mechanisms of antimicrobial and eukaryotic cells (fungi, protozoa, algae, and agents upon those organisms. An understanding plant, animal and human cells).12 Prokaryotes of which could lead to more careful practice of lack a true cell nucleus (Figure 2). Instead, the ssterile technique and better protection for the genetic material of the cell lies within the cyto­ patient and the surgical team. plasm. Unlike acellular organisms, unicellular forms contain both DNA and RNA and repro­ Classifications of microorganisms duce through binary fusion. Microbial cells can best be understood by catego­ Eukaryotes are larger than bacteria and their rizing their cellular organization into specific bio­ genetic material is separated from the cell cyto­ logic forms. These cells are divided into internal plasm by a nuclear membrane. Many reproduce compartments by membrane systems. The com­ by budding (yeast) or grow in colonies (mold). partments have specific activities for the mainte­ Type 3, Multicellular, consist of helminths nance of the functions of the cell. The nuclear (adult worms, larvae, and ova) and arthropods compartment (nucleus) contains the cells’ hered­ (lice, ticks, and fleas).12 Infections within this itary material (DNA). Outside the nuclear mem­ category depend on specie, total number of brane, the organelles of the cell (eg, ribosomes, helminths supported with the body of the host, Do you know the difference? Asepsis—the absence of pathogens in vivo Fungicide—an agent or process that kills fungi Antisepsis—the prevention of infection in vivo Microbiocidal—an agent or process that kills microbes Antiseptic—an agent or used to kill or remove microor­ Microbiostatic—an agent or process that inhibits growth ganisms on living tissue or reproduction of microorganisms through drying, freez­ Bacteriostatic—an agent or method that inhibits metab­ ing, antibiotics, etc. olism or reproduction of bacteria Sanitation—a method to reduce microorganisms to levels Bacteriocidal/bacteriocide—an agent or method that deemed safe by public health standards kills bacteria but not their spores Sterilization—complete destruction of all living organ­ Disinfection—a process of killing or removing microor­ isms, including cells, spores, and viruses ganisms from fomites through chemical or physical means Virucide—kills viruses Disinfectant—an agent used to kill or remove microor­ ganisms on fomites 12 The Surgical Technologist JUNE 2000 FIGURE 1 Types of viruses Nucleic Acid Dave Ludwig Ludwig Dave Envelope A helical virus A polyhedral virus An enveloped helical virus ILLUSTRATION Spikes and the host’s defenses. The damage to the host outer layer of these bacterial membranes is varies from species to species. An example is the thicker and is composed of lipoprotein and hookworm, which attaches directly to the lipopolysaccharide attached to the peptidoglycan intestinal mucosa and feeds on the blood often layer. This outer membrane contains the somatic causing anemia within the host. 0 antigens and the endotoxin characteristic of Arthropods are important medically because Gram-negative bacteria.10 they infest the human skin or serve as vectors in Gram-positive bacteria have a heavy, rigid transmission of other pathogens. Table 1 classi­ layer of peptidoglycan and teichoic acid that is fies common diseases by their type of pathogen. thicker than that of Gram-negative cells. Gram- positive cells are most sensitive to the enzyme Defense mechanisms of pathogens lysozyme, found in tears, saliva, and other body fluids, which hydrolyzes peptidoglycan. • CAPSULE A few organisms, including a number of disease-producing bacteria, are able to • CYTOPLASM AND CYTOPLASMIC MEMBRANE Removal manufacture a capsule that surrounds the entire of the cytoplasmic membrane surrounding the exterior of the cell wall. The role of the capsule in entire cell will lead to bacterial lysis because the the life of bacteria has yet to be discovered, but it cell is unable to withstand the osmotic pressures does serve as a protective structure from found in nature. phagocytosis. The cytoplasm contains ribosomes. Although the ribosomes function in a similar manner, it is • BACTERIAL CELL WALL The bacterial cell wall is possible to distinguish the ribosomes of rigid, provides protection, and gives shape to prokaryotic cells from those of eukaryotic cells the cell. The most abundant substance of the cell by their different sedimentation velocity in the wall is peptidoglycan, a complex of short ultra centrifuge. Bacterial ribosomes have a peptides and sugars.10 sedimentation value of 70s (svedberg units), Bacteria are divided into Gram-negative and whereas eukaryotic ribosomes are larger and Gram-positive groups based upon a reaction to a heavier with a sedimentation value of 80s.11 staining procedure, which is due to differences in their cell wall structures (Figure 3).10 Gram- • SPORES Approximately 150 types of bacteria negative bacteria have a very thin peptidoglycan produce spores. These bacteria form a tough layer next to the cytoplasmic membrane.10 The shell within the cell during a resting stage. This JUNE 2000 The Surgical Technologist 13 FIGURE 2 Examples of bacteria. Escherichia coli (transmission electron micrograph) with flagella, are Gram-negative intestinal bacterium that can cause diarrhea, urinary tract infection, White, MS, 1995 MS, White, and surgical site infection. CDC/Elizabeth H Pseudomonas Carr CDC/Janice aeruginosa (scanning electron micrograph) are Gram-negative bacteria that are an opportunistic pathogen in hospitals and important in causing lower respiratory and urinary tract infections. Streptococcus pneumoniae (scanning electron micrograph) are Gram-positive bacteria and a common respiratory pathogen. Bacillus anthracis are rod-shaped, Gram- Carr CDC/Janice Carr CDC/Janice positive bacteria that cause anthrax. The Enterococcus species (scanning electron micrograph) was formerly in the Streptococcus family.This Gram-positive bacteria is a common cause of surgical site infections. Legionella pneumophila (transmission electron micrograph) is Gram- negative,rod-shaped bacteria that causes Legionnaires’disease 1977 A Clark, CDC/William Carr CDC/Janice 14 The Surgical Technologist JUNE 2000 shell protects the bacteria from changes in its FIGURE 3 environment. During this stage, it can survive Gram-positive bacteria without moisture or food, and even survive Differences in extreme hot or cold temperatures. When environmental conditions return to normal, the the cell walls spore is able to grow and reproduce bacteria.2 of Gram- • RESISTANCE Microorganisms have an incredible ability to adapt to their environment. They are positive and able to mutate in several ways to avoid the negative effects of antimicrobial agents. They Gram- may change their cell membranes, receptor cites, or other aspects of their surfaces to keep the negative agent from binding with or entering the cell. Or, they may produce an enzyme that disables the bacteria antimicrobial