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There’s much more to surgery than just the procedure itself. Cutting into living flesh, whether it’s done surgically or traumatically, carries a risk of morbidity and mortality resulting from infection.
Surgical Microbiology
Perhaps the greatest challenge in any surgical procedure is the prevention of infection.
Surgical site infection, or SSI, is infection occurring in the 30 days following a surgery (or, in patients receiving implants, as much as 1 year after surgery).
SSIs are not all alike. The causative organism behind an SSI depends on:
• Type of surgery
• The surgical conscience of the members of the operating room team (i.e., surgical technologist, surgeon, and surgical nurse). (The concept of surgical conscience is discussed in Chapter 6.)
• The cleanliness of the surgical environment
• The origin of the microorganism (e.g., the resident flora)
• The health of the patient (e.g., immune defenses)
Centers for Disease Control and Prevention guidelines for the prevention of SSIs emphasize the importance of good patient preparation, aseptic practice, and attention to surgical technique; antimicrobial prophylaxis is also indicated in specific circumstances.
Characteristics of Bacteria
A solid understanding of cells—their types, structures, and means of multiplication and metabolism—is crucial for the surgical technologist, because it will help you determine the level and means of cleansing and type of pharmacology needed to eliminate a particular microorganism to help prevent SSIs.
Eukaryotes and Prokaryotes
Living cells are divided into two groups (Fig. 4.1):
• Eukaryotic cells make up animals and plants. Each eukaryotic cell has a nucleus and mitochondria, among other structures.
• A prokaryotic cell has no nucleus, mitochondria, or most of the other cell structures seen in eukaryotes. All bacteria are prokaryotes.
Gram Staining
One common means of differentiating cells is how they react to a process called Gram staining (Fig. 4.2). In this method of detecting bacteria, a specimen is treated first with crystal violet stain and then, to bind the crystal violet, iodide. The specimen is then washed with ethanol and finally counterstained with a dye called safranin. (Fig. 4.3 depicts a specimen in which one organism stained gram-positive.)
Gram-Positive Bacteria
On a positive Gram stain, bacteria retain the crystal violet after being treated with iodide and washed with ethanol, taking on a purple coloration. There are three types of gram-positive bacteria:
FIG. 4.1 Major features of prokaryotes and eukaryotes. (From Murray PR, Rosenthal KS, Pfaller MA: Medical microbiology, ed 8, Philadelphia, 2016, Elsevier.)
FIG. 4.2 Gram-stain morphology of bacteria. A, The crystal violet of Gram stain is precipitated by Gram iodine and is trapped in the thick peptidoglycan layer in gram-positive bacteria. The decolorizer disperses the gram-negative outer membrane and washes the crystal violet from the thin layer of peptidoglycan. Gram-negative bacteria are visualized by the red counterstain. B, Bacterial morphologies. (From Murray PR, Rosenthal KS, Pfaller MA: Medical microbiology, ed 8, Philadelphia, 2016, Elsevier.)
FIG. 4.3 Gram stain reveals a Mycobacterium pathogen (the purple rod-shaped bacilli) in a skin-derived tissue sample. (Courtesy Centers for Disease Control and Prevention/Dr. Roger Feldman.)
• Aerobic organisms require oxygen for survival. Examples include:
• Bacillus anthracis, which causes anthrax
• Corynebacterium diphtheriae, the cause of diphtheria
• Listeria monocytogenes, which causes listeriosis, a serious infection usually spread in contaminated food
• Lactobacillus species, “friendly” bacteria that normally live in our digestive, urinary, and genital tracts without causing disease
• Anaerobic organisms do not need oxygen to survive. Examples include:
• Clostridium perfringens, the most common cause of gas gangrene
• Clostridium botulinum, a spore-forming, motile bacterium that produces the neurotoxin botulinum; grows on food and produces toxins that, when ingested, cause paralysis
• Clostridium difficile, which causes diarrhea and more serious intestinal conditions such as colitis
• Facultative anaerobic organisms can use oxygen but also use anaerobic methods of energy production, making them able to survive in just about any environment. Examples include:
• Enterococcus species, which cause a variety of illnesses, including urinary tract infections, bacteremia, endocarditis, and meningitis.
• Staphylococcus aureus, which is responsible for several types of disorders and illnesses:
• Skin infection: small benign boils, folliculitis, impetigo, cellulitis, and more severe, invasive soft-tissue infections
• Bacteremia: presence of bacteria in the bloodstream, resulting in infection of various organs that can cause infective endocarditis, septic arthritis, and osteomyelitis
• Staphylococcus epidermis, a pathogen of particular concern for people with catheters or other surgical implants because it is known to form biofilms on such devices
• Streptococcus agalactiae, found in the human gastrointestinal flora and in the female urogenital tract and rectum; causes postpartum infection and is the most common cause of neonatal sepsis
• Streptococcus mutans, which is found in the human oral cavity and is a major contributor to tooth decay
• Streptococcus pneumonia, which causes community-acquired pneumonia (CAP), bacterial meningitis, bacteremia, and otitis media, as well as sinusitis, septic arthritis, osteomyelitis, peritonitis, and endocarditis
• Streptococcus pyogenes, which causes acute pharyngitis, toxic shock syndrome (TSS), and life-threatening skin and soft tissue infections, especially necrotizing fasciitis
Gram-Negative Bacteria
Bacteria that do not retain crystal violet after being treated with iodide and washed with ethanol are considered gram-negative. All gram-negative bacteria take up the safranin counterstain, which turns them hot pink or red. There are also three kinds of gram-negative bacteria:
• Aerobic gram-negative organisms include:
• Bordetella pertussis, which causes pertussis, better known as whooping cough
• Neisseria gonorrhoeae, which causes the sexually transmitted disease gonorrhea
• Neisseria meningitides, which causes meningococcal disease
• Moraxella catarrhalis, a common cause of otitis media in infants and children, responbsible for 15% to 20% of acute otitis media episodes
• Acinebacter species, the cause of many hospital-acquired (nosocomial) infections such as bacteremia, urinary tract infection (UTI), secondary meningitis, infective endocarditis, and wound and burn infections
• Bartonella species, which causes cat scratch disease (CSD), bacillary angiomatosis (BA), and other infections in patients with HIV infection, as well as endocarditis
• Legionella pneumophila, which causes a serious type of pneumonia (lung infection) called Legionnaires’ disease
• Pseudomonas aeruginosa, “blue-green pus bacteria,” a species that opportunistically infects people, especially those who are immunocompromised
• Helicobacter pylori, which causes ulcers in the lining of stomach and the upper part of the small intestine
• Rickettsia rickettsii, the cause of Rocky Mountain spotted fever (RMSF), which is transmitted to humans through the bites of infected tick species
• Campylobacter jejuni, the most common cause of community-acquired inflammatory enteritis, which produces an inflammatory, bloody diarrhea or dysentery syndrome
• Treponema pallidum, the cause of syphilis, pinta, bejel, and yaws, is sexually transmitted
• Anaerobic gram-negative bacteria include:
• Bacteroides fragilis, responsible for 90% of anaerobic peritoneal infections but also causes bacteremia associated with intraabdominal infections, peritonitis and abscesses following rupture of viscus, and subcutaneous abscesses or burns near the anus
• Porphyromonas gingivalis, which causes chronic adult periodontitis
• Facultative anaerobic gram-negative organisms include:
• Haemophilus influenzae, which causes severe illnesses such as meningitis (but can be prevented from infecting people with a vaccine)
• Gardnerella vaginalis, the cause of an infection of the female genital tract called vaginosis, characterized by a gray or yellow discharge with a “fishy” odor
• Escherichia coli, most of whose strains are largely harmless but, in some cases, can cause serious food poisoning in their hosts, occasionally necessitating food recalls because of contamination
• Klebsiella pneumoniae, which causes variant pneumonia, typically in the form of bronchopneumonia and also bronchitis
• Salmonella enterica, which causes salmonellosis, resulting in diarrhea, fever, vomiting, and abdominal cramps 12 to 72 hours after infection
• Salmonella typhi, the cause of typhoid fever
• Vibrio cholerae, which secretes cholera toxin, a protein that causes profuse watery diarrhea known as “rice-water stool”
• Proteus species, which are common causes of UTI in patients who must wear urinary catheters for long periods
Simple Staining
In this type of stain, a single dye is used to detect bacteria. One example is methylene blue (Fig. 4.4), which is retained by certain types of bacteria after the stained specimen is washed with water.
Acid-Fast Staining
In this type of staining, a red dye called carbol fuchsin is washed over the specimen, after which a solution containing hydrochloric acid is applied, followed by a dye in a contrasting color (generally methylene blue). Acid-fast bacteria remain red; non–acid-fast bacteria lose the red stain and take on the blue one. This method is used to detect, among other microbes, those of the Mycobacterium genus, which stain blue (Fig. 4.5).
Commonly Tested Microorganisms
Now that you’ve had a chance to review the basics of bacteria, let’s talk about the microorganisms you’re most likely to encounter on a certification exam (Table 4.1).
FIG. 4.4 This illustration depicts a photomicrographic view of a methylene blue–stained culture specimen revealing the presence of numerous Clostridium septicum bacteria. (Courtesy Centers for Disease Control and Prevention.)
Disinfection and Sterilization
A solid understanding of the various classifications of microorganisms gives you a basis for determining which procedures and chemicals to use in prepping surgical patients (e.g., showering with an antiseptic soap or solution), instrument sterilization (e.g., autoclaving), equipment, and the physical environment (e.g., temperature, humidity, laminar flow) to prevent SSI.
Disinfection
In the process of disinfection, nearly all microorganisms on inanimate surfaces (clothing, hard surfaces) and/or wounds are destroyed through the use of chemicals or other physical agents (Fig. 4.6). (Keep in mind, however, that disinfection doesn’t destroy spore-bearing microorganisms.)
FIG. 4.6 Processing area and washer-sterilizer or decontaminator used to process soiled instruments and equipment so that personnel can handle them for assembly, wrapping, and storage. (Courtesy STERIS Corporation 2008. All rights reserved.)
There is a hierarchy of disinfection methods, which we’ll review here.
Cleaning
• Physical removal of gross debris (bioburden) and human bodily fluids, including blood
• Mainly achieved with the use of soap and water
Low-Level Disinfection
• Isopropyl alcohol and ethyl alcohol (in a 60%–70% dilution)
• Used on noncritical surfaces (e.g., devices that come into contact with skin, such as a pneumatic tourniquet or pulse oximeter or the operating table) surfaces
• Achieves disinfection in 10 to 15 minutes
• Tuberculocidal
• Bactericidal
• Virucidal
• Fungicidal
Intermediate Disinfection
• Phenol (carbolic acid), usually diluted with tap water
• Used to disinfect large areas such as floors and countertops
• Achieves disinfection in 10 to 15 minutes
• Bactericidal
• Virucidal (non-hydrophilic viruses)
• Fungicidal
High-Level Disinfection
• Activated glutaraldehyde (one brand name is Cidex)
• Used on surgical devices such as rigid and flexible endoscopes that requires immersion for disinfection or sterilization
• For disinfection, instruments must be dry before being soaked or immersed for 20 minutes at room temperature
• For sterilization, instruments must be dry before being soaked or immersed for 10 hours at room temperature
• Tuberculocidal
• Bactericidal (gram-positive and -negative organisms)
• Virucidal
• Fungicidal
• Sporicidal
Sterilization
Steam Sterilization
See Fig. 4.7.
• Two types:
• Gravity displacement
• Prevacuum autoclave
• Four parameters of steam sterilization:
• The ideal type of steam for sterilization is dry saturated steam and entrained water (dryness fraction ≥ 97%).
• Pressure serves as a means of achieving the high temperatures necessary to quickly kill microorganisms.
• Specific temperatures must be achieved to ensure the destruction of microorganisms (microbicidal activity). The two common steam-sterilizing temperatures are 121° C (250° F) and 132° C (270° F). These temperatures (and other high temperatures) must be maintained for a set time to kill microorganisms.
• There are three important phases in both types of steam sterilization:
• In conditioning (gravity-displacement autoclave) and preconditioning (prevacuum autoclave), the air is removed and replaced with steam.
• Items must remain in the autoclave chamber for a particular exposure time (i.e., a specific duration and temperature).
• During drying time (a.k.a. exhaust time), the pressure in the chamber is reduced and loads are exposed to cool air before being placed on the shelf.
Biological Indicators
These devices are the only type of monitor that can confirm that an instrument has been rendered sterile.
• Steam sterilization–Geobacillus stearothermophilus
• The test pack is placed in the area of the sterilizer that is most difficult for the sterilant to reach. This represents the coldest area of the sterilizer, where air entrapment is most likely. The coldest point is on the bottom front of the sterilization cart, over the chamber drain.
• If the liquid remains red after incubation (after 24 hours, incubated at 131°–140°F [50°–55°]) it means that the spores have been destroyed (negative finding).
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