The Science of Infection
Those in the cleaning industry often talk about cleaning to prevent infection and protect the health of building occupants. However, in order to talk about infection prevention, we must first understand infection itself. How are pathogens introduced into the body? How do they lead to infection, and how does an infection manifest into a disease? While there is little a cleaning professional can do once someone has been infected by a pathogen, there are ways in which they can cut pathogens off at the pass before they have the chance to infect. In this blog, we break down the science of infection in order to empower cleaning professionals to improve their cleaning routines and create safer, healthier environments.
Pathogenicity & Virulence
When determining whether or not a microbial agent will cause disease, two factors come into play: pathogenicity and virulence.
Pathogenicity: the ability of a microbial agent to cause disease
Virulence: the degree to which an organism is pathogenic
The more virulent a pathogen is, the more likely it is to cause a disease.
More virulent doesn’t necessarily mean more dangerous. For example, people who are infected with Salmonella enterica serotype Typhimurium generally experience diarrhea, fever, and abdominal cramps and recover without treatment. This type of salmonella can create an active infection from a single cell. Another type of Salmonella, S. enterica serotype Typhi requires up to 1,000 cells to create an infection. However, this serotype causes a much more severe and deadly disease: Typhoid Fever.
It is a sobering realization that the Salmonella we associate with food poisoning is so virulent, just one cell can infect a customer. All the more reason for cleaners to understand both pathogenicity and virulence when it comes to infection prevention.
Types of Pathogens
Additionally, there are two types of pathogens, primary and opportunistic.
Primary Pathogens: can cause disease in a healthy individual, regardless of the host’s resident microbiota or immune system. (example: E. coli)
Opportunistic Pathogens: can only cause disease in an individual with compromised defenses. (example: Staphylococcus epidermidis – S. epidermis – one of the most frequent causes of nosocomial diseases)
The very young, the elderly, pregnant women, patients undergoing chemotherapy or recovering from surgery and individuals with immunodeficiencies are susceptible to opportunistic pathogens.
Infections and disease can be caused by pathogens in the environment or microbes in an individual’s resident microbiota. The yeast Candida is a normal microbiota of the skin, mouth, intestine, and vagina, but its population is kept in check by other microorganisms. However, if an individual is on an antibiotic course, that medication could kill off the regulating bacteria, causing an overgrowth of Candida that manifests as oral thrush or a vaginal yeast infection.
In schools, child care facilities, and senior care facilities, occupants can be at much higher risk for opportunistic pathogens. Cleaning professionals have the ability and responsibility to clean in a way that reduces these pathogens.
Stages of Pathogenesis
In order to cause disease, a pathogen must successfully achieve 4 stages of pathogenesis.
- Exposure (contact) – A pathogen must first gain access to host tissue through a portal of entry such as skin, mucous membranes or parenteral routes.
- Adhesion (colonization) – Adhesion or colonization is the capability of pathogenic microbes to attach to the cells of the body using adhesion factors. Different pathogens use different mechanisms to adhere to the cells of host tissues. Certain pathogens have molecules called adhesins that bind to specific receptors in host cells. Some bacterial pathogens produce glycocalyces (slime layers and capsules) to attach to cells. Biofilm growth can also act as an adhesion factor. A biofilm is a community of bacteria that produce a glycocalyx, known as extrapolymeric substance (EPS), that allows the biofilm to attach to a surface. The EPS allows the bacteria to adhere to the host cells and makes it harder for the host to physically remove the pathoghen, as well as providing the bacteria protection against the immune system and antibiotic treatment.
- Invasion – After a pathogen has successfully adhered, it can proceed with invasion throughout local tissues or the body. Pathogens may produce exoenzymes or toxins that serve as virulence factors and allow them to colonize deeper into the body or protect them against immune system defenses.
- Infection – Following invasion, successful multiplication of the pathogen leads to infection. Infections can be local (confined to one area of the body), focal (a localized infection that spreads to a secondary location) or systemic (an infection that has disseminated throughout the body). Secondary infections can occur when a host’s defenses are compromised from primary infection or antibiotic treatment for a primary infection.
Once someone is exposed to a pathogen, there is little a cleaner can do. Therefore, cleaning professionals must focus on prevention by capturing and removing pathogens before exposure occurs.
Transmission of Disease
For a pathogen to persist, it must leave the host through a portal of exit and be transmitted to a new host. Portals of exit are similar to portals of entry and include the skin and the respiratory, urogenital, and gastrointestinal tracts. Coughing and sneezing can expel thousands of virus particles into the air. Secretions and excretions can also transport pathogens, as can blood through insect bites or needles.
The best approach to avoid transmission is prevention. This is especially important in a contained environment such as an office. Once one person in a facility gets sick, the cycle of infection makes it harder and harder to manage. Pathogens cannot survive as long in a frequently cleaned environment.
Preventing the Spread of Pathogens
Once the science behind infections is understood, cleaning professionals can use this information to improve their cleaning practices. The best way to prevent the spread of pathogens is to approach cleaning as a two-step process: cleaning and disinfecting. A surface must be cleaned before it can be disinfected. But what is the difference between cleaning and disinfecting?
The CDC defines cleaning as the removal of germs, dirt, and impurities from a surface or object. It does not necessarily kill germs but lowers their numbers and the risk of spreading infection. Disinfecting, on the other hand, does not necessarily clean dirty surfaces or remove germs, but by killing germs on a surface after cleaning, it can further lower the risk of spreading infection. It is not only important to do both steps but to do them in the proper order. Germs can hide underneath dirt, and dirt can decrease the effectiveness of disinfectants. Additionally, not all cleaning processes are created equal. For example, cleaning with a mop often merely spreads bacteria from one room to another, whether staff has disinfected or not. Microbiologist Dr. Charles Gerba warns that, in some cases, “It may be better to not clean a surface than to clean it improperly by using soiled cleaning tools.” Those in the industry should take care to choose a process that thoroughly extracts dirt and germs from surfaces.
Whether a hospital, school, or office, the health of building occupants lies in the hands of the cleaning professional. Through proper cleaning and disinfecting, the spread of pathogens can be reduced, leaving behind safer, healthier facilities.