Understanding Chain of Infection and Modes of Transmission in Workplace

This presentation explains the chain of infection and modes of transmission in the workplace, with a focus on MRSA. It covers the reservoirs, portals of exit and entry, and hosts. It also provides measures to prevent infections at the workplace.

Chain of infections at the workplaceChain of infections at the workplace
Infectious disease results from the interaction between the agent, host and the environment.
Transmission occurs when the agent leaves the host via a portal of exit and enters through a portal of
entry for infecting a susceptible host. This sequence is called a chain of infections (CDC, 2012).
• Methicillin-resistant Staphylococcus aureus (MRSA) is a common form of infection that can be
resistant to a type of antibiotic known as Methicillin. Health care workers are in frequent contact with
MRSA and staphylococcus infected people. MRSA symptoms normally start as small skin rashes that
might resemble a pimple but might deteriorate if left untreated. The affected area can be full of puss and
drainage (Tong, Chen & Fowler, 2012, March) .
The six links include- the infectious agent, reservoir, portals of exit, mode of transmission, portals
of entry and host (O'Grady, 2017).
Chain of infection
Source:(CDC,2012) Figure 1
Figure 2. Source: (CDC,2012)
Reservoir
It is the habitat where the infectious agent normally grows, multiplies and mainly includes human,
environment, animals. The reservoir can or cannot be the source from which an agent can be transmitted
to a host.
Human reservoirs
Human reservoir is common for most of the infectious disease. Some of the diseases that are transmitted
between persons without any intermediaries include measles, mumps, streptococcal infection and
several respiratory pathogens. Humans are the only reservoirs for the small pox virus (CDC, 2012).
Any people, who can become infected with MRSA, can be the reservoir. People with uncleaned or open
wound are more susceptible to MRSA infection. The usual sites of colonisation with MRSA are the
groin, nostrils, wound and the axilla (Tong, Chen & Fowler, 2012, March).
Animal reservoirs
Diseases are also caused that have animal reservoirs. Many of the diseases are transmitted from an
animal to animal with humans to be the incidental hosts. Zoonosis is an infectious disease that is
transmissible from the vertebrate’s animals to the human beings. Zoonotic diseases include brucellosis,
anthrax, plague and rabies (Morse et al., 2014).
Environmental reservoirs
Environmental reservoirs can be plants, soil or water. Many funguses like the one that causes
histoplasmosis reside and reproduce in the soil. Legionnaires disease outbreak is often associated with
the water supplies in the evaporate condensers (Burillo, Pedro-Botet & Bouza, 2017).
Portals of exit
It is the path through which a pathogen leaves the host. The portals of exit are normally recognised as
that site where the infectious agent is localised. For example, Mycobacterium tuberculosis exits the
respiratory tract, Vibrio cholerae in excreta, Sarcoptes scabei in the skin lesions (World Health
Organization., 2015). It is known that there are some blood borne agents that can cross the placenta
from the mother to the baby such as in case of syphilis, rubella, toxoplasmosis, while there are others
that can exit through the cuts in the skin such as hepatitis or plasmodium for malaria. MRSA bacteria
exits the body through wounds, cuts or open sores (Popoola & Milstone, 2014).
Modes of transmission
Transmission of an infectious from the natural reservoir to a susceptible host can
occur by a number of ways. Modes of transmission can be classified as –
Direct
Direct contact
Droplet spread
Indirect
Airborne
Vehicle borne
Vector borne (mechanical or biologic)
Direct contact normally occurs from skin to skin , sexual intercourse and kissing.
It can also be referred to a direct contact with the soil harboring the infectious
agent. infectious mononucleosis (“kissing disease”) and gonorrhoea are normally
spread through skin to skin contact. The MRSA bacteria can spread through direct
contact with the infected material or the wound (Peters et al., 2013).
•Droplet contact- Large aerosols that are mainly produced by sneezing, coughing.
Aerosols might spread because of transmission over a few feet before they fall on
the ground. Meningococcal infections and pertussis are the examples of infections
spread by the droplets (Peters et al., 2012).
Indirect transmission can be referred to as the transfer of an infectious agent from a
reservoir to the host by the particles suspended in air or inanimate objects or the
vectors. Indirect contact transmission of MRSA takes place via the hand of a health
care worker or through a vehicle like contaminated object that is transiently
contaminated (CDC, 2012).
•Airborne transmission of the pathogens occur when the pathogens are carries by
the droplets of nuclei suspended in the air. The airborne dusts includes the deposits
on the surfaces and have become re-suspended by the air currents. Droplets nuclei
are dried residues of sizes less than 5 micron. Measles is an infection caused by the
airborne transmission.
•A vehicle carrying substances infection with pathogen can help in the
transmission. A vehicle might provide an environment suitable to the growth of the
microorganism, such as production of the botulinum toxin by Clostridium
botulinum in improperly canned foods.
Vectors like fleas , ticks and mosquitoes might carry the pathogen and help them
being transmitted to the host. For example- Fleas are the vectors of Yersinia pestis,
the causative agent of plague.
Portal of entry
It can be referred to as the manner in which a pathogen takes entry in to the body of
the host. The portal of entry must be such that it gives access to the tissue in which
the pathogen can reproduce. Example- Influenza virus exists the respiratory tract of
the source and enters the respiratory tract of the virus. “faecal oral route” is also
followed by many pathogens that are responsible for clinical conditions like
gastroenteritis.
The MRSA bacteria can enter the body of the host through open wounds, surgical
sites, new tattooed area and even the urinary tract (CDC, 2012).
Host
The final and the most important link in the chain of the infection is the susceptible host. The
susceptibility of the host depends upon genetic, environmental factors ,specific and the non specific
immunity of the host and the vaccination status of the host. For example, persons having sickle cell
anaemia are least protected from one type of malaria. Host for MRSA infections involve humans
and animals.
Susceptibility
People susceptible to MRSA infections are the elderly patients , children , surgery patients, athletes
and one with compromised immune system.
People who use injection for the drugs are also susceptible to the development of the infection.
Irrespective of the HIV status ,men having sex with men have also emerged as a risk factor for the
development of the community associated MRSA infections.
Immune deficiencies like granulomatous diseases, Chediak-Higashi syndrome can be the
predisposing factor for Staph infection. People having co morbidities like hemodialysis, diabetes
mellitus and rheumatoid arthritis are more susceptible to staph infections.
There are certain medications that weakens the immune system of the patients such as in the HIV
infected patients and high consumption of the antibiotics. Chemotherapeutic agents makes cancer
patients susceptible to infections.
Elderly patients face from many comormid condition that can affect their functional status and thus
restricts them to perform personal skin care and hygiene.
Genetic factors have also been found to be responsible for infections. There are rage genes
mutations that cause fatal vulnerability to specific classes of microbes , but there are subtle
differences that are common and arise from small variations in the genes. The genetic components
are often compounded by environmental factors that causes familial clustering and is further
complicated by some of the genes that are likely to be involved.
Source: (ABS, 2017)
Measures to prevent infection at workplace
Some of the generalised ways to avoid infections at workplace are:-
Getting an appropriate vaccine.
Using the single tissues
Abiding by an infection control plan.
Considering the cleaning of the workstation.
Allowing a proper ventilation system.
Some of the measures to prevent MRSA is to practice a good hygiene. Since most of the staph
infection among the health care workers takes place via hands, it is necessary to maintain a good
hand hygiene by maintaining 5 moments of hand hygiene, avoiding contact with infected person’s
wounds or bandages, avoiding sharing personal things like personal protective equipments or
razors, avoiding the use of swimming pools to prevent the transmission (Victoria State government.,
2015).
Comply with Infection Prevention and Control Policies and ProceduresComply with Infection Prevention and Control Policies and Procedures
References
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Transmission through wounds