Microbial Infections Arising From A Domestic Setting

Published Date: 02 Nov 2017

The term ‘Microorganisms’ refers to a collection of small organisms, visible only with the aid of microscopy. Antonie van Leeuwenhoek was one of the first to observe these in the 1600s using his own microscopic design (Porter, 1976).

The ability of such a microorganism to invade a host and multiply is known as infection. Early work conducted by microbiologists including Pasteur and Koch facilitated research on the microbial causation of infectious disease. Pasteur controverted the theory of ‘spontaneous generation’ by identifying that the process of putrefaction required living organisms and thus provided a basis for the ‘germ theory’. Koch’s formulation of the postulates and identification of the microbial causes of diseases, including anthrax and T.B, proved this ‘germ theory’ accurate (Baron et al., 2006).

Following this development in microbiology, substantial improvements in medicine have occurred. The development of antibiotic therapy to combat infectious disease is one of the most beneficial. Alexandra Fleming’s penicillin discovery has found a cure for many bacterial infections and has led to the development of other antibacterial agents (Sternbach et al., 1992). The immunisation programme has allowed eradication of certain diseases by preventing their development and spread, for example the last case of smallpox was recorded in 1980 (Strassburg, 1982).

1.2 Present concern of microbial infections

Although this progression in medicine has improved public health vastly over the last two centuries, areas of concern remain. Opportunistic infections are currently a major cause of mortality, particularly in the immunocompromised. Therefore emphasis on hygiene to control both the development and the spread of such diseases is necessary.

There is also growing concern over the ability of some microorganisms to resist the inhibitory action of antibiotic treatment (Tenover et al., 1996). This resistance has led to the development of infections which do not respond to treatment; individuals are infective for longer periods of time and so the spread of such infections is easier, particularly in those who are critically ill. There has also been an increase in mortality linked to this (Tenover, 2006).

Antibiotic resistance was first noticed in hospitals where excessive drug therapy was utilised (Levy, 1998). Over the years overuse of broad spectrum antibiotics has caused rapid progression of this problem. Common microorganisms showing resistance include Staphylococci, Enterococci, Klebsiella pneumoniae and Pseudomonas spp (Tenover, 2006).

The introduction of new antibacterial drugs to help relieve resistance and treat such infections has fallen by 50% over the last 20 years (Spellberg et al., 2004). Another method which may help overcome the resistance issue is to emphasise on public health. Educating the public on areas where potentially pathogenic microorganisms may harbour and on their elimination is important in order to reduce the number of infections arising from the domestic environment. Controlling infectious disease as such may help reduce antibiotic prescribing and stop the production of resistant bacteria.

1.3 Microbial infections arising from a domestic setting

Particular attention given to home hygiene in the 19th century led to a great decline in morbidity and mortality associated with infection. Adaptation of stringent food preparation methods showed the greatest drop in Salmonella related disease (Stanwell-Smith, 2003).

However, at present there is still great concern in the high number of cases of other intestinal infectious disease (IID) and respiratory infections linked to the home environment (Bloomfield et al., 2012). Such infections are most likely to infect high risk groups including the immunocompromised; such as those on invasive therapy, and the immunodeficient; such as the elderly, neonates, pregnant women and recently discharged hospital patients. Research indicates that 1 in 6 UK residents are within these high risk categories (Stanwell-Smith, 2003).

1.3.1 Intestinal infectious disease (IID)

The World Health Organisation (WHO) currently estimates over a million cases of food borne illness in the UK annually. Although many cases may be asymptomatic and self-limiting, there are a high number which cause hospitalisation and in severe cases, mortality (FSA, 2011).

Research based in England and Wales showed that after commercial catering services and residential settings, private homes were the third most likely areas for IID contraction (Hughes et al., 2007, Stanwell-Smith, 2003). A study conducted in Netherlands showed up to 80% of Salmonella and Campylobacter cases were contracted from private homes (Hilton et al., 2000). A number of other studies have also indicated that private homes are responsible for the greatest number of food borne illnesses; therefore emphasis has currently shifted away from catered services to private settings (Scott, 1996, Roberts, 1982).

Stanwell-smith (2003) research found that although cases of IID have decreased significantly; Campylobacter and salmonella are still the most prominent causes of food borne disease within the domestic setting (Stanwell-Smith, 2003). This is shown in figure 1.1 below.

Figure 1.1: The incidence of gastrointestinal infections in England and Wales (Stanwell-Smith, 2003).

Although the majority of these cases are linked to direct contact with food products, there is substantial evidence that cross contamination within the kitchen can cause such bacteria to spread to surfaces, cloths and other cleaning utensils (Humphrey et al., 1994, Cogan et al., 1999, Bloomfield et al., 1997). Therefore not only is adequate food preparation important but hygiene within the domestic setting is also important. A study showed that 34% of hamburger related infections caused by a strain of Escherichia coli could have been prevented by particular hand hygiene measures and by appropriate cleaning of work surfaces (Mead et al., 1997).

1.3.2 Respiratory infection

Respiratory disease is usually airborne and is most commonly spread via infected people within the home. However there is evidence that insufficient hand washing may lead to contamination of surfaces, door handles and cloths causing the virus to proliferate (Reed, 1975, Winther et al., 2007).

Research shows that common viruses found within the home include Rhinovirus, Parainfluenza virus and Influenza virus (Kramer et al., 2006, Boone et al., 2005). Influenza virus is accountable for a large number of fatalities annually in high risk groups; therefore it is crucial that measures are taken to decrease its spread. A US study showed that 59% of surfaces including telephone receivers, refrigerator handles, and kitchen faucets were contaminated with Influenza virus (Boone et al., 2005).

Furthermore complicated respiratory tract infections such as pneumonia, bronchitis and tuberculosis, may also spread via similar pathways. Particular concerns are for those with underlying respiratory conditions such as Chronic Obstructive Pulmonary Disease (COPD) or Cystic Fibrosis (CF). Denton et al conducted a study which showed that 42% of homes with CF children were contaminated with Stenotrophomonas maltophilia which may cause respiratory complications and mortality. Sites included dishcloths, sponges, kitchen surfaces and the washing machine (Denton et al., 1998).

1.4 Common bacteria found in a domestic setting

Although most bacteria found within the home are non-pathogenic, research has shown that pathogenic bacteria also exist. The first comprehensive study looking at opportunistic microorganisms within the domestic setting was conducted by Finch et al. A sample of 21 homes was inspected for the presence of microorganisms at various sites within the home. A large number of Micrococcus and Bacillus spp were found and pathogenic bacteria including Staphylococcus spp, Pseudomonas spp, Escherichia coli, Campylobacter, Corynebacteria and Salmonella was also collected (Finch et al., 1978). This research has been supported by many other studies (Scott et al., 1982, Speirs et al., 1995, Josephson et al., 1997).

1.4.1 Staphylococcus spp

The domestic environment shows contamination of Staphylococcus spp, particularly S. aureus and S. epidermis (Speirs et al., 1995, Scott et al., 1982, Finch et al., 1978).

Staphylococcus aureus is often carried by individuals within the nasopharyngeal cavity as part of the normal microbial flora. However it has the ability of causing both toxin-mediated and non-toxin mediated damage in immune deficient individuals and can often lead to systemic infections including infective endocarditis. Food poisoning can also occur if the toxin is ingested. Other common infections caused by this gram positive bacterium include impetigo and conjunctivitis (Hugo et al., 1995).

A study of 251 domestic homes conducted by Scott, Bloomfield and Barlow (1982), extracted 60 samples from various areas within the homes; including the kitchen and the bathroom. It was found that although the majority of contaminants were non-pathogenic, some potentially pathogenic species did exist. Staphylococcus aureus showed a percentage frequency of 31-35% (Scott et al., 1982).

A similar study focused particularly on the kitchen region within 46 homes. Samples were taken from various sites, of which wet areas around the sink and cloths used for wiping surfaces and drying equipment showed the highest colonisation. Of these 46 homes all showed some Staphylococcus spp persistence (Speirs et al., 1995).

Methicillin resistant Staphylococcus aureus (MRSA) is currently a major concern not only within hospital settings but also within the domestic environment. Recently discharged individuals may act as carriers of this organism and therefore it is important to emphasise to the public the importance of good hygiene measures (Bloomfield et al., 2012).

1.4.2 Pseudomonas spp

Pseudomonas aeruginosa is an opportunistic pathogen, only causing disease in those with compromised host defence systems including patients with cystic fibrosis, cancer or HIV diseases and those using intravenous drugs. It can lead to infections including malignant external otitis, endocarditis, pneumonia, septicaemia and meningitis (Bodey et al., 1983).

Pseudomonad bacteria have also showed up in research relating to the domestic environment. Scott et al (1982) found numerous Pseudomonas spp in the kitchen and bathroom at varying sites. P. aeruginosa was amongst these and the study also showed the persistence of many other unidentifiable pseudomonas bacteria. Common sites within the kitchen for P. aeruginosa were the sink u-tube, the draining board and the dishcloth; however frequency at each site was low (Scott et al., 1982).

Speirs et al (1995) also found similar results. This study showed that Gram negative bacteria as such collated near the sink region and Gram positive bacteria such as S. aureus persisted on cloth materials. The most common pseudomonad found was P. aeruginosa at 15.2% (Speirs et al., 1995).

1.4.3 Listeria spp

Listeria is a pathogen which normally contaminates dairy products. Pregnant women are at particular risk as infection may lead to miscarriages, premature births or serious illness in new-borns (Hugo et al., 1995).

A study conducted by Beumer et al (1996) found that listeria spp was present in 101 out of 213 homes. Listeria monocytogenes was present in 45 homes. The dishcloth showed high contamination, 40 out of 108 dishcloths sampled contained listeria spp of which 18 showed the presence of listeria monocytogenes (Beumer et al., 1996). Speirs et al also demonstrated its ability to grow at low temperature as they extracted L. monocytogenes from 2.2% of fridge surfaces (Speirs et al., 1995).

1.4.4 Escherichia coli

E.coli is a type of enterobacteria which may persist in undercooked food and if ingested may cause enteritis in young children leading to fatal GI symptoms such as bloody diarrhoea and dehydration. It also has the ability to infect the urinary tract and bladder leading to infections such as pyelitis, pyelonephritis and cystitis (Hugo et al., 1995).

Studies have shown its existence within the domestic environment, particularly due to cross contamination from raw meat (Speirs et al., 1995, Scott et al., 1982). An experimental study where untrained participants were asked to prepare a meal showed up to 10% contamination of E.coli on surfaces after the meal had been prepared. This study demonstrated that improper hand cleanliness and undercooked meat were common sources (Kennedy et al., 2011).

Scott et al (1982) found E.coli to persist in regions of the kitchen including the sink, the u-tube, the draining board and the dishcloth (Scott et al., 1982).

1.4.5 Klebsiella spp

Klebsiella bacteria often colonise the human gut, the pharynx and the skin. K. pneumonia is an opportunistic pathogen which may cause bronchopneumonia, if colonisation of the respiratory tract occurs. Several studies have shown that this bacterium persists in the domestic environment (Scott et al., 1982, Finch et al., 1978).

1.4.6 Salmonella and Campylobacter

Serious strains of Salmonella spp including Salmonella typhimurium may lead to the typhoid fever, whilst strains such as S. Typhimurium and S. Enteriditis have a link to bacterial food poisoning (Hugo et al., 1995).

As identified earlier salmonella and campylobacter are the greatest causes of food borne illness (Stanwell-Smith, 2003). The most common origin of such bacteria is raw food however research shows that many other sites within the kitchen can become contaminated. Cross contamination of Salmonella Enteriditis PT4 around the kitchen on to utensils and surfaces via contaminated egg shells has been identified (Humphrey et al., 1994).

Although the kitchen dishcloth and sponge have been identified as potential vehicles for such bacteria in the kitchen (Cogan et al., 2002); results within real domestic settings suggests no contamination of these items with these bacteria (Hilton et al., 2000, Bloomfield et al., 1997, Speirs et al., 1995).

1.5 Sources, dispersal and persistence of microbes in the domestic setting

Research has shown that although the majority of IID cases are food borne there is still a high number linked to cross contamination. Figure 1.2 shows that food borne contraction has decreased whereas non-food borne has increased (Hughes et al., 2007). The mode of transmission for these is said to be person to person spread or from surfaces to person. Similarly respiratory infections such as the common cold are often said to be spread by aerosol transmission but now there is growing evidence that a significant proportion are via hands and surfaces. This suggests that improved standards of personal and domestic hygiene may prevent outbreaks of both IID and respiratory infections (Bloomfield et al., 2012).

Figure 1.2: A comparison of the outbreaks of food borne and non-foodborne cases of IID (Hughes et al., 2007).

A number of studies show that water accumulating areas in the kitchen such as the sink area, drainage boards, u tubes, dish cloths, sponges and other cleaning items not only promote microbial growth but may also harbour opportunistic pathogens (Finch et al., 1978, Scott et al., 1982, Josephson et al., 1997, Speirs et al., 1995, Erdogrul et al., 2005).

The period of which the bacteria reside on these surfaces depends on the bacteria’s properties. Research shows that some bacteria are able to survive on surfaces, cloths, sponges and utensils for a number of days (Erdogrul et al., 2005). In particular it was found that on dry inanimate surfaces Klebsiella would normally last around 90 minutes, Salmonella a day, Campylobacter up to 6 days, E. coli from 1.5 hours to 16 months, S. aureus 7 days to 7 months and P. aeruginosa could last from 6 hours to 16 months (Kramer et al., 2006).

1.6 Ability of bacteria to bind to cloth materials

The fibres and intricate weaving of cloth materials makes them a good vector for viable bacteria. This has been of major concern particularly in the hospital environment where procedures are put in place to minimise infection risk (Neely et al., 2000).

A comparison study of paper and cloth towels found that cloth towels harboured a greater percentage of microorganisms (67.2%) compared to paper towels (33.3%). Bacillus spp was the greatest contaminant for both, Staphylococcus epidermis and Corynebacteria were most prevalent on cloth towels and Staphylococcus aureus occasionally contaminated cloth materials. This study emphasised that in terms of public health paper towels are much safer to use (Robinton et al., 1968).

Another study compared the bacteria binding and persistence properties of sponge dishcloths compared to cloth dishcloths (Hilton et al., 2000). This study showed that although sponge dishcloths harboured a greater number of Pseudomonas, klebsiella and Staphylococcus species it did not spread as many bacteria. Whereas a cloth dishcloth harboured less bacteria but spread was much easier. This was explained by contrast of the microstructure of both cloth types. The cavernous structure of the sponge provides a more protective environment for the microorganisms; therefore they are not removed easily. A cloth has a larger surface area and a smoother surface therefore bacteria are removed much easier (Hilton et al., 2000).

Adding to this, a study looked at the binding of opportunistic pathogens Pseudomonas aeruginosa and Staphylococcus aureus and found that both bound efficiently to acrylic, polyester and wool fibres of which polyester was the most contaminated. S. aureus did not bind to nylon fabrics however Pseudomonas aeruginosa did. Cotton showed the least contamination of such microorganisms (Takashima et al., 2004).

1.7 T-towels as a source and vector of microorganisms

T-towels/dish cloths play an important role in the dissemination of bacteria within the domestic kitchen (Scott et al., 1982, Finch et al., 1978, Josephson et al., 1997).

T-towels are often used during dish cleansing procedures, cooking procedures and surface cleaning processes. Gastrointestinal infecting species such as E.coli, Salmonella and Campylobacter may reside on dishes or surfaces from raw meat or infected individuals. S. aureus and Pseudomonas may be transferred from hands to tea towels, which are then used in the dish drying process causing bacterial spread.

Figure 1.3 illustrates how cleaning cloths are involved in the transmission of infection within the home. The cycle shows that sources of pathogens including infected people or contaminated food may transfer microorganisms to cloths. As such cloths are used for various processes within the kitchen they may act as vehicles causing dissemination of bacteria. This may eventually lead to the bacteria infecting a non-infected individual. This cycle is continuous and so the risk of spread is high (Bloomfield et al., 2012).

Studies of the bacterial contamination within the home show the highest number of total coliforms and faecal coliforms in the kitchen and the largest carrier to be the kitchen sponge and the kitchen dishcloth (Scott et al., 1982, Speirs et al., 1995, Rusin et al., 1998).

A study conducted by Scott and Bloomfield (1993) showed heavy contamination of dish cloths within hours of first use. The continued use of such cloths showed transfer of pathogens between surfaces and cloths; emphasising their ability to act as vectors (Scott et al., 1993).

Figure 1.3 The spread of infection within the domestic environment and the ability of cleaning cloths to act as vectors (Bloomfield et al., 2012)

1.8 Effect of laundering on tea towels

After usage, T- towels are often disinfected via the laundry process before they are utilised again, however research shows that laundering may not remove all traces of microorganisms. Studies have shown that some microorganisms causing ringworm, salmonellosis, adenovirus or hepatitis A may persist on fabrics if inadequate laundering procedures are used. Furthermore damp laundry may act as a habitat for bacterial growth. (Gerba et al., 2007)

Staphylococcus aureus has shown to be resistant to the laundry process; this is of particular concern in the hospital environment, where such microorganisms may cause infection in immune deficient individuals (Walter et al., 1975). Studies show that water temperature employed during laundering is an important factor in the reduction of bacterial species. A cycle at 60°c may reduce S. aureus bacteria to below detectable levels. Length of the washing cycle and the soil load do not show significant effects (Jaska et al., 1980).

Gerba and Kennedy (2007) emphasised the significance of detergent containing sodium hypochlorite (bleach) and the passage of washed items through the drying procedure; a reduction of 99.99% of enteric viruses such as rotavirus, hepatitis A and adenovirus were seen (Gerba et al., 2007).

Similar results were noticed in earlier studies (Rusin et al., 1998, Scott et al., 1984). Scott et al (1984) found that the use of detergent and hot water alone was ineffective in reducing the bacterial load, whereas the use of hypochlorite or phenolic disinfectants proved to decrease the bacterial load by 50% after 90 minutes. However bacteria reestablished after 3 hours (Scott et al., 1984).

1.9 The use of disinfectants

Often disinfectants or other cleaning agents are used to clean surfaces or areas within the domestic home. However there is much research suggesting that not all pathogenic microorganisms are sensitive to this and so they may still persist after its use.

Josephson et al (1997) conducted a 3 phase study; phase 1 was without the use of disinfectant, phase 2 was with casual use of the disinfectant and phase 3 was with targeted use of disinfectant. Casual use of the disinfectant did not see any significant reduction in the bacterial load however targeted use of the disinfectant saw a dramatic decrease (Josephson et al., 1997).

The effect of antibacterial dishwashing liquid was investigated on E. coli, S. aureus, Salmonella enteriditis and Bacillus cereus. In the suspension test, at 0.5% S. aureus and B. cereus were absent whereas Salmonella and E. coli survived. At 2-4% all organisms were below the detection limit. In used sponges the antibacterial wasn’t as effective (Kusumaningrum et al., 2002).