4. Discussion
Taking the criteria reported in the Directive 2001/471/EC as
parameters of a possible comparison for acceptability and unacceptability
of the surfaces sampled, the results obtained lead us to
conclude that about 50% of refrigerators of Italian consumers have
an unacceptable TVC on their inner walls, if we compare the inside
of a domestic refrigerator to the work surfaces of any food industry.
We did not isolate strains of Y. enterocolitica nor of L. monocytogenes
in any of the samples tested. Instead, in 8 samples (1.4%),
the presence of Salmonella enterica, serovar Muenster was detected.
It might have been more logical to expect a higher prevalence of
Y. enterocolitica and L. monocytogenes, distinctly psychrotolerant species, while Salmonella tends to be a mesophilic microorganism.
The results obtained, however, lead to the conclusion that the
probability of contamination of our refrigerators seems to be
greater for Salmonella. The bacterium evidently comes from several
specific foodstuffs, such as eggshells, raw meats and fresh vegetables.
It is our opinion that this confirms the need to strongly advise
consumers how to properly arrange different foodstuffs inside
household refrigerators, making sure that food potentially
contaminated with Salmonella is best enclosed and kept away from
other foods, thereby avoiding the spread of the bacterium.
We also found that the microbial flora on the walls of household
refrigerators of Italians consists mainly of pseudomonadales and
fungi. The most interesting fact in our opinion, however, is that the
microbial flora that circulate in domestic refrigerators are more
likely to gather on the bottom of the refrigerator than on the vertical
walls. The majority of studies (we can mention Beumer &
Kusumaningrum, 2003; Ojima et al., 2002; Redmond & Griffith,
2009; Speirs, Anderton, & Anderson, 1995) focus on work surfaces,
dishcloths, dishes, cutting boards, refrigerator handles and
exterior doors, surfaces which, if not properly sanitized, could
represent a starting point for cross-contaminations.
The microbiological results that we have obtained by analyzing
the internal surfaces of the refrigerator, match the findings of
several researchers: the French, Dieuleveux et al. (2005) identified
only one strain of L. innocua out of a total of 60 vegetable compartments
of domestic refrigerators, and the Americans, Jackson
et al. (1993), out of 195 refrigerators never isolated
L. monocytogenes on surfaces that came into contact with meat and
vegetables, the Iranians Maktabi, Jamnejad, and Faramarzian (2013)
detected one strain of L. monocytogenes and two strains of
L. innocua in three refrigerators out of 180 appliances from student
accommodation and private dwellings in Ahvaz, in the south-west
of Iran. Lastly, Jackson, Blair, McDowell, Kennedy, and Bolton
(2007), who analyzed the refrigerators of 342 households over
one year, isolated S. aureus (6.4%), L. monocytogenes (1.2%),
Y. enterocolitica (0.6%), but never encountered Campylobacter spp.,
Salmonella spp. or Escherichia coli O157:H7. The TVC and coliform
levels found were on average 7.4 log CFU cm2 respectively and
over 3 log CFU cm2
.
The data we gleaned, however, are decidedly better than those
obtained in Ireland by Bolton et al. (2005) who isolated strains of
S. aureus, Salmonella spp., L. monocytogenes and Y. enterocolitica in a
number varying from 2% to 40% in the refrigerators sampled in their
country. Furthermore, our data are also better compared with the
survey conducted on 86 domestic refrigerators in Portugal by
Azevedoa et al. (2005) who isolated L. monocytogenes in 4 appliances,
Listeria grayi in another 4 and L. innocua in 1. The same
compared with Kilonzo-Nthenge, Chen, and Godwin (2008) who
isolated Listeria spp. in 137 domestic refrigerators in Tennessee, as
well as a number of genera belonging to the Enterobacteriaceae
family, including Klebsiella pneumoniae (23%), Enterobacter (now,
Cronobacter) sakazakii (2.2%), and Y. enterocolitica. Many of these
strains were also resistant to different antibiotics. Veterinary researchers
in Sudan (Abdalla, Suliman, Alian, & Bakhiet, 2008)
showed S. aureus (9.5%), L. monocytogenes (3.8%), E. coli (2%) and
Y. enterocolitica (1.6%) and very high TVCs (up to 9.7 log CFU cm2
)
in 150 domestic refrigerators. Moreover, the Mexican researchers
Macías-Rodríguez et al. (2013) assessed the hygiene of 200 refrigerators
and gained particularly disappointing results as far as
high microbial psychrotrophic counts (over 5 log CFU cm2
) were
concerned, on the shelves, in the vegetable drawer and on the
cloths used to clean the appliances. Also L. monocytogenes and
Salmonella spp. were found on the shelves of several refrigerators
(respectively in 59.5% and 32.5% of the samples analyzed). Finally,
Rohini Kumar, Apurva, and RishuOsborne (2012) examined an unspecified
number of refrigerators in Vellore district, south India.
4. DiscussionTaking the criteria reported in the Directive 2001/471/EC asparameters of a possible comparison for acceptability and unacceptabilityof the surfaces sampled, the results obtained lead us toconclude that about 50% of refrigerators of Italian consumers havean unacceptable TVC on their inner walls, if we compare the insideof a domestic refrigerator to the work surfaces of any food industry.We did not isolate strains of Y. enterocolitica nor of L. monocytogenesin any of the samples tested. Instead, in 8 samples (1.4%),the presence of Salmonella enterica, serovar Muenster was detected.It might have been more logical to expect a higher prevalence ofY. enterocolitica and L. monocytogenes, distinctly psychrotolerant species, while Salmonella tends to be a mesophilic microorganism.The results obtained, however, lead to the conclusion that theprobability of contamination of our refrigerators seems to begreater for Salmonella. The bacterium evidently comes from severalspecific foodstuffs, such as eggshells, raw meats and fresh vegetables.It is our opinion that this confirms the need to strongly adviseconsumers how to properly arrange different foodstuffs insidehousehold refrigerators, making sure that food potentiallycontaminated with Salmonella is best enclosed and kept away fromother foods, thereby avoiding the spread of the bacterium.We also found that the microbial flora on the walls of householdrefrigerators of Italians consists mainly of pseudomonadales andfungi. The most interesting fact in our opinion, however, is that themicrobial flora that circulate in domestic refrigerators are morelikely to gather on the bottom of the refrigerator than on the verticalwalls. The majority of studies (we can mention Beumer &Kusumaningrum, 2003; Ojima et al., 2002; Redmond & Griffith,2009; Speirs, Anderton, & Anderson, 1995) focus on work surfaces,dishcloths, dishes, cutting boards, refrigerator handles andexterior doors, surfaces which, if not properly sanitized, couldrepresent a starting point for cross-contaminations.The microbiological results that we have obtained by analyzingthe internal surfaces of the refrigerator, match the findings ofseveral researchers: the French, Dieuleveux et al. (2005) identifiedonly one strain of L. innocua out of a total of 60 vegetable compartmentsof domestic refrigerators, and the Americans, Jacksonet al. (1993), out of 195 refrigerators never isolatedL. monocytogenes on surfaces that came into contact with meat andvegetables, the Iranians Maktabi, Jamnejad, and Faramarzian (2013)detected one strain of L. monocytogenes and two strains ofL. innocua in three refrigerators out of 180 appliances from studentaccommodation and private dwellings in Ahvaz, in the south-westof Iran. Lastly, Jackson, Blair, McDowell, Kennedy, and Bolton(2007), who analyzed the refrigerators of 342 households overone year, isolated S. aureus (6.4%), L. monocytogenes (1.2%),Y. enterocolitica (0.6%), but never encountered Campylobacter spp.,Salmonella spp. or Escherichia coli O157:H7. The TVC and coliformlevels found were on average 7.4 log CFU cm2 respectively andover 3 log CFU cm2.The data we gleaned, however, are decidedly better than thoseobtained in Ireland by Bolton et al. (2005) who isolated strains ofS. aureus, Salmonella spp., L. monocytogenes and Y. enterocolitica in anumber varying from 2% to 40% in the refrigerators sampled in theircountry. Furthermore, our data are also better compared with thesurvey conducted on 86 domestic refrigerators in Portugal byAzevedoa et al. (2005) who isolated L. monocytogenes in 4 appliances,Listeria grayi in another 4 and L. innocua in 1. The samecompared with Kilonzo-Nthenge, Chen, and Godwin (2008) whoisolated Listeria spp. in 137 domestic refrigerators in Tennessee, aswell as a number of genera belonging to the Enterobacteriaceaefamily, including Klebsiella pneumoniae (23%), Enterobacter (now,Cronobacter) sakazakii (2.2%), and Y. enterocolitica. Many of thesestrains were also resistant to different antibiotics. Veterinary researchersin Sudan (Abdalla, Suliman, Alian, & Bakhiet, 2008)showed S. aureus (9.5%), L. monocytogenes (3.8%), E. coli (2%) andY. enterocolitica (1.6%) and very high TVCs (up to 9.7 log CFU cm2)in 150 domestic refrigerators. Moreover, the Mexican researchersMacías-Rodríguez et al. (2013) assessed the hygiene of 200 refrigeratorsand gained particularly disappointing results as far ashigh microbial psychrotrophic counts (over 5 log CFU cm2) wereconcerned, on the shelves, in the vegetable drawer and on thecloths used to clean the appliances. Also L. monocytogenes andSalmonella spp. were found on the shelves of several refrigerators(respectively in 59.5% and 32.5% of the samples analyzed). Finally,Rohini Kumar, Apurva, and RishuOsborne (2012) examined an unspecifiednumber of refrigerators in Vellore district, south India.
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