Research Article
Patience Chisa Obinna-Echem
Patience Chisa Obinna-Echem
Corresponding Author
Food Science and Technology, Rivers State University, Nkpolu-Oroworukwo, Port Harcourt, Nigeria
E mail: patience.obinna-echem@ust.edu.ng; Tel: +234 90 9400 0342.
Godstime Uchechi Thomas
Godstime Uchechi Thomas
Food Science and
Technology, Rivers State University, Nkpolu-Oroworukwo, Port Harcourt, Nigeria
Abstract
Microbiological quality and antibiotic sensitivity of
potential pathogens from roasted skinned and unskinned groundnuts sold in the River
State University campus and its environs were evaluated. Samples obtained from
three locations namely: Back gate, Main gate and Shopping complex were coded
BSG, MSG and SSG respectively for skinned and BUG, MUG and SUG for the
unskinned. Samples transported to the laboratory in chilled cooler were
analyzed immediately as freshly purchased and after four weeks of cold storage
(15.0 ±2°C). Conventional microbiological methods were used for
analysis. Microbial
analysis (Log10 CFU/g) revealed that all freshly purchased samples
had total bacteria count (TBC) of 3.99 -
5.98, coliform (TCC), Salmonella
(TSC)
and mould (TMC) counts of
1.00, 4.30 and 5.11 in BUG, SUG and MUG respectively. Escherichia coli (TEC), Staphylococcus
(TSTC) and yeast (TYC) counts in three of the samples ranged respectively, from
1.35 – 2.70, 3.00 - 4.30 and 2.00 – 3.70. Total lactobacillus count (TLBC) was 2.70 –
4.49 for MSG and SUG. After storage, the microbial load
increased and counts for TBC, TCC, TLBC, TSTC, TEC, TSC, TYC and TMC ranged
from 5.04 – 7.89, 3.00 – 4.75, 2.70 – 3.00, 3.78 – 5.23, 1.35 – 4.48, 5.11 in
MSG, 1.20 – 4.85 respectively. Antibiotic
inhibition against Staphylococcus and Salmonella varied from 1.00 – 14.5 and 4.5 – 14.5
mm. E. coli was sensitive to
gentamycin, perfloxacin and ofloxacin with inhibition zones of 8.5, 12.5 and
13.5 mm respectively. Good hygienic practices and appropriate storage
facilities will minimize contamination and ensure safe roasted groundnuts for
consumption. The sensitivity test indicates
what can be utilized in the event of food poison.
Abstract Keywords
Roasted groundnuts, microbial quality, pathogens,
antibiotics sensitivity, inhibition zones
1. Introduction
Groundnut (Arachis
hypogaea L.), also known as earthnut and peanut is cultivated and consumed
in the tropics, subtropics and temperate regions of the world. The nut is made
up of oil and nutrient rich seed having a seed-coat enclosed in an epicarp
shell. The seed can be consumed raw, lightly roasted or boiled with or without
the shell, processed into a paste that is used as a spread for baked goods,
crushed for production of oil, candy bars, cookies and peanut brittle etc. [1]. Nigeria is the largest groundnut producing
country in West Africa, accounting for 51% of production in the region [2]. It is an important component of Nigerian diet
providing approximately 5% of the estimated 58.9 g of crude protein available
per head per day [3]. In Nigeria, especially
the southern part, the roasted shelled or unshelled, skinned or unskinned
groundnuts in different packing materials such as polyethylene bags, plastic
and glass bottles are sold in public places such as markets, offices, schools,
motor parks, bus stops, hospitals, restaurants, supermarkets and also hawked
along the expressway in both rural and urban areas. It is also used in
entertaining guests in many occasions where it is served with garden eggs as
roasted skinned or paste mixed with salt and different spices.
The awareness of nut associated food infection was created
by the outbreak of salmonellosis in peanut and peanut products [4, 5]. The preparations in unsanitary environment
and packaging materials in addition to poor handling and storage can lead to
post processing contamination with microorganisms that predispose to food
poisoning. Groundnuts like other nuts are highly susceptible to microbial
invasion especially fungal attack at various stages of processing due to low
moisture content and rich nutrient content [6]. Due
to low water activity, the pathogens may not proliferate but can survive resulting
in food poisoning when consumed.
Consequently, various microorganisms have been reportedly isolated from
groundnuts and their products by different authors especially, bacteria species
of the genera Bacillus, Enterobacter, Escherichia, Klebsiella, Shigella, Salmonella, Staphylococcus, Micrococcus, Proteus, Streptococcus
and fungi species such as Aspergillus,
Penicillium, Mucor Fusarium, Trichoderma and Rhizopus [5, 7-11].
Antibiotics are substances that inhibit the proliferation of
bacteria and are used in the body for treatment of various infections. They are
of different categories and act in specific ways to achieve inhibition. The
fluoroquinolone based antibiotics such as ciprofloxacin, act by inhibiting
bacterial DNA gyrase responsible for DNA replication and transportation [12], penicillin and cefuroxime-class such as
Amoxicillin, Ampiclox Rocephin and Zinacef and Erythromycin act against the
bacterial cell wall synthesis [13], Gentamicin
and streptomycin belong to the aminoglycoside based antibiotics that bind
irreversibly to the 16S rRNA subunit of the 30S ribosome and inhibit bacterial
protein synthesis [14, 15], some contain
substances that are not antibiotics but rather block the enzymes that
contribute to antibiotic resistance allowing the antibiotics to function
effectively. Example is the Beta-lactamase inhibitors in the clavulanic
potassium content of Augmentin [16]. Microbial
antibiotic sensitivity test is to find out which antibiotic can inhibit the
growth of the pathogen and the best for use in the treatment of any poisoning
arising from the consumption of food contaminated with the pathogens.
Some Authors have isolated pathogens in ready to eat
groundnuts [5, 7-11]. However, no
information on the microbiological quality of groundnuts sold at Rivers State
University and its environs. The aim of this study was to evaluate the
microbiological quality and antibiotics sensitivity of potential pathogens in
ready-to-eat roasted groundnuts sold in Rivers State University and its
environs.
2. Materials and methods
2.1
Groundnut samples
Roasted skinned and unskinned groundnut samples were
purchased from three locations mainly Main gate, Back gate and Shopping complex
of the Rivers State University, Port Harcourt Rivers State, Nigeria. The skinned
groundnut samples purchased from the back gate, main gates and shopping complex
were coded BSG, MSG and SSG respectively, while the unskinned samples were
coded BUG, MUG and SUG. The samples were
well labelled and transported in chilled cooler to the laboratory for analysis.
Samples were analyzed immediately after purchases as freshly purchased and
after four weeks of cold storage at 15.0±2°C, mimicking the
temperature of display in most supermarkets.
2.2.
Microbiological Analysis
Serial dilution to enumeration was carried out as described
by Obinna-Echem and Cookey, [17] while the method by Harrigan [18] was followed during isolation and
characterization. Antibiotic sensitivity test was as described by Barber et al [19].
2.2.1.
Media and plate preparation
Microbial media were prepared and sterilized following the
manufacturer’s (Sigma-Aldrich, Burlington, Massachusetts, USA) instruction.
Appropriate quantities were weighed into a beaker and dissolved in the right
amount of water by gentle heating with constant stirring on a hot plate.
Thereafter they were transferred into a 250 mL glass bottle and autoclaved at
121°C for 15 min. The sterile media were cooled to 45°C
in a water bath before dispensing approximately 10 mL into sterile Petri dishes
to set. Set plates were turned upside
down and stored away in the refrigerator till when needed for analysis.
2.2.2.
Serial dilution
This was carried out as described by Obinna-Echem and
Cookey, [17]. Serial dilution for each
sample was prepared by homogenizing 10 g of the sample with 90 mL of sterile
peptone water. Thereafter, 1 mL was aseptically withdrawn into 9 mL of sterile
peptone water in a sterile 20 mL tubes, vortexed for 3-5 s and serially diluted
to 105.
2.2.3.
Inoculation and incubation
Following the method described by Obinna-Echem and Cookey, [17], aliquots (100 uL) of appropriate dilutions:
10-5 for Nutrient agar (NA), 10-2 for Eosin methylene
blue agar (EMB), Salmonella Shigellla agar (SSA), MacConkey agar (MCA) and
Mannitol salt agar (MSA), and 10-1 for Potato dextrose agar (PDA),
and Sabaroud dextrose agar (SDA) were plated on appropriate microbial medium
for each microorganism. Total aerobic bacteria, coliform, Escherichia coli and Salmonella
were respectively, enumerated on NA, MCA, EMB and SSA. Total yeast, mould and Staphylococcus were enumerated on PDA,
SDA, and MSA respectively. Then NA, MCA, and SSA were incubated at 34°C
for 24 - 48 h while PDA and SDA were incubated at 25°C for 48h and
EMB was incubated at 45°C for 48 h.
2.2.4.
Enumeration and calculation
After incubation, visible colonies were counted and the
microbial numbers calculated as CFU/g = (Number of colonies X Dilution
factor)/Volume of inoculum. Values obtained were converted to Log10 CFU/g
[17].
2.2.5.
Isolation of potential pathogens
Colonies from the selected pathogen media were sub-cultured
by streak plating to obtain pure cultures that were confirmed and used for
sensitivity tests. E. coli on EMB
plates were sub-cultured and incubated at 44°C for 24-48 h, Staphylococcus and Salmonella were sub-cultured on MSA and SSA respectively and
incubated at 37°C for 24-48 h. At the end of the incubation period, plates were
examined to ensure that they contained pure cultures. Confirmation of the pure
culture was conducted by colony morphology characterization, Gram staining,
catalase and coagulase tests as described by Harrigan [18].
2.2.6.
Antibiotic Sensitivity test
Antibiotics in the gram-positive disc were: chloramphenicol
(30 µg), ampiclox (30 µg), rocephin (30 µg), ciprofloxacin (10 µg), septrin (30
µg), sparfloxacin (10 µ), erythromycin (30 µg) and pefloxacin (30 µg) while the
gram-negative disc had Septrin (30 µg), Ciproflaxain (10 µg), Amoxicillin (30
µg), Augmentin (30 µg), gentamycin (10 µg), pefloxacin, (30 µg), ofloxacin (10
µg) streptomycin (30 µg), sparfloxacin (10 µg), and chloramphenicol (30 µg).
The analysis was carried out as described by Barber et al., [18].
2.3 Statistical Analysis
Data obtained were
subjected to statistical analysis using Minitab (Release 18.1) Statistical
Software English (Minitab Ltd. Conventry, UK). Statistical differences and
relationships among variables were evaluated by analysis of variance under
general linear model and Turkey pairwise comparison at 95% confidence level.
3. Results
and discussion
Microbial counts
of roasted skinned and unskinned groundnuts freshly purchased from different
locations in Rivers State University campus and its environs are shown in Table
1, while counts after cold storage are shown in Table 2.
Table 1. Microbial quality (log10
CFU/g) of roasted
skinned and unskinned groundnuts freshly purchased from Rivers
State University campus and its environs
Samples |
TBC |
TCC |
TEC |
TSTC |
TLBC |
TSC |
TYC |
TMC |
BSG |
5.20a±0.71 |
NG |
1.35a±1.91 |
NG |
NG |
NG |
2.00c±0.00 |
NG |
BUG |
5.98a ±0.00 |
1.00±0.00 |
2.70a±0.00 |
3.60a±0.43 |
NG |
NG |
3.70a±0.00 |
NG |
MSG |
5.98a±0.03 |
NG |
NG |
3.00b±0.01 |
2.70b±0.01 |
NG |
NG |
NG |
MUG |
3.99b±0.35 |
NG |
NG |
NG |
NG |
NG |
NG |
2.70±0.01 |
SSG |
4.30b±0.00 |
NG |
2.70a±0.00 |
4.30a±0.00 |
NG |
NG |
2.70b±0.01 |
NG |
SUG |
4.50ab±1.13 |
NG |
NG |
NG |
4.49a±0.01 |
4.30±0.00 |
NG |
NG |
Values are means ± standard
deviation of duplicate samples. Means within a column with different
superscripts are significantly different at (p<0.05). BSG = Back gate
skinned roasted groundnut, BUG = Back gate unskinned roasted groundnut, MSG =
Main gate skinned roasted groundnut, MUG =Main gate unskinned roasted
groundnut, SSG = Shopping complex skinned roasted groundnut, SUG = Shopping
complex unskinned roasted groundnut, NG = No growth, TBC =Total bacteria count, TCC =
Total coliform count, TEC = Total Escherichia
coli count, TSTC = Total Staphylococcus
count, TLBC =Total Lactobacillus
count, TSC = Total Salmonella
Count, TYC = Total yeast count, TMC = Total mould count. |
Table 2. Microbial quality (log10
CFU/g) of roasted
skinned and unskinned groundnuts from Rivers State University campus
and its environs
after 4 weeks of storage.
Samples |
TBC |
TCC |
TEC |
TSTC |
TLBC |
TSC |
TYC |
TMC |
BSG |
7.89a±0.07 |
4.75a±0.01 |
2.70b±0.00 |
4.84c±0.01 |
1.35c±1.91 |
NG |
1.20b±1.70 |
4.74a±0.00 |
BUG |
7.06ab±2.21 |
3.00b±0.00 |
NG |
3.95e±0.00 |
NG |
NG |
2.70b±0.00 |
2.70c±0.00 |
MSG |
7.37ab±0.59 |
4.65a±0.00 |
2.70b±0.00 |
4.90b±0.00 |
4.48a±0.00 |
5.11a±0.00 |
4.85a±0.00 |
2.70c±0.00 |
MUG |
3.98b±0.00 |
3.20ab±0.71 |
NG |
3.98d±0.00 |
3.00b±0.00 |
NG |
2.70b±0.00 |
2.70c±0.00 |
SSG |
7.19ab±0.55 |
3.70ab±0.00 |
NG |
5.23a±0.00 |
NG |
NG |
4.19a±0.41 |
3.94b±0.34 |
SUG |
5.04ab±0.00 |
NG |
3.00a±0.00 |
3.78f±0.00 |
NG |
NG |
2.70b±0.00 |
2.70c±0.00 |
Values are means ± standard
deviation of duplicate samples. Means within a column with different
superscripts are significantly different at (p<0.05). BSG = Back gate
skinned roasted groundnut, BUG = Back gate unskinned roasted groundnut, MSG =
Main gate skinned roasted groundnut, MUG =Main gate unskinned roasted
groundnut, SSG = Shopping complex skinned roasted groundnut, SUG = Shopping
complex unskinned roasted groundnut, NG = No growth, TBC =Total bacteria count, TCC =
Total coliform count, TEC = Total Escherichia
coli count, TSTC = Total Staphylococcus
count, TLBC =Total Lactobacillus
count, TSC = Total Salmonella
Count, TYC = Total yeast count, TMC = Total mould count. |
The total
bacteria count (TBC) of the roasted skinned and unskinned groundnut
samples ranged from 4.30 – 5.98 and 3.99 – 5.98 Log10 CFU/g
respectively. After 4 weeks of storage at cold temperature, the counts ranged
from 7.19 – 7.89 and 3.98 – 7.06 Log10 CFU/g
for the roasted skinned and unskinned groundnut
samples respectively.
Total Bacteria Count of a
substance is a quantitative estimate of the number of microorganisms present in
a sample. The result revealed that there was no significant difference
(p>0.05) between the TBC of skinned and unskinned roasted groundnut samples
but there was significant (p<0.05) increase in TBC after storage. The
result of the freshly purchased samples were comparable to the findings made by
Akinnibosun and Osawaru [20] that TBC in
unskinned groundnut sold in Benin City in the range of 0.5 - 2.1 x 104 CFU/g
equivalent to 3.70 – 4.32 Log10 CFU/g and Oranusi and Braide [21] that TBC in groundnut sold along
Onitsha-Owerri expressway in the range of 1.1 - 58.0 x 104 CFU/g
equivalent to 4.54 – 5.76 Log10 CFU/g). TBC is also known as total
viable or aerobic count and it is the total number of bacteria able to grow in
an aerobic environment in moderate temperature. There are no applicable limits
in ready to eat foods [22]. However, high
levels indicate general poor quality and reduction in shelf life due to storage
and handling problems. The roasted groundnuts are packaged in open environment
with the possibility of contaminants in the environment settling on them in
addition to the hands of the food handlers.
The result of
total coliform count (TCC) indicated that there was no coliform growth in all
the freshly purchased samples except for unskinned sample from the back gate (BUG) that had a count of 1.00
Log10 CFU/g. After storage, there was significant (p<0.05) growth
of coliform in the samples, the values ranged from 3.70 – 4.75 and 3.00 – 3.20
Log10 CFU/g respectively, for the skinned and unskinned
samples. These values are in line with the report of 3.5 x 102 – 4.3
x 104 CFU/g equivalent to 2.54 – 4.63 Log10CFU/g for
groundnut sold along Onitsha-Owerri expressway [21].
This may imply that the groundnuts sold on the express must have either
been stored for some time or the conditions on the highways had made increased
contamination or growth compared to the freshly purchased samples. Coliform is
a group of microorganisms in the Enterobacteriacaea family and the value obtained in this study was within the
borderline of 2 – 4 Log10 CFU/g given by Centre for Food
Safety, [22] with the exception BSG and MSG
after storage.
Total
lactobacillus count (TLBC) in the freshly purchased roasted groundnut samples,
was only observed in sample MSG with count of 2.70 Log10 CFU/g for
the roasted skinned groundnut
and sample SUG with count of 4.49 Log10 CFU/g for the unskinned groundnut samples. After
storage, the TLBC in the skinned
sample ranged from 1.35 – 4.48 Log10 CFU/g in samples BSG and MSG,
respectively while the unskinned
sample had count of 3.00 Log10 CFU/g for sample MUG. The low count
of Lactobacillus spp a fermentative
organism in the groundnut samples was satisfactory since it is not a fermented
product. However, this observation may not be unconnected with the ubiquitous
nature and can come from the environment, food handlers, packaging materials
etc. These were not of any quality or
safety issue in the dried ready to eat nuts.
The total E. coli counts (TEC) in the freshly
purchased samples were 1.35, 2.70 and 2.70 Log10 CFU/g for BSG, SSG
and BUG respectively. After storage,
there was significant (p<0.05) increase in the TEC of BSG and BUG with
values of 2.70 and 3.00 Log10 CFU/g respectively, while there was no
increase in SSG. The presence of E. coli
in the samples could be due to the hygienic condition of the area as well as
the extent of hygienic practices by the vendors since E. coli is a common faecal indicator organism. Its presence in food
generally indicates direct or indirect faecal contamination [22]. According to the guidelines for ready to eat
foods by CFS, [22] the satisfactory level
for E. coli is < 20 CFU/g
(equivalent to < 1.03 Log CFU/g) while > 102 CFU/g (equivalent
to >2 Log CFU/g) is unsatisfactory. The level of E. coli detected in sample BSG, SSG and BUG before and after
storage are unsatisfactory and adequate personal hygiene practices, clean
environment and use of clean packing materials are highly solicited. Though in
developed world, this would call for investigation of the vendors.
The total Staphylococcus count (TSTC) showed that
the freshly purchased sample MSG and SSG had counts of 3.00 and 4.30 Log10
CFU/g respectively, while there was no growth in BSG. In the unskinned
groundnut samples, there was no growth in sample MSG and BSG while BUG had
counts of 3.60 Log10 CFU/g. After storage, the skinned samples had
TSTC in the range of 4.84 – 5.23 Log10 CFU/g for BSG and SSG
respectively. The unskinned samples had counts of 3.78 - 3.98 Log10 CFU/g
respectively for SUG and MUG. The
presence of Staphylococcus in
the ready to eat roasted skinned
and unskinned groundnuts is in
accordance with the finding of Kigigha et al., [10].
The values were higher than 1.92 – 2.29 Log10CFU/g reported
for unpeeled groundnut sold in
some locations in Yenagoa metropolis, Bayelsa state, Nigeria [10]. The levels in the freshly purchased samples
except for SSG and all the unskinned samples after storage were within the
satisfactory limits of <4 Log10 CFU/g [22].
Consumption of groundnut with unsatisfactory levels is a potential risk
to health although for the production of the heat-stable toxin levels >5 Log10
CFU/g is required.
The total Salmonella
count (TSC) revealed that the freshly purchased samples, had no growth of Salmonella except for SUG with count of
4.30 Log10
CFU/g. After storage, there
was increase in growth of Salmonella
in SUG to 5.11 Log10 CFU/g. The total Salmonella count in this study has
similarity with the study carried out by Kikigha et al., [10], where Salmonella
shigella was not detected in the various groundnut samples. The approved
safety level for Salmonella in ready
to eat nut like groundnut is absence of the pathogen (No growth) [22]. Sample SUG with Salmonella growth is unfit for consumption, though this might be
difficult to avoid as food with pathogens may look good as with the groundnut
samples.
The total yeast
count (TYC) in the freshly purchased roasted skinned groundnut samples was 2.00 – 2.70 Log10 CFU/g
for samples from BSG and SSG, respectively. There was no growth in the unskinned samples except for sample
BUG with the count of 3.70 Log10 CFU/g. The freshly purchased
samples had no mold growth except for sample MUG with count of 2.7 Log10 CFU/g.
After storage, the total
mould count of the roasted skinned groundnuts ranged from 2.70 – 4.74 Log10
CFU/g for samples MSG and BSG, respectively, while the roasted unskinned groundnuts had count of 2.70
Log10 CFU/g for all the samples. The fungi result from this present
study is in agreement with other reports on groundnut and its products sold in
other locations in Nigeria [8, 10, 20, 21]. The
major challenge with the presence of fungi in groundnuts is the production of
mycotoxins. Some fungi diversity found
in groundnuts revealed toxin producing microbes such as species of Penicillium, Fusarium and Aspergillus that are known to produces
mycotoxins in food [13, 23].
The
characteristics of isolated potential pathogens are shown in Table 3. The
preliminary identification showed that the pathogens are Staphylococcus aureus,
Escherichia coli and Salmonella Spp. Fig. 1 showed the antibiotic sensitivity of the
isolated Staph.
aureus on a gram-positive disc while the antibiotic
sensitivity of the isolated E. coli and Salmonella on a
gram-negative discs are shown in Fig. 2. The antibiotic sensitivity test
evaluated potential antibiotic that can inhibit the growth of the pathogen for
effective treatment of any poisoning arising from the consumption of the
roasted groundnuts.
Figure
1.
Antibiotic inhibition zones against Staphylococcus
isolated from roasted skinned and unskinned groundnut from Rivers State
University and its environs. (Bars and error bars represent mean inhibition
zones and standard deviation of duplicate measurement. Bar with the same
superscript are not significantly different at p<0.05. BUG – Back gate roasted unskinned
groundnut, MSG - Main gate roasted skinned groundnut, SSG – Shopping complex
roasted skinned groundnut)
Figure
2.
Antibiotic inhibition zones against Salmonella
and E. coli isolated from roasted
skinned and unskinned groundnut from Rivers State University and its environs.
(Bars and error bars represent mean inhibition zones and standard deviation of
duplicate measurement. Bar with the same superscript are not significantly different
at p<0.05. MUG - Main
gate roasted unskinned groundnut, BUG – Back gate roasted unskinned groundnut)
Table
3.
Characteristics of isolated potential pathogens from roasted skinned and
unskinned groundnut from Rivers State University and its environs.
Isolates |
Morphological
characteristics |
Biochemical test |
||||
|
Colony on media |
Shape |
Arrangement |
Gram
Reaction |
Catalase
reaction |
Coagulase
reaction |
Salmonella |
Opaque, round large on SSA |
Short rods |
Scattered in pairs and some single chain |
- |
+ |
+ |
E. coli |
Greenish to black on EMB |
Short rods |
Scattered singly, in pairs and small groups |
- |
- |
- |
Staph. aureus |
Smooth, thick yellow to orange on MSA |
cocci |
clusters |
+ |
- |
+ |
The antibiotics
used from the gram-positive disc were chloramphenicol, ampiclox, rocephin,
ciprofloxacin, septrin, sparfloxacin, erythromycin and pefloxacin. Staphylococcus spp isolated from roasted
skinned groundnut sample from back gate (BSG) was resistant to all the
antibiotics except for pefloxacin and ciprofloxacin with inhibition zones of
1.00 and 9.50 mm respectively. Isolate from skinned roasted groundnut from the
main gate (MSG) was resistant to gentamycin, ampiclox, rocephin and pefloxacin
while the inhibition zones for the other antibiotics ranged from 4.50 – 12.50
mm respectively, for sparfloxacin and ciprofloxacin respectively. Isolate from
skinned roasted groundnut from Shopping complex (SSG) was resistant to
gentamycin and amoxicillin but had inhibition zones in the range of 11.5 – 14.5
for erythromycin and ciprofloxacin respectively. Ciprofloxacin was inhibitory
to all the Staphylococcus spp
isolated and had significantly (p<0.05) the highest inhibition zones.
The antibiotics
from the gram-negative disc were septrin, ciprofloxacin, amoxicillin, augmentin,
gentamycin, pefloxacin, ofloxacin, streptomycin, sparfloxacin, and
chloramphenicol. Salmonella was
resistant to chloramphenicol and sensitive to all the other antibiotics with
inhibition zones in the range of 4.5 – 14.5 mm for septrin and ciprofloxacin
respectively. The inhibitory zones of sparfloxacin, augmentin and ofloxacin
against Salmonella did not differ
significantly (p>0.05) from ciprofloxacin. E. coli was sensitive to gentamycin, pefloxacin and ofloxacin with
inhibition zones of 8.5, 12.5 and 13.5 mm respectively.
The inhibitory
activities of antibiotics involve interference with cell wall synthesis,
strength and rigidity; DNA replication and protein synthesis; and blockage of
enzymes that increases resistance in pathogens [12,
15-16, 24]. The sensitivity of the pathogens was significantly
(p<0.05) higher with the fluoroquinolone antibiotics: ciprofloxacin,
sparfloxacin, ofloxacin and pefloxacin that act by inhibiting DNA replication.
This is in line with the report by Barber et al., [19]
and confirmed the report of excellent activities against gram-negative
and gram-positive bacteria [25]. The
resistance of gram-negative bacteria to antibiotics is usually attributed to
the induction, mutation or by acquisition of R-plasmids, or the inability of
the antibiotics to reach the active site [19]. The
sensitivity of these potential pathogens to the different antibiotics implies
that in the event of food poisoning from the consumption of contaminated
roasted groundnut, the use of such antibiotics can help in alleviating the
situation. Only selected antibiotics can be used for the Staphylococcus isolated from roasted groundnut from the main gate
and shopping complex while for isolate from back gate only ciprofloxacin and
pefloxacin will be helpful. The isolated Salmonella
can be handled with a wide range of antibiotics while gentamycin, pefloxacin
and ofloxacin will be effective for the isolated E coli.
4.
Conclusions
The study
revealed that all the freshly purchased samples had total bacteria count;
coliform, Salmonella and mould were found
in one sample: BUG, SUG and MUG respectively, three of the samples had E. coli, Staphylococcus and yeast counts and two samples (MSG and SUG) had lactobacillus. After storage, the
microbial counts revealed high level of total bacteria count (TBC), borderline
level of coliform (TCC), safe level of lactobacillus (TLBC), satisfactory level
of Staphylococcus (TSTC),
unsatisfactory level of E. coli (TEC),
unsafe level of Salmonella (TSC) and
high level yeast (TYC) and mould (TMC). Proper processing, hygienic practices and good storage
facilities will minimize contamination and ensure safe roasted groundnuts for
consumption. Isolated pathogens were Staphylococcus aureus,
Escherichia coli and Salmonella. They had varying sensitivities to antibiotics. Inhibition of the
pathogens by selected antibiotics suggests the likely antibiotics that can be
utilized in checking their proliferation and ill effect on consumers.
Authors’ contributions
Concept, data
analysis, literature search, final draft, and supervision, O.E.P.C.; Sample
collection and laboratory analyses, T.G.U.
Acknowledgements
The authors
appreciate the technical assistance of Ms. Earnest Nwiidebom of the
Microbiological Laboratory at the Department of Food Science and Technology.
Funding
The authors received no external
funding
Availability of data and materials
All data will be
made available on request according to the journal policy.
Conflicts of interest
Authors have
declared that no competing interests exist.
References
1.
Balogun,
M.A.; Karim, O.R.; Akintayo, O.A.; Oyeyinka, A.T.; Kolawole, F.L.; Okereke, E.E.
Effect of potash addition on groundnut
oil yield and quality of kulikuli (fried groundnut cake).
Agrosearch, 2020, 20(1), 23-33.
2.
Ajeigbe,
H.A.; Waliyar, F.; Echekwu, C.A.; Ayuba, K.; Motagi, B.N.; Eniayeju, D.; Inuwa,
A. A Farmer’s guide to groundnut production in nigeria. Patancheru 502 324,
Telangana, India: Int. Crop Res. Inst. Semi-Arid Trop. 2015, 36.
3.
Gana, I.M.; Mohammed, K.M.; Shehu, A.A.;
Tauheed, I.M. Development of a roasted groundnut skin peeling machine. Food
Nutr. J. 2018, 3, 193. DOI: 10.29011/2575-7091.100093
4.
Little,
C.L.; Jemmott, W.; Surman-Lee, S.; HucklesbY, L.; De Pinna. E. Assessment of
the microbiological safety of edible roasted nut kernels on retail sale in
England, with a Focus on Salmonella.
J. Food Protect., 2009, 72(4), 853–855.
5.
Chang,
A. S.; Streedharan, A.; Schneider, K. R.; Peanut and Peanut products: A Food
safety perspective. Food Control. 2013, 32(1), 296-303.
6.
Adetunji, M.C.; Alika, O.P.; Awa, N.P.;
Atanda, O.O.; Mwanza, M. Microbiological quality and risk assessment for
aflatoxins in groundnuts and roasted cashew nuts meant for human consumption. Hindawi
J. Toxicol. 2018, 1–11. https://doi.org/10.1155/2018/1308748
7.
Adebesin, A.A.; Saromi, O.T.; Amusa,
N.A.; Fagade, S.O. Microbiological quality of some groundnut products hawked in
Bauchi, a Nigerian City. J. Food Technol. Afri, 2001, 6(2), 53-55.
8.
Ezekiel, C.N.; Anokwuru, C.P.; Fari, A.;
Olorunfemi, M.F.; Fadairo, O.; Ekeh, H.A.; Ajoku, K.; Gbuzue, N.; Akinsanmi, F.
Microbiological quality and proximate composition of peanut cake (Kulikuli) in Nigerian markets. Acad.
Arena. 2011, 3(4), 103–111.
9.
Ezekiel, C.N.; Kayode, F.O.; Fapohunda,
S.O.; Olorunfemi, M.F.; Kponi, B.T. Aflatoxigenic moulds and aflatoxins in
street-vended snacks in Lagos, Nigeria. Inter. J. Food Saf. 2012, 14, 83-88
10.
Kigigha, L.T.; Igoya, U.O.S.; Izah, S.C.
Microbiological quality assessment of unpeeled groundnut sold in Yenagoa
metropolis, Nigeria. Int. J. Inno. Biochem. Microbiol. Res. 2016, 4(4), 11-22,
11.
Tobin-West, M.D.; Osakwe, J.A.; Dimkpa,
S.O.N. Bacteriological assessment of raw groundnut seeds vended in Port
Harcourt metropolis, Rivers State, Nigeria. Res. J. Agri. 2018, 5(3), 1 -10.
12.
Moore,
D. Antibiotic Classification and Mechanism. 2015.
https://www.orthobullets.com/basic-science/9059/antibiotic-drugs
13.
Page,
M.G.P. Beta-Lactam Antibiotics. In: Dougherty T., Pucci M. (eds) Antibiotic
Discovery and Development. Springer, Boston, MA 2012. ISBN 978-1-4614-1399-8.
14.
Hardman,
B.; Hunt, D.J.; Mojaab, D.; Naor, A. Sub-lethal gentamicin treatment of
Escherichia coli UB1005 induces the release of soluble factors that reduce susceptibility
to t7 bacteriophage infection. J. Exp. Microbial Immunol. 2017, 21, 128-133.
15. Armstrong, E.S.; Kostrub, C.F.; Cass, R.T.; Moser,
H.E.; Serio, A.W., Miller, G.H. Aminoglycosides, in: T.J. Dougherty, M.J. Pucci
(Eds.), Antibiotic Discovery and Development, 1, Springer, New York, 2012, pp.
229-269.
16. Duda, K.R.N. Choosing the right antibiotic for an
infection. Verywellhealth. 2018. https://www.verywellhealth.com/difference-between-amoxicillin-and-augmentin-4115052.
17. Obinna-Echem, P.C.; Cookey, F.I. Effect
of packaging materials and storage temperatures on the microbiological quality
of hibiscus sabdarifa drinks during ambient and refrigeration storage. Euro. J.
Nutri. Food Saf. 2022, 14(11),30-42,
18.
Harrigan, W.F. Laboratory methods in
Food Microbiology, (edn) Academic press Limited, London. 1998.
19.
Barber,
L.I.; Obinna-Echem, P.C.; Amadi, S.C. Microbiological quality and antibiotic
sensitivity of potential pathogens isolated from meat product (Suya) sold in
Rivers State University and its environs. Int. J. Biotechnol Food Sci. 2018,
6(4), 67-76
20.
Akinnibosun, F.I.; Osawaru, E.E. Quality
assessment of peeled and unpeeled roasted groundnut (Arachis hypogaea L.) Sold in Benin City, Nigeria. Int. Res. J. N.
Appl. Sci. 2015, 2(3), 18-32.
21.
Oranusi, U.S.; Braide, W.A study of
microbial safety of ready-to-eat foods vended on highways: Onitsha-Owerri,
south east Nigeria. Int. Res, J. Microbiol. 2012, 3(2), 066-071.
22.
CFS. Centre for Food Safety.
Microbiological Guidelines for Food (For ready-to-eat food in general and specific
food items). Food and Environmental Hygiene Department 43/F, Queensway
Government Offices, 66 Queensway, Hong Kong. August 2014 (revised)
23.
Dubey, R.C.; Maheshwari, D.K.A textbook
of Microbiology2013 Revised edition. S. Chad and Company LTD. Ram Nagar, New
Delhi. 2013
24. Niwa, T.; Morimoto, M.; Hirai, T.; Hata, T.; Hayashi,
M.; Imagawa, Y. Effect of
penicillin-based antibiotics, amoxicillin, ampicillin, and piperacillin, on
drug-metabolizing activities of human hepatic cytochromes P450. J. Toxicol. Sci.
2016, 41(1), 143-6. doi: 10.2131/jts.41.143.
25.
Nutanbala, N.G.; Hiren, R.T.; AlpshPur,
P.G.; Tejas, K.P.; Tripathi, C.B. Antibiotic sensitivity profile of bacterial
pathogens in postoperative wound infections at a tertiary care hospital in
Gujarat, India. J. Pharmacol. Pharmacother. 2011, 2(3), 158-164.
This work is licensed under the
Creative Commons Attribution
4.0
License (CC BY-NC 4.0).
Abstract
Microbiological quality and antibiotic sensitivity of
potential pathogens from roasted skinned and unskinned groundnuts sold in the River
State University campus and its environs were evaluated. Samples obtained from
three locations namely: Back gate, Main gate and Shopping complex were coded
BSG, MSG and SSG respectively for skinned and BUG, MUG and SUG for the
unskinned. Samples transported to the laboratory in chilled cooler were
analyzed immediately as freshly purchased and after four weeks of cold storage
(15.0 ±2°C). Conventional microbiological methods were used for
analysis. Microbial
analysis (Log10 CFU/g) revealed that all freshly purchased samples
had total bacteria count (TBC) of 3.99 -
5.98, coliform (TCC), Salmonella
(TSC)
and mould (TMC) counts of
1.00, 4.30 and 5.11 in BUG, SUG and MUG respectively. Escherichia coli (TEC), Staphylococcus
(TSTC) and yeast (TYC) counts in three of the samples ranged respectively, from
1.35 – 2.70, 3.00 - 4.30 and 2.00 – 3.70. Total lactobacillus count (TLBC) was 2.70 –
4.49 for MSG and SUG. After storage, the microbial load
increased and counts for TBC, TCC, TLBC, TSTC, TEC, TSC, TYC and TMC ranged
from 5.04 – 7.89, 3.00 – 4.75, 2.70 – 3.00, 3.78 – 5.23, 1.35 – 4.48, 5.11 in
MSG, 1.20 – 4.85 respectively. Antibiotic
inhibition against Staphylococcus and Salmonella varied from 1.00 – 14.5 and 4.5 – 14.5
mm. E. coli was sensitive to
gentamycin, perfloxacin and ofloxacin with inhibition zones of 8.5, 12.5 and
13.5 mm respectively. Good hygienic practices and appropriate storage
facilities will minimize contamination and ensure safe roasted groundnuts for
consumption. The sensitivity test indicates
what can be utilized in the event of food poison.
Abstract Keywords
Roasted groundnuts, microbial quality, pathogens,
antibiotics sensitivity, inhibition zones
This work is licensed under the
Creative Commons Attribution
4.0
License (CC BY-NC 4.0).
This work is licensed under the
Creative Commons Attribution 4.0
License.(CC BY-NC 4.0).