Brazilian Journal of Microbiology (2012): 1463-1466
OCCURRENCE OF SALMONELLA SP. AND COAGULASE-POSITIVE STAPHYLOCOCCI IN RAW EGGS AND
COALHO CHEESE: COMPARATIVE STUDY BETWEEN TWO CITIES OF BRAZIL’S NORTHEAST
Evêncio-Luz, L1, Lima-Filho, J.V.2 *, Evêncio-Neto, J.3 *
1Universidade Federal do Piauí, Departamento de Biologia, Picos, PI, Brasil; 2Universidade Federal Rural de Pernambuco,
Departamento de Biologia, Recife, PE, Brasil; 3Universidade Federal Rural de Pernambuco, Departamento de Morfologia e
Fisiologia Animal, Recife, PE, Brasil.
Submitted: May 09, 2011; Returned to authors for corrections: February 08, 2012; Approved: June 07, 2012.
Microbiological analyses of chicken eggs in Recife and Salvador have shown a high occurrence of
Salmonella in the egg shells and yolks. Likewise, the occurrence of Salmonella plus coagulase-positive
staphylococci in Coalho cheese reached alarming levels. The data revealed a significant risk of infections
and intoxications from consuming these foods in the cities.
Key words: Salmonella, Staphylococcus, Coalho cheese, eggs.
Risk of foodborne outbreaks in developing countries is
usually reported as derived from unsanitary conditions,
improper food storage and lack of hygiene during preparation
of food products (7). Although Brazilian law related to food
protection and surveillance is in accordance to international
rules, epidemiological studies regarding foodborne pathogens
involved in Brazilian outbreaks are rare. Especial attention has
been paid for raw or undercooked eggs because the hens act as
natural reservoirs of Salmonella sp. strains causing
gastroenteritis. In United States there are 1.4 million cases of
salmonellosis yearly and commercially produced eggs have
caused major epidemics due to Salmonella enterica serotype
Enteritidis (4). In Brazil, outbreaks of salmonellosis apparently
occurred because of consumption of contaminated mayonnaise
or sweet creams (14), which are commonly prepared with eggs.
The contamination occurs through the shell (15); but humidity,
temperature and storage time are critical for migration of
bacteria from the surface of the shell to the inner structures of
Also, farmhouse cheese is typically consumed in
population’s daily life in many parts of the globe. However, the
occurrence of Salmonella sp. besides coagulase-positive
staphylococci in Coalho cheese, a typical product of Brazil’s
northeast region, has been recorded (3, 8). The cheese is
generally produced in small operations, mostly made from raw
milk with the rennet obtained from cow stomachs due to the
presence of the enzyme renin (9). After food contamination,
staphylococci are able to release thermostable enterotoxins that
remain active in food and are resistant to proteolytic enzymes
of the human intestinal tract (2, 5). Therefore, continuous
surveillance is necessary to create helpful strategies to prevent
food poisoning and staphylococcal intoxications.
*Corresponding Author. Mailing address: ³Laboratório de Histologia, Universidade Federal Rural de Pernambuco, R. Dom Manoel de Medeiros s/n, Campus
Dois Irmãos, Recife, Pernambuco, CEP 52171-900, Brasil.; Tel: + 55 31 81 3320.6387.; E-mail: firstname.lastname@example.org / ²Laboratório de Microbiologia e
Imunologia, 52171-900, Recife, Brazil.; E-mail: email@example.com
Evêncio-Luz, L. et al. Salmonella sp. And staphylococci in raw eggs and Coalho cheese
The aim of the present study was to record the level of
contamination of raw eggs by Salmonella sp., besides the
occurrence of Salmonella sp. plus coagulase-positive
staphylococci in Coalho cheese in two major cities of
Brazil’s northeast, Salvador and Recife. Thus, the risk for
human health from consuming these foods are discussed in
light of previous studies carried out in the region.
The food analyses were carried out following the
recommendations of Downes and Ito (7) at the Laboratory of
Food Analyses (UNIME/ Salvador). Raw eggs and Coalho
cheese were purchased at stores of nine small markets of
Recife and Salvador, where no information about the food
origin or expiration date was informed. Samples of three yolks
or egg shells were evaluated as a pool whereas individual
pieces of cheese were weighted, and 25 grams were diluted in
225 mL (w:v) of 1% peptone water and incubated for 24h at 37
°C. For Salmonella analyses, 1 mL was inoculated into
Selenite-Cystine or Tetrationate-Novobiocin broth for 24h at
37 °C. After this time, the samples were cultured in
Salmonella-Shigella agar, xylose-lysine-deoxycholate agar or
MacConkey agar and typical colonies were sub-cultured in
tubes containing triple-sugar-iron agar. Then, suspect isolates
were submitted to biochemical tests to determine the genus.
The search for coagulase-positive staphylococci was
carried out after culturing samples in Baird-Parker agar for 24-
48h at 37 °C. The colony forming units were enumerated
(CFU/ g), and three typical colonies were selected for the
coagulase, catalase and Gram-staining tests. Samples
contaminated by coagulase-positive staphylococci were
considered not proper for human consuming when the number
of colony forming units reached above 103 CFU/ g. Results
were expressed as percentage of positive samples. Data were
analyzed statistically by the Student t-test or ANOVA, with the
level of significance set at p < 0.05.
Occurrence of Salmonella sp. in egg shells and yolks
ranged from 11.25 - 25 % in the cities of Recife and Salvador
(Table 1). Although the pathogen was more frequently detected
in yolks than in egg shells in samples from Salvador, the
overall contamination was similar between the two cities (p >
0.05). Among outbreaks of salmonellosis recorded from July
1993 to June 1997, in São Paulo State, 95.7% were related to
consumption of food containing raw or undercooked eggs (10).
The present data reinforced that contaminated eggs are
common sources of infection through food products, and
increases the chance of consumers to become ill. While
Brazilian Law (11) established the lack of Salmonella sp. in
food products, these regulations are not uniformly enforced due
to unofficial commerce of poultry products. In addition, eggs
sold at markets of Salvador and Recife were often maintained
at ambient temperature, which ranges from 27 - 35 C during
the whole year in Brazil’s northeast. This temperature range is
ideal for proliferation of mesophyli bacteria, such as
Table 1. Occurrence of Salmonella sp. in chicken eggs in Salvador and Recife, Brazil’s northeast.
Number of eggs
Pool of samples
Number of positive
pools of shells
Number of positive
pools of yolks
Evêncio-Luz, L. et al. Salmonella sp. And staphylococci in raw eggs and Coalho cheese
Food outbreaks related to staphylococcal strains were
previously recorded with 180 people in São Paulo (6). Also, the
incidence of vancomycin-resistant staphylococci reached 90.9 %
in Coalho cheese obtained in different states of Brazil’s northeast
(12). In the present study, the contamination levels of the cheese
by Salmonella sp. ranged from 12.7 - 7.8 % and coagulase-
positive staphylococci ranged 21-31.2% in Salvador and Recife,
respectively (Table 2). Due to high occurrence of Salmonella and
coagulase-positive staphylococci above the legal threshold of 10
CFU/ g, samples were not proper for human consuming (Table 2).
Previous studies carried out in other states of northeast region have
shown contamination levels by Salmonella ranging from 9 - 34.9
%; and by coagulase-positive staphylococci ranging from 23.3 -
72.7 %, respectively (1, 3, 8, 9, 13). Nevertheless, a significant
amount of samples were concurrently contaminated by Salmonella
and staphylococci (Table 2). Comparatively, the occurrence of
Salmonella sp. in cheese samples from Salvador and Recife was
considered low; but the occurrence of staphylococci was high and
more prevalent in samples from Recife than Salvador (p < 0.05).
Taken together, it is clear that risk of food poisoning outbreaks
from consuming Coalho cheese is spreading in all states of the
Table 2. Percentage of samples of Coalho cheese not proper for human consuming in Salvador and Recife.
Markets in Salvador Number of samples
Sal + Staph c
Sal + Staph c
N = 75 % out of 75:
Number of samples
Markets in Recife
N = 65 % out of 65:
a. Sal: Salmonella sp.
b. Staph: Coagulase-positive staphylococci - only samples with colony forming units higher than 103 CFU/g were considered not
proper for human consuming (ANVISA, RDC 12, 02/01/2001).
c.Percentage of samples concurrently contaminated with Salmonella sp. and coagulase-positive staphylococci.
The present data indicates an emergent risk for human
public health due to consuming of Coalho cheese and raw or
undercooked eggs in Recife and Salvador, two major cities of
Brazil’s northeast. As a practical application, the data
reinforced that continuous food surveillance is necessary to
minimize the chance of food poisoning and infection outbreaks
in the region.
The authors thank Andréa Campos (UNIME-BA) for
technical support; and the Brazilian National Research Council
(CNPq) for funding. Lima-Filho thanks the Tutorial Education
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