Food Protection Trends - September/October 2020 - 316
ethanol solution before taking the water sample. The pH and
chlorine residual concentrations of all water samples were
determined by using a pH meter (model pH 209, HANNA
Instruments, Sarmeola di Rubano-PD, Italy) and the N,Ndiethyl-p-phenylene-diamine method (25), respectively. Each
sample was tested for the presence of aerobic mesophilic
bacteria (AMB), total coliforms (TC), and fecal coliforms
(FC), following methods approved by the Mexican official
guidelines NOM-201-SSA1-2015 (25) and NOM-210SSA1-2014 (26). For the isolation of Escherichia coli, for
each E. coli tube positive for FC, a loopful was transferred to
tubes containing E. coli broth with 4-methylumbelliferyl-β-Dglucuronide and incubated for 24 h at 35 ± 0.5°C. Each tube
was examined for growth (turbidity, gas) and determined for
fluorescence production. From the positive tubes, a loopful
of broth was removed and streaked on an eosin methylene
blue agar plate that was incubated for 24 h at 35 ± 0.5°C. Two
to three E. coli-like colonies that grew were then selected and
biochemically characterized with the IMViC test (indole
test, methyl red test, Voges-Proskauer test, and citrate test).
All E. coli strains isolated from eosin methylene blue plates
were analyzed using two multiplex PCR assays to identify
different diarrheagenic E. coli pathotypes (6, 22). All data
were analyzed according to guideline NOM-041-SSA1-1993
(041 Guideline) (24). This guideline establishes that purified
water must have a pH between 6.5 and 8.5, a free of residual
chlorine concentration of up to 0.1 ppm, must not exceed
the limit of 2 log CFU/mL (100 CFU/mL) of aerobic
mesophilic bacteria (AMB), and the presence of TC must not
be detectable in any 100 mL (<1.1 most probable number
[MPN]/100 mL) of sample.
Isolation and identification of mycobacteria
Five hundred milliliters of water from each jug was filtered
using the CORNING sterile filtration system with a 0.22-µm
membrane. Subsequently, the membrane was placed onto
Middlebrook 7H10 agar plates (Difco, BD) supplemented
with albumin dextrose catalase (BD BBL prepared media),
cycloheximide (500 μg/mL), and the PANTA cocktail (BD
BBL: 40 U/mL polymyxin B, 4 μg/mL amphotericin B, 16
μg/mL nalidixic acid, 4 μg/mL trimethoprim, and 4 μg/mL
azlocillin). Plates were incubated at 35°C and were examined
daily for the first 8 days and thereafter once a week for 2
months. Once bacterial growth had been observed on the
Middlebrook 7H10 agar, the number of CFU/500 mL was
directly determined for each plate, and the identification
of acid-fast bacilli was carried out by Ziehl-Neelsen stain.
Isolates belonging to the genus Mycobacterium and to the
M. tuberculosis complex were identified by two PCR assays
described previously (8). NTM species were identified by
three methods: (i) PCR restriction enzyme pattern analysis
of the 65-kDa heat shock protein gene hsp65, as described
by Telenti et al. (37); (ii) sequencing of the hypervariable
region 2 of the 16S rRNA gene (20); and (iii) sequencing
316
Food Protection Trends September/October
of a fragment (723 bp) of the rpoB gene (2). Nucleotide
sequences were compared with known sequences in the
GenBank database by using the Blastn algorithm. Species
identifications were based on the 100% similarity cut-off for
the 16S rRNA gene and ≥97% for the rpoB gene.
RESULTS
Chemical and microbiological quality of purified water
The pH range of the water samples was found to be
between 6.8 and 7.8, and the chlorine concentration was
<0.1 ppm. All samples were thus found to be within the
chemical standards range for pH recommended by Mexico's
official guidelines for purified bottled water. Regarding the
microbiological quality, all 20 samples analyzed were positive
for AMB (Table 1). Concentrations of AMB ranged from
1.12 to 6.45 log CFU/mL. In total, 11 (55%), 6 (30%), and
2 (10%) water samples were positive for TC, FC, and E. coli,
respectively (Table 1). In the positive samples, TC and FC
concentration ranged from 1.1 to >8 MPN/100 mL and
from 1.1 to 4.6 MPN/100 mL for E. coli. None of the six
E. coli strains isolated from two water samples belonged to
diarrheagenic pathotypes. In total, 18 (90%) of the water
samples were found to fall outside Mexico's accepted official
guidelines: 7 (35%) water samples exceeded the maximum
allowed limit for AMB, 5 (25%) for TC, and 6 (30%) samples
exceeded both indicators (AMB plus TC; Table 2).
Mycobacteria isolation and identification
NTM were isolated from 5 (25%) of the 20 water samples,
recovering a total of five isolates. Concentrations of mycobacteria ranged from 3 to 25 CFU/500 mL. According to three
molecular methods (PCR restriction enzyme pattern analysis
of the gene hsp65 gene and the sequencing of the 16S rRNA
and rpoB genes), all NTM identified in this study belonged to
the Mycobacterium fortuitum complex: Mycobacterium porcinum (n = 2), M. fortuitum (n = 1), Mycobacterium conceptionense (n = 1), and Mycobacterium sp. (n = 1).
DISCUSSION
In this work, the microbiological quality of purified bottled
water obtained from small water purification plants was
evaluated, and 90% of purified bottled water samples did not
comply with the 041 Guideline. These results are similar to
those published by Cerna-Cortes et al. (7) in Mexico City
and Pant et al. (29) in Dharan, Nepal, who found that 72.9
and 87.5%, respectively, of bottled water samples analyzed
did not comply with the World Health Organization
microbiological criteria for drinking water (<100 CFU/
mL of AMB and absence of coliforms) (39, 40). However,
our results were higher than those reported by Abd ElSalam et al. (1) in Egypt and Halage et al. (13) in Kampala,
Uganda, who reported that 54.8 and 15%, respectively, of
bottled water samples evaluated exceeded the World Health
Organization guidelines.
Food Protection Trends - September/October 2020
Table of Contents for the Digital Edition of Food Protection Trends - September/October 2020
Self-Reported Food Safety Behaviors in Independent Chinese and Mexican Restaurants in Kansas
Microbiological Quality of Bottled Water Obtained from Mexican Small Water Purification Plants: A Pilot Study, Carried Out in Morelia (Central Mexico)
Listeria monocytogenes Occurrence and Adherence to Recommendations: Small and Large Retail Delicatessens in Iowa
Utilization of Quantitative and Qualitative Methods to Investigate the Impacts of a Pilot Media Campaign Targeting Safe Cooking Techniques and Proper Thermometer Use
Defining the Flow and Food Safety Behaviors of Actors in the Cambodian Vegetable Value Chain
Beyond the Bio Yaohua "Betty" Feng
PDG Highlight Meat and Poultry Safety and Quality PDG
General Interest Paper Identifying Vulnerable Populations at Risk of Foodborne Infection: People with Diabetes Mellitus
Industry Products
Coming Events
Food Protection Trends - September/October 2020 - Cover1
Food Protection Trends - September/October 2020 - Cover2
Food Protection Trends - September/October 2020 - 289
Food Protection Trends - September/October 2020 - 290
Food Protection Trends - September/October 2020 - 291
Food Protection Trends - September/October 2020 - 292
Food Protection Trends - September/October 2020 - 293
Food Protection Trends - September/October 2020 - 294
Food Protection Trends - September/October 2020 - 295
Food Protection Trends - September/October 2020 - Self-Reported Food Safety Behaviors in Independent Chinese and Mexican Restaurants in Kansas
Food Protection Trends - September/October 2020 - 297
Food Protection Trends - September/October 2020 - 298
Food Protection Trends - September/October 2020 - 299
Food Protection Trends - September/October 2020 - 300
Food Protection Trends - September/October 2020 - 301
Food Protection Trends - September/October 2020 - 302
Food Protection Trends - September/October 2020 - 303
Food Protection Trends - September/October 2020 - 304
Food Protection Trends - September/October 2020 - 305
Food Protection Trends - September/October 2020 - 306
Food Protection Trends - September/October 2020 - 307
Food Protection Trends - September/October 2020 - 308
Food Protection Trends - September/October 2020 - 309
Food Protection Trends - September/October 2020 - 310
Food Protection Trends - September/October 2020 - 311
Food Protection Trends - September/October 2020 - 312
Food Protection Trends - September/October 2020 - 313
Food Protection Trends - September/October 2020 - Microbiological Quality of Bottled Water Obtained from Mexican Small Water Purification Plants: A Pilot Study, Carried Out in Morelia (Central Mexico)
Food Protection Trends - September/October 2020 - 315
Food Protection Trends - September/October 2020 - 316
Food Protection Trends - September/October 2020 - 317
Food Protection Trends - September/October 2020 - 318
Food Protection Trends - September/October 2020 - 319
Food Protection Trends - September/October 2020 - Listeria monocytogenes Occurrence and Adherence to Recommendations: Small and Large Retail Delicatessens in Iowa
Food Protection Trends - September/October 2020 - 321
Food Protection Trends - September/October 2020 - 322
Food Protection Trends - September/October 2020 - 323
Food Protection Trends - September/October 2020 - 324
Food Protection Trends - September/October 2020 - 325
Food Protection Trends - September/October 2020 - 326
Food Protection Trends - September/October 2020 - 327
Food Protection Trends - September/October 2020 - 328
Food Protection Trends - September/October 2020 - 329
Food Protection Trends - September/October 2020 - 330
Food Protection Trends - September/October 2020 - 331
Food Protection Trends - September/October 2020 - Utilization of Quantitative and Qualitative Methods to Investigate the Impacts of a Pilot Media Campaign Targeting Safe Cooking Techniques and Proper Thermometer Use
Food Protection Trends - September/October 2020 - 333
Food Protection Trends - September/October 2020 - 334
Food Protection Trends - September/October 2020 - 335
Food Protection Trends - September/October 2020 - 336
Food Protection Trends - September/October 2020 - 337
Food Protection Trends - September/October 2020 - 338
Food Protection Trends - September/October 2020 - 339
Food Protection Trends - September/October 2020 - 340
Food Protection Trends - September/October 2020 - 341
Food Protection Trends - September/October 2020 - 342
Food Protection Trends - September/October 2020 - 343
Food Protection Trends - September/October 2020 - 344
Food Protection Trends - September/October 2020 - 345
Food Protection Trends - September/October 2020 - 346
Food Protection Trends - September/October 2020 - 347
Food Protection Trends - September/October 2020 - 348
Food Protection Trends - September/October 2020 - Defining the Flow and Food Safety Behaviors of Actors in the Cambodian Vegetable Value Chain
Food Protection Trends - September/October 2020 - 350
Food Protection Trends - September/October 2020 - 351
Food Protection Trends - September/October 2020 - 352
Food Protection Trends - September/October 2020 - 353
Food Protection Trends - September/October 2020 - 354
Food Protection Trends - September/October 2020 - 355
Food Protection Trends - September/October 2020 - 356
Food Protection Trends - September/October 2020 - 357
Food Protection Trends - September/October 2020 - 358
Food Protection Trends - September/October 2020 - 359
Food Protection Trends - September/October 2020 - 360
Food Protection Trends - September/October 2020 - 361
Food Protection Trends - September/October 2020 - 362
Food Protection Trends - September/October 2020 - 363
Food Protection Trends - September/October 2020 - Beyond the Bio Yaohua "Betty" Feng
Food Protection Trends - September/October 2020 - 365
Food Protection Trends - September/October 2020 - 366
Food Protection Trends - September/October 2020 - 367
Food Protection Trends - September/October 2020 - 368
Food Protection Trends - September/October 2020 - 369
Food Protection Trends - September/October 2020 - 370
Food Protection Trends - September/October 2020 - 371
Food Protection Trends - September/October 2020 - 372
Food Protection Trends - September/October 2020 - PDG Highlight Meat and Poultry Safety and Quality PDG
Food Protection Trends - September/October 2020 - General Interest Paper Identifying Vulnerable Populations at Risk of Foodborne Infection: People with Diabetes Mellitus
Food Protection Trends - September/October 2020 - 375
Food Protection Trends - September/October 2020 - 376
Food Protection Trends - September/October 2020 - 377
Food Protection Trends - September/October 2020 - 378
Food Protection Trends - September/October 2020 - 379
Food Protection Trends - September/October 2020 - Industry Products
Food Protection Trends - September/October 2020 - 381
Food Protection Trends - September/October 2020 - 382
Food Protection Trends - September/October 2020 - 383
Food Protection Trends - September/October 2020 - Coming Events
Food Protection Trends - September/October 2020 - Cover3
Food Protection Trends - September/October 2020 - Cover4
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