Conjugative transfer of an IncA/C plasmid-borne blaCMY-2 gene through genetic re-arrangements with an IncX1 plasmid.

BACKGROUND: Our observation that in the Mexican Salmonella Typhimurium population none of the ST19 and ST213 strains harbored both the Salmonella virulence plasmid (pSTV) and the prevalent IncA/C plasmid (pA/C) led us to hypothesize that restriction to horizontal transfer of these plasmids existed. We designed a conjugation scheme using ST213 strain YU39 as donor of the blaCMY-2 gene (conferring resistance to ceftriaxone; CRO) carried by pA/C, and two E. coli lab strains (DH5α and HB101) and two Typhimurium ST19 strains (SO1 and LT2) carrying pSTV as recipients. The aim of this study was to determine if the genetic background of the different recipient strains affected the transfer frequencies of pA/C. RESULTS: YU39 was able to transfer CRO resistance, via a novel conjugative mechanism, to all the recipient strains although at low frequencies (10-7 to 10-10). The presence of pSTV in the recipients had little effect on the conjugation frequency. The analysis of the transconjugants showed that three different phenomena were occurring associated to the transfer of blaCMY-2: 1) the co-integration of pA/C and pX1; 2) the transposition of the CMY region from pA/C to pX1; or 3) the rearrangement of pA/C. In addition, the co-lateral mobilization of a small (5 kb) ColE1-like plasmid was observed. The transconjugant plasmids involving pX1 re-arrangements (either via co-integration or ISEcp1-mediated transposition) obtained the capacity to conjugate at very high levels, similar to those found for pX1 (10-1). Two versions of the region containing blaCMY-2 were found to transpose to pX1: the large version was inserted into an intergenic region located where the "genetic load" operons are frequently inserted into pX1, while the short version was inserted into the stbDE operon involved in plasmid addiction system. This is the first study to report the acquisition of an extended spectrum cephalosporin (ESC)-resistance gene by an IncX1 plasmid. CONCLUSIONS: We showed that the transfer of the YU39 blaCMY-2 gene harbored on a non- conjugative pA/C requires the machinery of a highly conjugative pX1 plasmid. Our experiments demonstrate the complex interactions a single strain can exploit to contend with the challenge of horizontal transfer and antibiotic selective pressure.

Burden and transmission of zoonotic foodborne disease in a rural community in Mexico.

BACKGROUND: The foodborne transmission and human health impact of Salmonella and Campylobacter infections have rarely been evaluated at the population level in highly endemic settings. METHODS: A prospective 15-month cohort study of 127 infants and 119 elderly people was combined with animal and food surveillance to determine the incidence and severity of Salmonella and Campylobacter gastroenteritis in a comparatively prosperous rural community in Mexico. RESULTS: Salmonella and Campylobacter were isolated in up to 75% and 57%, respectively, of raw retail meat and in up to 4.5% of ready-to-eat foods. Rates of acute gastroenteritis of any etiology in infants and elderly people were, respectively, 2.1 and 0.7 episodes per person per year. The annual incidence density rate of Salmonella gastroenteritis was 17.8 per 100 infants and 7.9 per 100 elderly people; the rate of Campylobacter gastroenteritis was 11.7 per 100 infants and 0 per 100 elderly people. Pulsed-field gel electrophoresis analysis yielded multiple clusters of human, meat, and/or animal Salmonella and Campylobacter isolates with indistinguishable patterns. On average, gastroenteritis episodes with these pathogens lasted 3 days in infants and 2 days in elderly people. Medical attention was sought in 44% of diarrheal episodes in infants and in 26% of diarrheal episodes in elderly people; none required hospitalization. Infants with multidrug-resistant Salmonella gastroenteritis had a higher frequency of bloody stools and medical visits (50% vs 11%; odds ratio, 8.5; P = .04) than those with more susceptible strains. CONCLUSIONS: In this relatively advantaged Mexican rural community, the human health impact of a food chain heavily contaminated with Salmonella and Campylobacter was of low magnitude.

Antimicrobial-resistant Campylobacter in the food chain in Mexico.

We describe prevalence and antimicrobial susceptibility results for thermophilic Campylobacter isolates collected from humans, food, and food-animals in an integrated food chain surveillance network in Mexico. From 2003 to 2006, stool samples were collected from children with diarrhea at state sentinel hospitals. Concurrently, fecal samples from asymptomatic children in kindergartens, as well as raw chicken, pork and beef from retail outlets, and food-animal intestines from slaughterhouses were all collected in 65 cities from four different states. C. jejuni was identified with a standardized hippurate test. Hippurate negative, indoxyl acetate positive isolates were classified as Campylobacter spp. Susceptibility testing was performed by agar dilution according to Clinical and Laboratory Standards Institute guidelines. A total of 1,259 C. jejuni and 1,797 Campylobacter spp. isolates were recovered from 11,811 samples. Chicken was significantly more contaminated for both intestinal samples (93.6%) and meat products (58.3%), compared with swine (71.4%)/pork (14.6%) samples, and cattle (25.1%)/beef (5.3%) samples (p<0.001). Campylobacter was recovered from 5.1% of children with diarrhea and from 3.2% of asymptomatic children. Chicken was significantly more likely to harbor ciprofloxacin-resistant C. jejuni (85.8%) than swine (62.5%, OR=3.6), cattle (39.8%, OR=9.3), or humans (58.2%, OR=4.4). No significant differences were found for ciprofloxacin-resistant Campylobacter spp. among food-animals, but the rate in food-animals was significantly higher than in humans (84% vs. 56.7%, OR=4.0). Swine was significantly more likely to harbor erythromycin-resistant C. jejuni (14.8%) than chicken (3.5%, OR=4.9), cattle (1.8%, OR=9.3), or humans (3.0%, OR=5.7), and was associated with higher rates of erythromycin-resistant Campylobacter spp. (41.9%) than chicken (10.5%, OR=6.1) and humans (11.9%, OR=5.3). The high resistance rates to ciprofloxacin preclude the use of fluoroquinolones for treatment of campylobacteriosis in Mexico. Our results emphasize the need for ongoing and integrated surveillance of antimicrobial usage and antimicrobial susceptibility in humans and animals.

Salmonella Typhimurium ST213 is associated with two types of IncA/C plasmids carrying multiple resistance determinants.

BACKGROUND: Salmonella Typhimurium ST213 was first detected in the Mexican Typhimurium population in 2001. It is associated with a multi-drug resistance phenotype and a plasmid-borne blaCMY-2 gene conferring resistance to extended-spectrum cephalosporins. The objective of the current study was to examine the association between the ST213 genotype and blaCMY-2 plasmids. RESULTS: The blaCMY-2 gene was carried by an IncA/C plasmid. ST213 strains lacking the blaCMY-2 gene carried a different IncA/C plasmid. PCR analysis of seven DNA regions distributed throughout the plasmids showed that these IncA/C plasmids were related, but the presence and absence of DNA stretches produced two divergent types I and II. A class 1 integron (dfrA12, orfF and aadA2) was detected in most of the type I plasmids. Type I contained all the plasmids carrying the blaCMY-2 gene and a subset of plasmids lacking blaCMY-2. Type II included all of the remaining blaCMY-2-negative plasmids. A sequence comparison of the seven DNA regions showed that both types were closely related to IncA/C plasmids found in Escherichia, Salmonella, Yersinia, Photobacterium, Vibrio and Aeromonas. Analysis of our Typhimurium strains showed that the region containing the blaCMY-2 gene is inserted between traA and traC as a single copy, like in the E. coli plasmid pAR060302. The floR allele was identical to that of Newport pSN254, suggesting a mosaic pattern of ancestry with plasmids from other Salmonella serovars and E. coli. Only one of the tested strains was able to conjugate the IncA/C plasmid at very low frequencies (10-7 to 10-9). The lack of conjugation ability of our IncA/C plasmids agrees with the clonal dissemination trend suggested by the chromosomal backgrounds and plasmid pattern associations. CONCLUSIONS: The ecological success of the newly emerging Typhimurium ST213 genotype in Mexico may be related to the carriage of IncA/C plasmids. We conclude that types I and II of IncA/C plasmids originated from a common ancestor and that the insertion and deletion of DNA stretches have shaped their evolutionary histories.

New Insights Into DAEC and EAEC Pathogenesis and Phylogeny.

Diarrheagenic E. coli can be separated into six distinct pathotypes, with enteroaggregative (EAEC) and diffusely-adherent E. coli (DAEC) among the least characterized. To gain additional insights into these two pathotypes we performed whole genome sequencing of ten DAEC, nine EAEC strains, isolated from Mexican children with diarrhea, and one EAEC plus one commensal E. coli strains isolated from an adult with diarrhea and a healthy child, respectively. These genome sequences were compared to 85 E. coli genomes available in public databases. The EAEC and DAEC strains segregated into multiple different clades; however, six clades were heavily or exclusively comprised of EAEC and DAEC strains, suggesting a phylogenetic relationship between these two pathotypes. EAEC strains harbored the typical virulence factors under control of the activator AggR, but also several toxins, bacteriocins, and other virulence factors. DAEC strains harbored several iron-scavenging systems, toxins, adhesins, and complement resistance or Immune system evasion factors that suggest a pathogenic paradigm for this poorly understood pathotype. Several virulence factors for both EAEC and DAEC were associated with clinical presentations, not only suggesting the importance of these factors, but also potentially indicating opportunities for intervention. Our studies provide new insights into two distinct but related diarrheagenic organisms.

Association of virulence plasmid and antibiotic resistance determinants with chromosomal multilocus genotypes in Mexican Salmonella enterica serovar Typhimurium strains.

BACKGROUND: Bacterial genomes are mosaic structures composed of genes present in every strain of the same species (core genome), and genes present in some but not all strains of a species (accessory genome). The aim of this study was to compare the genetic diversity of core and accessory genes of a Salmonella enterica subspecies enterica serovar Typhimurium (Typhimurium) population isolated from food-animal and human sources in four regions of Mexico. Multilocus sequence typing (MLST) and macrorestriction fingerprints by pulsed-field gel electrophoresis (PFGE) were used to address the core genetic variation, and genes involved in pathogenesis and antibiotic resistance were selected to evaluate the accessory genome. RESULTS: We found a low genetic diversity for both housekeeping and accessory genes. Sequence type 19 (ST19) was supported as the founder genotype of STs 213, 302 and 429. We found a temporal pattern in which the derived ST213 is replacing the founder ST19 in the four geographic regions analyzed and a geographic trend in the number of resistance determinants. The distribution of the accessory genes was not random among chromosomal genotypes. We detected strong associations among the different accessory genes and the multilocus chromosomal genotypes (STs). First, the Salmonella virulence plasmid (pSTV) was found mostly in ST19 isolates. Second, the plasmid-borne betalactamase cmy-2 was found only in ST213 isolates. Third, the most abundant integron, IP-1 (dfrA12, orfF and aadA2), was found only in ST213 isolates. Fourth, the Salmonella genomic island (SGI1) was found mainly in a subgroup of ST19 isolates carrying pSTV. The mapping of accessory genes and multilocus genotypes on the dendrogram derived from macrorestiction fingerprints allowed the establishment of genetic subgroups within the population. CONCLUSION: Despite the low levels of genetic diversity of core and accessory genes, the non-random distribution of the accessory genes across chromosomal backgrounds allowed us to discover genetic subgroups within the population. This study provides information about the importance of the accessory genome in generating genetic variability within a bacterial population.

Draft Genome Sequence of Escherichia albertii Strain Mex-12/320a, Isolated from an Infant with Diarrhea and Harboring Virulence Genes Associated with Diarrheagenic Strains of Enteropathogenic Escherichia coli.

Escherichia albertii is an emerging human enteropathogen. We report the draft genome sequence of E. albertii strain Mex-12/320a, isolated from an infant with diarrhea. The presence of the pathogenic island O122/IE6 and the nleA gene, previously found in diarrheagenic enteropathogenic Escherichia coli strains, suggests that E. albertii may cause acute diarrhea.

Integrated food chain surveillance system for Salmonella spp. in Mexico.

Few developing countries have foodborne pathogen surveillance systems, and none of these integrates data from humans, food, and animals. We describe the implementation of a 4-state, integrated food chain surveillance system (IFCS) for Salmonella spp. in Mexico. Significant findings were 1) high rates of meat contamination (21.3%-36.4%), 2) high rates of ceftriaxone-resistant S. Typhimurium in chicken, ill humans, and swine (77.3%, 66.3%, and 40.4% of S. Typhimurium T isolates, respectively), and 3) the emergence of ciprofloxacin resistance in S. Heidelberg (10.4%) and S. Typhimurium (1.7%) from swine. A strong association between Salmonella spp. contamination in beef and asymptomatic Salmonella spp. infection was only observed in the state with the lowest poverty level (Pearson r = 0.91, p<0.001). Pulsed-field gel electrophoresis analysis of 311 S. Typhimurium isolates showed 14 clusters with 102 human, retail meat, and food-animal isolates with indistinguishable patterns. An IFCS is technically and economically feasible in developing countries and can effectively identify major public health priorities.

Competitive suppression of dengue virus replication occurs in chikungunya and dengue co-infected Mexican infants.

BACKGROUND: Co-circulation of dengue virus (DENV) and chikungunya virus (CHIKV) is increasing worldwide but information on the viral dynamics and immune response to DENV-CHIKV co-infection, particularly in young infants, is scant. METHODS: Blood samples were collected from 24 patients, aged 2 months to 82 years, during a CHIKV outbreak in Mexico. DENV and CHIKV were identified by RT-PCR; ELISA was used to detect IgM and IgG antibodies. CHIKV PCR products were cloned, sequenced and subjected to BLAST analysis. To address serological findings, HMEC-1 and Vero cells were inoculated with DENV-1, DENV-2 and CHIKV alone and in combination (DENV-2-CHIKV and DENV-1-CHIKV); viral titers were measured at 24, 48 and 72 h. RESULTS: Nine patients (38%) presented co-infection, of who eight were children. None of the patients presented severe illness. Sequence analysis showed that the circulating CHIKV virus belonged to the Asian lineage. Seroconversion to both viruses was only observed in the four patients five years or older, while the five infants under two years of age only seroconverted to CHIKV. Viral titers in the CHIKV mono-infected cells were greater than in the DENV-1 and DENV-2 mono-infected cells. Furthermore, we observed significantly increased CHIKV progeny and reduction of DENV progeny in the co-infected cells. CONCLUSIONS: In our population, DENV-CHIKV co-infection was not associated with increased clinical severity. Our in vitro assay findings strongly suggest that the lack of DENV IgG conversion in the co-infected infants is due to suppression of DENV replication by the Asian lineage CHIKV. The presence of maternal antibody and immature immune responses in the young infants may also play a role.

Optic neuropathy and congenital glaucoma associated with probable Zika virus infection in Venezuelan patients.

Introduction: Although the current Zika virus (ZIKV) epidemic is a major public health concern, most reports have focused on congenital ZIKV syndrome, its most devastating manifestation. Severe ocular complications associated with ZIKV infections and possible pathogenetic factors are rarely described. Here, we describe three Venezuelan patients who developed severe ocular manifestations following ZIKV infections. We also analyse their serological response to ZIKV and dengue virus (DENV). Case presentation: One adult with bilateral optic neuritis, a child of 4 years of age with retrobulbar neuritis [corrected]. and a newborn with bilateral congenital glaucoma had a recent history of an acute exanthematous infection consistent with ZIKV infection. The results of ELISA tests indicated that all patients were seropositive for ZIKV and four DENV serotypes. Conclusion: Patients with ZIKV infection can develop severe ocular complications. Anti-DENV antibodies from previous infections could play a role in the pathogenesis of these complications. Well-designed epidemiological studies are urgently needed to measure the risk of ZIKV ocular complications and confirm whether they are associated with the presence of anti-flaviviral antibodies.

Corrigendum: Optic neuropathy and congenital glaucoma associated with probable Zika virus infection in Venezuelan patients.

[This corrects the article DOI: 10.1099/jmmcr.0.005145.].

Shared and organism-specific host responses to childhood diarrheal diseases revealed by whole blood transcript profiling.

Globally, diarrheal diseases are a leading cause of death in children under five and disproportionately affect children in developing countries. Children who contract diarrheal diseases are rarely screened to identify the etiologic agent due to time and cost considerations associated with pathogen-specific screening and hence pathogen-directed therapy is uncommon. The development of biomarkers to rapidly identify underlying pathogens could improve treatment options and clinical outcomes in childhood diarrheal diseases. Here, we perform RNA sequencing on blood samples collected from children evaluated in an emergency room setting with diarrheal disease where the pathogen(s) present are known. We determine host response gene signatures specific to Salmonella, Shigella and rotavirus, but not E. coli, infections that distinguish them from each other and from healthy controls. Specifically, we observed differential expression of genes related to chemokine receptors or inflammasome signaling in Shigella cases, such as CCR3, CXCR8, and NLRC4, and interferon response genes, such as IFI44 and OASL, in rotavirus cases. Our findings add insight into the host peripheral immune response to these pathogens, and suggest strategies and limitations for the use host response transcript signatures for diagnosing the etiologic agent of childhood diarrheal diseases.

Nontyphoidal Salmonella from human clinical cases, asymptomatic children, and raw retail meats in Yucatan, Mexico.

BACKGROUND: We report the results of a 3-year Salmonella surveillance study of persons with diarrhea; asymptomatic children; and retail pork, poultry, and beef in Yucatan, Mexico. METHODS: Isolates were characterized according to serotype, antimicrobial susceptibility, and genetic relatedness with pulsed-field gel electrophoresis. RESULTS: Salmonella Typhimurium was the most common serotype found in ill humans (21.8% of isolates), followed by Salmonella Agona (21% of isolates). Salmonella Enteritidis was a minor serotype (4.2% of isolates). Asymptomatic children carried S. Agona (12.1% of isolates), Salmonella Meleagridis (11.6% of isolates), Salmonella Anatum (8% of isolates) and S. Enteritidis (5.8% of isolates). A high percentage of retail meat samples contained Salmonella; it was most commonly found in pork (58.1% of samples), followed by beef (54% of samples) and poultry (39.7% of samples). Resistance to oral drugs used for the treatment of salmonellosis was observed for ampicillin (14.6% of isolates were resistant), chloramphenicol (14.0% of isolates), and trimethoprim-sulfamethoxazole (19.7% of isolates). Resistance to ceftriaxone emerged in 2002 and was limited to the serotype S. Typhimurium. Twenty-seven percent of the isolates were resistant to nalidixic acid, and none were resistant to ciprofloxacin. Multidrug resistance was most common among isolates of serotypes S. Typhimurium and S. Anatum. Pulsed-field gel electrophoresis showed that strains found in retail meats were genetically identical to strains found in both asymptomatic children and ill patients. CONCLUSIONS: Our study found a high prevalence of Salmonella in retail meats and persons with enteric infection; many of these isolates were resistant to clinically important antimicrobials. A random selection of isolates from people and retail meat showed genetic relatedness, which suggests that, in Yucatan, considerable transfer of Salmonella occurs through the food chain.

Complete Genome Sequence of Salmonella enterica Serovar Typhimurium Strain YU15 (Sequence Type 19) Harboring the Salmonella Genomic Island 1 and Virulence Plasmid pSTV.

The complete genome ofSalmonella entericasubsp.entericaserovar Typhimurium sequence type 19 (ST19) strain YU15, isolated in Yucatán, Mexico, from a human baby stool culture, was determined using PacBio technology. The chromosome contains five intact prophages and theSalmonellagenomic island 1 (SGI1). This strain carries theSalmonellavirulence plasmid pSTV.

Complete Genome Sequence of Salmonella enterica Serovar Typhimurium Strain SO2 (Sequence Type 302) Isolated from an Asymptomatic Child in Mexico.

The complete genome sequence ofSalmonella entericaserovar Typhimurium strain SO2, isolated from an asymptomatic child in Mexico, was determined using PacBio single-molecule real-time technology. Strain SO2 has six complete chromosomal prophages, namely, ST104, Gifsy-2, ST64B, Gifsy-1, ELPhiS, and FSL SP-004, and carries aSalmonellavirulence plasmid.

Complete Genome Sequence of Salmonella enterica Serovar Typhimurium Strain SO3 (Sequence Type 302) Isolated from a Baby with Meningitis in Mexico.

The complete genome of ITALIC! Salmonella entericaserovar Typhimurium strain SO3 (sequence type 302), isolated from a fatal meningitis infection in Mexico, was determined using PacBio technology. The chromosome hosts six complete prophages and is predicted to harbor 51 genomic islands, including 13 pathogenicity islands (SPIs). It carries the ITALIC! Salmonellavirulence plasmid (pSTV).

Mexican unpasteurised fresh cheeses are contaminated with Salmonella spp., non-O157 Shiga toxin producing Escherichia coli and potential uropathogenic E. coli strains: A public health risk.

Fresh cheeses are a main garnish of Mexican food. Consumption of artisanal fresh cheeses is very common and most of them are made from unpasteurised cow milk. A total of 52 fresh unpasteurised cheeses of five different types were purchased from a variety of suppliers from Tabasco, Mexico. Using the most probable number method, 67% and 63% of samples were positive for faecal coliforms and E. coli, respectively; revealing their low microbiological quality. General hygienic conditions and practices of traditional cheese manufacturers were poor; most establishments had unclean cement floors, all lacked windows and doors screens, and none of the food-handlers wore aprons, surgical masks or bouffant caps. After analysing all E. coli isolates (121 strains) for the presence of 26 virulence genes, results showed that 9 (17%) samples were contaminated with diarrheagenic E. coli strains, 8 harboured non-O157 Shiga toxin producing E. coli (STEC), and one sample contained both STEC and diffusely adherent E. coli strains. All STEC strains carried the stx1 gene. Potential uropathogenic E. coli (UPEC) strains were isolated from 15 (29%) samples; the most frequent gene combination was fimA-agn43. Two samples were contaminated with Salmonella. The results demonstrated that unpasteurised fresh cheeses produced in Tabasco are of poor microbiological quality and may frequently harbour foodborne pathogens. Food safety authorities in Mexico need to conduct more rigorous surveillance of fresh cheeses. Furthermore, simple and inexpensive measures as establishing programs emphasizing good hand milking practices and hygienic manufacturing procedures may have a major effect on improving the microbiological quality of these food items.

Genomic Analysis of Salmonella enterica Serovar Typhimurium Characterizes Strain Diversity for Recent U.S. Salmonellosis Cases and Identifies Mutations Linked to Loss of Fitness under Nitrosative and Oxidative Stress.

UNLABELLED: Salmonella enterica serovar Typhimurium is one of the most common S. enterica serovars associated with U.S. foodborne outbreaks. S. Typhimurium bacteria isolated from humans exhibit wide-ranging virulence phenotypes in inbred mice, leading to speculation that some strains are more virulent in nature. However, it is unclear whether increased virulence in humans is related to organism characteristics or initial treatment failure due to antibiotic resistance. Strain diversity and genetic factors contributing to differential human pathogenicity remain poorly understood. We reconstructed phylogeny, resolved genetic population structure, determined gene content and nucleotide variants, and conducted targeted phenotyping assays for S. Typhimurium strains collected between 1946 and 2012 from humans and animals in the United States and abroad. Strains from recent U.S. salmonellosis cases were associated with five S. Typhimurium lineages distributed within three phylogenetic clades, which are not restricted by geography, year of acquisition, or host. Notably, two U.S. strains and four Mexican strains are more closely related to strains associated with human immunodeficiency virus (HIV)-infected individuals in sub-Saharan Africa than to other North American strains. Phenotyping studies linked variants specific to these strains in hmpA and katE to loss of fitness under nitrosative and oxidative stress, respectively. These results suggest that U.S. salmonellosis is caused by diverse S. Typhimurium strains circulating worldwide. One lineage has mutations in genes affecting fitness related to innate immune system strategies for fighting pathogens and may be adapting to immunocompromised humans by a reduction in virulence capability, possibly due to a lack of selection for its maintenance as a result of the worldwide HIV epidemic. IMPORTANCE: Nontyphoidal Salmonella bacteria cause an estimated 1.2 million illnesses annually in the United States, 80 million globally, due to ingestion of contaminated food or water. Salmonella Typhimurium is one of the most common serovars associated with foodborne illness, causing self-limiting gastroenteritis and, in approximately 5% of infected patients, systemic infection. Although some S. Typhimurium strains are speculated to be more virulent than others, it is unknown how strain diversity and genetic factors contribute to differential human pathogenicity. Ours is the first study to examine the diversity of S. Typhimurium associated with recent cases of U.S. salmonellosis and to provide some initial correlation between observed genotypes and phenotypes. Definition of specific S. Typhimurium lineages based on such phenotype/genotype correlations may identify strains with greater capability of associating with specific food sources, allowing outbreaks to be more quickly identified. Additionally, defining simple correlates of pathogenesis may have predictive value for patient outcome.

A collaborative initiative for the containment of antimicrobial resistance in Mexico.

Antimicrobial resistance exacts worldwide an increasingly significant clinical and economic toll. Despite the international calls for urgent action, antimicrobial use and resistance have been low on the Mexican government's policy agenda. In early 2010, a multidisciplinary group of experts launched a national initiative for containment of antimicrobial resistance that was endorsed by major medical, veterinary and public health institutions. The initiative called for seven priority actions including the creation of an ad hoc intersectoral advisory group, a requirement that human and veterinary antibiotics be dispensed only with prescription, and the establishment of effective surveillance systems. A consensus document was disseminated among key decision-makers at the ministries of Health and Agriculture and the legislature. The Ministry of Health (MoH) enacted a decree effective as of August 2010, which enforced the regulations that required medical prescriptions for the sale of human antibiotics. While the information disseminated by the MoH did focus on the dangers of self-medication, it failed to highlight the inherent perils of antibiotic resistance or the consequences of antibiotic use in food-animals. Following the decree, there was a surge of medical offices controlled by retail pharmacies. In the veterinary sector, voluntary guidelines were developed for good husbandry practices, including antibiotic use in food animals; five antimicrobials for use in food-animals were banned. No intersectoral advisory group or surveillance systems were established. This study describes a bottom-top approach in Mexico for the development of a national strategy to improve antibiotic use and contain antimicrobial resistance. Its experiences suggest that, in countries such as Mexico that lack strong regulatory systems and surveillance capacities, a more systemic approach is warranted. Future efforts should begin with early involvement of key stakeholders and informing policy makers, professionals and the population at large about the critical importance of antibiotic resistance.