Comparative Sensitivity Testing Of Escherichia Coli And Pseudomonas Aeruginosa Isolates From El Paso, Texas, USA And Ciudad Juarez, Mexico.
J Rivera, H Ho, S Antony, A Tyroch, M Ortiz
bacterial resistance, escherichia coli, pseudomonas aeruginosa, us-mexico border
J Rivera, H Ho, S Antony, A Tyroch, M Ortiz. Comparative Sensitivity Testing Of Escherichia Coli And Pseudomonas Aeruginosa Isolates From El Paso, Texas, USA And Ciudad Juarez, Mexico.. The Internet Journal of Infectious Diseases. 2009 Volume 9 Number 1.
This study was conducted in Ciudad Juarez, Chihuahua, Mexico and neighboring El Paso, Texas, USA which are within walking distance of each other. With a combined border population exceeding 2 million, Ciudad Juarez and El Paso, Texas comprise the largest population on the U.S.-Mexico border. Ciudad Juarez is more than twice the size of its sister city in the U.S. and is the fourth largest city in Mexico. It is estimated that 32 million1 people cross the northbound border legally each year, many of them crossing the border daily (more than 90 000) to work, shop, attend school, seek medical care, or to visit family and friends. Although exact figures are not available, it is known that many El Pasoans cross the southbound border for similar reasons, many of them seeking to purchase medications that are more accessible and less expensive. In a recent study2, approximately 35% of the El Paso population reported having purchased medications in Ciudad Juarez in the previous twelve month period. Because many prescription medicines including antibiotics are available without a prescription in Mexico, it has been speculated that overuse of these over-the-counter antibiotics could increase resistance patterns in this area.
In 1997, the World Health Organization (WHO) provided recommendations regarding how to best combat the escalation of bacterial resistance in developing countries.3 These recommendations clearly point out the important role that antibiotic misuse plays in the development of antibiotic resistance. Surveillance of these patterns is essential to evaluate the extent and impact of antibiotic use and misuse.
Although very few studies have looked at bacterial resistance patterns in Latin America, the SENTRY studies have produced some important findings. The SENTRY Antimicrobial Surveillance Program is a prospective, longitudinal, multinational study aimed at tracking the emergence of antimicrobial resistance worldwide.4 In some of the early reports,
The SENTRY study group also reported results from a number of studies that evaluated antimicrobial susceptibility patterns for bacterial isolates from Latin America. In one study of patients with pneumonia,5
MYSTIC is another global surveillance program that monitors resistance patterns in many medical centers around the world.7 This program evaluates and compares susceptibility patterns of meropenem against many gram negative and gram positive organisms and has produced large amounts of data. While antibiotic surveillance studies are seen as essential in monitoring bacterial resistance, neither of these two large groups has conducted any type of surveillance in cities along the U.S.-Mexico border, an area that possesses unique factors that make resistance an issue of increasing concern. To our knowledge, our group is the only one that has begun to evaluate antibiotic resistance patterns in this setting.
Specimens for bacterial culture were collected from patients seen and treated for infections at two hospitals in El Paso and two hospitals in Ciudad Juarez over a period of two years. Comparable hospitals were chosen on each side of the border (one county and one private hospital, each with a similar number of beds). Institutional Review Board approval was obtained at each of the four hospitals selected as well as at The University of Texas at El Paso. All organisms were batched and stored under appropriate conditions and were collected on a regular basis. All isolates obtained from participating hospitals were coded in a way such that only the investigators could know the hospital of origin.
Cultures of the organisms obtained from hospitals in Ciudad Juarez were transported according to CDC-approved guidelines for the transportation of biological samples.8 Importation permits were obtained from the CDC and USDA. A customs broker was used to manage the logistics of U.S. and Mexican Customs. The isolates were packaged and labeled to expedite clearance through the U.S. Public Health Service of Quarantine and release by U.S. Customs. They were also packaged to withstand breakage and leakage of the contents and labeled accordingly as specified in the following federal regulations: USPHS 42 CFR Part 72 – Interstate Shipment of Etiologic Agents and DOT 49 CFR Part 173 – Transportation of Etiologic Agents. All samples collected were identified by a hospital code, date of collection, body site, inpatient or outpatient status, and zip code. No patient identifiers were obtained with the samples.
Organisms were transported frozen in Microbank® vials on dry ice. Samples were transported to a reference microbiology laboratory in El Paso for microbial identification and antimicrobial susceptibility of
A total of 356
A total of 290
The short term implication associated with the observed difference in susceptibility relates to the empirical selection of antibiotics. Guidelines recently published by The Medical Letter, May 2007,11 recommended cefotaxime, ceftriaxone, cefepime, or ceftazidime as the empiric drug of choice for
Overall, empirical treatment of systemic
Guidelines recently published by The Medical Letter, 2007, recommend piperacillin/tazobactam plus or minus an aminoglycoside as the drug of choice for empirical therapy against
The rates of antimicrobial resistance associated with the two gram-negative organisms tested in the present study stand in contrast to findings from a previous study where we reported higher incidence of methicillin-resistant
We acknowledge that there are some important limitations to our study. Due to the complexity of this study, in terms of dealing with numerous institutions, logistics of border crossings in transporting isolates, and bi-national standards related to the practice of medicine, clinical and epidemiologic data was not collected. This type of data may have allowed for a more in depth examination of prescribed antibiotics, usage patterns, related indications and patient outcomes. Additionally, there were fewer cultures from Ciudad Juarez because routine cultures are not always obtained in Juarez hospitals. A greater number of samples may have allowed us to draw more robust conclusions from our data.
We documented significant differences in prevalence of antimicrobial resistance in Ciudad Juarez hospitals as compared to El Paso hospitals for both
Funded by a grant from Paso del Norte Health Foundation, El Paso, Texas, USA. Data collection and data entry by Jose C. Rodriguez, CPhT, CCRP. Additional contributions by Arturo Norte, M.D. and Refugio Pérez Ruvalcaba, M.D.
Conflict of interest
All authors have no conflicts of interest with the study. There are no financial nor personal relationships with other people or organizations that could inappropriately influence or bias our work.
This study was approved by the University of Texas at El Paso Institutional Review Board.