The Impact of Livestock Density on Hospital-Acquired MRSA Infections in California: A Spatial Analysis Open Access

Abstract

Increasing global food demands exert pressures for agricultural practices such as densely populated livestock facilities, but these productivity enhancements come at the cost of public health risks through increased antibiotic use and disease proliferating conditions. While the relationship between livestock and community-acquired MRSA has been studied, the association with hospital-acquired MRSA (HA-MRSA) is less known. This study analyzed 2022 California county-level livestock densities and their impact on HA-MRSA using negative binomial regressions and spatial epidemiological methods. Findings show a persistent presence of HA-MRSA since 2013, with significant clusters of infections present in Los Angeles, Yuba, Stanislaus, and Sacramento counties. Negative binomial regression shown a significant positive correlation between higher livestock densities and HA-MRSA incidences, yielding a risk ratio as high as 2.53 times compared to lower livestock density counties (95% CI = (1.17, 5.49)). Poverty was investigated as an effect modifier but was not found to significantly modify this relationship (p = 0.99). Findings highlight the importance of livestock management on public health, emphasizing the need for integrative approaches to infection control that consider both hospital and community-based factors on antibiotic-resistant infections cultivated in the hospital or beyond.

Table of Contents

Table of Contents

INTRODUCTION                                                                                                                                                                                1

Antibiotic Use in Livestock                                                                                                                                        1

Epidemiology of Antibiotic Use in Livestock                                                                                                 2

Human Antibiotic Resistance                                                                                                                                   3

Methicillin Resistant Staphylococcus Aureus and Hospital-Acquired Infections           4

Study Prospects                                                                                                                                                                6

METHODS                                                                                                                                                                                               7

Study Design                                                                                                                                                                        7

Data Acquisition                                                                                                                                                               7

Hospital-Acquired MRSA Incidence Analysis                                                                                                8

Livestock Analysis                                                                                                                                                           8

Poverty Analysis                                                                                                                                                               9

Spatial Analysis                                                                                                                                                                 9

Regression Analysis                                                                                                                                                     10

Models                                                                                                                                                                          11-12

RESULTS                                                                                                                                                                                               12

DISCUSSION                                                                                                                                                                                       15

REFERENCES                                                                                                                                                                                     19

FIGURES AND TABLES                                                                                                                                                               21

Table 1 – HA-MRSA Hospital Statistics (California, 2022)                                                            21

Figure 1 – HA-MRSA Incidence by County 2013-2022                                                                         22

Figure 2 – HA-MRSA Incidence by Beef Cow Count, 2022                                                                  22

Figure 3 – Kulldorff’s Scan Statistics of HA-MRSA, 2022                                                               23

Table 2 – Poverty Confounding Assessment                                                                                              23

Table 3 –Negative Binomial Regression Outputs                                                                                   24

SUPPLEMENTARY MATERIAL                                                                                                                                             25

Table 4 – Supplementary Suppressed County Information                                                              25

Supplementary Figure 1                                                                                                                                            25

About this Master's Thesis

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School	Rollins School of Public Health
Department	Epidemiology
Subfield / Discipline	Epidemiology - MPH & MSPH
Degree	M.P.H.
Submission	Master's Thesis
Language	English
Research Field	Health Sciences, Epidemiology Health Sciences, Public Health
Keyword	Hospital Acquired MRSA Livestock Negative Binomial Regression Epidemiology HAI Healthcare Acquired Infections Livestock Density HA-MRSA Regression Hospital Acquired Infections Community Acquired MRSA CA-MRSA HAIs Spatial Analysis Spatial Epidemiology
Committee Chair / Thesis Advisor	Michael Kramer, Emory University

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