(Adds background details) MEXICO CITY, Oct 29 (Reuters) - Mexico’s public sector ran a fiscal deficit of 99.578 billion pesos ($4.84 billion) in September, data from the finance ministry showed on Friday. The figure compares with a fiscal deficit of 19.759 billion pesos in August and a deficit of 11.480 billion pesos in July. $1 = 20.5760 Mexican pesos Reporting by Anthony Esposito; Editing by Daina Beth Solomon and Steve Orlofsky