\documentclass{beamer}
\usetheme{Madrid} 
\setbeamercovered{invisible}
\setbeamertemplate{navigation symbols}{}
\usepackage{multicol, graphicx}
\usepackage{graphics}
\def\ref{\textcolor{red}}


\usepackage{float}
\usepackage{graphicx}
\newtheorem{defi}{Definition}

\title{My MTBI Project Title}

\author{First Author$^1$, Second Author$^2$, Third Author$^3$, Fourth Author$^4$}
\institute[MTBI]
{My College$^1$, His College$^2$,  
Her University$^3$, Su Universidad$^4$}

%Note: grad student and advisor are NOT listed as authors of posters or oral presentation

\vskip .5cm


\date{\today}

\begin{document}
%\vskip-100in
\titlepage

\begin{frame}
\frametitle{Gonorrhea}
\begin{itemize}
\item While asymptotic it can cause:  
\begin{enumerate}
\item Pelvic inflammatory disease which can cause infertility
\item Ectopic pregnancy-pregnancy in the fallopian tubes, which does not result in viable births 
\item Epididymitis-inflammation of testicles which can result in infertility
\end{enumerate}
\item If left untreated long term:
\begin{enumerate}
\item Gonorrhea can spread to lungs, tissues, joints, bones, and the heart. Infections are characterized by lesions. 
\item Gonorrhea can be found in blood clots and can attack bones, the frequent target being the heel bones. 
\end{enumerate}
\end{itemize}
\end{frame}

\begin{frame}
\frametitle{Mathematical Model}
There are many different themes and styles that you can find (all free) online.  Do a Google search for 
``Beamer class" or "Beamer latex" (without quotes in both cases).
\end{frame}

\begin{frame}
\frametitle{Conclusions}
Give some highlights or important results of your work here.
\end{frame}

\begin{frame}
\frametitle{Acknowledgments}
{\small Use the official blurb from the Tecnical Report file.}
\end{frame}

\begin{frame}
\frametitle{Bibliography}
{\footnotesize
\begin{itemize}
\item Give a brief list (5-10) of the key articles used.  Your Technical Report will have the complete list.
\end{itemize}
}
\end{frame}

\end{document}