Here's a fix. I tested it only on articles and books:
\usepackage[backend=biber, style=authoryear, bibstyle=authortitle, natbib=true, maxcitenames=2, maxbibnames=99, isbn=false, url=false, firstinits=true, uniquename=false, uniquelist=false, terseinits]{biblatex}
\DeclareNameAlias{sortname}{last-first}
\renewcommand*{\revsdnamepunct}{}
\DeclareFieldFormat[article,inbook,incollection,inproceedings,patent,thesis,unpublished]{title}{{#1\isdot}}
\renewbibmacro{in:}{}
\DeclareFieldFormat{pages}{#1}
\renewcommand*{\bibpagespunct}{\addcolon}
% Normal title font (remove italic)
\DeclareFieldFormat{journaltitle}{#1\addperiod}
\DeclareFieldFormat{booktitle}{{#1}}
\DeclareFieldFormat{title}{{#1}}
% Year after title
\renewbibmacro*{journal+issuetitle}{%
\usebibmacro{journal}%
\setunit*{\addspace}%
\iffieldundef{series}
{}
{\newunit
\printfield{series}%
\setunit{\addspace}}%
\usebibmacro{issue+date}%
\setunit{\addsemicolon\addspace}%
\usebibmacro{volume+number+eid}%
\setunit{\addcolon\space}%
\usebibmacro{issue}%
\newunit%
}
% Print only the year
\renewbibmacro*{issue+date}{%
\printfield{year}%
}
% Remove "and" from list of authors
\renewcommand*{\finalnamedelim}{\multinamedelim}

APA. – Bernard Mar 11 '15 at 09:37biblatex-amastyle and from what you have posted it is not really easy to make out what it would look like, but it looks quite close to any of the standard styles with theinmacro chucked away,terseintsoption, and some weird stuff going on in thevolume/pagesdepartment. – moewe Mar 11 '15 at 09:38xpatch, which is done for that. – Bernard Mar 11 '15 at 09:45ama.bst(I suppose you know that) and is hazard the guess that the style is not so common outside AMA publications, so it is not very likely that someone has gone through the ordeal of creating, publishing and maintaining (!) abiblatexstyle for that. If you insist onbiblatex, your best bet is to find a standard style that comes closest to what you need (here are examples of all the standard styles), and then identify what bits you need changed. – moewe Mar 11 '15 at 09:45biblatexstyles to meet ones needs (have a look at the linked questions to that question as well). – moewe Mar 11 '15 at 09:57