Two Hartford-based medical centers and a pair of Springfield groups are among the institutions engaged in affiliation talks with Johnson Memorial Medical Center, which emerged from bankruptcy last October. The hospital's interim CEO, David Morgan, said he hopes a deal can be reached for the Stafford Springs hospital to join a larger system by the end of the summer. Johnson Memorial Medical Center is the non-profit parent company of Johnson Memorial Hospital, which also operates the Evergreen Health Care Center and Home & Community Health Services. Morgan, who recently took over as CEO after the sudden resignation of Peter J. Betts, said he's had affiliation talks recently with four hospitals including Hartford Healthcare and St. Francis Hospital and Medical Center. Massachusetts healthcare providers, including Baystate and Mercy medical centers in Springfield, are also in play.