Time after time Wednesday, Secret Service Director Mark Sullivan insisted last month’s prostitution scandal in Colombia was an aberration — just poor choices by a dozen agents under the influence of alcohol.

“This is not a cultural issue, this is not a systemic issue,” Sullivan told the Senate Homeland Security Committee, arguing that similar misconduct hasn’t occurred on thousands of other overseas trips by Secret Service agents. “On this particular trip, we had individuals who made very bad decisions.”

He maintained that view when Sen. Susan Collins, R-Maine, noted the agents used their own names when signing in prostitutes as overnight guests in their hotel rooms. Doesn’t that show the agents lacked any fear of disclosure or discipline, Collins asked.

Sullivan responded that “between the alcohol and I don’t know, the environment, these individuals did some dumb things,” adding that he did not believe they acted because they thought their behavior would be tolerated.

In his own Secret Service career spanning decades, Sullivan noted, he never witnessed such behavior.

To Collins and other senators on the panel investigating the night of heavy drinking and consorting with prostitutes in Cartagena, Sullivan’s personal dedication and loyalty to the agency he heads might be preventing him from accepting what seems obvious to them.

“I continue to believe that the problem is broader than you believe it to be,” Collins said to Sullivan at the end of Wednesday’s hearing. She later told reporters: “I think he has a difficult time coming to grips with the fact that he has a broader problem than just this one” episode.

Photos: A decade with the Secret Service

The hearing was the first by a congressional committee on the April incident that embarrassed the nearly 150-year-old agency and raised security concerns.

In Colombia as part of the advance details before President Barack Obama arrival to attend the Summit of the Americas, a dozen agents hit the clubs of Cartagena for a night of drinking that ended with them bringing women back to their hotel rooms.

A morning-after dispute between one agent and a woman over payment led to a dozen Secret Service members being sent home and the resulting media coverage and investigations.