NEW YORK (AP) — Giving letter grades to the thousands of restaurants in New York City — from humble delis to celebrity chef-powered eateries — has been a boon to business and has led to a decline in the number of cases of salmonella food poisoning, the mayor and health officials said Tuesday.

Some city council members, however, say the grading system is far from perfect and needs to be reviewed. Restaurant industry representatives complain of excessive inspections and burdensome fines on small businesses.

Mayor Michael Bloomberg, Health Commissioner Dr. Thomas A. Farley and other health officials announced initial data Tuesday showing salmonella infections decreased by 13.5 percent over the first full year the city has used letter grades. The Health Department said 1,296 cases of salmonella were reported in 2010 and preliminary data show 1,121 cases in 2011.

Further emphasizing that sanitary conditions are improving, the officials said more than 72 percent of the city’s 24,000 restaurants earned “A” grades compared to 65 percent a year ago. They also highlighted the most recent tax data available showing restaurant sales were up 9.3 percent from June 2010 to February 2011.

“It just may be that clean kitchens are as good for business as clean air is when a restaurant is smoke-free,” Bloomberg said at a news conference held at Zero Otto Nove in the Bronx.

The city started handing out letter grades in July 2010. Restaurants can get an A, B, or C, based on points for sanitary conditions. Restaurants have to post the grades in a visible area such as a street-facing window or door. Common sanitary violations include food stored at improper temperatures and evidence of vermin.

The largely positive announcement, which included the release of survey results showing New Yorkers largely approve of the grading system, came a day before the City Council was expected to hold a hearing on restaurant letter grades.

Council Speaker Christine C. Quinn, who supports the system, was nonetheless critical of it, saying in a statement Tuesday that the city’s data show “a wide variability” in grades from “inspector to inspector in the same restaurant and an enormous increase in fines.”

The Health Department officials said fines have been declining as restaurants improve their food safety practices. Inspectors go through rigorous training and must use computerized inspection worksheets for each restaurant, they said.

Andrew Rigie, a spokesman for the New York State Restaurant Association, said the grading system was punitive and a financial burden on small business owners.

“If you define success as taxing small business owners and making their lives miserable, then letter grades have been a complete success,” Rigie said in an email, adding that the association that represents 4,000 restaurants in the city hopes the City Council “will take a more enlightened approach toward public health.”

Restaurants can contest inspection findings at an administrative tribunal and have their grades changed, during which time a “grade pending” sign appears in place of the letter grade. Repeatedly receiving a “C” grade on inspections leads to an increased frequency of inspections.

Problems so severe that they cannot be corrected while an inspector is there — such as insufficient refrigeration — could put a restaurant at risk of being shut down.

City officials also announced Tuesday that the restaurant grades are now available on an app for iPhones and iPads called ABCEats NYC.

Associated Press writer Samantha Gross in New York contributed to this report.