July 16, 2007

 

Drug-resistant bacteria persists in US poultry years after usage stops

 

 

The effects of antibiotics apparently remained years after poultry producers said they have stopped using it on poultry, according to a John Hopkins study.

 

Poultry tested at a supermarket contained bacteria resistant to fluoroquinolones, an antibiotic banned for use in poultry in 2005.  

 

The antibiotic was used to treat respiratory disease in chickens and for also for treating food poisoning cases in people. Such food poisoning cases were caused by Campylobacter and the effectiveness of fluoroquinolones have been diminishing as more of the bacteria have become resistant to the antibiotic, resulting in the ban.

 

The researchers tested campylobacter in chickens sold in a Baltimore supermarket for 20 weeks in 2004 and 15 weeks in 2006.

 

Each week, chickens from five different producers were bought. Three producers had never used any antibiotics while two were major conventional producers who said they have stopped all use of fluoroquinolones as far back as in 2002.

 

The chickens were tested for Campylobacter using DNA analysis, then the bacteria were tested for antibiotic resistance using the minimal inhibitory concentration method.

 

The bacteria from conventional chicken were more likely to be fluoroquinolone-resistant than those from antibiotic-free products, the study found.

 

In both 2004 and 2006, the study found that the Campylobacter strains from the conventionally produced chicken were more likely to be resistant than the strains from antibiotic-free samples.

 

Meanwhile, the proportion of antibiotic-resistant bacteria on the conventionally produced chicken showed no significant change during the period, despite antibiotic use supposedly being discontinued 4 years ago.

 

There was no way to verify whether poultry producers had indeed stopped using the antibiotic years before the ban in 2005, as producers were not required to report on drug usage before the ban.

 

Apart from raising questions over whether the poultry producers have stopped antibiotic use as claimed, another possibility raised by the researchers is that resistant bacteria can linger in poultry farms' water distribution and ventilation systems and in reused litter.

 

To reduce resistant bacteria, measures such as thorough disinfection and regular litter changing in poultry houses, may be necessary, the study said.