They're everywhere 

New Scientist 16may01

More than one in 10 British children are carrying superbugs resistant to one or more antibiotics

More than one in 10 British children are carrying superbugs resistant to one or more antibiotics. The proportion of adult carriers could be even higher.

The superbugs are no immediate threat to those carrying them, but could cause dangerous infections after an operation, for example. Carriers can also infect other people.

The finding has serious public-health implications, warns Michael Millar of Bart's and the Royal London School of Medicine, the study's author. "This may be just the beginning of something that will take off in a big way. We need policies to control antibiotic resistance that go across boundaries."

Marcos Espinal, leader of the World Health Organization's surveillance project on drug-resistant tuberculosis, agrees. "These are very important findings," he says.

Gene swap

Superbugs such as MRSA are already a big problem in hospitals, but relatively little is known about the extent of resistance in the healthy population.

To find out, Millar and his colleagues took various samples from 539 seven and eight-year-old children in Bristol. He found that 11 per cent of stool samples contained bacteria such as E. coli that were resistant to chloramphenicol, a drug rarely given orally to children. Worryingly, three per cent of the children carried bacteria resistant to ceftazidime, an antibiotic reserved for treating serious conditions such as cystic fibrosis.

The researchers were surprised by how many children were carrying bacteria resistant to antibiotics they had never been given. Bacteria resistant to a particular drug should be most common in people given that drug, because this allows these bugs to thrive while susceptible strains die.

But the researchers found that resistance to drugs such as chloramphenicol was usually linked to resistance to more commonly used antibiotics, such as ampicillin, which is often given to children.

This implies that the genes that make the bacteria resistant are found on the same piece of bacterial DNA, and are passed on together. So giving people ampicillin can encourage bacteria to acquire and hang on to bits of DNA that make them resistant to other drugs as well.

Sparing use

Once resistant, bacteria can easily spread from person to person. People could pick them up from friends, family and pets. They might also get them from food and agricultural sources (New Scientist, 21 April, p 4).

Doctors had thought reducing antibiotic use would curb resistance, because bacteria would lose resistance genes if they didn't need them. But this isn't happening. A recent study in The Lancet (vol 357, p 1325) showed that despite a 45-fold reduction in the use of sulphonamide antibiotics between 1991 and 1999, there was no reduction in the level of resistance.

"You can't assume that by reducing the use of an antibiotic the resistance is going to disappear," says Lucinda Hall, also at Bart's and the Royal London School of Medicine, who led the study.

Instead, the key is to prevent resistance to antibiotics developing in the first place. That means using new antibiotics as sparingly as possible, for example.

Carriage of antibiotic-resistant bacteria by healthy children 

Journal of Antimicrobial Chemotherapy (2001) 47, 605-610 May01

M. R. Millar^a,*, T. R. Walsh^b, C. J. Linton^b, S. Zhang^b, J. P. Leeming^b, P. M. Bennett^b and The Alspac Study Team^,c

^a Department of Microbiology, The Royal London Hospital, Barts and The London NHS Trust, Whitechapel Road, London E1 1BB; ^b Department of Pathology and Microbiology, University of Bristol; ^c Department of Perinatal Epidemiology, University of Bristol, UK

The frequency of carriage of antibiotic-resistant bacteria in healthy 7- and 8-year-old children in Bristol was studied. Children born in Avon between 1 April 1991 and 31 December 1992, attending the Avon Longitudinal Study of Pregnancy and Childhood (ALSPAC) 7 year follow-up clinic, formed the study population. Carriage was estimated using mouth and stool samples. None of 105 children on whom information was available had received tetracycline, chloramphenicol, ciprofloxacin or an extended-spectrum cephalosporin in the previous year. Staphylococcus aureus was isolated from mouthwashes from 200 (37.1%) of 539 children sampled. Six (3%) of the isolates were resistant to chloramphenicol or tetracycline and four (2%) were methicillin resistant. Haemophilus spp. were isolated from 369 (72%) of 513 samples and 63 (17%) were ampicillin resistant, 49 (13.3%) were erythromycin resistant and seven (1.9%) were tetracycline resistant. Branhamella catarrhalis was isolated from 333 (74%) of 450 samples. Twenty-eight (8.4%) were erythromycin resistant and 14 (4.2%) strains were tetracycline resistant. Group A ß-haemolytic streptococci were isolated from 17 of 507 children sampled. One (5.9%) was tetracycline resistant. Stool samples were returned from 335 (62%) of 539 children from whom they were requested. Eleven per cent of samples yielded Gramnegative bacilli with high-level resistance to chloramphenicol, which was frequently linked to resistance to ampicillin, spectinomycin and streptomycin. Isolates demonstrating resistance to the third-generation cephalosporin ceftazidime were recovered from 17 subjects (3.2%). Six (35%) of 17 isolates possessed extended-spectrum ß-lactamases. Healthy children carry bacteria resistant to antibiotics to which children are not usually exposed. Resistance to ceftazidime, chloramphenicol and tetracycline may be co-selected by exposure to other antibiotics used in children or may be acquired from family members, pets, other children or food. These results suggest that antibiotic-resistant bacteria are widely disseminated and may be acquired by children before exposure to specific selection pressure.

^* Corresponding author. Tel: +44-20-7377-7080; Fax: +44-20-7377-7330; E-mail: M.R.Millar@mds.qmw.ac.uk