Notion of 'Global' Microbial Resistance May Be Oversimplified

MONTREAL-The rising worldwide incidence of microbial resistancestems from a wide variety of causes and does not reflect a singleglobal trend or etiology, Prof. Dr. Bernd Wiedemann, Universityof Bonn, Germany, said at a plenary session of the 19th InternationalCongress of Chemotherapy.

Although it may be tempting to oversimplify the situation andpin the blame on an overall cause, such as the misuse, overuse,or inappropriate use of antibiotics, Dr. Wiedemann claims thatlocal patterns of resistance arise from specific etiologies andmust therefore be attacked singly.

One possible cause of increased resistance, for example, may betraced to medical advances, such as organ transplantation andcancer chemotherapy, that have paradoxically resulted in patientswho are sicker and more vulnerable to infection with resistantorganisms.

Although resistance to antibiotics has been reported in many areasof the world, Dr. Wiedemann said that these reports are basedon highly variable standards. Comparisons are virtually meaninglessin the face of different testing methods, breakpoints, surveillancetechniques, and government regulations.

Establishing microbiologic standards is important, Dr. Wiedemannsaid, since "good epidemiology" is necessary to reallyunderstand global patterns and begin to devise preventive strategies.

He noted that specific migrations of resistant bacterial clonesaround the world have been documented. A resistant Streptococcuspneumoniae was traced, for instance, from South Africa toEurope and the United States, while a gentamicin-resistant Pseudomonasaeruginosa traversed the globe eastward, also arising in SouthAfrica, but spreading to Israel, Thailand, and Singapore.

Dr. Wiedemann said that some trends bear watching because of theirpotential impact on worldwide public health. The rising incidenceof resistant tuberculosis in drug addicts, he said, may eventuallyrepresent a serious problem in many countries, as might methicillin-resistantstaphylococci, vancomycin-resistant enterococci, penicillin- andtetracycline-resistant gonococci, and multiresistant Enterobacteriaceaeand Pseudomonas.

Some resistance issues are specific to certain geographic locations.In England, for example, only 1% of P aeruginosa were foundto be resistant to gentamicin, compared with more than 44% ofstrains in Italy, he said.

Escherichia coli resistance to ampicillin is increasingfaster in the United States than in Europe; in contrast E coliresistance to tetracycline is higher in Europe than in the UnitedStates. In some cases, he reiterated, the explanation for suchdiscrepancies may lie in the use of different breakpoints andnonstandard definitions of resistance.