Up, up, and away?
Has the problem of antimicrobial resistance gone beyond control?
By Sunly Coo, Contributing writer
Nothing so small, so invisible to the naked eye, could wreak so much havoc on humankind than microbes. The germs around us, thriving in seemingly infinite numbers, may have a mere fraction of a human being's life span, but it is perhaps this that has made them highly adaptable to environmental changes. While humans take three decades to create a generation, these microorganisms need only 20 to 30 minutes, and in a few generations, a lot of things can happen.
"Bacteria have the inherent genetic capability of mutating," says Dr. Celia Carlos, infectious-disease expert. "That means they can adjust spontaneously to tolerate any drug or chemical to which they are exposed, so that they survive instead of being killed."
The ability to alter their genetic makeup has turned the fight against many disease-causing microbes into a series of uphill battles. The problem is also confounded by the fact that nobody knows how long it takes for a specific microorganism to develop immunity against a drug.
"For some germs, it takes only two to three days' exposure to antibiotics and they become resistant, and we see that in the hospitals," she explains. "For instance, a patient comes in with pneumonia and we administer the usual first line of antibiotics. They may respond initially for two days, but by the third day we get surprised that the fever has recurred. Then we do a culture of the phlegm, for example, and we find out that compared to the first cultured specimen, it may be the same germs but this time it is already resistant to the antibiotics we gave."
It is a different story for Streptococcus pneumoniae. "It was originally sensitive to penicillin, but it took more than a decade of penicillin use before we saw our first penicillin-resistant S. pneumoniae, when everywhere in the world we were using penicillin, for reasons which are unclear," she says.
Doctors and scientists have to be on their toes, figuring out ways to outsmart these so-called superbugs. And one of their weapons is vigilance. As head of the Antimicrobial Resistance Surveillance program of the Department of Health since 1993, Carlos has been overseeing the gathering and analysis of culture samples from around the country every year. "We have a network of 17 tertiary hospitals in 11 regions and we have around 20,000 cultures per year," she adds.
Topping the Surveillance program's list of germs the public should be especially wary of is the silent killer behind most cases of bacterial pneumonia across different age groups. "The world has become alarmed with the emergence of this penicillin-resistant S. pneumoniae, because after that what we need to give patients are more expensive antibiotics," she says, "such as ceftriaxone which costs five to 10 times more than IV penicillin." Resistance to penicillin rose from five percent in 2004 to 11 percent in 2005, but has declined to six percent in 2006.
The second biggest threat are enteric pathogens, sources of high-mortality and high-morbidity diseases like diarrhea, gastroenteritis, and other food-borne illnesses. She explains: "Salmonella and shigella were previously sensitive to antibiotics like cotrimoxazole and ampicillin but are now resistant to high levels. In the Philippines, our latest figure for ampicillin resistance for shigella is 76 percent."
The bacteria's resistance to cotrimoxazole has dramatically jumped from 45.5 percent (2005) to 79 percent (2006); and to chloramphenicol, from 42.9 percent to 67 percent. Although resistance to nalidixic acid-a viable antimicrobial option for pediatric patients-has plunged to zero percent. Resistance to chloramphenicol, the other second-line treatment, has risen to six percent.
"Nontyphoidal Salmonella … [is] 12-percent resistant to ampicillin, whereas five years ago, it was less than five percent," she continues. However, from 2005 to 2006, significant decreases are noted in resistance rates against ampicillin, from 29 percent to 12 percent, and cotrimoxazole, from 27.7 percent to 17 percent.
Another public-health concern is the community-acquired methicillin-resistant Staphylococcus aureus, which has also recently made headlines in the global scene. Resistance to methicillin or oxacillin has remained high and stable for the past two years at 30 percent, a distinct upsurge from 2004's rate of 17 percent. (See article on MRSA for full story).
Other highlights of the study are as follows:
Vibrio cholerae's resistance to chloramphenicol and tetracycline is still zero, while to cotrimoxazole, it has dropped from 16 to nine percent.
Resistance rates of E. coli to a slew of antibiotics remain high-ampicillin, 78 percent; ampicillin-sulbactam, 24 percent; cefuroxime, 17 percent; ciprofloxacin, 37 percent; ceftriaxone, 11 percent; cephalothin, 49 percent; gentamicin, 24 percent; and cotrimoxazole, 67 percent.
Pseudomonas aeruginosa, a type of Gram-negative nonfermentative organism usually contracted in hospitals, has been reported to exhibit moderate to high resistance rates, between 11 and 23 percent, against all nine known antipseudomonal drugs.
Klebisella's resistance to antibiotics are also high. Only to imipenem have the bacteria responded, with more than 99-percent sensitivity.
These organisms exhibit highly variable resistance patterns from hospital to hospital: Enterobacteriaceae like E. coli; Staphylococci; and enteric pathogens like Salmonella and Shigella.
Who's to blame?
"Everyone is to blame."
Dr. Celia Carlos, head of the Antimicrobial Resistance Surveillance program of the Department of Health, says that virtually everybody has a hand in the rising rates of antimicrobial resistance in the country. But who exactly is this "everyone," and in what way is "everybody" to blame?
Doctors. "We admit we sometimes overprescribe antibiotics. When you prescribe too many to a patient, germs which are sensitive to the antibiotic are eradicated even if they are not the cause of the disease," Carlos says. The result is a particular strain becoming dominant, and then spreading to other people.
Laypeople. Self-medication and, specifically, antibiotic abuse-taking more than the required dosage-have forced the bacteria to evolve at a pace faster than medical science can cope with.
Drug manufacturers. To fatten up the bottom line, pharmaceutical firms have been aggressively promoting their products to physicians. "We do not say that the companies are forcing doctors, but doctors can get swayed to prescribe medicines that might not even be necessary," she says. On top of that, years of clever advertising have reared generations that believed in popping pills to alleviate even the most minor of physical discomforts, a habit willingly abetted by many belonging to the next group.
Drugstores. "Some drugstores are very lax in dispensing antibiotics without prescription. You can just go in and ask them what is good for my cough, and they will give you the medicine. If you go abroad you can't do that because all antibiotics are prescription-only drugs," Carlos explains.
Veterinarians. Administering high levels of antibiotics to livestock can engender antibiotic-resisting bacteria that may be transmitted to humans through consumption. To guard against it, developed countries strictly screen for antibiotic residues in animals imported from developing countries.
S.Coo
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