Vancomycin is generally considered as the last resort antibiotic
, although recently Europe approved quinupristin
(on the market as Synercid) for bacteria who gained resistance
to vancomycin. The Columbia Encyclopedia (6th ed., 2000) stated that bacterial resistence to vancomycin is rare. They are wrong.
So, what is this substance, what does it do, what about resistance and its use and is this really "the end" regarding treatment of bacterial infections?
First of all, the structure
of vancomycin can be viewed at http://www-micro.msb.le.ac.uk/Tutorials/dfwt/vanc.gif, originally purified from Streptomyces orientalis
. It belongs to the penicillin
-family of antibiotics in its function to kill Gram+
bacteria like staphylococci and enterococci who are resistant to ß-lactam antibiotics by interfering with the cell wall synthesis and causing damage to the cell membrane. Cell wall biosynthesis
is troubled because of the inhibition of cross-linking of peptide chain
strands); it is not exactly clear how it messes with the already built membrane
, it does not interfer with RNA synthesis)
Vancomycin was first used about 40 years ago. But at that time, antibiotics more convenient in use and with less side effects were available (aka: oral
intake instead of intravenous
); it gained popularity in the eighties again when serious troubles with antibiotic resistance started to arise and the purification
process of vancomycin was improved.
It is/was (...
) used to treat infection
s by bateria like Stapylococcus aureus
, Clostridium difficile
, S. haemolyticus
, S. pneumoniae
and Enterococcus faecarium
. However, they're getting resistant to vancomycin. Resistance in this case is defined as follows: susceptible
is <= 4 µg/ml, intermediate 8-16 µg/ml and resistant
>= 32 µg/ml (National Committee for Clinical Laboratory Standards in the USA). See also VRE
Vancomycin resistance in VRE is located on a gene cluster similar to Tn1546
(is a specialized transposon
and called an integron
). Ironically, it appears that resistance is promoted in tandem with the use of other antibiotics, due to the selective advantage
, but synergistic activity
with other antibiotics (oxacillin
) in a "cocktail
" is also documented. Thing to figure out is wich combinations are best in the long run.
In the case of vancomycin resistance, it originates with VRE (vancomycin resistant enterococci) in livestock
, mainly used in Europe
. The current hypothesis
is, that they got it because of the use of avoparcin
antimicrobial drug used as a feed additive) in "sutherapeutic doses" (i.e. not enough to kill the bacteria). It promotes animal growth, but it's not known why and how, it just does, and that's what the bio-industry
wants. Researchers don't know how it emerged in the hospital
s in the US, or elsewhere in the world.
Bacteria are everywhere; the bacterial world can be imagined as one huge multicellular organism
passing on some of their genes to each other all the time. It is supposed that the MRSA got its resistance genes from the VRE: both like hospitals very much. Especially in the USA, antibiotics are widely used, ok, misused, to kill certain micro-organisms, hence providing the selective advantage for survival
and growth of VRE and MRSA (i.e. Darwinism
at work). When patient
s who aquired a VRE infection in the hospital go home, they pass it on to family members etc.
Although it is quite alarming to know that there are bacteria out there resistant to about the 100 available antibiotics, it doesn't necessarily mean that human
s have lost the "war against bacterial infections". Like the quinupristin, new drugs are invented, although it is not clear if "we" can stay at least one step ahead of the bacteria. More important is the control
of the vancomycin resistant bacteria:
regulations properly implemented in hospitals;
- change in prescription
attitude by the medicals, aka the right antibiotic in the right dose for the target bacteria and not for viruses;
- patients who just have to finish an antibiotic treatment
, instead of halting a treatment by the time they start to feel well again;
- limited/restricted use of antibiotics in agriculture
- limited use (though I'd say a ban
) of antibacterial substances in consumer goods
. The even put antibiotics/antibacterial substances in certain toys "coz kids put the dirty stuff in their mouth", and some underwear "so you won't have the awful smell in your crotch" (no kidding! they are real ad slogans). Get real, most micro-organisms are good for you and help maintaining your immune system
On the other hand, these proposed regulations exist for at least five years, and nothing has been really put into practice, so maybe it is the end after all.
Time will tell.
Part of the information in this write-up was collected from 8 sources, most of them found after a google search on vancomycin. A nice article about prevalence, sources and public health implications can be viewed at http://www.cdc.gov/ncidod/EID/vol3no3/mcdonald.htm.