part 2-Kill Kinetics of BB
JWissmille
MURSIC) Author: RitaStanEmail:rita...@aol.comDate:1996/10/04Forums:sci.m
ed.disease
DISCUSSION
The main problems of Lyme disease are the lack of reliable diagnostic
tests for actual disease plus the fact that the therapy can often be
unsuccessful. The interpretation of serological tests and results may not
be straightforward, false-positive and false-negative results occur.
Negative serological results do not necessarily exclude a B. burgdorferi
s.l. infection (1-4). Furthermore, it is unknown whether a positive PCR
really indicates an active infection. Unfortunately, however, borreliae
are easy to overlook in patients' samples, and not easy to detect. The
overlapping symptomatology of the stages and the self-limited course of
the infection in primary and secondary stages of the disease make
diagnosis and therapy control more difficult. Accordong to Asbrink et al.
(19) 10-15% of European patients with an untreated erythema migrans will
develop neuroborreliosis. Months after the infection, 60% of untreated
American patients develop intermittent attacks of arthritis, 10% of the
patients with arthritis the inflammation persists despite antibiotic
treatment (20-21). However, the actual incidence of disseminated
infection with manifestation in the heart and other organs is unknown.
Furthermore, we have no data about the incidence of disseminated disease
despite antibiotic therapy. How often borreliae may persist in the CSF,
skin or other tissues, or their effect in producing atypical
manifestations of the disease is not known. Our results in the isolation
of B. afzelii from CSF during erythema migrans without inflammatory signs
and neurological symptoms support very early dissemination (4). the
isolation of B. burgdorferi sensu stricto (s.s.) from iris biopsy, after
several years of chronic recurrent uveitis and panuveitis with bilateral
iridocyclitis despite antibiotic treatment, is the best evidence for
long-term persistence of Borrelia apart from the CSF and skin (4). Also
in patients presented here, Borrelia survived months to years despite
seemingly adequate-aggressive antibiotic treatment. These persisters are
interesting because of the site of the perisitence as well as the
isolation after repeated antibiotic treatment. Especially interesting is
the isolation of non-motile atypical forms of borreliae which after
subcultures in the MKP medium become motile. This finding, as well as the
results of other examinations (22), suggested the formation of spheroplast
L-form variants in B. burgdorferi s.l. strains. According to experience
with other bacteria, these forms can be responsible for chronic-persistent
infection (23, 24).
The reason for the persistence of B. burgdorferi s.l. in patients after
treatment with antibiotics is not completely understood. In fact a number
of factors may play a role; e.g., virulence of borreliae, long generation
time of borreliae, biologic differences in strains, the site of the
infection, the ability of the drug to penetrate that site, insufficient
antibiotic therapy and many others. To what extent the immunological
status of a patient is of importance is unknown. The capacity of Borelia
to hide in various human tissues (heart,muscle, spleen, eyes, brain)
(25-27, 4, 11, 28), intracellular localization and an insufficient
antibiotic tissue level are critical for the therapy.
It is known that the therapy of late stages of Lyme disease can be
complicated. Frequently, there are known recurrences of the
manifestations and persistence of Borrelia despite seemingly adequate
antibiotic treatment. The persistence and clinical recurrence in the
erythema migrans stage are rarely noted, as the therapy seems to be mostly
effective and adequate (3). However, in most erythema migrans patients
clincal and serological control of the effect of therapy, if any, is done
a few months after the completion of antibiotic therapy, too short a
period for the final diagnosis. Furthermore, proof of a successful
therapy is based not only on the disappearance of clincal symptoms but
also on the elimination of Borrelia; this is difficult to demonstrate and
seldom done. The fact that antbodies against B. burgdorferi s.l. may
persist for months, can indicate prior exposure to borreliae as well as
active disease. Finally, we must take into consideration that changes in
clinical symptomology (after months; years) can lead patients to change
doctors.
The current antibiotic therapy (antibiotic, dosage, duration) of Lyme
borreliosis varies greatly, therefore we have very different clinical and
laboratory findings. Often the treatment seems to be wrong when
ineffective antibiotics such as co-trimoxazole, cefaclor and
aminoglycosides are given. According to the results of in vitro
examinations and data of a few clinical studies, the cephalosporins are
more efficient than penicillin G (29-31). On the other hand, some
investigators (32-34) have reported no differences in the outcome between
patients who received penicillin or those given cephalosporins.
Furthermore, the comparison of penicillin G and oral doxycycline for
treatment of neuroborreliosis (35) and azithromycin, doxycycline and
phenoxymethylpenicillin for erythema migrans (36) show similar efficacy.
The CSF concentrations of penicillin, cefotaxime and ceftriaxone
demonstrate that the cephalosporins penetrate to a greater extent than
penicillin (33, 37). The outcome of our studies on the kill kinetics and
the killing effect show that the kinetics of killing borreliae differ from
antibiotic to antibiotic. The killing rate of given antibiotics was
dependent on the concentration and reaction time. However, killing
Borrelia with beta-lactams was more time dependent. The tested antibiotic
first showed a significant killing effect between 48-72 h. The
antibiotics were slowly effective. An interesting observation was the
different effect of one antibiotic on various B. burgdorferi isolates in
the MKP medium as well as in serum of healthy volunteers. Furthermore,
the results suggest that the strains of B. afzelii and B. garinii have a
different susceptibility to antibiotics used in the treatment of Lyme
borreliosis. This individual action time of antibiotics in strains can be
of importance in the treatment regimen. It is usually recommended that
patients with erythema migrans be treated for at least 14 days with oral
antibiotics (doxycycline 2X100 mg/day, amoxicillin 2X400 mg/day and in
complicated or late disease for 2-3 weeks with a systemic (cefotaxime 3X2
g/day, ceftriaxone 1X2 g/day). However, with the unpredictable
progression of the disease and early dissemination of the borreliae, it
seems appropriate to treat patients in stage 1 as effectively as possible.
Complicated as well as late disease begin with early manifestation.
Furthermore, the results of randomized prospective therapy studies and
case reports show that with recommended antibiotic therapy cure is often
impossible with only one treatment course.
Therefore, for the potentiation of treatment, the intensification of
antibiotic therapy by establishing a new dosage regimen can be of great
importance. A combination of two antibiotics (cephalosporin/doxycycline,
cephalosporin/azithromycin, penicillin G/in combination) must be taken
into consideration. Likewise, a pulsed (interval) therapy with larger
doses of antibiotics for 4-5 days, twice with an antibiotic free interval
of 4-5 days, seems to be advantageous. This treatment regiment, which
takes into consideration the long generation time of Borrelia and the
antibiotic mechanism of action, can probably be more effective than the
regimen used. The higher doses of antibiotics reach correspondingly
effective higher serum, CSF and tissue antibiotic concentrations and
repeated doses of antimicrobial can kill the survivor borreliae as
effectively as the initial dose. Furthermore, it is known that the
bacteria in the post-antibiotic effect phase of growth are more
susceptible to the antibacterial activity of human leukocytes than
untreated bacteria.
In conclusion, the isolation of B. burgdorferi s.l. after antibiotic
treatment as well as the persistence of clinical signs demonstrate that
currently recommended treatment regimens are inadequate for some patients.
Because of this observation, it has become questionable whether a
definite eradication of borreliae with one antibiotic course is always
possible. The therapy ought to be realized and controlled more on an
individual basis. All patients respond differently. We consider the
optimal therapy for the erythem migrans stage to be very important in
early blocking of the dissemination of Borrelia. The association of B.
burgdorferi s.s., B. garinii and B. afzelii with different clinical
manifestations of Lyme disease we can not confirm (paper in preparation),
but we have found differences in the killing effect of various antibiotics
on strains of these three species. Perhaps we have a correlation here.
The questions of why a 100% eradication of borreliae is not possible, why
a 100% resolving of clinical symptoms is not achieved if borreliae are
susceptible to antibiotics used in treatment (treatment failure? other
factors?) could be answered only by extensive and rigorously designed
clinical and microbiological studies. Possibly, with persistence of
disease or recurrence of clinical symptoms we have to consider atypical
forms of B. burgdorferi s.l., spheroplast L-form variants. The
eradication of these forms as well as the intracellularly localized
borreliae (38) is difficult and with beta-lactam antibiotics practically
not obtainable. Here combination therapy with doxycycline or macrolides
is indicated.
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