Australian Dental Journal, February, 1975

An assessment of antibiotics for the treatment of pyogenic dental infections

Robin Woods

A s s m u c r e s t s made with a series of antibiotics against a number of different organisms indicate that if clinical evidence suggests a streptococcal infection, penicillin should be used otherwise erythromycin is preferred.

(Received for publication February, 1974)

Introduction In a study undertaken six years ago,’ 84 cases

of acute pyogenic dental infections were reviewed. In each case a pus sample had been obtained and the microorganisms present in the pus isolated and tested for its antibiotic sensitivity. A similar series of 80 cases is now presented and reviewed. The cases were collected over three years and were encountered in day to day general practice in a rural community. The teeth involved were pre- dominantly anterior but a number of bicuspid and molar teeth are included. The only cases I have reported were those from which a single strain microorganism was cultured.

Method All patients suffered an acute infection. Drain-

age was established via the root canal and some pus was allowed to escape. A sample of pus, obtained on a sterile paper point, was transferred to dextrose peptone broth (Oxoid) incubated at 37°C for 24 hours and plated out on diagnostic sensitivity test agar (Oxoid) which contained 10 per cent horse blood. An antibiotic impregnated paper disc (Oxoid Code ‘Sl’) was placed on the surface of the agar after the inoculation, which

contained the following: Chloramphenicol 10 ag Erythromycin 10 ag Sulphafurazole 100 ag Cloxacillin 5 aB Penicillin 1.5 units Ampicillin 2 CLB Streptomycin 10 Irg Tetracycline 10 Pg

In addition to these antibiotics in a number of tests the Cloxacillin was replaced with a Linco- mycin disc+ (10 pg). The microorganisms were classified after isolation: on the basis of mor- phology, being stained by Gram’s method; their appearance when grown on blood agar, mitis salivarius agar, litmus lactose agar and in the case of staphylococci, their ability to ferment mannitol. The organisms were classified according to Bergey’s Manual2 which divides streptococci into a pyogenic group corresponding to the beta haemolytic group, a viridans group and entero- cocci which include Streptococcus faecalis. Staphy- lococci are classified by Bergey as Staphylococcus pyogenes and it is distinguished by being able to ferment mannitol as well as being coagulase

1 Woods, Robin.-Antibiotic treatment of Pyopenic infec- tions of dental origin. Austral. D.J., 13:2, 151-153 (April) 1968.

* Provided by the Upjohn Company.

2 Bergey-Manual of determinative bacteriology. Edit., Breed, R. S., Murray, E. 0. D., and Smith, N. R. Baltimore, Williams and Wilkins Co., 7th ed.. 1957.

Australian Dental Journal, February, 1975 11

positive. The Escherichia coli, Pseudomonas pyocyanea and Klebsiella were also identified according to the principles set out in the manual.

Result? The results of the sensitivity test are presented

in Table 1. This Table shows the incidence of the various species of microorganisms encountered and also the incidence of the sensitivity of the various species to the antibiotics tested both in respect to individual microorganisms and all cases.

A comparison of the incidence of various species in both this report and the 1968 report1 is pre- sented in Table 2. The incidence of streptococci as a species remained constant although the distribution of the various types of streptococci changed. There was a marked drop in the inci- dence of Str. faecalis and an increase in the other two groups. The incidence of gram negative microorganisms was lower; the incidence of staphylococci rose from 5 to 10 per cent.

Sensitivity to antibiotics, set out in Table 3, compared with the previous report shows some changes. Erythromycin and chloromycetin are potent antibiotics. There is an increase in the incidence of sensitivity to penicillin and a decrease in the incidence of sensitivity to the tetracyclines.

Comparison of incidence of various microorganisms, 1968-1 974

TABLE 2

196s 1974

Per cent Per cent streptococcus viridans ..................... 38.0 46.2 Pyogenic streptococci ........................ 17.9 28.7 Streptococcus faecalis 6.3 Staphylococci ..................... 10.0 Escherichia coli ....._........ 5.0 Pseudomonas ............................................. 2.5

1.3 - TABLE 3

Comparison of incidence of sensitivity to various antibiotics of all cases, 1968-1974

1968 1974

Per cent Per cent Chloramphenicol 97.5

96.3 85.0 77.9 75.0

Tetracyclines 91.7 72.5 41.3 15.0

Sulphafurazole Streptomycin ...............................

This change in sensitivities has been brought about by a marked increase in the resistance to tetra- cyclines among the streptococci. In 1968, particu- larly with Str. viridans 97 per cent were sensitive to the tetracyclines and in the present report only 70 per cent were sensitive. The incidence of sensitivity of Str. faecalis to the tetracyclines

12 Australian Dental Jourixd, February, 1975

remains the same at 80 per cent; but the incidence of sensitivity of pyogenic streptococci has, however, dropped from 93 per cent to 82 per cent. These findings are consistent with those of Goodman and Gilman3 who reported that 10-30 per cent of pyogenic streptococci are resistant to tetra- cyclines. The incidence of sensitivity to tetra- cyclines among staphylococci and E. coli appears to be lower although the numbers of these micro- organisms encountered are too small to draw reliable conclusions.

On the other hand the incidence of sensitivity of all streptococci to penicillin has increased to 92 per cent from 76 per cent in the previous study. This may be related to the lower incidence of the penicillin resistant species, Str. faecalis. Relative effectiveness of the antibiotics

Of the various antibiotics tested chloramphenicol is included and reported purely because it rep- resents a convenient statistical control as far as technique is concerned. Because of its toxicity I do not believe it has any place at present in general dental practice.

Excluding chloramphenicol the incidence of sensitivity to various antibiotics in decreasing order is: erythromycin, ampicillin, lincomycin, penicillin, tetracyclines, sulpha drugs, strepto- mycin.

The choice of antibiotics Based purely on the incidence of susceptibility

of the microorganisms considered, erythromycin is the drug of choice with all dental infections. There are however, some reasons why one may not agree with this. Erythromycin is not easily absorbed when administered orally, also it costs approximately twice as much as penicillin. I would suggest that a clinical guide to the choice of drugs could be developed by dividing the infections into streptococcal infections and others. Streptococcal infections may be clinically separated from the balance on the basis of several factors. Firstly, if cellulitis is present inevitably the micro-organism responsible is a streptococcus. Secondly, pus from streptococcal lesions appears thinner and relatively pale. Thirdly, it has been my observation that where patients suffer from abscesses of a strepto- coccal origin the pain and tenderness to percussion although intense is not as exquisite as is the case with other infections.

Using these principles as a means of diagnosis of streptococcal infections and referring again to the results in Table 1, it is possible to recom-

3 Weinstein, L.-Chemotherapy of microbial diseases. Table 5: Current use of anti microbial agents in the therapy of infections. In. The pharmacological basis of thera- peutics. Goodman, L. S., and Gilman, A.. Edits. New York. Macmillan Co., 4th ed.. 1970 (p. 1160).

mend a priority for antibiotics for use in strepto- coccal infections. First priority must be given to penicillin which is 92 per cent effective; the second priority must be given to erythromycin which is 98 per cent effective and to lincomycin as a third choice, which is 92 per cent effective. Tetracyclines (75 per cent effective) do not seem, on the basis of these figures, to have a reliable place in the treatment of streptococcal infections.

The reason for not recommending ampicillin which is 97 per cent effective is that the principal objection to using penicillin for a patient would be allergy and this objection applies equally to ampicillin. The slightly increased reliability of ampicillin does not warrant its use as a substitute for penicillin in streptococcal infections. The effectiveness of ampicillin in infections other than streptococcal is not sufficient to recommend its use in these situations. It is however, a drug which should be kept in mind for possible future use in dentistry.

If the dental infection is not streptococcal, i e . if there is no cellulitis, a high degree of exquisite pain and extreme tenderness to percussion, it is likely that the abscess is caused by staphylococci or the gram negative organisms. Under these circumstances erythromycin would be the primary choice with the tetracycline as an alternative drug bearing in mind that it is not a really satisfactory alternative being only 60 per cent effective. A choice beyond this point would rely heavily for the guidance of a sensitivity test. Dosage

Where penicillin is the drug of choice I have found it conveniently administered orally as phenethicillin which in my hands has been a reliable form of penicillin. the dosage being 250 mg four times daily (before meals and at bedtime). Where erythromycin is the drug of choice the stearate form is available and again I have found a dose of 500 mg to commence with, followed by 250 mg four times daily (before meals and at bedtime) to be satisfactory. Children over three years may have half the usual adult dose and under three years, one quarter of the usual adult dose administered before meals and at bedtime. The duration of the course for both penicillin and erythromycin should be at least six days. This can be achieved by prescribing a minimum of 25 doses. The oral dosage of lincomycin recom- mended by Tolhurst, Buckle and Williams' is 500 mg eight hourly or where children are concerned 30 mg/kg body weight per day in

- 4 Tolhurst, 1. C., Buckle, G.. and Williams, S. W.-Chemo-

therapy with antibiotics and allied drugs. Canberra, National Health and Medical Research Council. 3rd cd., 1972 (p. 88).

Australian Dental Journal, February, 1975 13

divided doses. The dosage of tetracyclines will depend on the

form used. Tetracycline administered as tetra- cycline, tetracycline V, oxytetracycline or aureo- mycin, should be prescribed as 250 mg four times daily, six hourly. The tetracycline derivative, demethylchlortetracycline is a more stable form giving a higher blood level and it is recommended that this be prescribed in smaller amounts of either 150 mg six hourly, or 300 mg every twelve hours.

Doxycycline (Vibramycin, a recent derivative of tetracycline) is well absorbed when given orally and the dosage recommended here is 100 mg twelve hourly for three doses and then 100 mg daily. The development of small dose tetracycline preparations administered daily may have some attractions on the basis of convenience, although Tolhurst, Buckle and Williams5 state that in their field these preparations have no advantage.

In the treatment of pyogenic infections the first objective is drainage. Effective drainage is essential to successful therapy and the safety of the patient. Whether the drainage is established via the root canal to be followed by root filling or whether by extraction of the tooth is beyond the scope of this paper and is a choice governed by other con- siderations.

6Tdhurst. J. C.. Buckle. G.. and Williams, S. W . 4 p . cit., p.14.

Frequently drainage in itself is sufficient to permit the acute infection to be controlled. Con- servative treatment, e.g. root canal filling, may be necessary to prevent a recurrence of the infection. Whether to use antibiotics is a matter of judgement for the dentist when the particular circumstances of the case are known.

Summary Based on bacteriological analysis of the organ-

isms associated with a series of eighty cases of dental pyogenic infections I have made some recommendations regarding the choice of anti- biotic for use in dentistry for treatment of these infections.

It has been suggested that if, on the evidence of clinical examination, infections associated with streptococci can be diagnosed, in these cases penicillin remains the first choice. For micro- organisms other than streptococci, erythromycin is the first choice.

An increase in the incidence of tetracycline resistance among all the microorganisms examined, especially the streptococci, has been noted when compared with a similar survey reported six years ago.

Prescribing regimes for the recommended drugs have been suggested.

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