Asghar Mehdi1 , Mozaffer Rahim Hingorjo2 , Muhammad Mujtaba Ali3
How to CITE:
MehdiA,HingorjoMR,AliMM, Susceptibility pattern of streptococcal isolates fromoral cavity against commonly used antibiotics. J PakDentAssoc. 2012 (01): 35-38
To assess the susceptibility pattern of streptococcal isolates fromoral cavity against commonly used antibiotics.
Oral samples, including subgingival swabs, were collected from 120 patients aged 12 to 60 years. Two swabs were collected; first for rapid-strep testing for the presumptive diagnosis of Group A Streptococcal infection and second to culture for definitive bacterial identification. Antibiotic sensitivity of the isolated strains of streptococcus was done by direct disk diffusion method. Four different classes of antibiotics; Penicillin,Cephalosporin,Macrolide, andVancomycinwere tested to determine the sensitivity pattern.
Out of 100 isolates recovered, the prevalence of streptococcal species was 74%. The greatest zone of inhibition was achieved with amoxicillin, amoxicillin-clavulanic acid, and vancomycin (16, 17, and 18 mm respectively).Zones of inhibitionmeasured for cephalosporins andmacrolideswere less than the other groups (10.5 and 11mmrespectively).
Amoxicillin is still the drug of choice for prophylactic and therapeutic use in our dental settings not only for its better coverage on the streptococcus species but also due to its easy availability and affordability. This corresponds with the international literature, however, the importance of obtaining specimens for culture and sensitivity should be observed as a standard procedure, to minimize the chances of development of resistance and identify the changing trends of the infectivity mode.
Antibiotics, sensitivity pattern, oralmicroflora, streptococci.
he oral cavity is the breeding ground to a wide range of gram positive and gram negative bacteria.
This dynamic microflora changes with respect to age, hormonal status, diet, and health status of an individual. Aas et al, has found more than 700 bacterial species from healthy oral cavity. Some of these species show specificity as to individual subjects, others are specific to particular sites within the oral cavity.1 The dominant species associated with two of the most common oral health problems; dental caries and periodontitis are Streptococci and Actinomyces. High antibiotic consumption, without testing for culture and sensitivity, has resulted in the development of resistance to the particular organism.
The present study is designed in a way to investigate the sensitivity pattern of streptococcal isolates from oral cavity. Interest in Streptococcal species is important especially for the dental surgeon as it forms the major commensal flora of the oral cavity. Nasidze et al, studied the oral flora of individuals around the world and found Streptococcus to be the most common genus in oral cultures.2 Furthermore, Streptococci have a specific linear relationship with dental procedures and two of the most crippling heart diseases: Infective endocarditis and rheumatic fever.
Currently, the use of penicillin and its congeners (such as ampicillin, amoxicillin, and the semisynthetic penicillins) for the treatment of group A streptococcal pharyngitis is declining in favor ofmore potent antibiotics or antibiotics of other class, such as cephalosporins, macrolides and clindamycin. However, even after 50 years, penicillin remains the drug of choice due to its efficacy, low cost, and narrow spectrum.3Amoxicillin has also been investigated in this regard and has shown equal efficacy and may be preferred due to its once-daily dosing.4
The objective of the study was to assess the susceptibility pattern of streptococcal isolates from oral cavity against commonly used antibiotics & to suggest a cost effective antimicrobial to the health personnel, mainly dental surgeons, for prophylactic use during dental surgical procedures where indicated. This will significantly contribute to the control of increasing incidences of infective endocarditis and rheumatic fever in ourown settings.
A total of 120 adult patients aged 12-60 years, attending Fatima Jinnah Dental Hospital during February 2005, were included in the study. Those who had taken antibiotics within the past 10 to 14 days were excluded from the study. The samples were collected in 4 days, during morning clinics. Throat gingival swab and dental plaque were collected in early morning and taken to the laboratory the same day. The study was approved by the Research & Ethical committee of Fatima Jinnah Dental College.
Relevant medical and dental history was taken from all patients and samples were collected before any dental procedure. The swab was rubbed over tonsillar areas, posterior pharynx, and any inflamed or ulcerated areas. Any white patches (exudates) in the tonsillar area were sampled aswell. Standard collection technique5 was used for collection of subgingival plaque samples by sterile endodontic paper points6 (pocket depth 48 mm). To decrease the incidence of cross-contamination, the collection sites were dried supragingivally before inserting endodontic paper points into periodontal pockets.7
To reduce chances of errors, it was made sure that the swab did not touch the tongue, lips, cheeks (buccal mucosa), teeth and uvula. Two swabs were collected; first for rapid-strep testing for the presumptive diagnosis of GroupAStreptococcal infection and second to culture for definitive bacterial identification.
Bacteria other than Streptococcus pyogenes (Neisseria gonorrhoeae, Corynebacterium diphtheriae, Bordetella pertussis, Streptococcus C, F, and G, and others) and certain viruses also cause pharyngitis. A reference microbiology laboratory was consulted for proper collection and handling procedures for both bacteria and/or viruses if needed, as identification of these organisms ismost likely beyond the scope of the research.
After collection, the swab was placed immediately into a sterile tube or suitable container for transport.
The specimens collected, were directly inoculated, in their respective order, into nonselective (5% sheep blood agar [SBA]) and selective (5% SBA with colistinnalidixic acid [CNA] agarmedia andLIMbroths).Carbon dioxide environment was created and direct agar plates were incubated for 24 to 48 hours at 37°C. LIM broths were incubated for 18 to 24 hours in carbon dioxide at 37°C, followed by subculture onto a second SBA plate incubated for 24 hours in carbon dioxide at 37°C.GroupA & B Streptococci were identified using previously published conventionalmethods.
Antibiotic sensitivity of the isolated strains of streptococcus was done by the direct disk diffusion method. Four different classes of antibiotics; Penicillin, Cephalosporin, Macrolide, and Vancomycin were tested to determine the sensitivity pattern. These drugs were selected on the basis of the National Committee for Clinical Laboratory Standards (NCCLS ) recommendations and the sensitivity described in literature.8 Penicillin andMacrolide share approximately the same spectra of gram positive bacterial coverage, where as Cephalosporins cover not only grampositive but a significant population of gram negative strains as well. The last category comprises only two drugs; vancomycin and tiecoplanin. These two antibiotics cover excellently and exclusively grampositive strains.
Themean, standard deviation, standard error ofmean, was calculated using SPSS version 15. Student ‘t’ testwas used to compare between groups.A p < 0.05 was regarded as statistically significant and p <0.001 as highly significant.
Out of 120 adult patients 100were found to be culture positive (isolates). Out of 100 isolates recovered, the prevalence of streptococcal species was 74%. In the current study, four different classes of antibiotics: Penicillin, cephalosporin, macrolide, and vancomycin were used. Figure 1 shows the comparison of zones of inhibition of these antibiotics against streptococcal species cultured on sheep agar. The greatest zone of inhibition was achieved with amoxicillin, amoxicillinclavulanic acid, and vancomycin (16, 17, and 18 mm respectively).Based upon the size of inhibitionmeasured, therewas no significant difference among amoxicillin and amoxicillin-clavulanic acid, antibiotics of Penicillin group, with amoxicillin-clavulanic acid having an edge over the other two. The results of the three cephalosporins were identical, with cefaclor showing a larger area of inhibition as compared to other cephalosporins (cephalexin and cefriaxone). The three macrolides (calrithromycin, erythromycin, azithromycin) were identical in their effectiveness against streptococcus species. Zones of inhibition measured for cephalosporins and macrolides were less than the other groups (10.5 and 11 respectively). Vancomycin, that has exclusive gram positive coverage showed a zone of inhibition not significantly higher when compared with the penicillin group. The result also shows an inferior potential of Cephalosporins and Macrolides in inhibiting Streptococci, as compared to Penicillin group.
Figure 1: Susceptibility pattern of four different classes of antibiotics: Penicillin, cephalosporin, macrolide, and vancomycin showing zones of inhibition (in mm) of these antibiotics against streptococcal species cultured on sheep agar.
Prevention and effective treatment of oral infections involves an understanding of the oral microbial flora and the complex ways by which they interact within microenvironment of the oral cavity. It is also important to treat these oral health problems early due to their strong association with a wide array of systemic diseases such as poor glycemic control in diabetes, coronary artery disease, lowbirth-weight pre-termbabies, and others.9,10 A total of 120 samples were collected from patients attending the oral diagnosis department of Fatima Jinnah Dental College, out of which 74% cases were found to be positive for the culture of hemolytic Streptococcus,which shows a very high prevalence of Streptococcus infection in our local population.As proper sterilization techniques were followed as per recommendations and the samples were processed on the same day to avoid contamination, the chance of the result being false positive is low. Devi et al found 50% prevalence of Streptococcus sp. from dental plaque samples.11 Magnúsdóttir et al studied the phyaryngeal prevalence of Streptococcus pyogenes and methicillin-resistant Staphylococcus aureus among healthy children of Iceland and found an overall 22% prevalence for S.pygenes with highest carriage rate at 45% in first graders.12 Putnam et al found the pharyngeal colonization prevalence rates for Streptococcus pyogenes at 2.4%.13 Katrina et al, however, found an absence of streptococcus pyogenes from the pharyngeal flora in children aged 5 12 years. They have attributed this to an improvement in living standards, along with an active participation of local health centers in providing health care.14 Most of the streptococcal isolates were sensitive to Amoxicillin and Amoxicillin-Clavulanic acid, the conventional antibiotics recommended for Streptococcal pharyngitis, whereas the other expensive cephalosporins andmacrolides did not show a similar zone of inhibition as did penicillin. This compares well with a study conducted by Devi et al who tested the efficacy of 10 antibiotics against streptococcus by disc diffusion method and found amoxicillin and penicillin G to be the most effective antimicrobials for oral infections such as dental caries.11 Chardin et al, conducted a study on the use of amoxicillin to prevent oral streptococcal infection after tooth extraction. He found oral commensal flora consisting of streptococci resistant to amoxicillin in healthy patients and its rapid selection by amoxicillin treatment.15 The sensitivity for Vancomycin was found to be equivalent to that of amoxicillin-clavulanic acid, suggesting its role in difficult to treat infections. Its regular use should be avoided to prevent the development of resistance.
On the basis of the results of the current study it could be recommended that amoxicillin is still the drug of choice for prophylactic and therapeutic use in our dental settings not only for its better coverage on the streptococcus species but also due to its easy availability and affordability All the results and the inferences show validity and corresponds with the international literature, however, the importance of obtaining specimens and processing for culture and sensitivity should be observed as a standard procedure. This would help in minimizing the chances of development of resistance and judicious use of the antibiotics. Furthermore, it can also identify the changing trends of the infectivitymode.
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