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|Year : 1984 | Volume
| Issue : 1 | Page : 33-7
Correlation of antibiogram, phage typing and penicillinase production of Staphylococcus aureus isolated from clinical material.
Sunderrajan PP, Kale VV
|How to cite this article:|
Sunderrajan P P, Kale V V. Correlation of antibiogram, phage typing and penicillinase production of Staphylococcus aureus isolated from clinical material. J Postgrad Med 1984;30:33
|How to cite this URL:|
Sunderrajan P P, Kale V V. Correlation of antibiogram, phage typing and penicillinase production of Staphylococcus aureus isolated from clinical material. J Postgrad Med [serial online] 1984 [cited 2020 Feb 21];30:33. Available from: http://www.jpgmonline.com/text.asp?1984/30/1/33/5498
Staphylococci form the commonest agents of hospital infections and pose a major problem because of their growing resistance to the commonly used antimicrobial drugs. These strains cause a high rate of morbidity and complications and are the cause of grave concern to clinicians. The hospital environment may have anything like 30-40% carrier rate. The present study was undertaken to assess the prevalence of drug resistance of S. aureus to antibiotics used in our hospital and to correlate this with the penicillinase production and their phage groups.
One hundred and ten strains of Staphylococcus aureus were isolated from different clinical specimens in our laboratory. These were collected from the hospitalised patients admitted to the K.E.M. Hospital, Bombay, during the period between May and December, 1981. The isolates were grown on 10% horse blood agar and tube coagulase test was used for confirmation. Antibiotic sensitivity test was done by a disc diffusion method using Meuller-Hinton medium. Following antibiotics-streptomycin, chloramphenicol, ampicillin, tetracycline, kanamycin, gentamicin, erythromycin, penicillin and methicillin were used. Penicillinase production was tested on all samples by iodometric method and chromogenic cephalasporin (nitrocefin method. The phage typing of these strains was done by using a set of 23 phages used in RTD at National Staphylococcal Phage Typing, Centre, Maulana Azad Medical College, New Delhi. The untypable strains were tested by reverse phage typing after treatment with mitomycin C using the same 23 phage types and 3 additional new phages 1030, 18042 and W57. The strains which showed no major or minor reactions at RTD were tested at 100 x RTD.
The sources of clinical sampling were pus (46 samples), swabs from throat, vagina, trachea etc., (30 samples), catheter tips (14 samples), operation theatre (10 samples), blood (7 samples), sputum (2 samples) and CSF (1 sample). The antibiotic sensitivity pattern is shown in [Table - 1]. One hundred and four (94.5%,) strains showed resistance to penicillin, 9 (8.1%) strains to gentamicin and 63 (57.2%) strains showed drug resistance to 3 or more antibiotics. Of one hundred and ten strains, 72 (65.5%) were typable and 38 (34.5%) were untypable.
Eight untypable (21.4%) strains were typable after treatment with mitomycin C. The distribution of different strains into various phage groups is presented in [Table - 2]. The predominant phage type in our series belonged to a mixed group (40.5%) followed by Group 1 (33.3%). The common phage types are described in [Table - 3]. The phage type 29/81 was the most predominant one accounting for 24.5% and 29 was the next most common phage type.
By iodometric method, 80 (72.5%) strains gave an instantaneous positive end points whereas 30 (27.5%) gave the end point within 10 minutes. The penicillinase production was positive in 99 (90%) strains by cephalosporin method. The strains with multiple drug resistance showed rapid end point as compared to those showing resistance to 1 or 2 antibiotics. Penicillianse production was also very high in all phage groups varying from 80-100% as seen in [Table - 4]. Multiple drug resistance and penicillinase production was higher in isolates from operation theatres.
Many workers have shown a changing pattern of resistance to the commonly used antibiotics, specially penicillin. Bhujwala and Mohapatra have shown a resistance of 70.6 per cent and Kulkarni et al found 92.3 per cent strains being resistant to penicillin. Pahujani et al have reported an incidence of 47 per cent resistance to penicillin from this hospital. In the present study, the resistance pattern has almost been doubled. Bhujwala and Mohapatra have reported 15 percent strains being resistant to methicillin while in the present study 14.5 per cent strains were resistant to methicillin.
Although there are reports of increasing resistance among Gram-negative bacilli to gentamicin, resistance of S. aureus has been rare. In the present study, 8% strains were found to be resistant to gentamicin. Bint et al have reported an outbreak of gentamicin resistant strains of S. aureus in a British hospital. They advised restriction of the use of gentamicin to preserve its value in serious infections.
Of one hundred and ten strains of Staphylococcus aureus that were investigated, 74 (67.2 per cent) were typable and 36 (32.8%) were untypable. Only 8 strains which were untypable became typable after treatment with mitomycin C. Of these, 6 strains were from postoperative cases.
The different workers reported predominance of a particular phage type in their studies. The predominant phage type in this series was the mixed group (40.5 per cent). Agarwal et al observed similar findings in their study. Contrary to this finding, Blair and Carr, and Wallmark and Finland have found Group I to be the most common type. On the other hand, Chatterjee and Aikat, Chatterjee et al and Barrat et al found Group III to be the most frequent one in their series.
Predominant phage pattern amongst the individual group seems to vary in different studies. Phage type 8,0 has been reported to be the commonest by Rountree and Freeman. Phage type 53/75/77 has been similarly reported by Barber and Barber and Dutton. Pahujani et al noted phage group I with 80/81 complex frequently in their series. In the study of Rajvanshi et al, no predominant phage type was reported in any group. In the present study also, some phage types were detected often but none of them was found to be predominant as such.
Earlier studies have correlated the antibiotic pattern with phage group. Pahujani et al, Rountree and Freeman, Chatterjee et al and Sahai et al have reported 81.8% penicillin resistance in group III and 61.5% in group I.
57.5% of the strains in the present study showed multiple antibiotic resistance and 7.5% were resistant to all antibiotics. Kulkarni et al reported similar findings in their study. Bhujwala and Mohapatra reported only 10% multiple resistant strains in their study. This clearly shows that in the last decade the percentage of resistant strains has increased almost five times. This could be attributed to the frequent and unnecessary usage of antibiotics in our hospital.
For penicillinase production, iodometric method gave an instantaneous reaction in 72% of strains while cephalosporin method gave an instantaneous reaction in 90% strains. In 28% strains penicillinase production by iodometric method could not be detected immediately. So iodometric method was found to be superfluous. Cephalosporin method is easy to perform, more sensitive than iodometric method and there is no delayed reaction. The only disadvantage is that cephalosporin is not easily available and requires to be imported. Daniel and Shanmugam, in their study, observed penicillinase production in 85% strains by rapid slide test.
In the present series, ninety per cent strains produced penicillinase by cephalosporin method and it was high in phage groups II and III (100 per cent) followed by phage group I (92.5 per cent) and mixed group (80 per cent). The strains resistant to one or more antibiotics showed less penicillinase production as shown by delayed end point. The strains resistant to multiple antibiotics showed high penicillinase production as shown by rapid end point. This finding is agreeable with the view of Richmond et al who believed that strains resistant to more antibiotics usually produced more penicillinase.
The authors wish to thank Dr. C. K. Deshpande, Dean, Seth G.S. Medical College and K.E.M. Hospital, Parel, Bombay 400 012, for allowing them to publish the data and also to Dr. D. S. Agarwal, Professor of Microbiology, Officer-in-Charge, National Staphylococcal Phage Typing Centre, Maulana Azad Medical College, New Delhi, for phage typing our strains. The authors also thank the Medical Director, Glaxo Laboratories, Middlesex, London, for donating Nitrocefin brand chromogenic cephalosporin.
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