Swagata Roy and Debadatta Dhar (Chanda)

Department of Microbiology, Silchar Medical College & Hospital, Silchar, Assam – 788014, India.


This study was undertaken to determine the frequently isolated organism from pus culture and to determine the antibiotic sensitivity patterns so that it helps to manage the drug resistant organism well in time which poseschallenge to clinician to treat the patients. Total 2050 samples were collected from April 2016 to March 2017 to study antibiograms of various organisms. Organisms were identified as per standerd operative procedure and drug sensitivity was done as per CLSI guidelines. Most commonly encountered organism was Staphy.aureus followed by Klebsiella, Pseudomonas, Proteus, Citrobacter, E.coli and Acinetobacter. Staph.aureus was showing sensitivity towards Vancomycin, whereas gram negative organisms were showing sensitivity towards Imipenem,Gentamycin, Ciprofloxacin and Ceftriaxone.Antimicrobial resistence is a predictable outcome of antimicrobial use. Lengthy or inappropriate antimicrobial therapy allow microbes to mutate into new forms that help them to survive antibiotic treatment and quickly become resistance strain. Knowledge of local  common pathogens and their resistance status can guide clinician to choose appropriate antibiotic for empirical treatment of patients.

Keywords: Antimicrobial susceptibility, Pus, Pyogenic infection,Retrospective study.


Pyogenic infection are characterized by local and systemic inflammation with pus formation .Infection of soft tissue are generally associated with the production of pus and bacteria involved are said to be pyogenic (pus producing). Wide variety of aerobic and anaerobic species of bacteria may be present either singly or in combination in infection of wounds and soft tissue.Some infection resolve without specific therapy but some infection especially mixed infection can cause severe synergic therapy.[1] Antimicrobial resistence is a predictable outcome of antimicrobial use. Lengthy or inappropriate antimicrobial therapy allow microbes to mutate into new forms that help them to survive antibiotic treatment and quickly become resistance strain. Knowledge of local  common pathogens and their resistance status can guide clinician to choose appropriate antibiotic for empirical treatment of patients.(2)Various studies across the world have shown periodic monitoring of the bacterial profile in the pyogenic wound infection, which is helpful for the empirical treatment of the patient.Keeping this in mind this study has been undertaken to know the common organism involved and their antibiogram in our set up.



This is a Retrospective study conducted in department of Microbiology,Silchar Medical College,Silchar. In the present study the data was collected from the period  April 2016 to  March2017. The total number of 2050 pus  sample were collected from  cases of pyogenic infection attending both OPD and indoor in the department of Surgery, O&G, Orthopaedics and ENT. Under strict aseptic condition sample were collected and transported to the Department of Microbiology for processing.The media and reagents are purchased from HIMEDIA laboratories.Mumbai,India.First, samples were inoculated in 5% sheep Blood agar and MacConkey agar culture media, then it was subjected to Gram staining of direct smear and  Gram stain was examined for the presence of pus cells and any bacteria. The inoculated media were incubated aerobically at 37® Cfor 24 hours. If there was no growth, incubation time is extended up to 48 hours to be  considered sterile. All the bacteria growing on blood agar  andMacConkey agar were examined to look for the colony character, Gram staining and motility.Identification of isolates were done based on biochemical test like catalase test, oxidase test, coagulase test, Triple sugar iron  test, carbohydrate fermentation test, phenyl  pyruvic acid, Methyl red test, Nitrate reducticn test, Urease test, citrate utilization test ,  Indole test,Arginine dihydrolase production,  lysine and ornithine decarboxylase test, and  Hugh and leifson test.(3)The antimicrobial susceptibility testing were done by Kirby Bauer,s Disc Diffusion method and interpreted as per Clinical Laboratory Standard Institution (CLSI) guidelines(4).For antimicrobial sensitivity testing Muller Hinton  agar was used. The antimicrobial disc used were purchased from HiMedia laboratory Ltd. Inhibition zones were measured and reported as sensitive or resistant according to manufacturer, s guidelines. Escherichia coli ATCC 25922,Pseudomonas aeruginosa ATCC 27853 AND Staphylococcus aureus ATCC 25923 were used as quality control strains.Antimicrobial  discs used for sensitivity testing by disc diffusion method were Imepenem 10mcg, piperacillin/ tazobactam 100/10 mcg, Ceftazidime 30mcgCefotaxime 30mcg, Amikacin 30mcg, Gentamicin 10mcg, Levofloxacin 5mcg, Ceftroaxone30mcg, Cefoxitin 30mcg, Amoxycillin/Clavulanic acid 20/10mcg. Vancomycin 30mcg, Azithromycin15mcg, Linezolid 30mcg,Ampicillin10mcg, Ciprofloxacin5mcg, Cefuroxime30mcg, Ceftriaxone 30mcg, Aztreonam30mcg.



Out of 2050   pus samples obtained in the Microbiology laboratory  from various departments of Silchar Medical College,Silchar. 1040 were culture positive and 1010 were sterile.Out of 1040 ,439 (42.21%) were Stapylococcusaureus,Klebsiella species165(15.86%),Pseudomonas species159(15.28%),Proteus species 141(13.55%),Citrobacter98(9.4%),Escherichia Coli 20(1.9%),Acinetobacter 18(1.7%). The antibiogram of gram positive cocci showed 100% sensitivity to vancomycin and Linezolid followed by high sensitivity to Azithromycin, Cefuroxime while moderate sensitivity was observed to Cefoxitin, Levofloxacin Ampicillin and Amoxycillin/clavulanicacid.Gram positive cocci showed high resistence to Ciprofloxacin, Ceftriaxone and Amikacin. MRSA noted was 75.68%. The antibiogramof  enterobacteriaceae(Klebsiella and Proteus ) showed high susceptibility to Imipenem.E. coli showed highest susceptibility to Amikacin and Levofloxacin.Citrobacter showed highest susceptibility to Levofloxacin.Highresistence is observed towards Ceftazidime(Kebsiella),Aztreonam(E.coli), Cefuroxime(Proteus) and Citrobacter(Ceftriaxone) respectively.Pseudomonas and Acinetobacter showed maximam susceptibility to Piperacillin/tazobactam.







Fig.1 .Distribution of organism isolated from pus culture:-





Fig 2 Number of Culture Positive and Culture Negative                                                   Fig-3. Prevalence of MRSA & MSSA in Staphylococcus aureus

Table No. 1 Antibiogram of gram positive cocci.







Table No. 2 Antibiogram of Enterobacteriaciae


Antibiotics Klebsiella E.coli Proteus Citrobacter
Amikacin 90.90% 9.09% 100% 0% 85.1% 14.8% 55.1% 44.8%
Levofloxacin 98.18% 1.81% 100% 0% 70.9% 29.07% 98.9% 1.02%
Ceftazidime 6.06% 93.93% 50% 50% 28.3% 71.6% 81.6% 18.3%
Ceftriaxone 65.45% 34.54% 40% 60% 55.3% 44.6% 15.3% 84.6%
PIT 31.51% 68.48% 65% 35% 93.6% 6.3% 69.3% 30.6%
Cefotaxime 73.93% 26.06% 100% 0% 63.3% 36.1% 75.5% 24.4%
Gentamycin 67.87% 32.12% 80% 20% 92.1% 7.8% 10.2% 89.7%
Imipenem 100% 0% 90% 10% 100% 0% 93.8% 6.1%
Cefuroxime 67.87% 32.12% 0% 20% 7.09% 92.9% 63.2% 36.7%
Aztreonam 54.54% 45.45% 25% 75% 73.7% 26.2% 85.7% 16.6%
Ampicillin 52.12% 47.87% 75% 25% 11.3% 88.6% 66.3% 33.6%


Antibiotics Staph. aureus
Sensitive Resistant
Amoxycillin/Clavulanic (23.46%) (77.06%)
Vancomycin (100%) (0%)
Azithromycin (91.74%) (8.8%)
Levofloxacin (45.87%) (54.44 %)
Linezolid (100%) (0%)
Amikacin (17.76 %) (82.79%)
Ciprofloxacin (10.70 %) (89.90%)
Ampicillin (43.57%) (56.71 %)
Ceftriaxone (14.90%) (85.19%)
Cefuroxime (75.85 %) (24.31%)
Cefoxitin (47.24%) (53.07 %)











Table No. 3 Antibiogram of Pseudomonas and acinetobacter




Pseudomonas Acinetobacter
Amikacin 75.4% 24.5% 22.2% 77.7%
Levofloxacin 35.2% 64.7% 44.4% 55.5%
Ceftazidime 3.1% 96.8% 11.1% 88.8%
Ceftriaxome 37.7% 62.7% 44.4% 55.5%
PIT 94.3% 5.6% 55.5% 44.4%
Cefotaxime 57.8% 42.1% 11.1% 88.8%
Gentamycin 83.6% 16.3% 50% 50%
Imipenem 75.4% 24.5% 44.4% 55.5%
Cefuroxime 6.9% 93% 0% 100%
Ciprofloxacin 43.3% 56.6% 5.5% 94.4%
Aztreonam 91.8% 8.1% 5.5% 94.4%

PIT- Piperacillin/Tazobactam



The prevaience of culture positive pus samples in our study is 50.73% . The observation of this study very well coincide with the works reported by various authors across the country .S.aureus was found to be the most commonly occurring pathogen in study group  done by Tiwari et al(5), Lee C. Y et al(6), and zafar A et al(7). However Duggal Swati et al(8) and Basu et al(9) found Pseudomonas to be the most common isolate. Also ,Rameshkannan S et al(10). found Escherichia coli to be the most common organism isolated from pus samples.Staphylococcusaureus was found to be 100% sensitive to Vancomycin& Linezolid which agrees with studies ofChauhanet al(11).Enterobacteriseiae members mostly show high sensitivity towards Imepenem which is similar to the study done by Duggal Swati et al(8) and Chauhan M et al.Patients with Acinetobacter strains had shown high sensitivity towards Piperacillin/Tazobactam as found by other authors like RaoRaghav et al. (12)



The result of the above study exemplify there  is an increasing need for gaining knowledge about the pattern of microbes and their antibiotic sensitivity  and resistance, which varies in a geographical manner.The isolates from this study showed that Staphylococcus aureus was the most isolated organisms from the pus culture report followed by Klebsiella,Pseudomonas, Proteus, Citrobacter, E.coli and Acinetobacter.. In Staphylococcus  aureusVancomycin showed highest sensitivity followed by Enterobacterecia showed highest sensitivity toImepenem , Levofloxacin.Nonfermenter like pseudomonas and Acinetobacter also showed highest sensitivity toPiperacillin/Tazobactam.Knowledgeof causative agents of pyogenic infection and their antibiotic sensitivity pattern is very essential for the judicial administration of empirical therapy before culture result are available. Antibiotic sensitivity of microorganism varies from place to place and time to time, hence regular monitoring of bacterial sensitivity to antibiotics is essential. However there is a scope for further study of microorganism in  other clinical specimen also to know their antibiotic sensitivity will invariably add to the knowledge of our microbiologist and clinician.


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