The antibiogram gives the periodic summary of antimicrobial susceptibilities of local bacterial isolates submitted to the hospitals microbiology laboratory. Antibiogram can be of great use in assessing the local susceptibility rates and can serve as a tool in designing the empirical antibiotic therapy and also in monitoring the resistance trends over time within in an institution. Pus samples from various clinical conditions like abscess, cellulitis, necrotizing fasciitis, wound infections; diabetic foot ulcers were included in the study. A total of 1124 positive cultures were obtained out of which 736 yielded various Gram negative organisms and 488 were Gram positive organisms. Only Gram negative organisms were considered in the study as gram negative organisms are common etiological agents of skin and soft tissue infections and pose a great challenge to the treating physician as they are known to develop a high antimicrobial resistance. The organisms isolated in our hospital were Pseudomonas aeruginosa (192), Klebsiella pneumonia (173), Escherichia coli (168), Citrobacter species (117), Acinetobacter species (47), and Proteus species (39). In our study which aims at formulating an empirical therapy for Gram negative organisms the drugs with highest sensitivity were Imipenem (51%), Amikacin (43%), Meropenem (38%), Tobramycin (36%), and Ciprofloxacin (34%) Gentamicin (34%), Netimicin (33%), Cotrimoxazole (32%), Piperacillin (28%),Tetracycline (28%), Ceftazidime (28%), Levofloxacin (26%), Ceftriaxone (26%), Colistin (22%), Carbenecillin (21%), Cefoperazone (21%), Cefoperazone +Sulbactum (21%), Azonetrem (21%), Cefipime (20%), Cefuroxime (17%), Cephaxlein (15%), Ampicillin (12%), Amoxyclav (10%). With the knowledge of most commonly isolated organisms causing SSTIs and their antimicrobial susceptibility patterns the clinicians can start the most likely antibiotic and can change accordingly once the sensitivity report is available.
Resistance, Antibiogram, Empirical therapy, Pseudomonas aeruginosa, Klebsiella pneumonia
Antimicrobial resistance is a global challenge. Survival of the fittest strategy by acquisition of resistant genes like any other living being has been used by bacteria. This can be slowed down by reducing the selective pressure on bacteria causing infectious diseases1.
The antibiogram gives the periodic summary of antimicrobial susceptibilities of local bacterial isolates submitted to the hospitals microbiology laboratory. Antibiogram can be of great use in assessing the local susceptibility rates and can serve as a tool in designing the empirical antibiotic therapy and also in monitoring the resistance trends over time within in an institution2.
Antimicrobial resistance (AMR) in Gram negative bacteria (GNB) has been a significant cause of severe infections across the world, with increasing morbidity and mortality rates, prolonged hospitalization, significant increase in the cost of medical care and also increased rates of hospital acquired infections3.
Skin and Soft tissue infections involve the microbial invasion of the skin and underlying tissues and range from mild infections such as pyoderma to serious life threatening infections such as necrotizing fasciitis4.
The risk factors may be patient related to age more than 60 years, malnutrition, diabetes, immunosuppression, skin colonization with Methicillin Resistant Staphylococcus aureus (MRSA), presence of skin diseases, smoking and obesity. Procedure related risk factors like improper surgical scrub, inadequate skin antisepsis, prolonged operative time, inadequate antimicrobial prophylaxis, poor perioperative glycemic control surgical drains, inadequate disinfection and sterilization, emergency procedure and perioperative shaving 5.
There is a significant variation in the resistance profile of the pathogenic bacteria across the world though AMR is rising globally. It is therefore necessary to monitor the rates of AMR in the clinically important pathogens across the world. The changing trends in resistance pattern over time have to be tracked regularly in order to guide the appropriate therapeutic strategies to combat infections due to drug‑resistant pathogens. Many large‑scale surveillance studies are being conducted to monitor AMR across the globe. Studies have reported that the burden of AMR is high in Asian countries. However, surveillance studies in India being negligible, incidence rates and real burden of AMR in India is underreported. The study for monitoring AMR trend is a global surveillance program intended to monitor the efficacy of antimicrobials against GNB.6.
Hence the purpose of this study is to determine the current antimicrobial sensitivity pattern of Gram negative bacteria causing skin and soft tissue infection and formulate a comprehensive empirical antibiotic approach for managing the patients with skin and soft tissue infections caused by Gram negative organisms.
The study was carried out in the department of Microbiology (BLDE (DU) Shri B M Patil Medical College Hospital & Research Centre Vijaypur Karnataka India) from January 2019 to December 2019. All the cultures yielding Gram negative organisms were included in the study. Patients of both the sexes irrespective of age group admitted in the Department of General Surgery, Orthopedics, and Obstetrics for skin and soft tissue infections were included in the study.
Pus samples from various clinical conditions like abscess, cellulites, necrotizing fasciitis, wound infections; diabetic foot ulcers were included in the study. A total of 1124 positive cultures were obtained out of which 736 yielded various Gram negative organisms and 488 were Grampositive organisms.
The lesions were cleaned with sterile normal saline. Special care was taken to avoid contamination by normal flora of skin or mucus surface, where possible pus was aspirated or exudates collected. The specimens were transported in sterile, leak-proof containers. Pus samples were also collected aseptically using sterile swabs.
Swabs were inoculated on to Blood agar and Mac-Conkey’s agar plate. The plates were incubated aerobically at 37°C overnight. The isolates were identified by Gram staining, Colony morphology, Standard biochemical tests like Oxidase, Catalase, Indole, Methyl red, Vogues Proskauer test and Hydrogen sulphide production test.
The antimicrobial susceptibility testing was performed by modifiedKirby-Bauer disc diffusion technique following clinical and laboratory standards institute guidelines7.
The antibiotics tested were Ampicillin Amoxyclav, Cefuroxime, Tetracycline, Gentamicin, Cotrimoxazole, Ciprofloxacin, Cephalexin, Amikacin, Lomefloxacin, Netimicin, Tobramicin, Piperacillin, Ceftriaxone, Ceftazidime, Imipenem, Meropenem, Levofloxacin, Cefepime, Azonetrem, Cefoperazone +Sulbactum, Cefoperazone, Carbenecillin, Colistin. Antibiotics from all classes were selected.
A total of 1124 cultures yielded growth, out of which 736 were various Gram negative organisms and 488 were Gram positive organisms. Gram negative organisms were considered for the study. All the isolates were identified by the Gram Stain and biochemical reactions.
Out of 736 organisms isolated, 192 were Pseudomonas aeruginosa, 173 were Klebsiella pneumonia, 168 were Escherichia coli, 117 were Citrobacter species, 47 were Acinetobacter species, and 39 were Proteus species(Table No 1).
Bacteriological profile of Pus Samples.
|Sr. No.||Gram negative isolates||No of Isolates|
The antibiotics tested were Ampicillin Amoxyclav, Cefuroxime, Tetracycline, Gentamicin, Cotrimoxazole, Ciprofloxacin, Cephalexin, Amikacin, Lomefloxacin, Netilmicin, Tobramicin, Piperacillin, Ceftriazone, Ceftazidime, Imipenem, Meropenem, Levofloxacin, Cefipime, Azonetrem, Cefoperazone+Sulbactum, Cefoperazone, Carbenecillin, Colistin. Table 2 shows the sensitivity pattern of all the gram negative organisms.
Sensitivity Pattern of Gram Negative Bacteria.
|E. coli (N= 168) %||Acinetobacter Spp (N= 47) %||Klebsiella Spp (N= 173) %||Pseudomonas aeruginosa (N= 192) %||Citrobacter Spp
(N= 117) %
Table 3 shows the total sensitivity of all the antibiotics used in the treatment of Gram Negative Bacteria in decreasing order. Imipenem (51%), Amikacin (43%), Meropenem(38%), Tobramycin (36%), Ciprofloxacin (34%), Gentamicin (34%), Netilmicin(33%), Lomefloxacin (32%), Cotrimaxazole (28%), Piperacillin (28%), Tetracycline (28%), Ceftazidime (28%),Levofloxacin (26%), Ceftriaxone (26%), Colistin(22%), Carbenecillin (21%), Cefoperazone (21%), Cefoperazone + Sulbactum (21%), Azonetrem (21%),Cefipime (20%), Cefuroxime (17%), Cephalexin(15%), Ampicillin (12%), Amoxyclav (10%).
Total Sensitivity of all the Antibiotics used in the treatment of Gram Negative Bacteria in decreasing order.
Drugs used as Empirical therapy.
The organisms isolated in our hospital BLDE (DU) Shri B M Patil Medical College Hospital & Research Centre Vijaypur Karnataka India were Pseudomonas aeruginosa (192), Klebsiella pneumonia (173), Escherichia coli (168), Citrobacter species (117), Acinetobacter species (47), and Proteus species (39) (Table No 1).
Our study which aims at formulating an empirical therapy for Gram negative organisms the drugs with highest sensitivity were Imipenem (51%), Amikacin (43%), Meropenem (38%), Tobramycin (36%), and Ciprofloxacin (34%) Gentamicin (34%), Netimicin (33%), Cotrimoxazole (32%), Piperacillin (28%), Tetracycline (28%), Ceftazidime (28%), Levofloxacin (26%), Ceftriaxone (26%), Colistin (22%), Carbenecillin (21%), Cefoperazone(21%), Cefoperazone + Sulbactum (21%), Azonetrem (21%), Cefipime (20%), Cefuroxime (17%), Cephaxlein(15%), Ampicillin (12%), Amoxyclav (10%) (Table No 3)
Gram negative organisms recovered from Skin & Soft tissue infections among patients were more susceptible to Carbapenems (Imipenem, Meropenem), Aminoglycosides (Amikacin, Tobramycin, Gentamicin) followed by Ciprofloacin and Cotrimoxazole, Piperacillin, 3rd generation Cephalosporins (Ceftazidime, Ceftriaxone, Cefotaxime); Colistin, Carbenecillin 4th Generation Cephalosporins (Cefepime), β lactam/ β-lactamase inhibitor combinations (Cefoperazone-Sulbactaum).
After discussing with the clinicians mainly surgeons a list of first line of drugs was drawn Aminoglycosides (Amikacin, Gentamicin, Tobramicin and Netimicin) which are injectables were given the first priority followed by the 3rd generation Cephalosporins (Ceftazidime, Ceftriaxone, Cefotaxime) then by the 4th generation Cephalosporins (Cefepime) which are available orally also then by b-lactam/ β-lactamase inhibitor combinations (Cefoperazone-Sulbactam) then by the Colistin and keeping the Carbapenems (Imipenem and Meropenem) as reserved drugs both in terms of efficiency and cost though they have highest sensitivity. So list of drugs used as Empirical therapy in the treatment of Gram negative infections is as follows:
Hospital antibiogram can be a guiding tool for empirical therapy and can also track the emergence of resistance among the bacterial isolates in the nosocomial environment. There can be a wide variation in the manner in which the antibiograms are formulated and reported which results in intra and inter hospital comparisons8.
Though the treatment may be dependent on the culture, empirical therapy is necessary and should be designed so that it can cover the both Gram positive and Gram negative organisms till the culture report is available. Surveillance of the antibiotic sensitivity should be done on regular basis as the pathogens and their sensitivity keep on changing and also vary from unit to unit, hospital to hospital9,10.
It is very much essential that all the clinicians should understand the importance of antibiotic susceptibility testing. Always there has to be mutual sharing of expertise, cooperation and collaboration between the clinicians and microbiologist so that there can be optimum and appropriate use of antibiotics in the management of infectious diseases. Though many studies of regional antibiogram have been reported from India, there is a need for nationwide statics to be generated and made available to the clinicians11. An ICMR guideline 2019 for the use of antimicrobials is already available for guiding the empirical therapy but the local antibiogram of the hospital will give exact sensitivity pattern which can have a day to day application.
But again it is the treating physician/surgeons decision to choose the class of antibiotic as the antibiotic policy has many limitations and also the patient factor needs to be considered including the type and severity of infection, the infecting organism, past antibiotic history.
Bacterial antimicrobial resistance is a great challenge to the medical community and also to the patients in terms of increase in morbidity, mortality and economic burden. Political involvementie the health ministry has to come forward with strict implementation of national antibiotic policies with the cooperation of private corporate setups.
Clinician should not be pressurized to write an antibiotic on patient’s demand of early recovery; this will be possible only when the patient is aware of the judicious use of antibiotics which can be achieved through public education or campaigns just like other national health education programs12.
It is quite essential to define an antimicrobial stewardship program as an ongoing effort by an health care institution to optimize the antimicrobial use among hospitalized patients to improve patient outcomes, ensure cost effective therapy and reduce adverse squeal of antimicrobial use11.
The most commonly isolated gram negative organisms from the skin and soft tissue infections are Pseudomonas aeruginosa, Klebsiella pneumonia,Escherichia coli, Citrobacter species, and Acinetobacter species. The empirical therapy for the infections caused by these organisms are Aminoglycosides(Amikacin, Gentamicin, Tobramicin and Netimicin), 3rd generation Cephalosporins (Ceftazidime, Ceftriaxone, Cefotaxime),4th generation Cephalosporins (Cefepime), b-lactam/ b-lactamase inhibitor combinations (Cefoperazone-Sulbactam),Colistin and keeping the Carbapenems(Imipenem and Meropenem) as reserved drugs both in terms of efficiency and cost though they have highest sensitivity.
CONFLICT OF INTEREST
The authors declare that there is no conflict of interest.
All authors listed have made a substantial, direct and intellectual contribution tothe work, and approved it for publication.
AVAILABILITY OF DATA
All data generated or analysed during this study are included in the manuscript.
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