PHARMA SCIENCE MONITOR

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1 PHARMA SCIENCE MONITOR AN INTERNATIONAL JOURNAL OF PHARMACEUTICAL SCIENCES STUDIED ON IN-VITRO SENSITIVITY AND RESISTANCE PATTERN OF LISTERIA SPP. FROM RAW MEAT AGAINST ANTIBACTERIAL DRUGS JB Nayak*, MN Brahmbhatt and KA Sadariya Department of Veterinary Public Health, College of Veterinary Science and Animal Husbandry, Anand Agricultural University, Anand, Gujarat (INDIA). ABSTRACT The present study was carried out with a view to isolate and identifies Listeria spp. from different samples of buffalo meat, chevon and mutton sold in retail market as well as from butcher s hand and their instruments in Anand city. The antimicrobial drug sensitivity and resistance pattern of Listeria spp. to various antibiotics commonly used in human and veterinary treatment were carried out. In vitro antibiotic sensitivity test of 27 isolates was conducted against fifteen different antimicrobial drugs. The highest degree of sensitivity of Listeria isolates was observed towards gentamicin (96.3%) followed by ampicillin and ciprofloxacin (92.6% each); tetracycline and erythromycin (88.9% each); chloramphenicol and penicillin G (85.2% each) while isolates were resistant to ceftriaxone (81.5%) and cefotaxime (70.4 %). The antibiogram of L. monocytogenes isolates showed cent percent sensitivity to penicillin G followed by ampicillin, chloramphenicol, ciprofloxacin, tetracycline (92.3% each), erythromycin (84.7%), gentamicin, rifampicin (76.9%), where as the maximum resistance was recorded against ceftriaxone, cefotaxime and ceftazidime. Keywords: Listeria spp., antibiogram, In-vitro antibiotic sensitivity, raw meat. INTRODUCTION Listeria spp. has emerged as an important food-borne pathogen during last decade, causing several outbreaks and sporadic cases of food borne listeriosis in human beings. The first outbreak of food-borne listeriosis was reported from the Maritime Province of Canada in 1981 due to Coleslaw consumption. [1] The major outbreaks of listeriosis have been associated with consumption of foods of animal origin. [2] A number of reports have indicated the occurrence of the organism in various meat and meat products with overall incidence rate varying from 0 to 92.0 per cent. [1] Listeriosis is one of the important food-borne bacterial zoonotic infection worldwide caused by Listeria spp. Among the different species, L. monocytogens is known to cause listeriosis in humans and in more than 40 species of animal and 22 species of birds. [3] IC Value

2 The genus Listeria consists of a group of gram-positive bacteria of low G+C content. They are facultative anaerobic rods of 0.4 x 1 to 1.5 µm size that do not form spores, have no capsule, show characteristic tumbling motility by peritrichous flagella in a narrow temperature range between 20 0 C to 25 C. They are catalase positive and oxidase negative. The genus Listeria currently has six species viz L. grayi, L. innocua, L. ivanovii L. monocytogenes, L. seeligeri, and L. welshimeri. Listeria species are isolated from a diversity of environmental sources, including soil, water, effluents, a large variety of foods and the feces of humans and animals. [4] In India, listeriosis was first time reported as circling disease in sheep in Hyderabad state. Ubiquitous spread of listeria organism coupled with its ability to survive under adverse environmental conditions and various stages of food production, processing and storage makes the presence of the organism as a part of microbial ecosystem in food chain almost unavoidable. [5] Due to increasing reports of outbreaks associated with different raw meat required the monitoring and surveillance of Listeria species by using rapid and reliable methods. Therefore, keeping in view the above facts, magnitude of the problems and gap of knowledge regarding these aspects, the present study is aimed to undertake the lacking part with objective to determine antibiotic sensitivity pattern of Listeria organisms from raw meat to various antibiotics. MATERIALS AND METHODS The antibiotic susceptibility tests were performed as per method described by Bauer et al., (1966) to find out the antibiotic resistance pattern of all Listeria isolates. [6] In vitro antibiotic sensitivity test of the isolates was conducted by paper disc diffusion method using fifteen types of antibiotic viz. Ampicillin, Cefotaxime, Ceftazidime, Ceftriaxone, Chloramphenicol, Ciprofloxacin, Clindamycin, Erythromycin, Gentamicin, Penicillin-G, Rifampicin, Streptomycin, Tetracycline, Trimethoprim and Vancomycin (Table-1) supplied by HiMedia Laboratories Pvt. Ltd., Mumbai (India). Sensitivity and resistant of individual isolate to various drugs was interpreted on the size of the inhibition zones around the disc according to the manufacturer s instructions. Listeria isolates were grown in Brain Heart Infusion (BHI) broth (HiMedia) for hours. The grown cultures were swabbed on Muller-Hinton agar plates No.2 (HiMedia) using sterile cotton swabs and left for 30 minutes for pre-diffusion time. Then IC Value

3 using an ethanol dipped and flamed forcep different antibiotic discs were placed on the agar surface at about two cm apart. The discs were slightly pressed with the forcep to make complete contact with the medium. The plates were incubated at 37 o C for hours. After the incubation period, the diameter of inhibition zones were measured and compared with interpretative chart provided by the manufacturer and zones were graded as sensitive, intermediate and resistant. TABLE 1: ANTIMICROBIAL DISCS USED, THEIR SYMBOLS AND CONCENTRATIONS Sr. No. Antimicrobial discs Symbol Concentration (mcg) 1 Ampicillin A 25 2 Cephotaxime Ce 10 3 Ceftazidime CA 5 4 Ceftriaxone Ci 10 5 Chloramphenicol C 30 6 Ciprofloxacin Cf 10 7 Clindamycin Cd 10 8 Erythromycin E 10 9 Gentamicin G Penicillin-G P Rifampicin R Streptomycin S Tetracycline T Trimethoprim Tr Vancomycin Va 30 RESULTS The antibiotic susceptibility tests of 27 Listeria isolates were performed by agar disc diffusion method to find out the antibiotic resistance pattern using fifteen different antibiotic discs viz. Ampicillin, Cefotaxime, Ceftazidime, Ceftriaxone, Chloramphenicol, Ciprofloxacin, Clindamycin, Erythromycin, Gentamicin, Penicillin-G, Rifampicin, Streptomycin, Tetracycline, Trimethoprim and Vancomycin. Sensitivity and resistance of individual isolate to various drugs was interpreted on the size of the inhibition zones around the disc according to the manufacturer s instructions by comparing with IC Value

4 interpretative chart and zones were graded as sensitive, intermediate and resistant (Table- 2). The overall antibiotic sensitivity pattern of listeria isolates towards fifteen antimicrobial agents is shown in Table-3. In the present study, listeria isolates were found variably resistant to the antibiotics tested. The pattern clearly indicates that the over all high percent of isolates were resistant to ceftriaxone (81.5%) followed by cefotaxime (70.4%) while moderately high per cent of isolates were resistant to clindamycin and Ceftazidime (48.2% each), trimethoprim (40.7%) and rifampicin (22.2%). Lesser percent of isolates were found resistant to vancomycin (14.8%), tetracycline and chloramphenicol (7.4% each) while, least number of resistant isolates were found against gentamicin and penicillin G (3.7% each) (Table-3) Highest degree of overall sensitivity was observed towards gentamicin (96.3%) followed by ampicillin and ciprofloxacin (92.6% each); tetracycline and erythromycin (88.9% each); chloramphenicol and penicillin G (85.2% each); streptomycin (81.5%); Vancomycin (74.1%); rifampicin (62.9 %); trimethoprim (33.3%); clindamycin and Ceftazidime (22.2 % each); cefotaxime (11.1%) and ceftriaxone (7.4%) (Table-3 and Fig. 1). IC Value

5 Sr no 1 TABLE 2: IN-VITRO ANTIBIOTIC SENSITIVITY RESULTS OF THE LISTERIA ISOLATES Sample Isolate no Species identified Antibiotic sensitivity A Ce CA Ci C Cf Cd E G P R S T Tr Va B3 L. innocua S R I R S S R S S S S S S I S 2 B12 L. monocytogenes S R R S S S I S I S S S S R I 3 B37 L. innocua S R R I S S R S S I I S R R S 4 B54 L. seeligeri S S S R I S R I S S S I S S S 5 Buffalo meat B87 L. welshimeri S R I R S S I S S I R S S I S 6 B89 L. monocytogenes S R R R S S S S S S S S S I R 7 B95 L. monocytogenes S R R R R S I S S S R S S S I 8 B99 L. seeligeri S R R R S S R S S S S S S R S 9 B115 L. seeligeri S R I R S S S S S S S S S R I 10 B132 L. monocytogenes S R S I S S I S I S S S S S S 11 M4 L. monocytogenes S I R R S I R S S S S I S R S 12 M11 L. monocytogenes I R I R S S S S S S S I S R S 13 M29 L. innocua S R S R I S R S S S I S S I S 14 M39 L. seeligeri S S R R S S I S S S R S S S R 15 Mutton M53 L. monocytogenes S I R R S S S S S S S S R S S 16 M63 L. innocua S R S S S S R S I I S S S R S 17 M87 L. monocytogenes S R R R S S R I S S I S S I R 18 M104 L. monocytogenes S I I R S S R S S S S I S R S 19 M111 L. innocua S R R R S I I S S S S S S S S 20 M135 L. seeligeri S I S I S S R S S S I S S I S 21 M141 L. monocytogenes S R R R R S S S R S S S S R S 22 C11 L. welshimeri S S I R S S I S S S R S I S S 23 Chevon C21 L. monocytogenes S R R R S S R S S S S S S I S 24 C54 L. innocua I R R R S S S S S S S S S R R 25 C127 L. monocytogenes S R S R S S I S S S S I S R S 26 Hand swab HS4 L. monocytogenes S I I R S S R I S S R S S S I 27 Knife swab KS13 L. innocua S R I R S S R S S R R S S S S S = Sensitive, R= resistance and I= Intermediate IC Value

6 TABLE 3: OVERALL SENSITIVITY OF LISTERIA ISOLATES TO ANTIMICROBIAL AGENTS Sr. No. Name of the antibiotic Sensitive Intermediate Resistant 1 Ampicillin (A) 25 (92.6%) 2(7.4%) 0 2 Cefotaxime (Ce) 3 (11.1 %) 5(18.5 %) 19(70.4 %) 3 Ceftazidime(CA) 6 (22.2 %) 8(29.6 %) 13(48.2 %) 4 Ceftriaxone (Ci) 2 (7.4 %) 3(11.1 %) 22(81.5 %) 5 Chloramphenicol (C) 23 (85.2 %) 2(7.4 %) 2(7.4 %) 6 Ciprofloxacin (Cf) 25 (92.6 %) 2(7.4 %) 0 7 Clindamycin (Cd) 6 (22.2 %) 8(29.6 %) 13(48.2 %) 8 Erythromycin (E) 24 (88.9 %) 3(11.1 %) 0 9 Gentamicin (G) 26 (96.3 %) 0 1(3.7 %) 10 Penicillin-G (P) 23 (85.2 %) 3(11.1 %) 1(3.7 %) 11 Rifampicin (R) 17 (62.9 %) 4(14.8 %) 6(22.2 %) 12 Streptomycin (S) 22 (81.5 %) 5(18.5 %) 0 13 Tetracycline (T) 24 (88.9 %) 1(3.7 %) 2(7.4 %) 14 Trimethoprim (Tr) 9 (33.3 %) 7(25.9 %) 11(40.7 %) 15 Vancomycin (Va) 20 (74.1%) 3(11.1 %) 4(14.8 %) Figure 1 Antibiogram of Listeria spp. from different samples. The overall sensitivity pattern of L. monocytogenes isolates shows cent percent sensitivity to penicillin G followed by ampicillin, chloramphenicol, ciprofloxacin, tetracycline, Erythromycin, Gentamicin, Rifampicin, Streptomycin Vancomycin IC Value

7 Trimethoprim where as the maximum resistance was recorded against Ceftriaxone, Cefotaxime and Ceftazidime (Table-4). The antibiogram of L. monocytogenes isolates from buffalo meat shows complete sensitivity towards ampicillin, chloramphenicol, ciporofloxacin, erythromycin, streptomycin and tetracycline followed by rifampicin, gentamicin and trimethoprim, with complete resistant to cefotaxime followed by ceftazidime and ceftriaxone (Table-5). However, antibiogram of L. monocytogenes isolated from mutton were cent percent sensitive to only penicillin G followed by ampicillin, chloramphenicol, ciprofloxacin, erythromycin, gentamicin, rifampicin, tetracycline, vancomycin and trimethoprim while the highest degree of resistance to ceftriaxone (100.0%), Ceftazidime (66.7%) and clindamycin (50.0%) (Table-6). The study reports that L.monocytogenes isolates from chevon were completely sensitive to ampicillin, chloramphenicol, ciprofloxacin, erythromycin, gentamicin, penicillin G, rifampicin, tetracycline and vancomicin and completely resistant towards cefotaxime and ceftriaxone (Table-7). The antibiogram of L. monocytogenes isolated from hand swab revealed complete sensitivity towards ampicillin, chloramphenicol, ciprofloxacin, gentamicin, penicillin G, streptomycin, trimethoprim, tetracycline, where as completely resistant to ceftriaxone, clindamycin and rifampicin (Table-8). The overall sensitive pattern of L. innocua isolates revealed maximum sensitivity for ampicillin, chloramphinicol, ciprofloxacin, gentamicin, streptomycin, tetracyclin followed by erythromycin, penicillin G and refampicin while all isolates were resistant to cefotaxime followed by clindamycin, ceftriaxone, ceftazidime and trimethoprim (Table- 4). All L. innocua isolates from buffalo meat were cent percent sensitive towards ampicillin, chloramphenicol, ciprofloxacin, erythromycin, gentamicin, streptomicin and vancomicin where as isolates were completely resistant to cefotaxime and clindamicin (Table-5). IC Value

8 TABLE 4: ANTIBIOGRAM OF DIFFERENT LISTERIA SPP. Sr.No. Antimicrobial discs L.monocytogenes (n=13) L.innocua (n=7) L.seeligeri (n=5) L.welshimeri (n=2) S (%) R (%) S (%) R (%) S (%) R (%) S (%) R (%) 1 Ampicillin 12(92.3) 0 6(85.7) 0 3(60.0) 0 2(100) 2 Cefotaxime 0 9(69.2) 0 7(100.0) 2(40.0) 2(40.0) 1(50.0) 1(50.0) 3 Ceftazidime 2(15.4) 8(61.5) 2(28.6) 3(42.9) 2(40.0) 2(40.0) Ceftriaxone 1(7.7) 11(84.6) 1(14.3) 5(71.4) 0 4(80.0) 0 2(100.0) 5 Chloramphenicol 12(92.3) 1(7.7) 6(85.7) 0 4(80.0) 0 2(100.0) 0 6 Ciprofloxacin 12(92.3) 0 6(85.7) 0 5(100.0) 0 2(100.0) 0 7 Clindamycin 4(30.87) 5(38.4) 1(14.3) 5(71.4) 1(20.0) 3(60.0) Erythromycin 11(84.6) 0 4(57.1) 0 4(80.0) 0 2(100.0) 0 9 Gentamicin 10(76.9) 0 6(85.7) 0 5(100.0) 0 2(100.0) 0 10 Penicillin-G 13(100.0) 0 4(57.1) 1(14.3) 5(100.0) 0 1(50.0) 0 11 Rifampicin 10(76.9) 2(15.4) 4(57.1) 1(14.3) 3(60.0) 1(20.0) 0 2(100.0) 12 Streptomycin 9(69.2) 0 6(85.71) 0 4(80.00) 0 2(100) 0 13 Tetracycline 12(92.3) 1(7.69) 6(85.71) 1(14.29) 5(100) 0 1(50.00) 0 14 Trimethoprim 7(53.9) 3(23.08) 2(28.57) 3(42.86) 2(40.00) 2(40.00) 1(50.00) 0 15 Vancomycin 8(61.5) 2(15.38) 6(85.71) 1(14.29) 2(40.00) 2(40.00) 2(100) 0 IC Value

9 TABLE 5: ANTIBIOGRAM OF DIFFERENT LISTERIA SPP. FROM BUFFALO MEAT Sr.No. Antimicrobial discs L.monocytogenes (n=4) L.innocua (n=2) L.seeligeri (n=3) L.welshimeri (n=1) S(%) R(%) S(%) R(%) S(%) R(%) S(%) R(%) 1 Ampicillin 4(100.0) 0 2(100) 0 1(33.33) 0 1(100) 0 2 Cefotaxime 0 4(100.0) 0 2(100.0) 1(33.3) 2(66.7) 0 1(100.0) 3 Ceftazidime 1(25.0) 3(75.0) 0 1(50.0) 1(33.3) 1(33.3) Ceftriaxone 1(25.0) 2(50.0) 0 1(50.0) 0 3(100.0) 0 1(100.0) 5 Chloramphenicol 4(100.0) 0 2(100) 0 2(66.7) 0 1(100.0) 0 6 Ciprofloxacin 4(100.0) 0 2(100) 0 3(100.0) 0 1(100.0) 0 7 Clindamycin 1(25.0) 0 0 2(100.0) 1(33.3) 2(66.7) Erythromycin 4(100.0) 0 2(100) 0 2(66.7) 0 1(100.0) 0 9 Gentamicin 2(50.0) 0 2(100) 0 3(100.0) 0 1(100.0) 0 10 Penicillin-G 4(100.0) 0 1(50.00) 0 3(100.0) Rifampicin 3(75.0) 1(25.0) 1(50.00) 0 3(100.0) 0 0 1(100) 12 Streptomycin 4(100.0) 0 2(100) 0 2(66.7) 0 1(100.0) 0 13 Tetracycline 4(100.0) 0 1(50.00) 1(50.0) 3(100.0) 0 1(100.0) 0 14 Trimethoprim 2(50.0) 1(25.0) 0 1(50.0) 1(33.3) 2(66.7) Vancomycin 1(25.0) 1(25.0) 2(100) 0 1(33.3) 11(33.3) 1(100.0) 0 TABLE 6: ANTIBIOGRAM OF DIFFERENT LISTERIA SPP. FROM MUTTON Sr.No. Antimicrobial discs L. monocytogenes (n=6) L. innocua (n=3) L. seeligeri (n=2) S(%) R(%) S(%) R(%) S(%) R(%) 1 Ampicillin 5(83.3) 0 3(100.0) 0 2(100.0) 0 2 Cefotaxime 0 3(50.0) 0 3(100.0) 1(50.0) 0 3 Ceftazidime 0 44(66.7) 2(66.7) 1(33.3) 1(50.0) 1(50.0) 4 Ceftriaxone 0 6(100.0) 1(33.3) 2(66.7) 0 1(50.0) 5 Chloramphenicol 5(83.3) 1(16.7) 2(66.7) 0 2(100.0) 0 6 Ciprofloxacin 5(83.3) 0 2(66.7) 0 2(100.0) 0 7 Clindamycin 3(50.0) 3(50.0) 0 2(66.7) 0 1(50.0) 8 Erythromycin 5(83.3) (100.0) 0 9 Gentamicin 5(83.3) 0 2(66.7) 0 2(100.0) 0 10 Penicillin-G 6(100.0) 0 2(66.7) 0 2(100.0) 0 11 Rifampicin 5(83.3) 0 2(66.7) 0 0 1(50.0) 12 Streptomycin 3(50.0) 0 2(66.7) 0 2(100.0) 0 13 Tetracycline 5(83.3) 1(16.7) 3(100.0) 0 2(100.0) 0 14 Trimethoprim 4(66.7) 1(16.7) 1(33.3) 1(33.3) 1(50.0) 0 15 Vancomycin 5(83.3) 1(16.7) 3(100.0) 0 1(50.0) 1(50.0) IC Value

10 TABLE 7: ANTIBIOGRAM OF DIFFERENT LISTERIA SPP. FROM CHEVON Sr.No Antimicrobial discs L.monocytogenes (n=2) L.innocua (n=1) L.welshimeri (n=1) S(%) R(%) S(%) R(%) S(%) R(%) 1 Ampicillin 2(100.0) (100.0) 0 2 Cefotaxime 0 2(100.0) 0 1(100) 1(100.0) 0 3 Ceftazidime 1(50.0) 1(50.0) 0 1(100) Ceftriaxone 0 2(100.0) 0 1(100) 0 1(100.0) 5 Chloramphenicol 2(100.0) 0 1(100.0) 0 1(100.0) 0 6 Ciprofloxacin 2(100.0) 0 1(100.0) 0 1(100.0) 0 7 Clindamycin 0 1(50.0) 1(100.0) Erythromycin 2(100.0) 0 1(100.0) 0 1(100.0) 0 9 Gentamicin 2(100.0) 0 1(100.0) 0 1(100.0) 0 10 Penicillin-G 2(100.0) 0 1(100.0) 0 1(100.0) 0 11 Rifampicin 2(100.0) 0 1(100.0) 0 0 1(100.0) 12 Streptomycin 1 (50.0) 0 1(100.0) 0 1(100.0) 0 13 Tetracycline 2(100.0) 0 1(100.0) Trimethoprim 0 1(50.0) 0 1(100.0) 1(100.0) 0 15 Vancomycin 2(100.0) 0 0 1(100.0) 1(100.0) 0 TABLE 8: ANTIBIOGRAM OF DIFFERENT LISTERIA SPP. FROM SWAB Sr.No. Antimicrobial discs L.monocytogenes (n=1) L.innocua (n=1) S(%) R(%) S(%) R(%) 1 Ampicillin 1(100.0) 0 1(100) 0 2 Cefotaxime (100.0) 3 Ceftazidime Ceftriaxone 0 1(100.0) 0 1(100.0) 5 Chloramphenicol 1(100.0) 0 1(100.0) 0 6 Ciprofloxacin 1(100.0) 0 1(100.0) 0 7 Clindamycin 0 1(100.0) 0 1(100.0) 8 Erythromycin 0 0 1(100.0) 0 9 Gentamicin 1(100.0) 0 1(100.0) 0 10 Penicillin-G 1(100.0) 0 0 1(100.0) 11 Rifampicin 0 1(100.0) 0 1(100.0) 12 Streptomycin 1(100.0) 0 1(100.0) 0 13 Tetracycline 1(100.0) 0 1(100.0) 0 14 Trimethoprim 1(100.0) 0 1(100.0) 0 15 Vancomycin 0 0 1(100.0) 0 DISCUSSION Listeria spp. were known for uniform susceptibility to various antibiotics used against gram positive bacteria such as ampicillin or penicillin and/or combined with aminoglycoside such as gentamicin, streptomycin, erythromycin etc. Antimicrobial IC Value

11 resistance in the food borne pathogen Listeria is emerging in recent years. Studies have shown that several species of Listeria isolated from humans or from food production or processing facilities are resistant to one or more antibiotics. The Resistance pattern of L. monocytogenes and other Listeria spp. isolated from raw meat sample to 15 antibotics (Ampicillin, Cefotaxime, Ceftazidime, Ceftriaxone, Chloramphenicol, Ciprofloxacin, Clindamycin, Erythromycin, Gentamicin, Penicillin-G, Rifampicin, Streptomycin, Tetracycline, Trimethoprim and Vancomycin) is studied by disc diffusion method (Table-1). In the present study, Listeria isolates were found variably resistant to the antibiotics tested. The pattern clearly indicates that the over all high percent of isolates were resistant to ceftriaxone (81.5%) followed by cefotaxime (70.4%) while moderately high per cent of isolates were resistant to ceftazidime and clindamycin (48.1% each), trimethoprim (40.7%) and rifampicin (22.2%). Lesser percent of isolates were resistant to vancomycin (14.8%), tetracycline and chloramphenicol (7.4% each) while least number of resistant isolates was found against gentamicin and penicillin G (3.7% each). Highest degree of sensitivity was observed towards gentamicin (96.3%) followed by ampicillin and ciprofloxacin (92.6% each); tetracycline and erythromycin (88.9% each); chloramphenicol and penicillin G (85.2% each); streptomycin (81.5%); Vancomycin (74.1%); rifampicin (62.9%); trimethoprim (33.3%); clindamycin and ceftazidime (22.2% each); cefotaxime (11.1%) and ceftriaxone (7.0%) (Table-3). The over all sensitivity pattern of L. monocytogenes isolates shows cent percent sensitivity to penicillin G followed by ampicillin, chloramphenicol, ciprofloxacin tetracycline, Erythromycin, Gentamicin, Rifampicin, Streptomycin Vancomycin Trimethoprim where as the maximum resistance was recorded against Ceftriaxone, Cefotaxime and Ceftazidime (Table-4). In present study, over all 92.6 per cent of listeria isolates found sensitive to ampicillin, while 92.3 per cent, 85.7 per cent, 60.0 per cent and per cent isolates of L. monocytogenes, L. innocua, L. seeligeri and L. welshmeri were found sensitive to ampicillin. The overall sensitivity pattern of L. monocytogenes to ampicillin are in agreement with reports of previous workers. [7,8,9] However, in contrast Njagi et al., (2004) reported per cent resistance of L. monocytogenes and Rota et al., (1996) and Conter IC Value

12 et al., (2007) recorded strains resistant to ampicillin. [10,11,12] The resistance pattern (48.1%) for ceftazidime of Listeria spp. in the present study can be compared with observations of Rodas-Suarez et al., (2006). [13] L. monocytogenes, L. innocua and L. seeligeri isolates revealed 61.5 per cent, 42.9 per cent and 40.0 per cent resistance, respectively while high degree of resistance (100.0%) were observed in previous studies. [14,15,16] Listeria spp. isolates revealed higher degree of resistance (81.5%) to ceftrixone where as 84.5 per cent, 71.3 per cent, 80.0 per cent and per cent isolates of L. monocytogens, L. inocua, L. seeligeri and L.welshimeri were found resistant to ceftriaxone. The resistance pattern in this study is in accordance with Troxler et al., (2000) who stated per cent resistance of Listeria spp. to ceftriaxone. [15] Similarly, Steven et al., (2008) observed 97.0 per cent resistance of L. monocytogenes while, Davis et al., (2009) reported 72.0 per cent of L. monocytogenes, 75.0 per cent of L. innocua and none of the isolates of L. welshimeri found resistant to ceftriaxone. [17,18] The findings of the present study revealed that gentamicin is effective against most of the listeria isolates, which is in agreement with those of Abuin et al., (1994) and Franco et al., (1995) observed maximum sensitivity towards gentamicin. [19,20] However, Rota et al., (1996) and Rodas-Suarez et al., (2006) reported 27.8 per cent and 5.9 per cent resistance. [11,13] In our study, L. monocytogenes showed 76.9 per cent susceptibility against gentamicin, which is lower as compare to that of previous workers. [7,8,21,22] On the other hand Sharda et al., (1991) reported 33.3 per cent resistance of L. monocytogenes to gentamicin. [23] Abuin et al., (1994) recorded gentamicin was active against all tested strains of L. innocua and L. seeligeri where as in present study 85.7 per cent isolates of L. innocua and per cent isolates of L. seeligeri were sensitive to gentamicin however, Rodas-Suarez et al., (2006) reported 8.1 per cent isolates of L. innocua were resistant. [13,19] Overall antibiotic sensitivity pattern of the Listeria spp. in the present findings indicate the presence of multiple drug resistance among L. monocytogenes and other Listeria spp. is alarming evidence of the emergence of multi resistant Listeria strains, pointing to an increase in the potential threat to human health posed by this pathogen through the consumption of contaminated meat and meat products. Moreover, this study IC Value

13 confirms that major changes in the nature and incidence of antibiotic resistance among Listeria spp. have occurred within the last decade. CONCLUSIONS The highest degree of sensitivity of Listeria isolates was observed towards gentamicin (96.3%) followed by ampicillin and ciprofloxacin (92.6% each); tetracycline and erythromycin (88.9% each); chloramphenicol and penicillin G (85.2% each) while isolates were resistant to ceftriaxone (81.5%) and cefotaxime (70.4 %). The antibiogram of L. monocytogenes isolates showed cent percent sensitivity to penicillin G followed by ampicillin, chloramphenicol, ciprofloxacin, tetracycline (92.3% each), erythromycin (84.7%), gentamicin, rifampicin (76.9%), where as the maximum resistance was recorded against ceftriaxone, cefotaxime and ceftazidime. Moreover, the judicious selection of antibiotics/antimicrobial agents, preferably after in vitro antimicrobial drug sensitivity testing and using such agents at an adequate dose for sufficient duration for effective treatment for Listeria in this area. REFERENCES 1. Farber JM and Peterkin PI: Listeria monocytogenes, a foodborne pathogen. Microbiology Reviews 1991; 55: Zaito H, Purwati E, Radu S, Rahim RA and Rusul G: Prevalence of Listeria species and Listeria monocytogenes in meat and fermented fish in Malaysia. South East Asian Journal of Tropical Medicine and Public Health 2001; 32(2): Gray ML and Killinger AH: Listeria monocytogenes and Listeric Infections. Bacteriological Reviews 1966; 30(2): Vanquez-Boland JA, Kuhn M, Berche P, Chakraborty T, Dominguez-Bernal G, Goebel W, Gonzalez-Zorn B, Wehl J and Kreft J: Listeria Pathogenesis and Molecular Virulence Determinants. Clinical Microbiology Reviews 2001; 14(3): Morgan F, Bonnin V, Mallereau MP and Perrin G: Survival of L. monocytogenes during manufacture, ripening and storage of soft cheese made from raw goat milk. International Journal of Food Microbiology 2001; 64(1-2): IC Value

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15 Infection 2000; 6(10): Ennaji H, Timinouni M, Ennaji MM, Hassar M and Cohen N: Characterization and antibiotic susceptibility of Listeria monocytogenes isolated from poultry and red meat in Morocco. Infection and Drug Resistance 2008; 1: Steven L, Berrang M, Cray P and Fletcher D: Antimicrobial resistance of Listeria monocytogenes isolated from a poultry further processing plant. Foodborne Pathogens and Disease 2008; 5(3): Davis JA and Jackson CR: Comparative Antimicrobial Susceptibility of Listeria monocytogenes, L. innocua and L. welshimeri. Microbial Drug Resistance 2009; 15(1): Abuin F, Quinto-Fernandez CM, Fente Sampayo C, Rodriguez Otero JL, Dominguez Rodriguez L and Cepeda Saez A: Susceptibilities of Listeria species isolated from food to nine antimicrobial agents. Antimicrobial Agents and Chemotherapy 1994; 38: Franco CM, Quinto EJ, Fente C, Rodrıguez-Otero JL, Domınguez L and Cepeda A: Determination of the principal sources of Listeria spp. contamination in poultry meat and poultry processing plant. Journal of Food Protection 1995; 58: Brahmbhatt MN and Anjaria JM: Analysis of market meat for possible contamination with Listeria. Indian Journal of Animal Sciences 1993; 63(6): Mayrhofer S, Paulsen P, Smulders FJM and Hilbert F: Antimicrobial resistance profile of five major food-borne pathogens isolated from beef, pork and poultry. International Journal of Food Microbiology 2004; 97: Sharda R, Moghe MN and Tanwani SK: Antibiotic sensitivity patterns of bacteria isolated from repeat breeding animals. Indian Veterinary Journal 1991; 68: For Correspondence: Dr. J.B. Nayak, jbn_anand@yahoo.com IC Value