PHARMA SCIENCE MONITOR

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] www.pharmasm.com IC Value 4.01 103

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 12-18 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 www.pharmasm.com IC Value 4.01 104

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 18-24 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 30 10 Penicillin-G P 10 11 Rifampicin R 30 12 Streptomycin S 26 13 Tetracycline T 30 14 Trimethoprim Tr 30 15 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 www.pharmasm.com IC Value 4.01 105

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). www.pharmasm.com IC Value 4.01 106

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 www.pharmasm.com IC Value 4.01 107

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 www.pharmasm.com IC Value 4.01 108

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). www.pharmasm.com IC Value 4.01 109

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) 0 0 4 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) 0 0 8 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 www.pharmasm.com IC Value 4.01 110

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) 0 0 4 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) 0 0 8 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) 0 0 0 11 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) 0 0 15 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) 0 0 0 2(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) www.pharmasm.com IC Value 4.01 111

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) 0 0 0 1(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) 0 0 4 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) 0 0 0 8 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) 0 0 0 14 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 0 0 0 1(100.0) 3 Ceftazidime 0 0 0 0 4 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 www.pharmasm.com IC Value 4.01 112

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 100.0 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 100.0 per cent resistance of L. monocytogenes and Rota et al., (1996) and Conter www.pharmasm.com IC Value 4.01 113

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 100.0 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 100.0 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 100.0 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 www.pharmasm.com IC Value 4.01 114

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: 476-511. 2. 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):402-407. 3. Gray ML and Killinger AH: Listeria monocytogenes and Listeric Infections. Bacteriological Reviews 1966; 30(2): 309-382. 4. 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): 584 640. 5. 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): 217-221. www.pharmasm.com IC Value 4.01 115

6. Bauer AW, Kirby WMM, Shernis JC and Turek M: Antibiotic susceptibility testing by standardized single disc method. American Journal of Clinical Pathology 1966; 45:493-496. 7. Wong HC, Chao WL and Lee SJ: Incidence and Characterization of Listeria monocytogenes in Foods Available in Taiwan. Applied and Environmental Microbiology 1990; 1(2): 93-100. 8. Navratilova P, Schelegelova J, Sustackova A, Napranikova E, Lukasova J and Klimova E: Prevalence of Listeria monocytogenes in milk, meat and foodstuff of animal origin and the phenotype of antibiotic resistance of isolated strains. Veterinary medicine Czech 2004; 49(7): 243 252. 9. Mauro C, Paludi D, Orio V, Vergara A and Ianieri A: Antimicrobial susceptibility of Listeria monocytogenes isolated from food and food-processing environment. Ann Fac Medic Vet di Parma 2007; 27:157-164. 10. Njagi LW, Muthia PG, Bebora LC, Nyaga PN, Minga U and Olsen JE: Sensitivity of Listeria species, recovered from indigenous chickens to antibiotics and disinfectants. East African Medical Journal 2004; 81(10): 534-537. 11. Rota C, Yanguela J, Blanco D, Carraminana JJ, Arino A and Herrera A: High prevalence of multiple resistances to antibiotics in 144. Listeria isolates from Spanish dairy and meat products. Journal of Food Protection 1996; 59: 938-943. 12. Conter M, Domenico P, Vincenzo D, Alberto V and Adriana I: Antimicrobial susceptibility of Listeria monocytogenes isolated from food and food-processing environment. Ann Fac Medic Vet di Parma 2007; 27:157-164. 13. Rodas-Suarez OR, Flores-Pedroche JF, Betancourt-Rule JM, Quinones-Ramırez EI and Vazquez-Salinas C: Occurrence and Antibiotic Sensitivity of Listeria monocytogenes Strains Isolated from Oysters, Fish, and Estuarine Water. Applied and Environmental Microbiology 2006; 72 (11): 7410 7412. 14. Barbuti S, Maggi A and Casoli C: Antibiotic resistance in strains of Listeria spp from meat products. Letters in applied microbiology 1992; 15(2):56-58. 15. Troxler R, Von Graevenitz A, Funke G, Wiedemann B and Stoca I: Natural antibiotic susceptibility of Listeria species: L. grayi, L. innocua, L. ivanovii, L. monocytogenes, L. seeligeri and L. welshimeri strains. Clinical Microbiology and www.pharmasm.com IC Value 4.01 116

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