Anti-Infective Agents, 2012, 10, 000-000 1

2211-3626/12 $58.00+.00 © 2012 Bentham Science Publishers

Evaluation of In Vivo and In Vitro Antimicrobial Activities of a Selective Serotonin Reuptake Inhibitor Sertraline Hydrochloride

Amalesh Samantaa, Debprasad Chattopadhyay

b,*,+, Chandrima Sinha

a,+, Ananda Dulal Jana

a,+,

Soma Ghosha, Anurup Mandal

a Ananya Banerjee

a, Oliver Hendricks

c, Jørn B. Christensen

d and

Jette Elisabeth Kristiansene,+

aDivision of Microbiology, Department of Pharmaceutical Technology, Jadavpur University, Kolkata 700 032, India;

bICMR Virus Unit, ID and BG Hospital, GB-4, First Floor, 57 Dr Suresh C Banerjee Road, Beliaghata, Kolkata 700

010, India; cDepartment of Research, Sygehus Sønderjylland, Denmark and King Christian X Hospital for Rheumatic

Diseases, Gråsten, Denmark; dDepartment of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100

Copenhagen, Denmark; eMember of MEMPHYS Center for Biomembrane Physics, Department of Physics and Chemis-

try Campusvej 55, DK-5230 Odense M, Denmark

Abstract: We investigated the in vitro and in vivo antimicrobial potential of a selective serotonin reuptake inhibitor ser-

traline hydrochloride, against clinical isolates of bacteria and Candida species. Minimum Inhibitory Concentration of ser-

traline against 161 human isolates of 12 Gram negative and 5 Gram positive genera, Candida albicans ATCC10231 and

Candida tropicalis ATCC13803 was determined by spot inoculation, broth and agar dilution methods along with its post-

antibiotic effect following a short drug exposure. The toxicity and protective efficacy was tested in vivo with a mouse-

virulent strain of Salmonella typhimurium NCTC74.The MIC was 20-200μg/ml for bacteria, and 200μg/ml for Candida.

The growth inhibitory study with Bacillus subtilis UC564 and Shigella dysenteriae NCTC599/52 revealed that the drug is

bacteriostatic at its MIC and cidal at higher concentrations. Study on its post-antibiotic effect following a short drug expo-

sure revealed that Sertraline has a time- and dose-dependent effect. Treatment for 4h at concentrations below and equipo-

tent to the minimal static concentration resulted in a lag of regrowth at 8-24h for Candida isolates. The in vivo study with

Salmonella typhimurium in Swiss mice showed that the median lethal dose was 1.9 x 107

cfu and 50 LD50 was 0.95x109.

Interestingly, the drug at a non-toxic single dose provides significant protection (P<0.001) to the mice challenged with

S. typhimurium. Sertraline remarkably reduced the number of viable bacteria in organ homogenates and blood of the

treated animals and demonstrate both in vitro and in vivo antibacterial potential at lower dose than its predesignated phar-

macological activity.

Keywords: Sertraline hydrochloride, SSRI, antibacterial activity, antifungal activity, non-antibiotic.

1. INTRODUCTION

The unrestricted use of the conventional antimicrobials renders emergence of ‘antibiotic resistance’ and new infec-tious diseases. Thus, the effectiveness of many broad spec-trum antibiotics, the major protective agents against micro-bial infections, is reduced gradually and their toxic side ef-fects are increasing, and thus many antibiotics lose their sig-nificance. Today the use of conventional antimicrobials and antibiotics is becoming more and more limited and the search for antimicrobial activity among the different phar-macologically active drugs has been initiated. Moreover, drugs are basically multifunctional, as a single drug can pro-duce different pharmacological action at different dose level [1, 2]. The drugs which are not categorized as antimicrobials but showed profound antimicrobial activity are classified as ‘Non-antibiotics’ [3-6]. Several studies throughout the world

*Address correspondence to this author at the ICMR Virus Unit, ID & BG

Hospital, General Block 4, First Floor, 57 Dr. Suresh C Banerjee Road,

Beliaghata, Kolkata 700 010, India; Tel: 91 33 2353 7425; Fax: 91 33 2353 7425; E-mails: debprasadc@yahoo.coin; debprasadc@hotmail.com

+Contributed equally to the study.

reported antimicrobial potential of many antihistaminic [7-16], antipsychotic-antidepressants [7, 17-34], anti-inflam-matory [35- 44], antispasmodic [45, 46], antihypertensive [47], cardiovascular drugs [48-54], and even some local an-aesthetics [55-58]. They can inhibit diverse classes of mi-crobes including prion related Creutfeldt-Jacob disease [59], mycoplasma [60], malaria [61, 62], leishmaniasis [63], amoebic diseases [64], opportunistic infections in HIV/AIDS [65, 66], and even drug resistant microbes at different dose levels by modifying the ultrastructure of microbial cell wall [67], cell membrane [55, 68-70], membrane permeability [71] or its multidrug efflux pumps [72-75] and even by in-hibiting DNA synthesis [37]. More importantly some of these drugs can alter or reverse the multidrug resistant clini-cal isolates of many bacteria [72, 76-83], chloroquine resis-tant P. falciparum [84] and even highly drug resistant Myco-bacterium tuberculosis [66, 85- 97].

The antimicrobial activity of psychotropic phenothiazine was first described in 1975 in intestinal anaerobic bacteria [4, 98]. Since then,

several non-antibacterial agents, includ-

ing thioxanthenes and the Selective Serotonin Reuptake In-hibitors

(SSRIs) that were used as the first-line therapy for

2 Anti-Infective Agents, 2012, Vol. 10, No. 2 Samanta et al.

severe premenstrual syndrome (PMS) and as antidepressants [5, 6, 99] have been tested. Some SSRI´s have significant in vitro antibacterial activity [3, 27, 32], mainly against Gram-positive bacteria [33, 100], and even against chloroquine resistant Plasmodium falciparum [101]. Many of these com-pounds having antibacterial activity possess two to three benzene rings, as evident from methotrexate [102], a naph-thalene derivatives, and femoxetine, a 4-phenylpiperidines SSRI and its stereochemical analogs [6, 29], which can in-hibit diarrhoea producing enterobacteria [27]. Sertraline, a SSRI is the (+) cis compound and one of the 4 stereochemi-cal possibilities in the same chemical structure is shown in

Fig (1). These drug has in vivo antibacterial [103], antifungal [104, 105], and antiparasitic activities [106, 107]. Moreover sertraline produce in vitro synergism between SSRI`s and some antibiotics [29, 33, 100, 103]. However, to date no in vivo investigations on antibiotic resistant intestinal patho-genic bacteria with the SSRIs have been elucidated. Thus, this paper deals with in vitro and in vivo antimicrobial poten-tial of Sertraline, one of the most potent SSRI antimicrobials.

Fig. (1). Sertraline. The commercial product is the (+, cis) Ser-

traline hydrochloride.

2. MATERIALS AND METHODS

2.1. Bacteria and Fungi

A total of 161 fully characterized bacterial isolates be-longing to 5 Gram-positive and 12 Gram-negative genera and two Candida species were tested. Some of these strains are from the American Type Culture Collection (ATCC), USA, and the National Collection of Type Cultures (NCTC), London; while majority are human isolates obtained from different laboratories in India as a gift. All these strains were maintained in the Division of Microbiology, Department of Pharmaceutical Technology, Jadavpur University, Kolkata, identified as described by Barrow and Feltham [108] and Collee et al. [109], and are preserved in the freeze-dried state as well as at 4

oC in stab slant agar. Three strains of bacteria

(S. aureus ATCC 25923, E. coli ATCC 25922, P. aerugi-nosa ATCC 27853) and two Candida spp. (C. albicans ATCC 10231 and C. tropicalis ATCC 13803) were served as standard quality controls strains for assessment of the anti-bacterial and antifungal activity.

2.2. Drug

The drug Sertraline HCl (systemic IUPAC name (1S-Cis)-4-(3,4-dichlorophenyl)-1,2,3,4-tetrahydro-N-methyl-1-naphthalenamine hydrochloride: C17H17Cl2N.HCl; Fig. (1)); Molecular weight 342.7, obtained as a pure white crystalline powder from Ranbaxy Laboratories Ltd (Solan, India) was used for

in vitro studies; while for in vivo studies the oral

tablet (Sun Pharmaceuticals) was used. The drug was slightly

soluble in water and isopropyl alcohol, sparingly soluble in ethanol at room temperature, and remained stable in aqueous solution. The tablet was suspended

in

PBS at the desired dose

and the drug was dissolved in sterile distilled water and kept at 4

oC. Other chemicals and reagents used were of analytical

grade.

2.3. Media

The media used were peptone water (PW; prepared with 1.0% bacteriological peptone (Oxoid) and 0.5% Analar NaCl), nutrient broth (NB), Mueller Hinton broth (MHB; Difco, USA); nutrient agar (NA, Oxoid, UK), desoxycholate citrate agar (DCA, Oxoid), Mueller Hinton agar (MHA; Difco) and Sabouraud’s Dextrose Agar (SDA, Oxoid, UK). The pH of all bacteriological media was maintained at 7.2-7.4, while the fungal media SDA was used at pH 5.4 [110].

2.4. Animal

Four to six weeks old Swiss strains of albino mice, main-tained in the animal house of the Department of Pharmaceu-tical Technology, Jadavpur University, Kolkata at standard temperature (21±1°C) and relative humidity (50-60%) with a photoperiod of 14:10h of light and darkness. Water and a dry pellet diet were given ad libitum. Animal experiments were conducted following the guidelines of the Institutional Ani-mal Ethics Committee (IAEC), Department of Pharmaceuti-cal Technology, Jadavpur University, Kolkata, India (Ap-proval no. CPCSEA 0367/01/C/CPCSEA/2008; dated 27.01.2008).

2.5. In Vitro Antibacterial Activity of Sertraline Hydro-

chloride

The drug was dissolved in sterile distilled water and added to molten MHA at a concentrations of 0 (control), 5, 10, 25, 50, 100 and 200 g/ml and then poured into sterile Petri dishes aseptically [3, 63]. Gram-positive bacteria were grown in NB or MHB and Gram negative bacteria in PW or MHB for 18h and were harvested in stationary growth phase. The suspension was diluted with saline or broth to a density equivalent to the McFarland standard of 0.5% (a turbidity standard prepared by adding 0.5 ml of a barium chloride solution to 99.5 ml of 1% H2SO4) [111], corresponding to 5x10

5 CFU/ml with a UV visible spectrophotometer

(Chemito 66 Technology Pvt Ltd, Nasik, India) at 625 nm by diluting the broth cultures with saline or broth and the stan-dardization was maintained throughout the study. One loop-ful (internal diameter 2 mm) of the diluted bacterial suspen-sion was inoculated on the MHA plates containing increas-ing amounts of the drug, with control (antibiotic control and quality control strains). The plates were incubated at 37°C for 18-72h and examined daily for the appearance of growth

Cl

Cl

HN

H3C

H

H

HCl

Evaluation of In Vivo and In Vitro Antimicrobial Activities of a Selective Serotonin Anti-Infective Agents, 2012, Vol. 10, No. 2 3

[9]. The tests were performed in triplicate for each organism, and repeated if required.

2.5.1. Determination of MIC of Sertraline Hydrochloride

Both broth and agar dilution methods were used to de-

termine the MIC of Sertraline hydrochloride with respect to

different test bacteria [110, 112, 113]. For these tests, Ser-

traline hydrochloride was added to each tube or plate at con-

centrations of 0 (control), 5, 10, 25, 50, 100 and 200 μg/ml.

Since one solid agar medium containing the drug could be

used for inoculation of a large number of bacteria at a time,

this was done at least three times for every test bacterium and the results of agar dilution method were presented.

2.6. In Vitro Screening of Sertraline Hydrochloride for

Antifungal Activity

The fungal strains were grown overnight at 35ºC on

Sabouraud’s dextrose agar plates. The suspension was pre-

pared by diluting the overnight culture with saline to a 0.5%

McFarland standard corresponding to 2.5x104cells/ml. The

drug was added to Sabouraud’s dextrose agar tubes to get a

final concentration of 0 (control), 100, 200, 500 and 1000

g/ml. One loopful (internal diameter 2mm) of fungal sus-

pension was then inoculated on to the tubes and incubated at

28ºC. The end points were noted when growth of the colo-

nies of control were clearly visible after incubation for 5-

7days. The MIC was calculated as the lowest concentration

of Sertraline that showed absolutely no growth on the tube

[102,108].

2.7. Determination of Mode of Action of Sertraline Hy-

drochloride [114]

Two bacterial strains Bacillus subtilis UC564 and Shig-

ella dysenteriae NCTC599/52, sensitive to sertraline hydro-

chloride were grown in MHB for 18h. An aliquot (2ml) of

this culture was then added to 4ml of fresh media and incu-

bated at 37oC for 2h to get logarithmic growth phase culture.

At this log phase, the Sertraline hydrochloride was added at a

concentration higher than its respective MIC concentration

(50 g/ml) and the colony forming units (cfu)/ml counts were determined at 2 hourly intervals up to 18h [21, 71].

2.8. In Vivo Tests

Swiss strains of albino male mice, weighing 18-20 gm

each were used to enhance the virulence of the test strain.

The virulence of the mouse pathogenic test strain Salmonella

typhimurium NCTC 74 was exalted by repeated mouse pas-

sages, and the median lethal dose (MLD or LD50) of the pas-

saged strain was determined using separate batches of ani-

mals. The LD50 corresponding to 0.95 x109 CFU/mouse was

suspended in 0.5 ml NB served as the challenge dose [115] for the test groups of animals.

2.8.1. Determination of Toxicity of Sertraline Hydrochloride

To determine the toxicity of the drug, 20 mice were in-jected intraperitoneally with 50μg of Sertraline hydrochlo-ride, and the rest 20 received 25μg of the drug [109]. All the animals were kept under observation up to 100h.

2.8.2. Protective Efficacy of the Drug

To test the efficacy of Sertraline hydrochloride the two

groups of 20 mice (n=20) each weighing 18-20 gm was used.

Group I was administered with 30μg Sertraline per mouse

(0.1 ml from 300 μg/ml solution), and group II was given

60μg of the drug per mouse (0.1 ml from 600μg/ml solution

of Sertraline) intraperitoneally. After 3h, mice in both the

groups challenged with 50 MLD of S. typhimurium 74. A

control group of 60 mice was also injected similarly with the

same challenge and 0.1 ml sterile saline instead of Sertraline.

The protective capacity of the drug was determined by re-

cording the mortality of the mice in different groups up to 100h.

50 MLD of S. typhimurium 74 (0.95 x109 CFUs) sus-

pended in 0.5ml broth, was used as the challenge dose [103,

109]. The reproducibility was confirmed by standardizing its

optical density at 640 nm in a Klett Summerson Colorimeter

(Klett Manufacturing Company, New York). In a separate

experiment eight groups of mice, 10 animals per group

(n=10) were kept in separate cages. Group I was intraperito-

neally administered with 200 g of Sertraline hydrochloride

per mouse, Group II with 400 g/mouse, Group III with

600 g/mouse while Group IV, V, VI, VII and VIII were

received 800, 1000, 1200, 1300 and 1400 g Sertraline hy-

drochloride per mouse respectively in 0.1 ml sterile solution

of drug. After 3 hours each animal within all the groups was

challenged with 50 MLD of S. typhimurium NCTC 74. A

control group of 30 mice (n=30) were also injected with the

same challenge and 0.1 ml of sterile water instead of the

drug. The protective ability of the drug was determined by

recording the mortality of the mice in different groups up to

100 hours after treatment, and statistically by Chi-square

test.

In a similar experiment 10 mice were divided into 2

groups of 5 each (n=5), and all were injected with the chal-

lenge dose. Group I was given Sertraline hydrochloride

(1300 μg/ml per mouse) while group II received sterile saline

of the same volume before the challenge. All of the animals

of group I and II were autopsied 18h after the challenge.

Their livers and spleen were removed, homogenized in a

sterile glass homogenizer and preserved at -20oC for subse-

quent determination of viable counts (CFU/ml). A 0.2-0.4ml

portion of heart blood was also collected aseptically at the

same time. The CFU/ml counts for the individual organs

were determined separately. The concentration of Sertraline

hydrochloride in mouse blood was assayed by measuring the

diameter of the inhibition zones by serum soaked filter paper

discs (6 mm diameter, 3 mm thick, Millipore, USA absorb-

ing 0.03ml volume) on a lawn flooded with 106 bacteria from

an 18h broth culture of S. typhimurium 74 on peptone agar.

The drug concentrations in serum samples were determined

by referring these values to a standard calibration curve pre-pared with known concentrations of the drugs [45, 103, 109].

2.9. Statistical Analysis

The data were analysed using Students t-test and Chi-square test.

4 Anti-Infective Agents, 2012, Vol. 10, No. 2 Samanta et al.

3. RESULTS

3.1. In Vitro Antibacterial Activity of Sertraline Hydro-

chloride

The results presented in Table 1 shows the antimicrobial activity of Sertraline hydrochloride against 161 strains of bacteria and three quality control strains tested. The inhibi-tory spectrum revealed that 34 bacterial isolates were inhib-ited at 10μg/ml, 45 at 25μg/ml, 19 at 50μg/ml, 32 at 100 μg/ml and 23 strains at 200μg/ml of Sertraline hydrochloride respectively. The results also revealed that the drug has sig-

nificant inhibitory action on Staphylococcus spp., Bacillus spp. Shigella dysenteriae, E. coli, Micrococcus spp. and V. cholerae. Moderate inhibitory activity was noted with Sal-monella spp and Klebsiella pneumoniae; while V. para-haemolyticus, Pseudomonas spp. and Proteus sp. are resis-tant up to the highest concentration tested.

3.2. In Vitro Antifungal Activity of Sertraline Hydrochloride

The results presented in Table 2 revealed that both Can-dida albicans and Candida tropicalis were inhibited at 200μg/mL concentration of Sertraline hydrochloride.

Table 1. In Vitro Antibacterial Profile of Sertraline Hydrochloride on Gram Positive and Gram Negative Bacteria

No. of Strains Inhibited by Sertraline Hydrochloride (μg/ml) Name of Bacteria No of Strains Tested

10 25 50 100 200 >200

Staphylococcus spp. 45 15 23 2 4 1 -

Streptococcus faecalis 1 - 1 - - - -

Micrococcus luteus 2 1 1 - - - -

Bacillus subtilis 6 1 4 - - - 1

Shigella spp. 33 6 5 8 13 - 1

Salmonella spp. 11 - 3 1 1 5 1

Vibrio cholerae 13 6 2 - 2 3 -

Vibrio parahaemolyticus 6 - - 2 3 - 1

Escherichia coli 21 3 1 5 5 7 -

Klebsiella pneumoniae 7 - 1 1 2 3 -

Pseudomonas aeruginosa 9 2 1 - 1 1 4

Proteus vulgaris 3 - - - - 1 2

Citrobacter fruendii 1 - 1 - - - -

Providencia spp. 1 - - - - 1 -

Enterobacter cloacae 1 - - - - 1 -

Lactobacillus sporogenes 1 - - - - - 1

S. aureus ATCC 25923 1 - 1 - - - -

E. coli ATCC 25922 1 - 1 - - - -

P. aeruginosa ATCC 27853 1 - - - 1 - -

Total 164 34 45 19 32 23 11

Table 2. Inhibitory Effect of Sertraline Hydrochloride on Candida spp.

Growth in SDA Containing different Concentration of Sertraline Hydrochloride(μg/ml) Name of Fungal Strains

0* 100 200 500 1000

Candida albicans ATCC10231 + + - - -

Candida tropicalis ATCC13803 + + - - -

* Control without drug; +, growth; - , no growth.

Evaluation of In Vivo and In Vitro Antimicrobial Activities of a Selective Serotonin Anti-Infective Agents, 2012, Vol. 10, No. 2 5

3.3. Bacteriostatic Action of Sertraline Hydrochloride

The MIC of sertraline hydrochloride against Bacillus subtilis UC564 and Shigella dysenteriae NCTC 599/52 was 25μg/ml and 10μg/ml respectively. For Bacillus subtilis UC564 the initial colony count was 4.5x10

9 CFU/ml before

the addition of the drug. Subsequently the viable counts at 2h intervals was 5x10

4, at 4h it was 6x10

3, 0.6x10

3 after 6h and

4x102

at the end of 18h (Fig. 2) Similar experiments with Shigella dysenteriae NCTC 599/52 using 4x10

8 CFU/ml

showed that after 2h of drug treatment the viable count was reduced to 8x10

6, while after 4h it was 7x10

6, 7x10

5 after 6h

and 6.4x105 at the end of 18h respectively (Fig. 2). Thus, the

data indicated that Sertraline hydrochloride is bacteriostatic against both the Gram positive and Gram negative bacterial isolates tested.

3.4. In Vivo Tests

The results of animal study depicted in Table 3 show that Sertraline hydrochloride can protect the mice challenged with S. typhimurium NCTC 74 for which the MIC value for Sertraline was 50 g/ml. In the saline control group, 25 (83.3%) of the 30 animals died within 100h of the lethal challenge. The difference between the drug-treated (1300μg/ mouse) and control was significant according to the Chi-square test (P<0.001). Similarly, the results presented in Ta-ble 4 showed that Sertraline hydrochloride significantly re-duced the number of viable bacteria in heart blood, liver and spleen of the mice at 18h after challenge compared with the saline control group (P < 0.01).

4. DISCUSSION

The reason for selecting and investigating the antipsy-chotic drug Sertraline hydrochloride, is its chemical purity,

long term therapeutic use and its versatile stereochemistry. SSRI’s are 4-phenylpiperidins having two chiral centers and thus exist in four stereoisomeric forms that may be used for chemical modification for increased antimicrobial activity.

In our study we found that sertraline possess powerful antibacterial activity in vitro, as the drug inhibited 150 (93.75%) bacterial isolates at a concentration of 10 to 200 g/ml; and the two Candida spp. at 200 g/m. The iso-lates of Staphylococcus aureus, Bacillus subtilis, Vibrio cholerae, Escherichia coli, Shigella dysenteriae and Salmo-nella spp were found to be sensitive to the drug while Pseu-domonads and Klebsiella spp. were moderately sensitive; but Vibrio parahaemolyticus, Proteus vulgaris, Lactobacillus sporogenes and Enterobactor cloaca were almost resistant to this drug. On the other hand the drug possesses good anti-fungal activity against Candida albicans ATCC10231 and Candida tropicalis ATCC13803 strains tested. A further in vitro study with susceptible bacterial isolates revealed that the drug is bacteriostatic at MIC dose, while at higher con-centration it was bactericidal. These results are in accordance with the earlier studies on sertraline hydrochloride, particu-larly against Staphylococcus aureus, S. epidermidis, S. fae-calis, Streptococcus pyogenes and S. pneumoniae [33] and against Candida and Aspergillus spp. [104, 105].

Herein, we also report in vivo antibacterial activity of Sertraline

against a Gram negative mouse pathogen Salmo-

nella enterica serovar Typhimurium NCTC 74. To the best of our knowledge,

this is the first report of Sertraline, as a

promising in vivo antibacterial agent, which is effectual orally for significant reduction in

the bacterial load in in-

fected mice. The human therapeutic dose (10 mg/kg) is 55

times lower than the LD50 value (acute toxicity, 548 mg/kg in

mice) of this drug [116]. The toxicity studies with the treated

dose (10mg/kg) on normal mice showed that kidney, liver

Fig. (2). Mode of action of Sertraline hydrochloride on Bacillus subtilis UC564 and on Shigella dysenteriae NCTC599/52.

6 Anti-Infective Agents, 2012, Vol. 10, No. 2 Samanta et al.

and heart functions were within safe and normal limits at

post-treatment (data not shown) which is well within the limit reported earlier [117]. Sertraline hydrochloride is rou-tinely used in the treatment of major depression, obsessive-, compulsive-, and posttraumatic disorders [118], and its anti-bacterial [33,103] antifungal [104,105], antiprotozoal [101, 106,107], spermicidal, antitrichomonas and anticancer [119, 121], activity prove its versatility as a chemotherapeutic

agent. Earlier studies showed that that well-known neurolep-

tic drugs chlorpromazine and its analogues have lethal effects

on bacteria, fungi and protozoa either through enzymatic inhibition or through some other mechanism, completely

different from their parent antipsychotic and anxiolytic prop-erties [63, 106]. However, the mechanism by which Ser-traline acts as an antimicrobial agent is at present not clearly understood. The antifungal activity probably results from an interaction with the fungal membrane transport system [104,105], or of the extracellular phospholipase activity that reduce the fungal virulence [122], or inhibition of respiratory enzyme leading to cell death [119].

In our study the protection offered by sertraline to the mice challenged with a virulent S. typhimurium NCTC 74 was found to be highly significant (p<0.001), as noticed with other psychotropic non-antibiotic agent thioridazine and oth-ers [2,123-125]. Sertraline hydrochloride was totally non-toxic upto 1400 μg/mouse, while the protection offered by the drug at 1300 μg/mouse was significant. Interestingly our data showed that the antibacterial protection to the chal-lenged mice by sertraline was achieved after a single dose

while as antidepressant drug it is administered daily for sev-eral months. The structure-activity relationships (SAR) stud-ies showed that the antimicrobial properties of sertraline might be linked to its naphthalene ring system [125]. Further analysis indicated that the two cyclic rings along with nitro-gen in the secondary state and chlorine substitutions in the benzene ring [126] may be crucial in conferring antimicro-bial activity. SAR studies also revealed that there are 4 dif-ferent possibilities with sertraline as a lead compound and our animal study points towards the immunostimulating ac-tivity of this neurotropic drugs, which has been observed earlier with other psychotropic agents [29,127], and with some structural analogs of phenylpiperidine SSRIs that in-hibited the function of two unique multidrug efflux pumps of Staphylococcus aureus [74, 75]. From the comparative analysis of our data we can reasonably conclude that the sen-sitivity of the tested microbes is totally independent of the “classical antibiotic/antifungal spectrum”, and its SSRI activ-ity is independent of its antimicrobial potentiality. Moreover, our in vivo data suggested that SSRIs might have a potential to be used as lead compounds for the development of new antimicrobials. However, detailed in vitro investigation and animal studies are still required to understand

the potential

role of Sertraline induced mode of cell death in bacteria and fungi.

CONFLICT OF INTEREST

There is no conflict of interest in any form between the authors.

Table 3. Effect of Sertraline Hydrochloride on Survival of Mice Challenged with Salmonella Typhimurium NCTC 74

Drug Dose (μg/ml)

Challenge

(0.95 x 109 CFU

in 0.5 ml Broth)

No of Animal Tested No of Animal Died Type of Experiment

1300 Yes 10 2* Test

1300 No 10 0 Control

1400 Yes 10 2* Test

Sertraline

hydrochloride

1400 No 10 0 Control

NIL 0.1 ml sterile water Yes 30 25 Control

* P<0.001 according to Chi-square test, after elimination of the toxic effects due to the drug alone (test- control).

Table 4. Efficacy of Sertraline Hydrochloride in Reducing Bacterial Counts in Challenged Mice

CFU/ml Counts in Time of

Sampling Group No of Mice Drug μg/Mouse

Heart Blood Liver Spleen

18 h I 5 Sertraline hydrochloride 1300μg

5.8x103

to

7.2x104

8.2x103

to

9.5x104

6.8x103

to

5.5x105

18h II 5 Sterile water (control)

5.2x107

to

4.5x108

6.7x107

to

3.9x108

3.2x107

to

5.4x108

Evaluation of In Vivo and In Vitro Antimicrobial Activities of a Selective Serotonin Anti-Infective Agents, 2012, Vol. 10, No. 2 7

ACKNOWLEDGEMENT

We are thankful to Ranbaxy Laboratories Ltd (Solan, India) for supplying the gift sample of Sertraline hydrochlo-ride to carry out the study.

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Received: ??????????? Revised: ??????????? Accepted: ???????????