|Year : 2017 | Volume
| Issue : 1 | Page : 124-128
Antimicrobial susceptibility of Leptospira spp. isolated from environmental, human and animal sources in Malaysia
Douadi Benacer1, Siti Nursheena Mohd Zain1, Peck Toung Ooi2, Kwai Lin Thong1
1 Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur, Malaysia
2 Faculty of Veterinary Medicine, Universiti Putra Malaysia, Selangor, Malaysia
|Date of Web Publication||16-Mar-2017|
Kwai Lin Thong
Faculty of Science, Institute of Biological Sciences, University of Malaya, 50603 Kuala Lumpur
Source of Support: None, Conflict of Interest: None
Leptospirosis is a zoonosis with worldwide distribution caused by pathogenic spirochetes of the genus Leptospira. The aim of this study was to evaluate the susceptibility of isolates obtained from different hosts. A total of 65 Leptospira isolates from humans (n = 1), zoonoses (rat, n = 60; dog, n = 1; swine, n = 1) and environment (n = 2) were tested against six antibiotics. All the isolates were resistant to trimethoprim and sulphamethoxazole and had high MIC toward chloramphenicol (MIC90: 6.25 μg/ml). All except one environment isolate were sensitive to ampicillin, doxycycline and penicillin G.
Keywords: Antimicrobial susceptibility, Leptospira, leptospirosis, minimal inhibitory concentration
|How to cite this article:|
Benacer D, Zain SN, Ooi PT, Thong KL. Antimicrobial susceptibility of Leptospira spp. isolated from environmental, human and animal sources in Malaysia. Indian J Med Microbiol 2017;35:124-8
|How to cite this URL:|
Benacer D, Zain SN, Ooi PT, Thong KL. Antimicrobial susceptibility of Leptospira spp. isolated from environmental, human and animal sources in Malaysia. Indian J Med Microbiol [serial online] 2017 [cited 2017 Mar 26];35:124-8. Available from: http://www.ijmm.org/text.asp?2017/35/1/124/202325
| ~ Introduction|| |
Leptospirosis is an emerging zoonotic disease with worldwide distribution. It is caused by pathogenic spirochetes of the genus Leptospira. Approximately, one-half of the pathogenic serovars belong to Leptospira interrogans or Leptospira borgpetersenii. Rodents are the principal known maintenance hosts, besides domestic animals, livestock and wild animals. Humans become accidental hosts by acquiring the infection through direct contact with urine, blood or infected animal tissue or indirect contact with water or soil contaminated with the urine from reservoir animals. Clinically, symptoms of infection may range in severity from mild to fatal, depending on the infection stage. However, the clinical presentation of leptospirosis is unspecific, which frequently leads to misdiagnosis. In Malaysia, misdiagnosis of this infection has become a critical issue, where dengue, malaria and other infectious diseases with overlapping clinical presentations are endemic. Treatment normally follows an empirical chemotherapy route, which requires information regarding the susceptibilities of Leptospira isolates to various antimicrobial agents. Effective and appropriate antibiotic selection for treatment is essential to prevent complications. Several studies have been carried out on Leptospira isolates' susceptibilities. However, these studies have a number of limitations, such as using laboratory-passaged strains or a small number of Leptospira strains. Due to the endemicity of leptospirosis in Malaysia  as well as the dramatic increase in reported cases over the last decade, there is a critical need to determine the effectiveness of common antibiotics in controlling this organism. However, no information is available on the antimicrobial susceptibilities of Malaysian Leptospira isolates. Therefore, the aim of this study is to monitor and evaluate the susceptibility of recent local isolates obtained from different hosts and sites to traditional antimicrobial compounds used for leptospirosis treatment.
| ~ Materials and Methods|| |
Sixty-five Leptospira isolates representing four different species and at least five serovars were included in the testing. These isolates from environmental (water, n = 2) and animal sources (rat, n = 60; dog, n = 1; swine, n = 1) were isolated between 2011 and 2014 from different sites in six states in Peninsular Malaysia., One clinical isolate was provided by the Royal Tropical Institute (KIT), Amsterdam, Netherlands. The strain was originally isolated from a human in Malaysia by Alexander et al. The isolates were maintained in culture in Ellinghausen-McCullough-Johnson-Harris (EMJH) medium. Information on the isolates is summarised in [Table 1].
|Table 1: Strains of Leptospira tested and their susceptibility to six antimicrobial agents|
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The antimicrobial solutions employed in this study were prepared from reagent grade powders to produce 1 mg/ml solutions using solvents and diluents suggested in the Clinical and Laboratory Standards Institute document M100-S22 or according to the manufacturer's suggestions if available. Six antimicrobial agents, including doxycycline, penicillin G, trimethoprim, ampicillin, chloramphenicol (MP Biomedicals, France) and sulphamethaxazole (Sigma-Aldrich; St. Louis, MO, USA) were used to test the Leptospira isolates' antimicrobial susceptibility. The stock antimicrobial solutions were stored at −80°C in divided one-time use aliquots.
Broth microdilution testing was performed as reported by Murray and Hospenthal  and Chakraborty et al. The antibiotic concentrations ranged from 25.0 to 0.01 µg/ml (units/ml for penicillin), with the exception of sulphamethaxazole and trimethoprim, which were tested at 3200 to 12.5 µg/ml. The strain L. interrogans serovar Icterohaemorrhagiae was used for internal validation with minimal inhibitory concentration (MIC) parameters and served as the control strain. All tests were performed in triplicate and included positive (bacteria only) and negative controls (medium only). The Leptospira inoculum used for testing was prepared from 7-day-old cultures grown in liquid EMJH medium at 30°C. Then, 100 µl Leptospira inoculum of 2 × 106 leptospiral organisms/ml was added, and the 96 well plates were incubated at 30°C, with each well having a final volume of 200 µl. Following 3 days of incubation, 20 µl of 10X alamarBlue (Invitrogen, Cleveland, OH, USA) was added to each well. AlamarBlue is an oxidation-reduction indicator that changes colour from dark blue to bright pink in response to the chemical reduction of the growth medium resulting from cell development. The colour of each well was documented on the 5th day of incubation, and the MICs were recorded as the concentration in the well containing the lowest concentration without blue-to-pink colour change.
| ~ Results|| |
The MIC90 values are reported in [Table 1]. All isolates were resistant to trimethoprim and sulphamethoxazole (MIC90: 1600 µg/ml). All isolates had an MIC90 range of 3.13–6.25 µg/ml to chloramphenicol, except that from swine (LS01/11) and one isolate from rat (LR31/13) which showed higher MICs of 12.5 and 25 µg/ml, respectively. Overall, penicillin G and ampicillin appeared to be effective for all clinical and zoonotic isolates with MIC90 between 0.1 and 0.2 µg/ml. Only the dog isolate showed a slightly higher MIC toward penicillin G (0.39 µg/ml) compare to the rest while the lowest was toward the swine isolate (<0.01 µg/ml). However, the environmental isolate L. kirschneri (LE02/11) was resistant to penicillin G and ampicillin as the MIC reported was 25 µg/ml. The MICs of doxycycline ranged from 0.2 to 0.78 µg/ml, but one zoonotic (LS01/11) and 2 environmental isolates (LE01/11, LE02/11) displayed a higher MIC toward doxycycline (3.13 µg/ml) compared to the other isolates although still remained susceptible. Overall, doxycycline was more effective on all isolates tested compared to ampicillin and penicillin G.
| ~ Discussion|| |
Leptospirosis is an endemic disease in Malaysia, occurring in both urban and rural locations. The local absence of sensitive, specific and rapid methods of diagnosing leptospirosis makes it difficult to distinguish it from other febrile illnesses. The misdiagnosis of leptospirosis often leads to treatment with a broad range of antimicrobials that cover the febrile syndromes of various local illnesses. Therefore, this study was carried out to monitor and determine the susceptibility patterns in the different isolates of leptospirosis reflecting on their effectiveness in the treatment of leptospirosis.
In our study, both trimethoprim and sulphamethoxazole were found ineffective against all isolates tested. This finding is in agreement with previous studies., Trimethoprim and sulphamethoxazole have sometimes been applied in combination for their synergistic action in providing a broad-spectrum bactericidal antimicrobial coverage before definitive diagnosis. However, the resistance of Leptospira strains to these antibiotics may compel health workers to consider other antileptospiral drugs in cases where the diagnosis of leptospirosis is inconclusive.
The local isolates demonstrated a higher MIC toward chloramphenicol, which is in agreement with the findings of Murray and Hospenthal. Previously, chloramphenicol appeared to be effective against Leptospira in experimental mice. However, a higher concentration was required to produce an inhibition or a bactericidal effect on Leptospira strains. Unlike chloramphenicol, ampicillin displayed a lower MIC to the isolates tested, except for one environmental isolate that was resistant (MIC: 25 µg/ml). Administration of ampicillin was a potential option in the treatment of this illness both in vivo and in vitro.,, However, the action of ampicillin against leptospirosis is restricted and cannot be distributed to all organ tissues, such as the kidneys and the heart, rendering it ineffective in clearing leptospires located in protected sites. Currently, penicillin G and doxycycline are recognised as ideal drugs for the treatment of leptospirosis. The MIC results of penicillin G were similar to those produced by ampicillin. However, penicillin G is generally recommended for treating severe leptospirosis. The advantages of using penicillin G include low toxicity and the potential to administer the drug intramuscularly or intravenously at high doses in the early stages of infection. The efficacy of penicillin was compared with ceftriaxone in a trial study in treatment of severe leptospirosis, where one group (n = 86) was given intravenous penicillin G 1.5 million unit/6 h and second group (n = 87) was given intravenous ceftriaxone 1 g daily for 7 days. After 7 days follow-up, no significant difference was observed for median duration of fever, mortality and complications such as renal failure, jaundice and thrombocytopenia.
In this study, one environmental and one zoonotic isolate showed a slightly higher MIC with doxycycline than the rest of the isolates. However, this antibiotic was still effective on all isolates – a finding which correlated with previous studies., Doxycycline has been widely recommended and utilised for the prophylaxis and treatment of mild leptospirosis. In the leptospirosis outbreak that occurred in an eco-challenge multisport competition in Sabah, Malaysia, athletes who had taken doxycycline before the challenge were spared from infection. Truccolo et al. used quantitative PCR assay to evaluate ampicillin, ofloxacin and doxycycline for treatment of experimental leptospirosis. The results showed the ability of ampicillin at a high dose (100 mg/kg of body weight) to clear leptospires from the host, except from kidneys and heart, where 102 leptospires/g remained at day 6. Ofloxacin (30 mg/kg) was unable to clear bacteria from blood or kidneys. With doxycycline (10 mg/kg), the clearance of leptospires occurred in 2 days in all the target organs studied, with the exception of liver, which required 3 days. They concluded that doxycycline had the potential for the treatment of leptospirosis cases compared to other two antibiotics used.
The environmental isolate L. kirschneri had higher MIC with the antibiotics tested compared to clinical and zoonotic isolates. In a study performed by Murray and Hospenthal, the results indicated that L. kirschneri had a higher MIC toward some of the antibiotics tested compared to other species.
| ~ Conclusion|| |
Doxycycline, ampicillin and penicillin G are still effective against all clinical and zoonotic isolates. However, further testing on larger numbers of environmental isolates is required to determine the most suitable antibiotic treatment for leptospirosis.
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Conflicts of interest
There are no conflicts of interest.
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