Abstract
This objective of the study was to determine the inhibitory effect of zinc sulfate against the clinical isolates of Pseudomonas aeruginosa and Acinetobacter baumannii. The inhibitory effect of zinc sulfate was determined against the 120 clinical isolates (60 isolates of P. aeruginosa and 60 isolates of A. baumannii) by agar dilution method. The findings indicate that zinc has an inhibitory effect on the clinical isolates of P. aeruginosa and A. baumannii at a concentration ranging from 0.25to 1mg/ml of zinc sulfate by agar dilution method.
Keywords: Acinetobacter baumannii, inhibitory effect, Pseudomonas aeruginosa, zinc sulfate
INTRODUCTION
Zinc, an essential trace element with an estimated total body content of 2–3g, has a proven role in many physiologic enzymatic and structural functions. It is also used as an adjunct in the treatment of diarrheal diseases in the form of supplemental systemic oral administration.[1] Studies have shown the antibacterial action of zinc ions in vitro against Gram-positive and Gram-negative bacteria.[2,3] Nosocomial infections are one of the important complications of hospitalization, leading to increased morbidity and mortality, with Pseudomonas aeruginosa and Acinetobacter baumannii being the most common nosocomial pathogens. The present study was undertaken to determine the inhibitory effect of zinc sulfate on the clinical isolates of P. aeruginosa and A. baumannii.
MICROBIOLOGY REPORT
A laboratory-based cross-sectional study was carried out in the Department of Microbiology at Pondicherry Institute of Medical Sciences from May to June 2018. A total of 120 clinical isolates (60 clinical isolates of P. aeruginosa and 60 clinical isolates of A. baumannii) from exudates, respiratory specimens, urine, and tissues from infected wounds were included in the study. The clinical specimens received in the Department of Microbiology were processed, and the organisms isolated were identified according to the standard guidelines.[4] The minimum inhibitory effect of zinc sulfate was determined against the clinical isolates of P. aeruginosa and A. baumannii by agar dilution method[5] [Figures 1 and 2]. Zinc sulfate (ZnSO4.H2O) manufactured by Sigma Aldrich (99.9 trace metal basis purity) was used in the study. The minimum inhibitory concentration of active zinc in ZnSO4. H2O ranging from 0.03 to 1mg/ml was tested based on the results of the previous study.[3] ATCC P. aeruginosa was included as a control strain. The inhibition concentration was recorded as the lowest concentration of zinc sulfate that completely inhibited growth, disregarding single colony or faint haze caused by the inoculum. All the 120 clinical isolates (60 P. aeruginosa and 60 A. baumannii) were inhibited at a concentration ranging from 0.25 to 1mg/ml of zinc sulfate [Table 1]. In a study conducted by Faizetal., they found that the enteric bacterial pathogens were inhibited at a concentration of 0.06 to 0.5 mg/ml.[3] In our study, the inhibitory concentration wasslightly higher; this could be because of the multidrug-resistant clinical isolates of P. aeruginosa and A. baumannii. We also found that the clinical isolates of A. baumannii were all inhibited at 0.5 mg/ml of zinc sulfate when compared to clinical isolates P. aeruginosa which were inhibited at 1 mg/ml.
Figure 1.
Minimum inhibitory concentration of zinc among clinical isolates of Pseudomonas aeruginosa
Figure 2.
Minimum inhibitory concentration of zinc among clinical isolates of Acinetobacter baumannii
Table 1.
Number of Isolates inhibited by different concentrations of zinc sulfate (mg/ml)
| Isolates | Number of isolates inhibited by various concentrations of ZnSO4.H2O (mg/ml) |
Total | |||||
|---|---|---|---|---|---|---|---|
| 0.03 | 0.06 | 0.125 | 0.25 | 0.5 | 1.0 | ||
| Pseudomonas aeruginosa | 0 | 0 | 0 | 1 | 6 | 60 | 60 |
| Acinetobacter baumannii | 0 | 0 | 0 | 0 | 52 | 60 | 60 |
ZnSO4.H2O: Zinc sulfate
Nosocomial infections caused by multidrug-resistant Gram-negative organisms, especially A. baumannii and P. aeruginosa, are becoming difficult to treat and have led to longer hospital stay, higher medical costs, and increased mortality. The search for alternate agents having antimicrobial agents is on, and the results of the present study revealed the antibacterial effect of zinc against the bacterial pathogens P. aeruginosa and A. baumannii.
CONCLUSION
Use of zinc as an additional agent or addition of zinc to antibiotic formulations could help in controlling infections caused by these organisms.
Financial support and sponsorship
ICMR STS Fellowship Project, 2018 supported the study.
Conflicts of interest
There are no conflicts of interest.
Acknowledgment
The authors acknowledge the Indian Council of Medical Research, New Delhi, India, for providing Short-Term Research Studentship (STS 2018-02226) to the first author.
REFERENCES
- 1.Strand TA, Chandyo RK, Bahl R, Sharma PR, Adhikari RK, Bhandari N, et al. Effectiveness and efficacy of zinc for the treatment of acute diarrhea in young children. Pediatrics. 2002;109:898–903. doi: 10.1542/peds.109.5.898. [DOI] [PubMed] [Google Scholar]
- 2.Khan F, Patoare Y, Karim P, Rayhan I, Quadir MA, Hasnat A. Effect of magnesium and zinc on antimicrobial activities of some antibiotics. Pak J Pharm Sci. 2005;18:57–61. [PubMed] [Google Scholar]
- 3.Faiz U, Butt T, Satti L, Hussain W, Hanif F. Efficacy of zinc as an antibacterial agent against enteric bacterial pathogens. J Ayub Med Coll Abbottabad. 2011;23:18–21. [PubMed] [Google Scholar]
- 4.Winn WC. Introduction to Microbiology Part II: Guidelines for the collection, transport, processing, analysis, and reporting of cultures from specific specimen scouces. In: Koneman EW, editor. Koneman's Color Atlas and Textbook of Diagnostic Microbiology. Philadelphia: Lippincott Williams and Wilkins; 2006. [Google Scholar]
- 5.Clinical and Laboratory Standards Institute. Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria that Grow Aerobically, Approved Standard. M07-A10. 10th ed. Wayne, PA USA: CLSI; 2015. [Google Scholar]