|Year : 2022 | Volume
| Issue : 1 | Page : 25-29
Study of gram-positive isolates from cases of septicemia and their antibiotic sensitivity pattern with special reference to methicillin-resistant Staphylococcus aureus
Shital Moreshwarrao Mahajan
Department of Microbiology, JNMC, Wardha, Maharashtra, India
|Date of Submission||17-Jan-2022|
|Date of Decision||28-Feb-2022|
|Date of Acceptance||16-Mar-2022|
|Date of Web Publication||25-Jul-2022|
Dr. Shital Moreshwarrao Mahajan
Department of Microbiology, JNMC, Sawangi, Wardha, Maharashtra
Source of Support: None, Conflict of Interest: None
Background: Infections of the bloodstream are a leading source of illness and mortality in all types of communities. Bacteremia is the presence of bacteria in the bloodstream for long or short periods. Aim and Objectives: Dissemination of the bacteria throughout the body with evidence of systemic responses toward microorganisms is septicemia. Many organisms including Gram positive such as Coagulase negative staphylococci, Staphylococcus aureus, Streptococcus pneumoniae, Streptococcus pyogenes, Streptococcus agalactiae, and Enterococcus faecium can cause septicemia. Many precipitating factors such as presence of intravenous catheters, immunocompromised state, and use of cytotoxic drugs may lead to increase in cases of septicemia. Isolation of the offending pathogens and knowledge about sensitivity and resistance pattern of the isolates remain the mainstay of the diagnosis. This study was conducted to cite the bacteriological etiology of septicemia in adults as well as in neonates and to decide the strategy for the cure of septicemia cases along with their antibiotic susceptibility profile. Materials and Methods: Duration of this study was 3 months. In this duration, 100 blood samples from suspected cases of septicemia were processed. Results: Gram positive organisms isolated from the specimens were collected and identified by standard protocols. Antibiotic sensitivity and detection of methicillin resistant Staphylococcus aureus were done by using Kirby Bauer disc diffusion method. Conclusion: Various causative agents were isolated from blood samples. Some of them are resistant to the drugs that are commonly used for the treatment of septicemia. Hence, isolation of the etiological agent along with the detection of its antibiogram pattern is important for early diagnosis and treatment of cases of septicemia.
Keywords: Bacteremia, inducible clindamycin resistance, methicillin-resistant Staphylococcus aureus, septicemia
|How to cite this article:|
Mahajan SM. Study of gram-positive isolates from cases of septicemia and their antibiotic sensitivity pattern with special reference to methicillin-resistant Staphylococcus aureus. J Datta Meghe Inst Med Sci Univ 2022;17:25-9
|How to cite this URL:|
Mahajan SM. Study of gram-positive isolates from cases of septicemia and their antibiotic sensitivity pattern with special reference to methicillin-resistant Staphylococcus aureus. J Datta Meghe Inst Med Sci Univ [serial online] 2022 [cited 2022 Aug 16];17:25-9. Available from: http://www.journaldmims.com/text.asp?2022/17/1/25/352217
| Introduction|| |
Infections of the bloodstream are a leading source of illness and mortality in all types of communities. Bacteremia is the presence of bacteria in the bloodstream for long or short periods. Septicemia is the spread of bacteria throughout the body with indications of systemic reactions to microorganisms.
Septicemia is a serious bloodstream infection. In underdeveloped countries, the rise in cases of septicemia poses major challenge for a clinician to treat and manage the causative etiology. Nowadays, these cases have become more complicated due to the development of multidrug resistance in the causative agent, which is the mainstay of treatment for septicemia. Septicemia can be caused by a variety of species, including Gram-positive bacteria such coagulase-negative staphylococci (CONS), Staphylococcus aureus, Streptococcus pneumoniae, Streptococcus pyogenes, Streptococcus agalactiae, and Enterococcus faecium.
Many precipitating factors such as presence of intravenous devices, immunocompromised state, and use of cytotoxic drugs are associated with rise in cases of septicemia, especially in critical patients from critical units. Isolation of the offending pathogens by culture on different media and report about sensitivity pattern of the isolates remains the mainstay of diagnosis and treatment of septicemia. Neonatal septicemia is a leading cause of neonatal impairment and death. Septicemia in newborns is defined as a widespread bacterial infection confirmed by a positive blood culture within the first 4 weeks of life. According to the World Health Organization, out of 5 million neonatal deaths a year, 98% are occurring in underdeveloped countries.
Septicemia is becoming more common due to multidrug-resistant bacteria all over the world. The widespread availability of over-the-counter medicines and the widespread usage of broad-spectrum antibiotics in the population may explain the multidrug resistance problem.
Septicemia-causing microbes have gained enhanced multidrug resistance to commonly prescribed medicines, making therapy extremely challenging. Thus, having all knowledge regarding the most frequent etiological agents that cause septicemia, as well as their antimicrobial susceptibility patterns, is critical for selecting suitable antimicrobial therapy. These pathogens vary geographically in their antimicrobial susceptibility patterns and are temporally dependent on the commonly used antibiotics and the local pathogens.
As a result, this study was carried out to determine the microbiological etiology of septicemia in adults and neonates, as well as to create a strategy and correct approach for septicemia care based on their antibiotic susceptibility profile.
| Materials and Methods|| |
From June to August 2019, the current investigation was conducted in a tertiary care hospital's department of microbiology.
With a disposable needle and syringe, 2 ml (in neonates) and 5 ml (in adults) of blood were extracted and inoculated into blood culture bottles containing 20 ml and 50 ml of brain–heart infusion broth, respectively. The blood and broth were gently mixed, and the bottles were transferred to the laboratory and incubated aerobically at 37°C. Then, use 5% sheep blood agar (BA) and MacConkey agar (MA) plates to subculture. Gram staining, colony features, and biochemical properties were used to identify the isolates. If there was no growth after 1 week of incubation, the culture was labeled as negative. According to the CLSI 2019 standards, all bacterial isolates were tested for antimicrobial susceptibility using the Kirby-Bauer disc diffusion technique.,
Processing of the specimen
Standard microbiological techniques were used to identify Enterobacteriaceae isolates by examining their shape, colony features, and biochemical responses.
BA and MA were used to inoculate the samples. The plates were incubated for 18–24 h at 37°C overnight.
Identification of isolates
Standard microbiological procedures were used to identify the isolates, which included looking at colony features, morphology, and biochemical reactions.
- Colony characteristics were investigated including size, shape, elevation, margin, surface, opacity, consistency, medium change, and pigment production
- Morphology: A Gram stain was applied to the fixed smear as stated
- Biochemical reactions: Catalase, oxidase, coagulase, carbohydrate fermentation (lactose, glucose, mannitol, and sucrose), indole, methyl red, citrate utilization, urease generation, H2S production test, and other biochemical reactions were carried out according to conventional protocols. All biochemical tests included appropriate positive and negative controls.
Identification of genus Staphylococcus
| Catalase test|| |
The catalase test is the most popular way to tell the difference between Staphylococcaceae and Streptococcaceae bacteria. Catalase is present in Staphylococcus and Micrococcus, but not in Stomatococcus, which has a mild response.
Identification of species Staphylococcus aureus
| Coagulase test|| |
| Slide coagulase test|| |
The bound coagulase is determined by slide coagulase (clumping factor). When floating in plasma, the clumping factor attaches to the bacterial cell wall, and fibrin threads develop between the bacterial cells, causing them to clump into visible aggregates (fibrinogen).
Human plasma with EDTA.
The coagulability of the plasma was determined by adding one drop of 5% calcium chloride to 0.5 ml plasma. Within 10–15 s, a clot should form.
- Positive control – S. aureus
- Negative control – Staphylococcus epidermidis.
Appearance of coarse clumps within 10–15 s was considered positive test.
Staphylococcus lugdunensis may also give slide coagulase test positive. If no clumping was noticed after 2 min, the test was declared negative. All of the isolates were then subjected to a tube coagulase test.
| Antimicrobial susceptibility testing|| |
Each isolate was subjected to antimicrobial susceptibility test as per the CLSI 2019 guidelines by Kirby-Bauer disk diffusion technique.
| Kirby-Bauer disk diffusion technique|| |
Muller-Hinton agar (MHA) was put into a flat-bottomed 9 cm Petri dish More Details to a depth of 4 mm (25 ml).
The inoculum was prepared from the primary culture plate, by touching the tops of 3–5 colonies and suspended in peptone water. The turbidity was set to McFarland standards of 0.5.
Commercially available (HiMedia Lab, Mumbai) disks of 6 mm diameter with recommended potencies were used. Disks used were as follows:
- Piperacillin (100 μg)
- Piperacillin-tazobactam (100/10 μg)
- Cefoxitin (30 μg)
- Ceftazidime (30 μg)
- Ceftazidime-clavulanic acid (30/10 μg)
- Imipenem (10 μg)
- Imipenem-EDTA (10/750 μg)Gentamicin (10 μg)
- Amikacin (30 μg)
- Netilmicin (30 μg)
- Ciprofloxacin (5 μg).
Reading and interpretation
The antibiotic disc was used to measure the diameters of the zone of inhibition. Interpretation, i.e., susceptible, intermediate, and resistant, was done with reference to the CLSI 2019 guidelines.
Each batch of MHA and antibiotic disks were tested by using Escherichia More Details coli ATCC 25922 control strains.
| Methicillin-resistant Staphylococcus aureus detection|| |
| Cefoxitin disc diffusion testing|| |
A cefoxitin disc diffusion test was performed on all S. aureus isolates using a 30 g disc. The isolate was produced as a 0.5 McFarland standard suspension and then cultured on MHA plate. Zone diameters were measured after a 24-h incubation period at 37°C. A resistance zone diameter of <21 mm was observed, whereas a sensitive zone diameter of more than 22 mm was reported.
| Inducible clindamycin resistance: D-zone test|| |
The inducible clindamycin resistance of S. aureus isolates was investigated using a double-disc diffusion test (D-zone test). On the MHA plate inoculated with the test organism, a clindamycin disc (2 g) was placed 15 mm apart from an erythromycin disc (15 g). The strain S. aureus ATCC 25923 was used as a control. After 16–18 h of incubation at 35°C, the plates were examined.
| Reading and interpretation|| |
Positive D-zone test, i.e., existence of inducible clindamycin resistance, was demonstrated by flattening the zone (D shaped) of the clindamycin disc toward the side facing the erythromycin disc. Growth of the organism <14 mm zone of inhibition was taken as constitutive clindamycin resistance. The MS phenotype was defined as staphylococcal isolates that were resistant to erythromycin (zone size 13 mm) but sensitive to clindamycin (zone size 21 mm) and gave a circular zone of inhibition around clindamycin.
| Observations and Results|| |
In the present study, a total of 32 isolates isolated from clinically suspected cases of septicemia were included.
[Table 1] shows the maximum growth of S. aureus, i.e., 16. Rest of the organisms isolated were CONS and Enterococcus sp.
[Table 2] shows that all isolates are sensitive to vancomycin and linezolid. In the present study, out of 16 isolates of S. aureus, 75% were sensitive to clindamycin followed by erythromycin (62.5%) and cefoxitin (50%).
[Table 3] shows that 29.6% of S. aureus were MRSA by cefoxitin disk diffusion test and 14.8% were CONS which are methicillin resistant. 3.7% of S. aureus and 7.4% of CONS showed inducible clindamycin resistant.
|Table 3: Methicillin and inducible clindamycin resistance in staphylococci (n=27)|
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| Discussion|| |
In the present study, a total of 32 isolates isolated from clinically suspected cases of septicemia were included. A total of 32 blood samples were collected from patients and processed in the microbiology department.
Distribution of organisms in septicemia
From [Table 1], Gram-positive organisms, 16% were S. aureus, 11% were CONS, and 5% were Enterococcus sp.
According to Muley et al. reported in 2015, the most common Gram-positive pathogen was S. aureus (22.9%).
Antibiotic sensitivity pattern of Gram-positive organisms
[Table 2] demonstrates that all Gram-positive organisms were susceptible to vancomycin and linezolid, except 12 (75%) S. aureus, 5 (45.5%) CONS, and 1 (20%) Enterococcus sp., which were clindamycin resistant. Cefoxitin sensitivity was found in 50% of S. aureus and 36.4% of CONS. It indicates that these isolates were sensitive to methicillin. 62.5% of S. aureus and 27.3% of CONS were resistant to erythromycin.
Galhotra et al. in 2015 discovered that all Gram-positive isolates were susceptible to vancomycin and linezolid. This finding is similar to the finding in the present study. Prabhu et al. in 2011 observed that 54 (28.42%) of S. aureus were erythromycin resistant which is also a similar finding to the present study. The incidence of methicillin resistance is discussed in [Table 3].
Methicillin and inducible clindamycin resistance in staphylococci
[Table 3] shows that 44.4% were resistant to methicillin and 11.1% were inducible clindamycin resistant. In methicillin-resistant Gram-positive cocci, 29.6% were S aureus and 14.8% were CONS. In inducible clindamycin resistance, 3.7% were S. aureus and 7.4% were CONS.
Kumari et al. in 2008 also reported that the prevalence of MRSA was 26.14%. Galhotra et al. in 2015 observed in their study that from all staphylococcal isolates, 50% were MRSA and 60% were methicillin-resistant CONS (MR-CONS).
According to Ciraj et al., 26 (17.3%) of the 150 S. aureus strains were MRSA and 124 (82.6%) were methicillin-sensitive S. aureus (MSSA). There were 90 methicillin-sensitive CONS and four MR-CONS among the CONS.
Muley et al. reported 18.1% of the Staphylococcus isolates were MRSA. Deotale et al. in 2010 observed that inducible clindamycin resistance was 14.5% in all isolates of S. aureus isolated from clinical samples by using D-test.
In 2011, Prabhu et al. in 2011 found that 20 (37.52%) of all S. aureus isolates were positive for inducible clindamycin resistance using the D-test.
| Conclusion|| |
The present study identified various causative agents of septicemia in adults and neonates such as CONS and S. aureus.
- Along with the etiological agents, antibiotic sensitivity and various resistance patterns are demonstrated
- The detection of etiological agents and their antibiotic sensitivity would undoubtedly aid ineffectual preventative efforts, timely and accurate diagnoses, and subsequent delivery of tailored medication to reduce the disease's excessive burden
- In the present study, MRSA, MR-CONS, and inducible clindamycin resistance in Gram-positive organisms are seen.
- Antibiotic resistance is a concerning sign for the creation of antibiotic policies and procedures for septicemia therapy
- The pathogen pattern of septicemia is changing time to time and over regions so that regular re-evolution of various etiological agents is necessary for an early and accurate diagnosis and correct treatment
- More epidemiological and clinical research is needed to track changes in the bacteria that cause newborn sepsis in the future.
I am thankful to all the technical staff of the department of microbiology.
Financial support and sponsorship
The project was funded by ICMR.
Conflicts of interest
There are no conflicts of interest.
| References|| |
Dagnew M, Yismaw G, Gizachew M, Gadisa A, Abebe T, Tadesse T, et al
. Bacterial profile and antimicrobial susceptibility pattern in septicemia suspected patients attending Gondar University Hospital, Northwest Ethiopia. BMC Res Notes 2013;6:283.
Mohanty A, Singh ST, Kabi A, Gupta P, Gupta P, Kumar P. Bacteriological profile and antibiotic sensitivity pattern of hospital acquired septicaemia in a tertiary care hospital in north east India. Asian J Pharm Clin Res 2017;10: 186-9.
Alam MS, Pillai PK, Kapur P, Pillai KK. Resistant patterns of bacteria isolated from bloodstream infections at a university hospital in Delhi. J Pharm Bioallied Sci 2011;3:525-30.
Agnihotri N, Kaistha N, Gupta V. Antimicrobial susceptibility of isolates from neonatal septicemia. Jpn J Infect Dis 2004;57:273-5.
Jyothi P, Basavaraj MC, Basavaraj PV. Bacteriological profile of neonatal septicemia and antibiotic susceptibility pattern of the isolates. J Nat Sci Biol Med 2013;4:306-9.
Motara F, Ballot DE, Perovic O. Epidemiology of neonatal sepsis at Johannesburg Hospital. South Afr J Epidemiol Infect 2005;20:90-3.
Collee JG, Marr W. Culture of bacteria. In: Collee JG, Marmion BP, Simmons A, editors. Mackie and McCartney Practical Medical Microbiology. 14th
ed. New York: Churchill-Livingstone; 1996. p. 113-29.
CLSI. Performance Standards for Antimicrobial Susceptibility Testing. 29th
ed. CLSI Supplement M100. Vol. 39. Wayne, PA: Clinical and Laboratory Standards Institute; 2019.
Winn WC, Allen SD, Janda WM, Koneman EW, Procop GW, Woods GL, et al
. Introduction to microbiology. In: Koneman's Color Atlas and Textbook of Diagnostic Microbiology. 6th
ed. Philadelphia: Lippincott Williams & Wilkins; 2006. p. 67-110.
Collee JG, Duguid JP, Fraser AG, Marmion BP, Simmons A. Laboratory strategy in the diagnosis of infective syndromes. In: Collee JG, Fraser AG, Marmion BP, Simmons A, editors. Mackie and McCartney Practical Medical Microbiology. 14th
ed. Delhi: Churchill Livingstone; 2007. p. 53-94.
Burke V. Notes on the gram stain with description of a new method. J Bacteriol 1922;7:159-82.
Collee JG, Miles RS, Watt B. Tests for the identification of bacteria. In: Collee JG, Fraser AG, Marmion BP, Simmons A, editors. Mackie and McCartney Practical Medical Microbiology. 14th
ed. Delhi: Churchill Livingstone; 2007. p. 131-49.
Williams RE, harper GJ. Determination of coagulase and alpha hemolysin production by staphylococci. Br J Experimental Pathol 1946;27:72-81.
Bauer AW, Kirby WM, Sherris JC, Turck M. Antibiotic susceptibility testing by a standardized single disk method. Am J Clin Pathol 1966;45:493-6.
Muley VA, Ghadage DP, Bhore AV. Bacteriological profile of neonatal septicemia in a tertiary care hospital from western India. J Glob Infect Dis 2015;7:75-7.
Galhotra S, Gupta V, Bains HS, Chhina D. Clinico-bacteriological profile of neonatal septicemia in a tertiary care hospital. J Mahatma Gandhi Inst Med Sci 2015;20:148. [Full text]
Prabhu K, Rao S, Rao V. Inducible clindamycin resistance in Staphylococcus aureus
isolated from clinical samples. J Lab Physicians 2011;3:25-7.
] [Full text]
Kumari N, Mohapatra TM, Sing YI. Prevalence of methicillin resistant Staphylococcus aureus
(MRSA) in tertiary – Care hospital in eastern Nepal. J Nepal Med Assoc 2008;47:53-6.
Ciraj AM, Vinod P, Sreejith G, Rajani K. Inducible clindamycin resistance among clinical isolates of Staphylococci
. Indian J Pathol Microbiol 2009;52:49-51.
] [Full text]
Deotale V, Mendiratta DK, Raut U, Narang P. Inducible clindamycin resistance in Staphylococcus aureus
isolated from clinical samples. Indian J Med Microbiol 2010;28:124-6.
] [Full text]
[Table 1], [Table 2], [Table 3]