Discussion and Conclusion on MRSA Infections PDF

CHAPTER- 6 DISCUSSION F  DISCUSSION S. aureus is one of the common causes of nosocomial and community-acquired infections with high mortality and morbidity. Increased methicillin resistance among Staphylococci has posed great difficulty managing such infecti...

CHAPTER- 6 DISCUSSION F  DISCUSSION S. aureus is one of the common causes of nosocomial and community-acquired infections with high mortality and morbidity. Increased methicillin resistance among Staphylococci has posed great difficulty managing such infections. Hence, an accurate and rapid detection of methicillin resistance is essential to choose appropriate antibiotics and control the spread of MRSA. Many phenotypic methods to detect MRSA have been developed but are slow and vary in sensitivity and specificity. Detecting the mec-A gene by PCR is the gold standard for MRSA identification. However, using molecular methods for routine practice is not affordable for many resource-constrained laboratories. Therefore, it is essential to develop a rapid, accurate, and sensitive phenotypic method to detect MRSA. Staphylococcus aureus, a common pathogen causing various human infections , has been the subject of numerous studies on its prevalence, antimicrobial susceptibility, phage types, and molecular characteristics of MRSA in India. However, the scarcity of published literature on the molecular characteristics of MRSA in India underscores the need for a collaborative effort. We have joined forces to study MRSA's phenotypic and genotypic characteristics, recognizing that only through teamwork can we provide a comprehensive understanding of its clinical and epidemiological aspects. In our study, out of 45 MRSA isolates; the maximum isolation of MRSA was from pus 25(27%), followed by Urine 9(36%), Blood 5(38%), ear swab 3(33%), and tip culture 3(33%). This is consistent with the study done in Yemen and Kerala In contrast to our study, other studies from Iran and Nigeria reported a high rate of isolation from blood (29%) and urine (76%), respectively. A Kenyatta study observed a high isolation rate from pus (68%). An increased isolation rate of S. aureus from pus may be due to the exposure of wounds or skin breaches, making them more prone to invasion of S. aureus infections. In many cases, poor hygiene is a predisposing factor. In our study, the prevalence rate of MRSA was 30%, which was higher than the survey done by Oberoi et al. , who reported a prevalence of 28.86% in their study in northern 82  India, which was lower than ours. Silvana et al 109. Their survey in Brazil documented a prevalence of 37.7% of S. aureus in ICU patients. A study from Southeast Nigeria revealed a prevalence of 60.4%. In another study from Odisha, India, the prevalence rate of MRSA was 31%, slightly higher than our finding. On the contrary, Tebelay et al. observed a 14.3% S. aureus prevalence in their study at Yekatit, Ethiopia, from September 2013 to April 2014. Overall, this was very low compared to our study. Overall, the prevalence varies from place to place and from time to time. There was a male predominance in staphylococcal infections, which could be related to their susceptibility to staphylococcal infections such as pyogenic, traumatic or other environmental causes. Moreover, when they go outside, males are likely to consume antimicrobials, subjecting them to multidrug-resistant infection. Apart from the socio- cultural practices prevalent in this area, people give much importance to males, and hence, sick males are often taken to hospitals for treatment of the underlying disease and their complications frequently by the family member and the spouse. Since male patients are exposed to different environments and injuries, either due to their occupation or trauma, they get admitted or consult surgical specialties. Hence, in the present study, not only patients suffer from MRSA, but they also suffered from one or other surgical causes. In the present study, 45(30%) of 150 staphylococcus aureus isolates were MRSA stains. The incidence rate of male MRSA is 30/45 (66.7%), and female MRSA is 15/45 (33.3%). Most MRSA were from the male patient’s 31-40 age group (8), and females were from the 31-40 age group (5). In the present study, comparing two phenotypic methods proved that the cefoxitin (30μg) disc diffusion method is better than the oxacillin (1μg) disc diffusion method in screening MRSA strains. 83 Another significant finding of this study showed that all MRSA isolates were significantly less sensitive to antibiotics than MSSA. However, all S. aureus isolates were sensitive to vancomycin and linezolid. The sensitivity pattern of MRSA strains with other antibiotics was 86.7% were sensitive to Co-trimoxazole, 84.4% were sensitive to clindamycin, 82.2% were sensitive to gentamycin, 75.6% were sensitive to erythromycin, and 64.4% were sensitive to ciprofloxacin. Like many other studies from India and Iran , all the isolates, irrespective of their methicillin sensitivity or resistance status, were sensitive to linezolid (100%), teicoplanin (100%) and vancomycin (100%). Our study adds to the existing facts that glycopeptides (vancomycin and teicoplanin) and linezolid appear to be the most beneficial options available for treating MRSA infections. In our study, the isolation rate of HA-MRSA and CA-MRSA was 40 % and 60 %, respectively. In discordance with our study, Nagaraju et al. reported a low prevalence of 11.8% CA-MRSA in their study. John et al. documented almost equal prevalence of HA-MRSA (54%) and CA-MRSA (52%) in their study. A study from Raichur, Karnataka, reported 75% and 25% prevalence of HA-MRSA and CA-MRSA, respectively. D’souza et al. reported 54% CA-MRSA. Available reports demonstrated variations in the prevalence of HA and CA MRSA in different places at different times. The prevalence of CA-MRSA infections in males was noticed in many studies. Naimi et al. found the prevalence of CA and HA MRSA was 12% and 85%, respectively, in their study in the USA. Out of 45 strains of MRSA analysed for the presence of the mecA gene, it was found to be positive in 40 strains (88.9%). The remaining, though negative, might have carried other methicillin resistance genes like mec B and mecC genes , or there could be a loss or mutation in the gene or hyperproduction of β-lactamase, production of normal PBP with altered binding capacity and other unidentified factors. Though cefoxitin is a better inducer of the mecA gene, in our study, there is a discrepancy between the phenotypic resistance to cefoxitin and the presence of the mecA gene in PCR. However, 84 few other studies reported almost no disagreement between phenotypic cefoxitin disc diffusion test and molecular mecA gene detection. Among the 45 strains processed for the PVL gene, 31 (68.9%) were positive, highly represented among community-acquired MRSA strains. PVL is a leucocyte-destroying cytotoxin responsible for severe necrotising pneumonia and skin and soft tissue infections. In this study, Kaur et al. from Belgaum, South India, and D'Souza et al. from Mumbai reported 85% and 64% positivity for the PVL gene among MRSA, respectively. The higher prevalence of the PVL gene in these studies might be due to the misuse, overuse and abuse of antibiotics, indicating the progress of resistant strains along with this PVL gene. MRSA strains with the PVL gene get transmitted from draining wounds. SCCmec typing is one of the molecular techniques used to correlate the relationship of MRSA strains with their source -community or hospital-acquired. It has been reported that SCCmec V and IV are associated with community-acquired strains. Similarly, in this study, out of the 45 strains processed for SCC mec typing, 16(35.6%) had SCC mec type III, 13 (28.9%) had SCC IV type, 7(15.6%) had SCC mec III type, 4(8.9%) and 5 (11.1%) which are prevalent among CA-MRSA strains and 5(11.1%) were negative for SCCmec. This study revealed that community strains are being introduced into hospitals. This contrasts with the study from Mumbai, which showed that among the MRSA, 25% of the isolates were SCCmec III, 34% were SCCmec IV, and 41% were SCCmec V. Goolam et al. observed 53% of SCCmec type I and 47% of SCCmec type IV among MRSA. A study from Iran by Javid et al. documented the prevalence of SCCmec as follows: SCCmec types were type III (48.31%), type V (19.1%), type I (16.85%), and type IV (3.37%). Some of their isolates (13.3%) were not typable, similar to other studies from various world regions. Five of the 45 MRSA strains, which were also negative for the mecA gene, were found to be nontypable under SCCmec typing. Due to technical constraints, further SCCmec typing beyond SCCmec V was not attempted. 85 The study's limitations are its single-centre design and the non-availability of whole genome sequencing. The sample size for the genotypic characterization was limited to 45. Analysis of SCCmec was limited to SCCmec I-V types only. Phage typing could not be completed for this study's MRSA strains. 86 CHAPTER- 7 CONCLUSION AND SUMMARY G  CONCLUSION Staphylococcus aureus contributes to hospital-acquired infections (HAI) and considerably increases the burden on the healthcare system due to its morbidity and mortality. This study was carried out with the S. aureus strains isolated from 18 months with the objectives to find out the rate of isolation of MRSA among them and their antimicrobial susceptibility pattern, study the molecular characterization of selected MRSA strains and elicit its association with clinical and selected epidemiological parameters. Standard laboratory methods were followed for collection, transport, isolation, identification, antimicrobial susceptibility testing, phage typing, and molecular tests. Based on the tests, the following conclusions were drawn. 1. During the study period, 150 strains of S were totalled. aureus was isolated among the total bacterial isolates from heterogeneous clinical samples, namely pus, urine, blood and tip culture. 2. of 150 staphylococcus aureus isolates in this study, 45(30%) were MRSA stains. The incidence rate of male MRSA is 30/45 (66.7%), and female MRSA is 15/45 (33.3%). Most MRSA was from the male patient’s 31-40 age group (8), and females were from the 31-40 age group. 3. Out of 150 S. aureus isolates, the highest number of S. aureus were isolated from pus samples 92(61.3%), followed by urine 25(16.7%), blood 13(8.7%), ear swab 11(7.3%) and catheter tip culture 9 (6%) and isolates 45 were MRSA, the maximum isolation of MRSA was from pus 25(27%), followed by Urine 9(36%), Blood 5(38%), ear swab 3(33%), and tip culture 3(33%). 4. In our study, the prevalence rate of MRSA was 30% (n=45). The variations observed were attributable to the nature of infections, previous antimicrobial exposure, duration of therapy and adherence. Overall, methicillin resistance was going up globally and implicated to use, misuse and overuse of antimicrobial agents. 5. During the study period, many MRSA isolates were sensitive to commonly used antimicrobial agents, probably due to their minimal utilization in clinical practice. 87 6. The antibiotic sensitivity pattern amongst the MRSA isolates shows that 100% were sensitive to vancomycin and linezolid, 86.7% were sensitive to Co-trimoxazole, 84.4% were sensitive to clindamycin, 82.2% were sensitive to gentamycin, 75.6% were sensitive to erythromycin, and 64.4% were sensitive to ciprofloxacin. Similarly, no resistance was seen with vancomycin and linezolid. 7. All 45 MRSA strains were sensitive to linezolid and vancomycin, as these are kept as reserved drugs. 8. In this study, All MRSA isolates confirmed by phenotypic and genotypic methods were further categorized into HA-MRSA and CA-MRSA based on the Centers for Disease Control and Prevention (CDC) definition. Based on the CDC definition, the 45 confirmed MRSA isolates were categorised into 18(40%) HA-MRSA and 27 (60%) CA-MRSA. 9. Confirmation of MRSA: The overall percentage of MRSA production was 45/150(30%) among the three tests. The Oxacillin was observed in 43 isolates, whereas 45 isolates showed MRSA production by the remaining two tests, including Cefoxitin & E-test 10. Molecular characterization of these isolates revealed the presence of the mecA gene in 40 of 45 strains. 40 of these had SCCmec, 16(35.6%) had SCC mec type III, 13 (28.9%) had SCC IV type, 7(15.6%) had SCC mec III type, 4(8.9%) and 5 (11.1%) had not been detected. 11. The PVL gene was detected in 31 of the 45 MRSA strains studied. The clinical outcomes didn’t correlate with the presence of the PVL gene in the MRSA isolates. In this study, cefoxitin was superior to oxacillin for the detection of MRSA by disc diffusion method. Results of cefoxitin disc diffusion, ORSA and E-test concord with PCR results. PCR is too costly to be routinely implemented in most clinical laboratories. Therefore, cefoxitin can be a good surrogate marker for detecting MRSA. However, another high-sensitivity and specificity test, like the E-test, should combine cefoxitin disc diffusion to confirm S. aureus strains showing inhibition zone diameter between 20-22 mm. Linezolid & vancomycin were the highly sensitive drugs against MRSA isolates. 88 90