The increasing prevalence of antimicrobial resistance in pathogens, especially among the hospitalized patients, requires swift and precise identification of infectious agents. The necessity for prompt intervention is emphasized, as suitable antibiotic therapy can markedly enhance patient outcomes.¹⁰ The establishment of new microbiological and the use of novel microbial identification media are essential for timely disease diagnosis and monitoring of antimicrobial resistance. This study investigates the effectiveness of Chrom agar for identifying the bacteria associated with pyogenic infections, emphasizing bacteriological profiles, antibiotic susceptibility patterns, and comparing turnaround times with traditional culture methods.

The specimen collected in the present study were mostly from the female participants (53 percent), with the mean age of all the participants being 49.55 ± 20.72 years. The higher proportion of specimen obtained from females suggested a greater prevalence of pyogenic infections, such as those affecting skin and tissues. For instance, studies had shown that S. aureus is a common isolate in wound infections, and its prevalence could vary based on gender demographics.^11,12 Understanding this distribution is crucial for tailoring appropriate treatment protocols and antibiotic stewardship programs.

Regarding the clinical presentation of pyogenic infections among the participants, the majority of samples (66%) were pus, highlighting the actual nature of these infections, followed by wound samples (21%). The results were in contrast with a study conducted by Kalita et al., where the majority samples were wound swabs (75.53%), followed by pus aspirate (24.47%), which highlights the variability in sample types with pyogenic infections across different groups and study settings.¹³

Available evidence had shown that prior antibiotic exposure could significantly influence the outcomes of microbial cultures. Studies had shown that administering antibiotics before collecting samples could lead to negative results in culture. For instance, researches had indicated that samples from the patients who received antibiotics prior to sample collection often exhibited lower isolation rate due to suppression of bacterial growth or selection for resistant strains.^14,15 In the present study, the lack of prior antibiotic treatment among 71 percent of the participants enhanced the likelihood of obtaining reliable culture results, as these samples were less likely to be affected by antibiotic-induced alterations in microbial flora.

Regarding the Gram’s reaction, Gram-negative rods were predominant 53 percent, highlighting their role in these infections, while Gram-positive cocci in pairs were also present (48 percent). Results of a study conducted by Kalita et al. reported that Gram-negative organisms were predominantly isolated followed by Gram-positive cocci, which was in line with the findings of the present study.¹¹ Many studies had reported the prevalence of Gram-negative organisms in causing pyogenic wound and skin-and-soft-tissue infections, encompassing abscesses, cellulitis, furunculosis, folliculitis, and surgical-site or other purulent wound infections.^13,16-18 The results suggested that Gram-negative organisms play a major role in the aetiology of pyogenic infections, followed by Gram-positive cocci. Notably, the observation of 22 samples showing no bacterial growth suggested the need to identify potential non-bacterial aetiologies and necessitating the use of advanced identification techniques.

The finding that 22 of the sample cultures showed no bacterial growth indicates the possibility of non-infectious causes or the existence of fastidious organisms that standard culture methods may not have identified. This observation was significant as it underscores the limitations of HiChrome agar and conventional culture techniques, which might not identify certain pathogens, especially those necessitating specialized growth conditions. The results of the present study regarding the bacterial organisms isolated aligned with the reports of Trojan et al. which identified E. coli (51.2%) as the most prevalent organisms from pus samples, followed by S. aureus (21%), K. pneumoniae (11.6%), P. aeruginosa (5.8%), Citrobacter spp. (3.5%), A. baumannii (2.3%), P. mirabilis (2.3%), and Streptococcus spp. (2.3%).¹⁹

This emphasizes the diagnostic value of chromogenic agar in identifying bacteria from purulent infections. The present study examined purulent infections other than UTIs; however, the recurrent isolation of E. coli across various infection types indicated a wider pathogenic capacity. S. aureus was detected in 13% of participants, highlighting the persistent involvement of Gram-positive cocci in pyogenic infections. S. aureus is a significant pathogen associated with skin and soft tissue infections, such as abscesses and cellulitis. The isolation rate was in accordance with findings corresponds with findings of Sudhaharan et al., which identified S. aureus as the predominant Gram-positive isolate in comparable contexts, accounting for 91.7% of Gram-positive isolates in purulent samples.¹⁶ The consistency observed in various studies underscores the significance of S. aureus in pyogenic infections and its implications for clinical practice. The result of the present study aligned with those of Poolman et al., who identified E. coli and S. aureus as key pathogens linked to bacteraemia and nosocomial infections, especially in older populations.²⁰ The repeated identification of these organisms in multiple studies indicated that E. coli and S. aureus are the most significant causative organisms for infections, underscoring their importance as primary targets for antibiotic therapy.

In antibiogram, variations in antibiotic susceptibility could be observed among different isolates, underscoring the necessity for tailored antibiotic therapy. E. coli and K. pneumoniae exhibited significant sensitivity to netilmicin, tobramycin, imipenem, amikacin, and meropenem, suggesting the efficacy of carbapenems against these Gram-negative bacteria, consistent with the findings of Swain et al., P. aeruginosa demonstrated 85.71% sensitivity to tobramycin and the susceptibility to carbapenems and ciprofloxacin.²¹ However, it exhibited reduced susceptibility to gentamicin (42.86%) and piperacillin-tazobactam (14.29%), highlighting the necessity for judicious antibiotic selection. K. pneumoniae exhibited sensitivity to gentamicin; however, other studies had documented varying susceptibility patterns among Gram-negative isolates.²¹ All tested strains of S. aureus were susceptible to linezolid, aligning with the findings of Swain et al., indicating that linezolid is an effective treatment option for S. aureus infections.²¹ E. faecalis and E. faecium demonstrated susceptibility to gentamicin, ampicillin, and vancomycin; however, the limited number of isolates might constrain the generalisation of these findings. Continuous monitoring of antibiotic resistance patterns is crucial for effective infection control.

The results of the current study underscore a troubling trend in antimicrobial resistance (AMR), especially in pathogens like S. aureus and K. pneumoniae. As per the study, K. pneumoniae was a significant pathogen associated with pyogenic infections, consistent with the earlier research which showed a rising prevalence of multidrug-resistant strains in both community and hospital environments.²² The rising incidence of MRSA, associated with a notable increase in global mortality, highlights the critical need to tackle AMR. The existence of (ESBL) possessing pathogens, especially E. coli, often hampers the treatment options due to their resistance to various antibiotic classes.²³ In addition, the rise in multidrug-resistant pathogens highlights a global challenge of antimicrobial resistance, fuelled by inadequate stewardship and the widespread misuse of antibiotics in both clinical and agricultural practices.²³ A recent analysis from The Lancet indicated that antibiotic-resistant illnesses might result in almost 8 million fatalities each year by 2050 if prevailing trends persist, underscoring the urgent necessity for enhanced healthcare systems and antibiotic stewardship initiatives.²⁴

A matching rate of 100 percent was observed with HiCrome agar regarding the isolation of E. coli and K. pneumoniae in comparison with conventional culture media, which highlighted the effectiveness of HiCrome agar in isolating these organisms in clinical settings. Similarly, 100 percent matching rate was observed with respect to the isolation of P. mirabilis and E. faecium, suggesting HiCrome agar as a reliable medium for the isolation of these pathogens as well.

In contrast, S. aureus showed a matching rate of 92.31%, while the detection rate for P. aeruginosa was 85.71%, and 80% for E. faecalis. Significant drawbacks were noted for P. vulgaris, P. putida, and C. albicans, which exhibited 0% matching rates. The results indicated that even though the medium is effective in general, it might not consistently detect all microorganisms because of the varied utilisation of media components.²⁵

Previous studies had reported the use of chromogenic agar for detecting uropathogens, MRSA, and Shiga-toxin-producing E. coli, among others.^17,26-33 The results of a study by Jangla et al. were similar to that of the present study with the colony characteristics of E. coli, K. pneumoniae, P. aeruginosa, S. aureus in HiCrome being similar to identification by Vitek 2 Compact.³⁴ A study by Nahar et al., reported that both HiCrome UTI agar and Blood agar media supported the growth of all the bacteria under study, while MacConkey agar yielded an isolation rate of 91.72%, which showed the efficacy of HiCrome agar in identifying the uropathogens.³⁵ The present study represented the first report of using chromogenic agar specifically for detecting the microorganisms responsible for pyogenic infections, further validating its application in diverse clinical contexts.

The comparison of (TAT) for bacterial identification between conventional culture methods and chromogenic agar revealed significant differences in efficiency and effectiveness. In the study, the conventional method required 48 h for bacterial identification, while Chrom agar demonstrated a remarkable capability, with 57.55% of isolates reported within 24 h. This difference was statistically significant (p <0.0001), indicating that Chrom agar was effective for rapid identification of pathogens. However, while Chrom agar showed a 42.5% success rate at 48 h, the conventional method achieved a 100% success rate at the same time point. This difference could be explained by the fact that the reference culture on chrome agar had shown 100 percent match, however, identification of certain organisms required further biochemical tests, which caused a delay in TAT. The results suggested that Chrom agar was particularly useful for immediate outcomes, making it advantageous in clinical settings, where rapid diagnosis is critical. In addition, the findings also aligned with recent studies that emphasised the utility of chromogenic media in reducing TAT for bacterial identification. For instance, research had shown that Chrom agar could facilitate quicker identification of various pathogens, including E. coli and S. aureus, compared to traditional methods.^36-38 However, the conventional method remains reliable for comprehensive identification over longer periods, as it consistently yields accurate results across all tested organisms.

The effectiveness of Chrom agar in short-term identification is crucial in acute care settings, where timely intervention can significantly impact patient outcomes. Nevertheless, the conventional method’s reliability over extended periods underscores the importance of evaluating both short-term and long-term effectiveness while selecting diagnostic methods. This dual approach ensures that clinicians can make informed decisions based on immediate needs while maintaining a high standard of accuracy in pathogen identification.

The present study recognized considerable limitations, notably its limited sample size, which constrained the generalisation of the results. The data from a restricted sample size might not reliably reflect the broader population dynamics, particularly concerning various diseases and resistance patterns in different situations. Although chromogenic agar facilitated expedited bacterial identification within 24 h it failed to yield exhaustive results for all isolates. Conversely, traditional approaches attained a 100% identification rate within 48 h indicating that chromogenic agar might not reliably expedite identification for rare or fastidious species, thus jeopardizing diagnostic accuracy when timely identification is essential.

This was the first investigation regarding the efficacy of chromogenic media in isolating and identifying pyogenic organisms, juxtaposing its findings with traditional approaches to elucidate their different advantages and disadvantages. By enabling visual, colour-based presumptive identification directly from the primary plate, HiCrome reduced the need for secondary media and cut the average reporting time from 48 h to approximately 24 h, translating into a measurable decrease in technician workload and overall laboratory costs. The clinical implications are substantial: swift identification facilitates expedited therapy decisions in acute care environments. Clinicians must acknowledge the constraints of chromogenic agar with certain organisms, while appreciating the dependability of traditional approaches. Combining both methodologies enhances diagnosis, hence improving patient care through prompt interventions and increased precision.