Pattern of Polymicrobial Isolates and Antimicrobial Susceptibility from Blood

Area of Science:

• Medical Microbiology
• Infectious Diseases
• Clinical Pathology

Background:

• Bloodstream infections (BSIs) pose a significant global health challenge.
• Understanding the etiological agents and their antimicrobial susceptibility patterns is crucial for effective treatment.

Purpose of the Study:

• To investigate the prevalence of polymicrobial isolates in blood cultures.
• To determine the antimicrobial susceptibility patterns of these isolates in a tertiary care hospital.

Main Methods:

• A cross-sectional study was conducted at the Sindh Institute of Urology and Transplantation (SIUT), Karachi.
• Blood cultures were processed using the BACTEC 9240 system.
• Antimicrobial susceptibility testing followed Clinical and Laboratory Standards Institute (CLSI) guidelines.

Main Results:

• Out of 7251 samples, 40.42% showed positive growth, with 18.5% being polymicrobial.
• Gram-positive bacteria (51.84%) were more frequent than Gram-negative bacteria (48.15%) in polymicrobial infections.
• High rates of resistance were observed, including Methicillin-resistant Staphylococcus aureus (24.65%), third-generation cephalosporin resistance in Klebsiella spp. (63.6%) and E. coli (58%), and carbapenem resistance in Pseudomonas aeruginosa (5.9%) and Acinetobacter spp. (17.6%).

Conclusions:

• Gram-positive bacteria, particularly Coagulase-negative Staphylococcus, are common in polymicrobial BSIs.
• Methicillin-resistant Staphylococcus aureus constitutes a significant proportion of isolates.
• Elevated resistance to third-generation cephalosporins and carbapenems highlights the need for vigilant antimicrobial stewardship.