Multidrug resistant gram-negative bacteria in clinical isolates from Karachi

Area of Science:

• Microbiology
• Molecular Biology
• Clinical Science

Background:

• Antibiotic resistance in bacteria is a growing global health concern.
• Gram-negative bacteria are common causes of hospital-acquired infections.
• The prevalence and characteristics of R plasmids in clinical settings require ongoing investigation.

Purpose of the Study:

• To screen gram-negative bacteria from clinical sources in Karachi for antibiotic resistance.
• To determine the frequency of transferable R plasmids among resistant isolates.
• To assess the stability and characteristics of identified R plasmids.

Main Methods:

• Screening of 54 gram-negative bacterial isolates from Karachi labs and hospitals.
• Testing resistance against ampicillin, chloramphenicol, gentamycin, kanamycin, neomycin, streptomycin, and tetracycline.
• Conjugation experiments to identify transferable R plasmids and curing assays with acridine orange.

Main Results:

• 50 out of 54 isolates (92.6%) showed resistance to at least one antibiotic.
• 13 out of 28 resistant isolates (46.4%) transferred resistance via conjugation, indicating the presence of transferable R plasmids.
• Several conjugative (e.g., pAK series) and non-conjugative (pMT14, pZ26) R plasmids were identified.
• R plasmid pAK15 demonstrated significant spontaneous segregation and marker loss upon curing, highlighting plasmid stability concerns.

Conclusions:

• A high prevalence of antibiotic resistance exists in clinical gram-negative bacteria in Karachi.
• Transferable R plasmids are common in these resistant bacteria, contributing to the spread of antibiotic resistance.
• The stability of these R plasmids is a significant clinical concern, potentially exacerbating treatment challenges.