Deaths from drug-resistant Acinetobacter baumannii in Pakistan fell 41% over three decades

Deaths attributable to antimicrobial-resistant Acinetobacter baumannii in Pakistan have fallen sharply over three decades, according to a descriptive trend analysis of Global Burden of Disease (GBD) 2021 estimates published in Discover Bacteria. The age-standardised death rate for resistance to one or more antibiotics dropped by 41.0%, from 5.767 per 100,000 population in 1990 to 3.403 per 100,000 in 2021, after peaking at 6.544 per 100,000 in 1999. The decline accelerated after 2012, with a particularly steep reduction between 2014 and 2021, yet the burden remains substantial and heavily concentrated in a single antibiotic class.

A. baumannii is a Gram-negative, non-motile, aerobic coccobacillus that has evolved from a low-virulence environmental organism into one of the most dangerous hospital pathogens worldwide. It survives on dry hospital surfaces, resists desiccation, forms biofilms and acquires resistance genes through horizontal gene transfer, making it exceptionally well suited to healthcare settings. Today it is found most often in intensive care units, where it primarily strikes critically ill patients who are immunocompromised, on mechanical ventilation or undergoing lengthy invasive procedures. The World Health Organization classifies it as a critical-priority pathogen because of its high capacity for antimicrobial resistance.

The new analysis, led by Muhammad Nabeel Saddique and colleagues, extracted data from the IHME MICROBE online visualisation tool using parameters specific to Pakistan, both sexes combined, age-standardised rates, deaths per 100,000, the attributable counterfactual and the years 1990 to 2021. The GBD 2021 AMR framework integrates data from 520 million individual records or isolates across 19,513 study-location-years, drawing on cause-of-death data, hospital discharge records, microbiology data, published literature, surveillance networks, pharmaceutical sales, antibiotic use surveys and insurance claims. Because Pakistan-only data would be insufficient to produce stable annual estimates across all pathogen-drug combinations, the framework uses global datasets with spatiotemporal modelling to generate country-specific estimates.

The counterfactual used is important for interpreting the numbers. The attributable burden counterfactual estimates the excess mortality that would be averted if all drug-resistant infections were replaced by drug-susceptible infections of the same pathogen and infectious syndrome, isolating the mortality impact of resistance itself rather than the burden of infection as a whole. Point estimates were accompanied by 95% uncertainty intervals derived from the 2.5th and 97.5th percentiles of 100 posterior draws from the estimation process. The MICROBE estimates for A. baumannii cover all infectious syndromes modelled within the GBD framework for this pathogen, including bloodstream infections and lower respiratory infections, and are not restricted to a single syndrome.

Carbapenems carried the highest individual-class burden throughout the 32-year period. The death rate attributable to carbapenem-resistant A. baumannii was 2.277 per 100,000 in 1990, rose to a peak of 2.980 per 100,000 in 2004 and then declined to 1.581 per 100,000 in 2021, a 30.6% reduction from the 1990 baseline. Even after this decline, carbapenems remained the single largest contributor to drug-class-specific AMR-attributable mortality in 2021, accounting for approximately 46.5% of the composite burden. The authors note that resistance to last-line medications such as tigecycline and colistin, which are increasingly reported in Pakistani isolates, is not captured by the current framework.

The largest relative declines occurred in other classes. Anti-pseudomonal penicillin/beta-lactamase inhibitor combinations fell by 79.8%, from 0.494 per 100,000 in 1990 to 0.100 in 2021. Fourth-generation cephalosporins dropped by 79.1%, from 0.118 to 0.025, though they peaked at 0.195 in 2005 before declining. Third-generation cephalosporins showed a consistent downward trend from 0.578 in 1990 to 0.156 in 2021, a 73.1% reduction and the second-largest relative decline among the seven classes. Aminoglycoside resistance fell by 44.5%, from 1.018 per 100,000 in 1990 to 0.565 in 2021, after peaking at 1.165 in 2000.

Fluoroquinolone resistance followed a distinct inverted-U trajectory, rising from 1.244 per 100,000 in 1990 to a peak of 1.599 in 2010 before falling to 0.938 in 2021, a 24.6% decline from baseline. The authors suggest this delayed peak may reflect prolonged and widespread empirical fluoroquinolone use for urinary tract infections and community-acquired pneumonia, supported by low cost, oral bioavailability and widespread over-the-counter access that remained only partially regulated after Pakistan’s 2017 National Action Plan on AMR. This pattern deviates from GBD drug-class analyses for Gram-negative bacteria, which typically show fluoroquinolone resistance peaking between 1998 and 2005.

Beta-lactam/beta-lactamase inhibitor resistance was the only class showing a nominal net increase, rising 5.9% from 0.038 to 0.040 per 100,000. The authors caution that the wide, substantially overlapping uncertainty intervals for the 1990 and 2021 estimates mean this change is not statistically distinguishable from zero and should be interpreted with caution, particularly given the sparse underlying data for this combination in Pakistan. The class nonetheless had the lowest absolute burden and fluctuated notably, peaking at 0.127 per 100,000 in 2012, a timing that coincided with the global expansion of the NDM-1 resistance mechanism.

Joinpoint regression confirmed statistically significant declining trends for most classes. The composite resistance measure had an average annual percentage change of minus 1.7% over 1990 to 2021, with a joinpoint at 1999 separating an initial rising segment from a sustained declining segment. Carbapenem resistance showed an average annual change of minus 1.2% with a joinpoint at 2004, while fluoroquinolone resistance had a joinpoint at 2010, with an initial rising segment followed by a declining segment of minus 4.1% per year. The average annual change for beta-lactam/BLI resistance was plus 0.2%, confirming that its endpoint increase was not statistically significant.

The authors emphasise that the findings should be read alongside important limitations. Pakistan’s vital registration coverage is only about 30% of deaths, so significant modelling is required to produce national estimates, and the observed decline may partly reflect changes in model inputs rather than genuine reductions in AMR burden. Class-specific contributions may be misclassified where multiple coexisting resistance mechanisms are present, and differences in healthcare consumption and diagnostic techniques may influence trends irrespective of true resistance dynamics. The analysis is ecological and cannot establish causal relationships between policy interventions and mortality trends; the decline in fact preceded the National Action Plan by nearly two decades. Nevertheless, the authors argue the persistent dominance of carbapenem resistance underscores the urgent need for strengthened antimicrobial stewardship, infection prevention in healthcare facilities and investment in novel therapeutic agents, providing an evidence base for national AMR action planning in Pakistan.

Subject of Research: Trends in mortality attributable to antimicrobial-resistant Acinetobacter baumannii in Pakistan from 1990 to 2021

Article Title: Trends in mortality attributed to antimicrobial-resistant Acinetobacter baumannii in Pakistan from 1990 to 2021 based on the global burden of disease study 2021

Article References: Saddique, M. N., Qadri, M., Mehmood, M. S., & Mehmood, Q. (2026). Trends in mortality attributed to antimicrobial-resistant Acinetobacter baumannii in Pakistan from 1990 to 2021 based on the global burden of disease study 2021. Discover Bacteria, 3(1), Article 20. https://doi.org/10.1007/s44351-026-00055-9

Image Credits: AI Generated

DOI: 10.1007/s44351-026-00055-9

Keywords: Acinetobacter baumannii, antimicrobial resistance, Global Burden of Disease, Pakistan, carbapenem resistance, age-standardised mortality, antibiotic classes, GBD 2021, healthcare-associated infections, antimicrobial stewardship, Trends, mortality