Identification and determination of the AST pattern of Acinetobacter species isolated from different clinical samples by VITEK circled2 Compact

This study conducted at SGT Hospital in Haryana identified 35 *Acinetobacter* isolates from 6673 clinical samples, revealing that the majority were *A. baumannii* primarily found in blood specimens and exhibiting high resistance to most antibiotics except for a high susceptibility rate to colistin.

The Gist

Imagine a hospital as a bustling city. In this city, there are invisible invaders called Acinetobacter. Think of these bacteria as "super-spy" burglars. They are small, tough, and incredibly good at hiding. While some are harmless, the most famous one, Acinetobacter baumannii, is a notorious criminal that loves to cause trouble in hospitals, especially for patients who are already weak or sick (like those in the ICU).

Here is the story of a recent investigation into these "burglars" at SGT Hospital in Gurugram, India, told in simple terms.

1. The Great Detective Hunt

The researchers (our detectives) looked at 6,673 samples taken from patients over one year. These samples were like "crime scene evidence"—blood, pus, urine, and swabs from wounds or lungs.

• The Find: Out of all that evidence, they found 595 samples that had some kind of bacteria growing.
• The Culprit: Out of those 595, only 35 were the specific "super-spy" Acinetobacter we are worried about.
• The Profile: These spies were found mostly in blood (almost half of them!), followed by pus from wounds and fluids from breathing tubes. They seemed to prefer attacking men slightly more than women.

2. Who Are the Criminals?

The detectives identified exactly which "gang members" were responsible:

• The Boss: Acinetobacter baumannii was the main villain, making up 88% of the cases.
• The Minions: A few were Acinetobacter lwoffii and just one was Acinetobacter haemolyticus.

3. The "Super-Weapon" Problem (Antibiotic Resistance)

This is the most critical part of the story. Imagine antibiotics as magic shields that doctors use to protect patients from these bacteria. The researchers tested if these shields worked.

The Bad News:
The Acinetobacter burglars had developed super-shields against almost everything.

• They were 100% immune to common shields like Piperacillin/Tazobactam, Ceftriaxone, Amikacin, and Gentamicin. It's like trying to stop a tank with a water pistol; it just doesn't work.
• They were also very strong against Ciprofloxacin and Ceftazidime (over 90% resistance).

The "Last Line of Defense":
There was one shield that still worked for most of them: Colistin.

• About 88% of the bacteria were still vulnerable to Colistin.
• However, this is a bit like having only one key to a vault. If the bacteria learn to break this key too, we will have no way to stop them.

4. The "Multi-Drug Resistant" (MDR) Label

The study found that 74% of these bacteria were MDR.

• Analogy: Think of MDR as a criminal who has learned to pick every lock in the city. They have stolen the keys to almost every door (antibiotic) the police have. Once they are MDR, they are incredibly hard to catch and kill.

5. Why Does This Matter?

The researchers concluded that these bacteria are opportunistic.

• Analogy: They are like sharks that only attack when the water is murky and the fish are weak. They don't usually attack healthy people, but in a hospital (where people are sick, have catheters, or are on ventilators), they strike hard.

The study highlights a scary trend: because people use antibiotics too freely (like using a sledgehammer to crack a nut), the bacteria are learning to become stronger. The "magic shields" are losing their power.

The Takeaway for Everyone

• The Enemy is Real: Acinetobacter is a tough, hospital-based germ that is getting harder to kill.
• The Solution: We need to be smarter about how we use antibiotics. We can't just keep using the same old shields; we need to save the ones that still work (like Colistin) and find new ways to fight back.
• The Goal: By understanding exactly which bacteria are in our hospitals and which drugs they hate, doctors can stop infections before they spread, keeping the "city" (the hospital) safe for everyone.

In short: The bacteria are winning the arms race with our current weapons. We need to be smarter, use our remaining weapons carefully, and keep our defenses high.

Technical Summary

1. Problem Statement

• Clinical Challenge: Acinetobacter species, particularly A. baumannii, are emerging as critical nosocomial (hospital-acquired) and opportunistic pathogens. They are classified as ESKAPE pathogens (along with Enterococcus, Staphylococcus, Klebsiella, Pseudomonas, and Enterobacter), posing a severe global threat due to their ability to "escape" the lethal action of antibiotics.
• Resistance Mechanisms: These bacteria exhibit high levels of multidrug resistance (MDR) due to low outer membrane permeability and the accumulation of resistance genes via integrons, plasmids, and transposons.
• Knowledge Gap: There is a need for localized surveillance data to understand the specific prevalence, species distribution, and antimicrobial susceptibility patterns (AST) of Acinetobacter in specific healthcare settings (specifically the Delhi NCR region of India) to guide empirical therapy and infection control.

2. Methodology

• Study Design: Retrospective cross-sectional study conducted over one year (January 1, 2023 – December 31, 2023).
• Setting: Department of Microbiology, SGT University Hospital, Gurugram, Haryana, India.
• Sample Collection:
  • Total Samples: 6,673 clinical specimens received from Inpatient (IPD), Outpatient (OPD), and various ICU units.
  • Sample Types: Blood, urine, pus, respiratory specimens (sputum, endotracheal aspirates, tracheal aspirates, BAL), CSF, tissue, and others.
• Isolation and Identification:
  • Samples were cultured on standard media (Blood agar, MacConkey agar, CLED for urine; Bact/Alert for blood).
  • Preliminary identification was based on Gram staining (Gram-negative coccobacilli), colony morphology, and biochemical tests (Oxidase negative, Catalase positive, Citrate positive, non-motile).
  • Definitive Identification: Confirmed using the VITEK 2 Compact automated system.
• Antimicrobial Susceptibility Testing (AST):
  • Performed using VITEK 2 cards.
  • Antibiotics Tested: Piperacillin/Tazobactam, Ceftriaxone, Cefoperazone/Sulbactam, Cefepime, Imipenem, Meropenem, Amikacin, Gentamicin, Ciprofloxacin, Colistin, Trimethoprim/Sulfamethoxazole, Ceftazidime, Levofloxacin, and Minocycline.

3. Key Contributions

• Localized Epidemiological Data: Provides specific prevalence rates and species distribution of Acinetobacter in the Gurugram/Delhi NCR region, a high-density urban area.
• Species Differentiation: Successfully differentiated between A. baumannii, A. lwoffii, and A. haemolyticus within the hospital setting.
• Resistance Profiling: Established a comprehensive resistance profile against a wide range of beta-lactams, aminoglycosides, and fluoroquinolones, highlighting the extent of MDR in this specific cohort.
• Validation of Diagnostic Tools: Demonstrated the efficacy of the VITEK 2 Compact system for rapid identification and AST of Acinetobacter in a clinical laboratory setting.

4. Key Results

• Prevalence:
  • Out of 6,673 total samples, 595 were culture-positive for bacterial growth.
  • 35 isolates were identified as Acinetobacter species, representing a prevalence of 5.88% among positive isolates.
• Demographics:
  • Gender: Higher prevalence in males (57.14%) compared to females (42.86%).
  • Source: The majority of isolates came from the Inpatient Department (IPD) (49.24%).
• Species Distribution:
  • A. baumannii: 31 isolates (88.57%) – The dominant pathogen.
  • A. lwoffii: 3 isolates (8.57%).
  • A. haemolyticus: 1 isolate (2.85%).
• Sample Distribution (for Acinetobacter):
  • Blood: 48.57% (17 isolates) – The most common source.
  • Pus: 22.85% (8 isolates).
  • Endotracheal (E.T.) aspirates: 22.85% (8 isolates).
  • Tracheal aspirates & Eye swabs: 2.85% each.
• Antimicrobial Susceptibility Patterns:
  • 100% Resistance: Observed against Piperacillin/Tazobactam, Ceftriaxone, Amikacin, and Gentamicin.
  • High Resistance (>88%): Ciprofloxacin (91.42%), Ceftazidime (91.42%), Cefepime (88.57%), Levofloxacin (88.57%).
  • Moderate Resistance: Imipenem (91.42%), Meropenem (91.42%), Trimethoprim/Sulfamethoxazole (74.28%).
  • Susceptibility: Colistin showed the highest efficacy, with 88.57% of isolates (31/35) being sensitive. Minocycline showed 37.14% sensitivity.
• Multidrug Resistance (MDR):
  • 74.28% (26/35) of the isolates were classified as MDR.
  • All MDR isolates belonged to the A. baumannii species.

5. Significance and Conclusion

• Therapeutic Implications: The study confirms that Acinetobacter, particularly A. baumannii, is a major cause of bloodstream and respiratory infections in the studied hospital. The near-universal resistance to first-line agents (carbapenems, aminoglycosides, and fluoroquinolones) renders standard empirical therapies ineffective.
• Colistin as a Last Resort: Colistin remains the most effective agent (88.57% sensitivity), reinforcing its role as a last-line treatment for MDR Acinetobacter, though the emergence of resistance to it is a concern.
• Infection Control: The high prevalence in ICU and IPD settings underscores the need for stringent infection control practices, including hand hygiene, environmental disinfection, and stewardship programs to prevent the spread of MDR strains.
• Public Health Impact: The findings highlight the urgent need for continuous surveillance and the development of new antimicrobial strategies, as Acinetobacter continues to evolve as a lethal, drug-resistant pathogen in the Indian healthcare landscape.

Note: As this is a preprint, the data has not yet undergone peer review and should be interpreted with caution regarding clinical practice guidelines.