Characteristics of Pathogens Detected in Adults with Hematological Malignancies and Nosocomial Infections in the Tropics

Tropical regions are known for their warm, humid climates—but these same conditions that attract tourists also create a breeding ground for bacteria, fungi, and other pathogens. For adults with hematological malignancies (cancers of the blood, like leukemia or lymphoma), this is a dangerous combination: their weakened immune systems make them far more likely to develop hospital-acquired (nosocomial) infections. A study from Hainan Island, China—a tropical paradise with an average annual temperature of 24.4°C and 82% humidity—reveals unique patterns of these infections that could change how doctors treat patients in similar climates.

Who Was Studied?

Researchers from the Hainan Branch of the People’s Liberation Army (PLA) General Hospital (Sanya, Hainan) and the First Medical Center of the PLA General Hospital (Beijing) analyzed 1,817 adults with hematological malignancies admitted between June 2014 and March 2018. The patients included those with:

Acute leukemia (AL): 421 cases
Chronic leukemia (CL): 133 cases
Non-Hodgkin lymphoma (NHL): 587 cases
Multiple myeloma (MM): 471 cases
Hodgkin lymphoma (HL): 121 cases
Myelodysplastic syndrome (MDS): 84 cases

All patients were hospitalized for at least 48 hours (to ensure infections were hospital-acquired, not pre-existing). Median age was 56 years (range: 13–87 years).

How Were Pathogens Detected?

Samples included sputum, blood, midstream urine, central catheter tubing, and wound secretions. Repeat tests from the same patient and site were excluded to avoid bias. Pathogens were identified using:

BioMérieux BacTAlerT 3D 240: A gold-standard blood culture system.
VITEK 2 COMPACT: An automated tool for species identification and drug-sensitivity testing.

All procedures followed China’s 2006 National Operating Procedures for Clinical Tests.

What Did the Study Find?

Out of 1,817 patients, 198 (10.9%) developed nosocomial infections, with 269 pathogen strains detected. Here’s the breakdown:

Pathogen Type	Percentage	Key Species
Gram-negative bacteria	40.5%	E. coli, Pseudomonas aeruginosa, Klebsiella pneumoniae
Fungi	29.4%	Candida (76 strains), filamentous fungi (3 strains)
Gram-positive bacteria	29.7%	Enterococcus, Staphylococcus aureus

Sputum Cultures: A Fungal Hotspot

Sputum was the most informative sample type—117 positive cultures yielded 154 strains. Nearly half (49.4%) were fungi, mostly:

Candida albicans (26 strains)
Unclassified Candida (36 strains)
Filamentous fungi (3 strains)

This is a sharp contrast to non-tropical regions, where fungal infections in blood cancer patients are often dominated by Aspergillus (a mold that prefers cooler temperatures, 25–28°C).

Pathogens by Cancer Type

The three most common malignancies (AL, NHL, MM) had similar pathogen patterns (P = 0.2):

AL: 94 strains (27.7% fungi, 42.6% Gram-negative, 28.7% Gram-positive)
NHL: 71 strains (24% fungi, 36.6% Gram-negative, 39.4% Gram-positive)
MM: 58 strains (29.3% fungi, 46.6% Gram-negative, 24.1% Gram-positive)

Co-Infections Are Common

Over a third of fungal strains (39.2%) were paired with bacteria, and 28.7% of bacterial strains were paired with fungi. This means doctors must check for multiple pathogens—not just one.

Why Does This Matter for Tropical Clinics?

The study’s biggest takeaway? Climate directly shapes infection risks. Candida, a yeast, thrives in Hainan’s warm, humid conditions (24.4°C average temperature). In cooler regions, molds like Aspergillus (which prefer 25–28°C) are more common. For blood cancer patients in the tropics, this means:

Prioritize Candida in Empirical Treatment: Start antifungals that target Candida while waiting for test results.
Move to Targeted Treatment Fast: Once pathogens are identified, switch from “broad-spectrum” drugs to those that specifically treat the infection. This reduces drug resistance and imbalanced gut flora (dysbacteriosis).
Test for Co-Infections: Don’t stop at one pathogen—check for both fungi and bacteria.

Ethical and Funding Notes

All patients gave informed consent under the Declaration of Helsinki. The study was funded in part by the Hainan Provincial Natural Science Foundation of China (No. 818MS157). The authors report no conflicts of interest.

Key Takeaways

For patients with hematological malignancies in tropical regions, climate isn’t just a weather topic—it’s a medical priority. This study is one of the first to link local climate to infection patterns, and its findings could save lives by helping doctors tailor treatment to what actually makes patients sick.

References:

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Liu H, Zhao J, Xing Y, et al. Nosocomial infection in adult admissions with hematological malignancies originating from different lineages: a prospective observational study. PLOS One. 2014;9(11):e113506. doi: 10.1371/journal.pone.0113506
Wisplinghoff H, Seifert H, Wenzel RP, Edmond MB. Current trends in the epidemiology of nosocomial bloodstream infections in patients with hematological malignancies and solid neoplasms in hospitals in the United States. Clin Infect Dis. 2003;36(9):1103-1110. doi: 10.1086/374339
Huoi C, Vanhems P, Nicolle MC, et al. Incidence of hospital-acquired pneumonia, bacteraemia and urinary tract infections in patients with haematological malignancies, 2004-2010: a surveillance-based study. PLOS One. 2013;8(3):e58121. doi: 10.1371/journal.pone.0058121
King J, Pana ZD, Lehrnbecher T, et al. Recognition and clinical presentation of invasive fungal disease in neonates and children. J Pediatric Infect Dis Soc. 2017;6(Suppl 1):S12-S21. doi: 10.1093/jpids/pix053

doi: 10.1097/CM9.0000000000000939

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