The study included 3,586 patients who had been tested with a multiplex real-time PCR respiratory panel after initially testing negative for SARS-CoV-2. This design choice is important: because the COVID-19 pandemic dominated respiratory diagnostics from 2020 onward, patients negative for the coronavirus were typically then screened with broader panels capable of detecting a wide range of viruses and bacteria simultaneously. Multiplex PCR works by amplifying genetic material from multiple target organisms in a single reaction, allowing laboratories to identify pathogens such as influenza viruses, respiratory syncytial virus, rhinoviruses, adenoviruses, and bacterial species like Streptococcus pneumoniae and Haemophilus influenzae from one sample. The technique has become a cornerstone of modern respiratory surveillance, particularly in settings where clinical symptoms alone cannot distinguish between viral and bacterial causes of infection. In this cohort, 62.4 percent of the patients were children, reflecting the fact that young people bear a disproportionate burden of acute respiratory tract infections and are tested more frequently with these panels.

Overall, at least one pathogen was detected in 52.6 percent of the samples, but the identity of those pathogens was striking. The most frequently detected organism was Streptococcus pneumoniae, found in 36.7 percent of samples, followed by Haemophilus influenzae at 8.2 percent, rhinovirus at 6.1 percent, and human bocavirus and influenza A, each at 2.8 percent. The dominance of bacterial detections, particularly pneumococcus, is notable because multiplex PCR detects genetic material rather than viable organisms, and colonizing bacteria can be present in the airways without causing disease. Nevertheless, the pattern provides a snapshot of what was circulating in the population’s respiratory tracts during the study window. Positivity rates were dramatically higher in children than in adults, at 64.5 percent versus 33.0 percent, a difference that was highly statistically significant. Detection also peaked in autumn and winter, consistent with the well-documented seasonality of respiratory infections in temperate climates, where indoor crowding and lower humidity favor transmission.

The temporal trends across the four years were equally revealing. Overall positivity declined from 57.5 percent in 2021 to 34.8 percent in 2023, and then rebounded sharply to 60.7 percent in 2024. This trajectory mirrors patterns observed globally after the COVID-19 pandemic, when widespread masking, distancing, and lockdowns suppressed transmission of many common respiratory pathogens, only for them to return with unusual intensity once restrictions lifted. The dip in 2023 is particularly interesting because it coincides with the year of the earthquakes, which struck in February and upended daily life across the region. Yet the researchers found that the overall rate of pathogen detection was almost identical before and after the earthquakes, at 52.5 percent versus 52.7 percent. On the surface, the disaster appeared to have left the total burden of detectable respiratory pathogens essentially unchanged.

Beneath that stable overall figure, however, the composition of detected pathogens shifted in ways that initially seemed alarming. In unadjusted comparisons, bacterial positivity rose from 34.2 percent before the earthquakes to 44.9 percent afterward, while viral positivity fell from 31.2 percent to 19.8 percent. This pattern would be consistent with what disaster epidemiologists might predict: displacement into crowded shelters, interruption of routine healthcare, and stress-induced immune suppression could plausibly increase bacterial carriage and transmission, while reduced social mixing in some settings or altered testing patterns might suppress viral detection. When the researchers built multivariable logistic regression models adjusting for age group, sex, season, clinical setting, year of sampling, and PCR platform, the signal persisted in some analyses. Compared with 2021, the adjusted odds of bacterial detection in 2024 were 5.50 times higher, with a 95 percent confidence interval of 3.51 to 8.63, a substantial and statistically robust increase.

But the story took a decisive turn when the team applied sensitivity analyses designed to test the robustness of the earthquake association. When they restricted the post-earthquake period to just the first 12 months after the disaster, the increases in bacterial and pneumococcal detection disappeared. When they restricted the analysis to samples tested only with the Bio-Speedy platform, one of the PCR systems used in the laboratory during the study period, the increases were not reproduced either. These findings matter because they suggest that the apparent post-earthquake bacterial surge may have been an artifact of how the comparison windows were defined or of changes in testing platforms and laboratory workflows over time, rather than a genuine biological effect of the earthquakes. The authors explicitly state that the differences between pre- and post-earthquake periods varied according to the time window and analytic subset examined, and that the data do not support attributing these differences specifically to the earthquakes.

This methodological caution is one of the study’s most valuable contributions. Natural experiments like earthquakes generate enormous public health interest, and observational data from affected regions are often the only evidence available in the chaotic aftermath of disaster. Yet such data are vulnerable to confounding by indication, changes in who gets tested, shifts in laboratory capacity, and the simple passage of time. A patient tested in late 2024 differs from one tested in 2021 not only in earthquake exposure but also in pandemic-era immune history, vaccination status, healthcare access, and the diagnostic technology applied to their sample. By showing that a seemingly compelling association dissolved under alternative analytic choices, the study offers a template for how respiratory surveillance data should be interrogated before dramatic conclusions are drawn about disaster-driven outbreaks.

The findings also carry practical implications for laboratories and public health agencies. Multiplex PCR panels are powerful tools, but their results depend on the specific platform, the panel composition, and the clinical context in which testing is ordered. The fact that restricting the analysis to a single PCR platform changed the results underscores how technical factors can shape epidemiological signals. The authors argue that multiplex PCR-based surveillance may be valuable for monitoring respiratory pathogen dynamics during periods of epidemiological disruption, precisely because such periods are when conventional assumptions about seasonality and pathogen distribution break down. Continuous, standardized surveillance, they suggest, is the best defense against both missed outbreaks and false alarms.

The research was supported by the Scientific Research Projects Coordination Unit of Mersin University and approved by the university’s Health Sciences Research Ethics Committee, which waived the requirement for informed consent given the retrospective design and use of anonymized routine clinical data. As the region continues to recover from one of the deadliest earthquakes in modern history, the study provides reassurance that the disaster did not produce a measurable, sustained shift in the overall burden of detectable respiratory pathogens, while simultaneously demonstrating how much careful statistical work is required to separate genuine epidemiological change from the noise of a health system in upheaval. For infectious disease watchers, the message is twofold: respiratory pathogens in southern Türkiye followed their own temporal rhythms through pandemic and earthquake alike, and the tools we use to watch them must be scrutinized as rigorously as the pathogens themselves.

Subject of Research: Temporal patterns of respiratory pathogen detection by multiplex PCR in southern Türkiye before and after the 2023 earthquakes

Article Title: Temporal patterns of respiratory pathogen detection in southern Türkiye: a retrospective multiplex PCR study with pre- and post-earthquake comparisons

Article References: Gülbudak, H., Bozok, T., Bekci, A., Ülger, S. T., & Aslan, G. (2026). Temporal patterns of respiratory pathogen detection in southern Türkiye: a retrospective multiplex PCR study with pre- and post-earthquake comparisons. BMC Infectious Diseases. https://doi.org/10.1186/s12879-026-14638-z

Image Credits: AI Generated

DOI: 10.1186/s12879-026-14638-z

Keywords: respiratory pathogens, multiplex PCR, Streptococcus pneumoniae, earthquakes, Türkiye, epidemiology, respiratory tract infections, post-pandemic, surveillance, BMC Infectious Diseases, bacterial detection, rhinovirus

To understand why the finding matters, it helps to revisit how the innate immune system detects bacterial invaders. Immune cells called macrophages patrol tissues armed with pattern recognition receptors, molecular sensors that spot conserved microbial signatures. Among the most potent of these signatures is lipopolysaccharide, or LPS, a component of the outer membrane of Gram-negative bacteria. When bacteria multiply, they shed LPS-rich outer membrane vesicles, tiny blebs of membrane that can travel to distant sites in the body, sneak inside immune cells, and ignite inflammation far from the original infection. This dissemination of inflammatory triggers is a hallmark of systemic inflammatory conditions, sepsis chief among them.

Once intracellular LPS is detected, the cell deploys an inflammasome, a multiprotein machine that acts as both alarm and weapon. Inflammasomes come in two flavors. The canonical pathway relies on well-studied sensors such as NLRP3, while the non-canonical pathway is triggered directly by intracellular LPS through the inflammatory caspase-11 in mice, and caspase-4 and caspase-5 in humans. Activation of either pathway leads caspase-1 to process pro-inflammatory cytokines, most notably interleukin-1 beta, and to cleave Gasdermin-D, the executioner protein that punches holes in the cell membrane and drives inflammatory cell death. While decades of research have mapped how post-translational modifications tune the canonical pathway, the modifications governing the non-canonical route have remained largely mysterious. That gap is precisely where the McGill team, led by Michel L. Tremblay, focused its attention.

The researchers zeroed in on PTPN2, an enzyme that removes phosphate groups from tyrosine residues on target proteins, thereby switching signaling circuits on or off. To probe its role, they generated mice lacking Ptpn2 specifically in myeloid cells, the lineage that includes macrophages, and challenged these animals with LPS-rich outer membrane vesicles and with acute sepsis models. The results were striking. In macrophages deficient in Ptpn2, the transcription of interleukin-1 beta, the flagship cytokine of inflammasome biology, was markedly impaired. The defect traced back to dysregulated signaling through TLR4, the cell-surface LPS receptor, and the p38 MAPK pathway, a cascade that normally drives the priming phase of inflammasome activation by ramping up cytokine gene expression.

Intriguingly, the compromised priming did not translate into wholesale collapse of the inflammasome machinery. Levels of caspase-11, caspase-1, and Gasdermin-D remained unchanged in the knockout cells, indicating that the enzyme’s influence is exerted upstream, at the level of inflammatory gene transcription and signal tuning, rather than by altering the abundance of the core inflammasome components themselves. This distinction is biologically important: it suggests PTPN2 shapes the intensity of the inflammatory output rather than the mere presence of the detonator, a nuance that could matter greatly when designing drugs that target the pathway.

The study also uncovered a novel substrate for PTPN2, adding a fresh branch to the enzyme’s known interaction map. The team found that Lyn, a member of the Src-family of kinases, becomes hyperphosphorylated in the absence of Ptpn2. Because phosphatases and kinases operate in opposing pairs, this observation identifies Lyn as a direct or proximal target whose phosphorylation state PTPN2 normally restrains. Src-family kinases sit at hubs connecting receptor activation to downstream signaling, so their dysregulation in Ptpn2-deficient macrophages provides a mechanistic thread linking the phosphatase to the altered TLR4 and p38 MAPK signaling observed in the knockout animals.

Adding a second layer of complexity, the researchers found that loss of PTPN2 unleashes a STAT1-mediated program that boosts production of nitric oxide, a reactive molecule with a double-edged role in immunity. While nitric oxide can help kill pathogens, the study showed that in this context it undermines inflammasome activity by compromising mitochondrial fitness. Mitochondria are not merely cellular power plants; they supply signals and metabolites that feed inflammasome activation, and their dysfunction can blunt the cell’s inflammatory capacity. In Ptpn2-deficient macrophages, therefore, excessive nitric oxide erodes the very organelles the inflammasome depends upon, further dampening the response.

The in vivo consequences of these cellular defects became clear when the mice were subjected to acute sepsis. Animals lacking Ptpn2 in myeloid cells exhibited reduced numbers of small peritoneal macrophages, a key resident immune population, and lower serum levels of interleukin-1 beta following the septic challenge. Together, these findings indicate a dampened pro-inflammatory response in the absence of the phosphatase. In the context of sepsis, where excessive inflammation drives organ damage and death, a blunted response might at first glance seem protective. But the picture is nuanced: interleukin-1 beta also mobilizes host defenses, and the reduced macrophage population suggests that PTPN2 supports aspects of immune competence as well as inflammation. The enzyme, in other words, is not simply a brake or an accelerator but a fine-tuner of the response.

That dual role is what makes PTPN2 an attractive therapeutic candidate. Phosphatases were long considered undruggable, but recent advances in medicinal chemistry have brought PTPN2 inhibitors into clinical consideration, particularly in oncology, where the enzyme’s effects on T cells and tumor immunity have drawn intense interest. The McGill study adds a new dimension to that conversation: in sepsis and systemic inflammation, modulating PTPN2 activity could, in principle, recalibrate the non-canonical inflammasome axis and the cytokine output that fuels inflammatory injury. The authors highlight this potential, positioning the enzyme as a target for managing systemic inflammation. Any such strategy would need to account for the pathway’s complexity, since the same enzyme that supports cytokine production also, through its restraint of STAT1 and nitric oxide, protects mitochondrial fitness and inflammasome function.

The work also carries broader conceptual weight for immunology. By demonstrating that a tyrosine phosphatase governs the non-canonical inflammasome pathway, the study establishes that this arm of innate immunity, often treated as a parallel, LPS-triggered circuit, is subject to the same intricate layers of post-translational regulation that shape its canonical counterpart. It connects outer membrane vesicle biology, TLR4 signaling, Src-family kinase activity, STAT1 activation, mitochondrial health, and cytokine secretion into a single regulatory network centered on one enzyme. For clinicians confronting sepsis, a syndrome that kills millions each year and for which treatment remains largely supportive, the identification of a tunable node in the inflammatory circuitry offers a genuine reason for optimism. For basic researchers, it opens a set of new questions: how PTPN2 is itself regulated during infection, whether the Lyn and STAT1 branches operate independently, and whether human patients with altered PTPN2 activity show different sepsis trajectories. The answers could shape the next generation of anti-inflammatory therapies.

Subject of Research: Role of the phosphatase PTPN2 in regulating non-canonical inflammasome activation and inflammatory responses in sepsis

Article Title: PTPN2 sustains non-canonical inflammasome activation and shapes the inflammatory response to sepsis

Article References: Colalillo, B., Aubry, I., Aumont, P., Poirier, A. J., Hincapie, A. M., Wu, C., St-Laurent, E., Martinez Cordova, Z., & Tremblay, M. L. (2026). PTPN2 sustains non-canonical inflammasome activation and shapes the inflammatory response to sepsis. Cellular and Molecular Life Sciences. https://doi.org/10.1007/s00018-026-06469-7

Image Credits: AI Generated

DOI: 10.1007/s00018-026-06469-7

Keywords: PTPN2, sepsis, inflammasome, non-canonical pathway, interleukin-1 beta, LPS, macrophages, TLR4, p38 MAPK, Lyn kinase, STAT1, nitric oxide

The team, based in Hungary and collaborating internationally, engineered the K1F bacteriophage, a T7-family virus that specifically infects Escherichia coli strains shielded by a K1 polysaccharide capsule, a feature associated with invasive, clinically dangerous E. coli such as those causing neonatal meningitis. Rather than relying on the classical strategy of reporter phages, which carry a transgene that the infected bacterium must transcribe and translate before any signal appears, the researchers exploited the sequence of ejection proteins that T7-like phages deliver into the host cytoplasm at the very start of infection. These intracapsid proteins, known as ICPs, are packed inside the viral head and are propelled into the bacterium in a defined order, where several of them refold to build the ejectosome, a tubular channel through which the viral genome passes.

The reporters in this system exploit the peculiar biochemistry of nanoluciferase, a small and intensely bright enzyme derived from the deep-sea shrimp Oplophorus gracilirostris. Nanoluciferase can be split into two fragments, a larger C-terminal piece and a smaller N-terminal piece, neither of which glows on its own. Crucially, when the fragments meet in solution in the presence of the substrate Furimazine, they spontaneously reassemble into an active enzyme that emits blue light. The researchers fused the small N-terminal fragment, abbreviated NnLuc, to two of the phage’s ICPs, gp6.7 and gp14, ensuring that the reporter fragment would travel inside the capsid, inert and sequestered, until the virus encountered a host it could infect.

Constructing such phages required careful genetic engineering. The team built donor plasmids carrying extra copies of the g6.7 or g14 genes fused in-frame to the NnLuc sequence and inserted these constructs into the K1F genome at a position previously shown to tolerate foreign DNA without instability. Recombinant phages were then selected using a CRISPR-Cas9 counter-selection system that cleaves the genomes of wild-type phages, allowing only the engineered versions to propagate. Phenotypic testing confirmed that the modified viruses grew to titres similar to wild type, with only a slight reduction in plaque size for one construct, indicating that the fusion proteins imposed minimal fitness costs on the viruses.

Initial experiments verified that the fusion proteins were indeed packaged into the phage heads and remained functional. When the researchers heat-treated the engineered phages to crack open the capsids and released their contents into a solution containing the purified C-terminal nanoluciferase fragment, the mixtures glowed brightly, confirming that the packaged NnLuc fusions could reconstitute active luciferase once liberated. Controls using wild-type phage, plasmid-free bacterial extracts, or intact capsids produced little or no signal, with one exception: intact K1Fe6.7::NnLuc particles produced a modest background glow, apparently due to soluble fusion protein contaminating the phage lysate, a problem the team believes can be solved with ultrafiltration purification.

The decisive experiments followed in living cells. When E. coli EV36, a K1-capsulated strain carrying a plasmid that expressed the C-terminal fragment, was challenged with either engineered phage, luminescence rose significantly above controls within minutes. In contrast, E. coli Nissle 1917, which expresses the reporter fragment but wears a non-cognate K5 capsule that the K1F phage cannot dock onto, produced no signal at all, demonstrating that phage binding and injection are strict prerequisites for light emission. Kinetic measurements showed the signal became statistically significant roughly seven minutes and fifty seconds after phage addition, and a more sensitive protocol detected a robust difference as early as five minutes and forty-five seconds after infection.

Those early time points matter because, in the T7 phage family, transcription and translation of late viral genes, including the g6.7 and g14 genes whose products were tagged, do not begin until at least seven to eight minutes after infection. Any luminescence detected before that window therefore cannot originate from the host expressing the reporter gene; it must come from proteins physically injected from the viral capsid. To seal the argument, the researchers treated infected cells with rifampicin, a transcription inhibitor, or tetracycline, a translation inhibitor. At six and a half minutes post-infection, the luminescent signal from cells infected with K1Fe14::NnLuc was completely unaffected by either inhibitor, while K1Fe6.7::NnLuc retained the majority of its signal, providing the first direct evidence that protein injection alone can betray a successful phage infection.

Of course, a diagnostic that only detects bacteria pre-engineered to express half of a luciferase would be of little practical use. To address this, the team built a model diagnostic system in which wild-type, unmodified bacteria are infected by the reporter phages and then supplied externally with column-purified C-terminal nanoluciferase along with the NanoGlo reagent, which contains the Furimazine substrate and a lysis agent that opens the bacterial envelope and allows the two fragments to meet. In this configuration, the cognate K1-capsulated strain generated signals two orders of magnitude brighter than in earlier experiments, and positive versus negative samples were clearly distinguished just three minutes after phage addition, the strongest evidence yet that the emitted light arises purely from injected protein.

Sensitivity testing revealed an important trade-off between speed and detection limit. When cell lysis occurred after only eight minutes of infection, relying solely on the injected enzyme fragments, roughly 690,000 cells per well, corresponding to about 23 million cells per milliliter, were required for reliable detection. Extending the infection to fifteen minutes, which allowed some de novo reporter production, and lengthening the luminescence incubation lowered the limit to 12,000 cells per well, roughly 3.5 million cells per milliliter. The authors note that reported bacterial concentrations in cerebrospinal fluid of children with E. coli K1 meningitis range from about 20,000 to 40 million cells per milliliter, with a mean near 200,000, meaning that even this unoptimized prototype already operates within a clinically relevant range.

The researchers envision the technology as the foundation of cheap, lateral-flow-style tests in which all reactive components, the dried C-terminal fragment, the substrate, and the engineered phage, are pre-loaded in a device, and the user supplies only the sample and moisture. Background noise could be further reduced by purifying phage lysates more stringently, deleting the wild-type copies of the ICP genes to load more reporter per capsid, or deploying the chemistry in microfluidic lab-on-a-chip devices that concentrate reactions into tiny volumes. In the longer term, combinatorial multichannel chips could classify bacteria by genus, species, and strain in sequence. Because phage binding directly reports viral sensitivity, the same platform could help physicians assemble personalized phage-therapy cocktails on the spot, potentially shrinking the turnaround of precision antibacterial treatment from hours to the few minutes that can decide outcomes in severe infection.

Subject of Research: Expression-free bacteriophage-based detection of target bacteria via conditional release of encapsidated reporter proteins

Article Title: Rapid, expression‐free bacteriophage‐based specific detection of target bacteria by conditional release of encapsidated reporter molecules

Article References: Avramucz, Á., Wheatley, J. P., Liyanagedera, S. B. W., Fehér, T., & Amaee, R. (2026). Rapid, expression‐free bacteriophage‐based specific detection of target bacteria by conditional release of encapsidated reporter molecules. Bioengineering & Translational Medicine, Article e70171. https://doi.org/10.1002/btm2.70171

Image Credits: AI Generated

DOI: 10.1002/btm2.70171

Keywords: bacteriophage, bacterial detection, nanoluciferase, diagnostics, K1F phage, E. coli, ejectosome, intracapsid proteins, biosensor, phage therapy, antimicrobial resistance, rapid testing