Diabetes mellitus (DM), is a chronic metabolic disorder consisting of hyperglycemia due to deficient insulin secretion or impaired insulin action. It is now increasingly becoming a global health burden characterized by multifaceted systemic complications. One of the impacts of chronic diabetes mellitus is on the immune system. It predisposes diabetics to higher risk and severity of infections, particularly those affecting the respiratory system, such as pleuropulmonary infections (PPIs) [1]. The primary exposure of lungs to the external environment makes PPI a serious health issue for diabetic individuals because of their compromised host defense systems. Pleuropulmonary infections include a broad spectrum of conditions that include pneumonia, tuberculosis, lung abscess, empyema, and fungal infections. When diabetic individuals develop these infections, they experience unusual disease progression combined with more serious symptoms than observed in patients without diabetes. Research indicates that elevated blood sugar levels diminish neutrophil movement toward pathogens along with their ability for bacterial engulfment and destruction [2]. The presence of multiple medical conditions together with poor nutrition cardiovascular diseases and chronic kidney disease makes diabetic patients more prone to and more vulnerable to PPI complications [3]. TB persists as a significant pleuropulmonary infection in diabetics particularly within developing regions where community-wide occurrence of both diseases exists. The risk factor of diabetes increases a person's chance of developing TB from primary infection and delayed latent TB reactivation [4]. Furthermore, diabetes patients tend to have a higher incidence of severe radiological manifestations together with delayed sputum conversion. Research findings demonstrate that diabetic patients suffer increased cases of both CAP and HAP in addition to exhibiting more severe conditions of these pulmonary infections. The medical community often links primary diagnosis and reactivation of tuberculosis to Streptococcus pneumoniae, Klebsiella pneumoniae, Staphylococcus aureus, and several Gram-negative bacilli which tend to present multidrug resistance [5].

Fungal infections caused by both Aspergillus species and Mucorales have become dangerous complications that kill various diabetic patients including ketoacidosis sufferers. Such patients suffer from weakened pulmonary immune functions which enable fungal infections to spread quickly toward necrotizing pneumonia or invasive pulmonary disease [6]. Diabetic patients who experience pleural infections such as empyema require more surgical interventions than their non-diabetic counterparts because conventional antibiotics prove ineffective in their cases [7]. Pleuropulmonary infections in diabetic patients appear in atypical or nonspecific ways that delay their diagnosis. The autonomic neuropathy combined with impaired inflammatory response can suppress the standard symptoms of fever, cough, and dyspnea together with pleuritic pain. The radiologic findings in these patients range from local tissue damage to widespread lung involvement or buildup of fluid between the lung and chest wall. Diabetic patients require early diagnosis of pleuropulmonary infections because the subsequent individualized treatment helps prevent poor clinical results and decreased survival rates [8]. This study investigates pleuropulmonary infections that develop in diabetic patients as well as their symptoms and microbial characteristics X-ray manifestations and treatment results. The identification of these patterns through research will enable prompt diagnosis and selection of proper therapeutic approaches for vulnerable diabetic patients.

This was a hospital-based, observational, cross-sectional study conducted in the Department of Respiratory Medicine, Government Medical College, Jayshankar Bhupalpally, Telangana. Institutional Ethical approval was obtained for the study. Written consent was obtained from all the participants of the study after explaining the nature of the study in vernacular language. The study aimed to evaluate the clinical spectrum of pleuropulmonary infections among patients with diabetes mellitus.

Study Population: The study included adult patients (aged ≥18 years) diagnosed with diabetes mellitus (type 2) who presented with clinical and radiological features suggestive of pleuropulmonary infections.

Inclusion Criteria:

1. Patients with a confirmed diagnosis of diabetes mellitus as per American Diabetes Association criteria.
2. Patients presenting with signs and symptoms suggestive of pleuropulmonary infections such as fever, cough, dyspnea, chest pain, and radiological evidence of pneumonia, pleural effusion, empyema, lung abscess, or pulmonary tuberculosis.
3. Patients who provided informed consent to participate in the study.

Exclusion Criteria:

1. Patients with pre-existing chronic lung diseases such as bronchiectasis, interstitial lung disease, or chronic obstructive pulmonary disease unless present with a superimposed acute infection.
2. Patients with immunosuppressive conditions (e.g., HIV/AIDS, malignancy, post-transplant) other than diabetes.
3. Patients on long-term corticosteroids or immunosuppressive drugs.
4. Pregnant or lactating women.

Data Collection: After obtaining informed written consent, detailed demographic and clinical data were recorded for each patient using a structured proforma. The following parameters were documented:

1. Clinical Evaluation:
   • Presenting symptoms (fever, cough, sputum production, hemoptysis, dyspnea, chest pain).
   • Duration and progression of symptoms.
   • History of tuberculosis or recurrent respiratory infections.
   • Duration and type of diabetes, glycemic control (HbA1c levels), and associated comorbidities.
2. Physical Examination:
   • General and systemic examination with a focus on respiratory findings (e.g., breath sounds, crackles, dullness to percussion).
   • Vital signs and oxygen saturation.
3. Laboratory Investigations:
   • Complete blood count (CBC), random blood sugar (RBS), fasting blood sugar (FBS), HbA1c.
   • Renal and liver function tests.
   • Sputum examination for Gram stain, acid-fast bacilli (AFB), and fungal elements.
   • Sputum and/or blood culture and sensitivity.
   • Pleural fluid analysis in cases of pleural effusion/empyema (biochemical, cytological, microbiological).
   • Mantoux test and GeneXpert (as indicated).
4. Radiological Assessment:
   • Chest X-ray (PA view) for all patients.
   • High-resolution computed tomography (HRCT) chest in selected cases for detailed evaluation.

Microbiological Assessment: Identification of causative organisms through sputum culture, pleural fluid culture, and blood culture. Antimicrobial susceptibility testing was performed using standard laboratory protocols.

Statistical Analysis: Data were compiled and entered into Microsoft Excel and analyzed using SPSS version [specify version]. Descriptive statistics such as mean, standard deviation, frequency, and percentages were used for continuous and categorical variables. The chi-square test and Student's t-test were used to assess associations between clinical parameters and types of infections. A p-value <0.05 was considered statistically significant.

A total of N=70 cases of type 2 diabetes mellitus were included in the study during the study period based on the inclusion and exclusion criteria. Table 1 depicts the demographic and clinical profile of patients included in the study.  The mean age of the study cohort was 58.4 ± 9.2 years. This shows that the population mainly consisted of middle-aged to older adults. The mean duration of diabetes among the participants was 7.5 ± 4.8 years. Similarly, the mean HbA1c was 9.1 ± 2.3% showing relatively poor control of diabetes mellitus in the cohort. There was a high prevalence of fever and cough which are the typical signs of respiratory infections. There was the presence of pleuritic chest pain showing the involvement of pleura and dyspnea suggesting lung involvement highlighting the nature of the pleuropulmonary infections in this diabetic population.

Table 2 depicts the types of pleuropulmonary infections diagnosed in the study population of 70 individuals with diabetes mellitus. Community-acquired pneumonia (CAP) was the most common type of infection in 64.3% of cases. The common pathogens identified were Streptococcus pneumoniae (42%) and Klebsiella pneumoniae (29%). Tuberculosis was the second most frequent infection in the study involving 25.7% of cases. In all these cases the identified pathogen was  Mycobacterium Tuberculosis (100%). Lung abscess was found in 7.1% of cases. In the majority of cases, 80% were associated with mixed anaerobic bacteria. Empyema was the least common with 2.9% affected cases. The identified pathogens in these cases were Staphylococcus aureus (50%) and Escherichia coli (50%). The high incidence of CAP and the specific pathogens identified, particularly S. pneumoniae and K. pneumoniae, underscore the increased susceptibility of diabetic patients to bacterial lung infections. Poor glycemic control shown by high HbA1c levels in Table 1 could be the major contributory factor. The considerable proportion of TB cases shows the link between diabetes mellitus and tuberculosis.

Table 3 demonstrates the spectrum of radiological findings in pleuropulmonary infections among individuals with diabetes. Consolidation, indicating alveolar filling with fluid or inflammatory exudate, was the most common radiological finding, observed in 39 patients (55.7%). It was predominantly associated with Community-Acquired Pneumonia (CAP), accounting for 82% of the cases with consolidation, and also seen in 40% of the Lung Abscess cases. Cavitation, characterized by the formation of cavities within lung tissue, was found in 11 patients (15.7%). It was most strongly associated with Tuberculosis (TB), present in 73% of the cases with cavitation, and also seen in 27% of the Lung Abscess cases. Pleural effusion was observed in 23 patients (32.9%). It was associated with Tuberculosis in 52% of these cases and with Community-Acquired Pneumonia in 39% of the cases with effusion. Involvement of both lungs was noted in 14 patients (20%). This finding was more frequently associated with Tuberculosis (64%) and Severe Community-Acquired Pneumonia (36%).

Table 4 shows the microbiological profile of the 53 culture-positive cases out of the total 70 patients in the study on pleuropulmonary infections in diabetes mellitus. Streptococcus pneumoniae: This was identified in 15 cases, representing 28.3% of the culture-positive isolates. Among these, 67% were sensitive to penicillin and 93% were sensitive to ceftriaxone. Klebsiella pneumoniae: This organism was found in 12 cases, accounting for 22.6% of the culture-positive isolates. The sensitivity pattern showed that 92% were sensitive to carbapenems, while 58% were positive for ESBL (Extended-Spectrum Beta-Lactamase) production, indicating resistance to many common antibiotics. Mycobacterium tuberculosis: This was the most frequently identified organism, found in 18 cases, which is 34% of the culture-positive cases. The sensitivity pattern indicated that 89% of these isolates were sensitive to Anti-Tuberculosis Therapy (ATT). Staphylococcus aureus (MSSA): Methicillin-sensitive Staphylococcus aureus was identified in 5 cases, making up 9.4% of the culture-positive isolates. All of these isolates (100%) were sensitive to clindamycin. Mixed anaerobes: Mixed anaerobic bacteria were cultured in 3 cases, representing 5.7% of the culture-positive cases. All these isolates (100%) were sensitive to metronidazole.

The high prevalence of S. pneumoniae and K. pneumoniae in community-acquired pneumonia suggests that empirical antibiotic regimens for diabetic patients with pneumonia should cover these pathogens. However, the significant rate of ESBL-producing K. pneumoniae necessitates considering broader-spectrum antibiotics, especially in severe cases or if there is a lack of clinical improvement with initial therapy. Screening for Tuberculosis: The high proportion of tuberculosis cases emphasizes the importance of actively screening diabetic patients presenting with respiratory symptoms for TB, especially in endemic regions. The good sensitivity to ATT in most cases is reassuring for treatment outcomes of TB. Consideration of Atypical Pathogens: While not specifically listed in this table, the 17 culture-negative cases suggest that other pathogens, including atypical bacteria, viruses, or fungi, might also be involved in pleuropulmonary infections in diabetic patients. Further investigations might be needed to identify these cases.

Table 5 summarizes the treatment outcomes for the 70 patients with pleuropulmonary infections and diabetes mellitus. The majority of patients, 52 (74.3%), were classified as cured. Their median hospital stay was 10 days, with an interquartile range (IQR) of 8 to 14 days. Eleven patients (15.7%) showed improvement but were left with sequelae (residual conditions or complications). This group had a longer median hospital stay of 16 days, with an IQR of 12 to 21 days. Four patients (5.7%) experienced treatment failure. Their median hospital stay was the longest among the surviving groups, at 22 days, with an IQR of 18 to 28 days. Unfortunately, 3 patients (4.3%) in the study died. Factors linked to poor outcomes: The table also shows that HbA1c levels greater than 9%, the presence of bilateral infiltrates on chest X-ray, and a history of chronic kidney disease (CKD) were linked to poor outcomes.

This study was conducted to determine the clinical, microbiological, and radiological spectrum of pleuropulmonary infections in patients with type 2 diabetes mellitus. The results of this study show that diabetic patients are at a significantly increased risk for respiratory infections, particularly pneumonia and tuberculosis due to impaired immune functions which is a consequence of sustained hyperglycemia [9]. The results of this study show that the mean age of the cohort was 58.4 years indicating that middle-aged to elderly individuals constitute the most vulnerable demographic for pleuropulmonary infections in diabetes. This observation is consistent with prior literature where older adults with diabetes were found to have an increased risk of infections due to the existence of comorbidities and impaired immune functions [10]. The evidence of poor glycemic control in this cohort was known by the mean HbA1c of 9.1%. The increased HbA1c values are associated with an increased risk of infection and poor outcomes in diabetic patients [11]. Community-acquired pneumonia (CAP) proved to be the most common pleuropulmonary infection affecting 64.3% of patients. Most infections originated from Streptococcus pneumoniae and Klebsiella pneumoniae in accordance with global research showing these bacteria cause the majority of CAP infections in diabetic patients [12]. It is crucial to recognize that the dangerous ESBL-producing Klebsiella organisms have been detected in 51.2% of isolates due to antibiotic resistance growth in this population. The data highlights a need for researchers to develop antibiotic treatment plans with comprehensive protection that must be used specifically for diabetic patients who have moderate or severe pneumonia or who do not respond well to initial treatment [13]. The second most prevalent infection observed was tuberculosis which made up 25.7% of diagnosed cases. Research confirms that diabetes and tuberculosis exist in an epidemiological association that characterizes countries like India that have high tuberculosis rates. Scientific research shows that diabetes raises TB risk by between two and three times [14]. Our research indicates that diabetic persons who experience prolonged respiratory symptoms need routine tuberculosis assessment particularly when their chest scans demonstrate cavities or show evidence of bilateral lung involvement. Among all cases of pneumonia, consolidation appeared as the primary radiographic abnormality most frequently detected specifically in patients with CAP but tuberculosis patients displayed cavitation most prominently. Pleural effusion occurred in almost one-third of cases and was present in both TB and CAP. The presence of bilateral involvement happened most frequently in TB patients alongside those with severe CAP causing poor clinical outcomes. Current literature supports the use of radiographic patterns for determining disease severity and formulating diagnostic approaches because research has consistently shown these findings [15].

Radiologically, consolidation was the most common finding, especially among CAP cases, while cavitation was most frequently seen in tuberculosis. Pleural effusion, seen in nearly one-third of patients, was linked with both TB and CAP. Notably, bilateral involvement was seen more often in TB and severe CAP and was associated with poorer outcomes. Similar findings have been reported in previous studies, underscoring the utility of radiographic patterns in predicting disease severity and guiding diagnostic considerations [15]. A microbiological analysis demonstrated culture-positive results in 75.7% of all cases tested. The high frequency of M. tuberculosis in cases as well as the therapy-sensitive nature of 89% cases (89%) supports optimistic findings. The therapeutic challenge increases as healthcare providers must deal with ESBL-producing K. pneumoniae which demonstrates multidrug-resistant behavior. The search for Staphylococcus aureus and mixed anaerobes reinforces the diverse pathogen presence in diabetic lung infections since their detection mainly occurs in empyema cases together with lung abscess cases [16]. The majority of patients had successful treatment outcomes because 74.3% of them received complete clinical cures. The clinical outcomes were unfavorable for approximately twenty-four percent of patients who showed treatment failure or persistent sequelae or died. The combination of uncontrolled blood sugar (HbA1c > 9%) with bilateral lung infections on imaging tests coupled with chronic kidney disease led to an increased risk of poor outcomes. Early targeted respiratory infection treatment combined with aggressive glycemic control represents essential care for diabetic patients with such infections [17].

In conclusion, pleuropulmonary infections in diabetics present with diverse clinical and radiological features and are commonly caused by typical bacterial and mycobacterial pathogens. Poor glycemic control and comorbid conditions are key factors influencing disease severity and outcomes. These findings reinforce the need for integrated management strategies involving glycemic optimization, prompt microbiological evaluation, appropriate antimicrobial therapy, and routine screening for tuberculosis, especially in endemic areas.

1. Casqueiro J, Casqueiro J, Alves C. Infections in patients with diabetes mellitus: A review of pathogenesis. Indian J Endocrinol Metab. 2012;16(Suppl1):S27–S36.
2. Geerlings SE, Hoepelman AI. Immune dysfunction in patients with diabetes mellitus (DM). FEMS Immunol Med Microbiol. 1999;26(3-4):259–265.
3. Muller LM, et al. Increased risk of common infections in patients with type 1 and type 2 diabetes mellitus. Clin Infect Dis. 2005;41(3):281–288.
4. Dooley KE, Chaisson RE. Tuberculosis and diabetes mellitus: convergence of two epidemics. Lancet Infect Dis. 2009;9(12):737–746.
5. Shah BR, Hux JE. Quantifying the risk of infectious diseases for people with diabetes. Diabetes Care. 2003;26(2):510–513.
6. Roden MM, et al. Epidemiology and outcome of zygomycosis: a review of 929 reported cases. Clin Infect Dis. 2005;41(5):634–653.
7. Hassan M, et al. Empyema thoracis: a comparative analysis of 125 patients with and without diabetes mellitus. J Ayub Med Coll Abbottabad. 2014;26(3):305–308.
8. Perez-Guzman C, et al. Atypical radiological images of pulmonary tuberculosis in 192 diabetic patients: a comparative study. Int J Tuberc Lung Dis. 2001;5(5):455–461.
9. Casqueiro J, Casqueiro J, Alves C. Infections in patients with diabetes mellitus: A review of pathogenesis. Indian J Endocrinol Metab. 2012;16(Suppl 1):S27–S36.
10. Muller LM, Gorter KJ, Hak E, et al. Increased risk of common infections in patients with type 1 and type 2 diabetes mellitus. Clin Infect Dis. 2005;41(3):281–288.
11. Pearson-Stuttard J, Blundell S, Harris T, et al. Diabetes and infection: Assessing the association with glycaemic control in population-based studies. Lancet Diabetes Endocrinol. 2016;4(2):148–158.
12. Shah BR, Hux JE. Quantifying the risk of infectious diseases for people with diabetes. Diabetes Care. 2003;26(2):510–513.
13. Lin JC, Siu LK, Fung CP, et al. Impacts of appropriate antimicrobial therapy on the outcome of patients with community-onset bacteremia. Crit Care Med. 2006;34(5):1193–1199.
14. Dooley KE, Chaisson RE. Tuberculosis and diabetes mellitus: convergence of two epidemics. Lancet Infect Dis. 2009;9(12):737–746.
15. Perez-Guzman C, Vargas MH, Torres-Cruz A, et al. Does aging modify pulmonary tuberculosis? A meta-analytical review. Chest. 1999;116(4):961–967.
16. Roden MM, Zaoutis TE, Buchanan WL, et al. Epidemiology and outcome of zygomycosis: A review of 929 reported cases. Clin Infect Dis. 2005;41(5):634–653.
17. Falagas ME, Peppas G, Matthaiou DK, et al. Effect of diabetes mellitus on the outcome of patients with bacteremia. Scand J Infect Dis. 2007;39(9):807–815.