Microbiology Research Journal International

Carbapenems Retain High in Vitro Activity against Clinical Bacterial Isolates in a Nigerian Tertiary Hospital: Implications for Antimicrobial Stewardship in a Resource-limited Setting

Constancy Prisca Aleru-Obogai — 2026-03-21

Background: Antimicrobial resistance (AMR) is a growing global public health threat that undermines the effective treatment of infectious diseases. The increasing prevalence of resistant bacterial strains has reduced the efficacy of commonly used antibiotics, resulting in treatment failures, prolonged hospitalisation, increased healthcare costs, and higher morbidity and mortality. Continuous monitoring of local antimicrobial susceptibility profiles is therefore essential to guide evidence-based empirical therapy, strengthen antimicrobial stewardship, and improve patient outcomes.

Objective: The present study determines the in vitro antimicrobial susceptibility patterns of bacterial isolates recovered from clinical specimens in a Nigerian tertiary hospital and to evaluate the relative effectiveness of quinolones, cephalosporins, and carbapenems.

Methods: A laboratory-based cross-sectional study was conducted between January 2024 and December 2024 using 100 non-duplicate bacterial isolates recovered from routine clinical specimens processed at a tertiary healthcare facility in Southern Nigeria. The specimens were obtained from patients presenting with various clinical infections and included samples such as urine, high vaginal swabs, wound swabs, sputum, and blood, depending on clinical indication. Only the first isolate per patient was included to avoid duplication and ensure representativeness of the data. All samples were processed in the medical microbiology laboratory under standard operating procedures. Primary isolation was carried out on appropriate culture media, including blood agar, MacConkey agar, and chocolate agar where indicated, followed by incubation under suitable atmospheric and temperature conditions. Bacterial identification was performed using conventional microbiological methods. Antimicrobial susceptibility testing was performed using the Kirby–Bauer disc diffusion technique on Mueller–Hinton agar. Standardised inocula equivalent to 0.5 McFarland turbidity standard were prepared and evenly inoculated onto the agar surface before placement of antibiotic discs.

Results: Among the 100 bacterial isolates analysed, Staphylococcus species were the most frequently recovered bacteria, accounting for 41% of isolates. This was followed by Klebsiella species (15%), Escherichia coli (14%), Streptococcus species (13%), and Pseudomonas species (12%), while Proteus species were the least common, representing 5% of the isolates. Antimicrobial susceptibility testing showed that ertapenem demonstrated the highest activity, with 99% susceptibility among the isolates. Ciprofloxacin showed 75% susceptibility, indicating moderate effectiveness. In contrast, markedly lower susceptibility rates were observed for cephalosporins, including cephalexin (36%), cefuroxime (21%), and cefepime (10%).

Conclusion: The findings of this study indicate that carbapenems, particularly ertapenem, continue to demonstrate substantial in vitro activity against a broad range of bacterial clinical isolates within this healthcare setting. Additionally, continuous surveillance of local and regional antimicrobial resistance trends is essential to guide clinicians in making evidence-based treatment decisions, update hospital formularies, and inform national antibiotic policies. Implementing rational antibiotic prescribing practices, combined with infection prevention and control measures, is vital to curb the spread of multidrug-resistant bacteria and improve patient outcomes. Collectively, these strategies will support sustainable management of bacterial infections and help mitigate the public health impact of antimicrobial resistance in Nigeria and similar resource-limited settings.

Profiling Cellulolytic Bacteria Isolated from Tropical Atlantic Ocean Coastal Sediment in Escravos, Nigeria

Sophia O. Ogbonna — 2026-03-24

Background: Marine sediments contain diverse, underexplored cellulose-degrading bacteria important for nutrient cycling. Coastal tropical regions, in particular, may offer promising strains for biotechnological applications.

Aims: A diversity of microorganisms inhabits the marine environment. These organisms including cellulolytic bacteria can be useful in biotechnological applications. This study was therefore undertaken to ascertain the presence and identity of cellulose-degrading bacteria in Nigerian coastal sediments.

Study Design: Laboratory tests were designed to isolate and identify cellulose-degrading bacteria from sediment and wood samples collected from the coastline of Escravos, Nigeria.

Place and Duration of Study: The study was undertaken over a period of 6 months (April-September, 2024) using the Microbiology laboratory of Delta State University, Abraka, Nigeria.

Methodology: Carboxyl Methyl Cellulose (CMC) and microcrystalline (MCC) agar were used to isolate cellulolytic bacteria and determine their cellulolytic index (CI) under aerobic and anaerobic conditions. Identification of isolates was by morphological, biochemical and molecular tests.

Results: The cellulolytic bacterial isolates were 52 with 22 and 30 isolated under aerobic and anaerobic conditions, respectively. The isolates belong to the genera Bacillus, Pseudomonas, Klebsiella, Clostridium and Staphylococcus. Cellulolytic clearance diameter of the isolates on seawater CMC agar did not differ from those on mineral salts CMC agar under aerobic condition except Klebsiella (P=0.025). Anaerobically, clearance zones on the two media differed (P=0.029) with respect to Staphylococcus and Pseudomonas only. Bacillus was the most prevalent (40.4%) and also had the highest CI of 3.2-3.5; others had <2.0. The CI of all isolates in CMC differed significantly (P=0.000-0.020) from that of MCC except Bacillus. Molecular characterization of the Bacillus isolates as the most prevalent and cellulolytic confirmed them as Bacillus cereus (S2_907R_G08_20.ab1), Bacillus sanguinis (S6_907R_B09_06.ab1), Bacillus albus (S7_907R_C09_09.ab1), Bacillus thuringiensis (S8_907R_D09_12.ab1), Lysinibacillus fusiformis (S1_907R_F08_17.ab1), Lysinibacillus boronitolerans (S3_907R_H08_23.ab1), Lysinibacillus sphaericus (S5_907R_A09_03.ab1) and Lysinibacillus xylanilyticus (S10_907R_E09_15.ab1). CI of Bacillus and Lysinibacillus species varied, but were not markedly different.

Conclusion: Bacillus and Lysinibacillus were the dominant cellulolytic bacteria in the coastal sediment. Their cellulolytic capabilities can be potentially useful in biotechnological applications.

Prevalence, Molecular Identification and Antimicrobial Resistance Profiles of Klebsiella pneumoniae Isolated from Mastitic Cattle and Buffaloes, Menofia Governorate, Egypt

Mohamed Sabry Abdelraheam Elsayed — 2026-03-30

Background: Bovine mastitis remains a primary global challenge for the dairy sector, representing one of the most economically taxing diseases. Bacterial-induced intramammary infections, in particular, result in significant financial deficits driven by diminished milk yields, compromised milk quality, escalating healthcare expenditures, and the involuntary culling of livestock. This study investigated the prevalence, molecular characteristics, and antimicrobial resistance of K. pneumoniae.

Methodology: The study included 400 milk samples (250 clinical; 150 subclinical) from mastitic cows and buffaloes. Isolates were identified using bacteriological and molecular methods, followed by comprehensive susceptibility testing using Kirby Bauer disc diffusion method per CLSI guidelines to establish resistance profiles.

Results: K. pneumoniae was isolated from 8.75% (35/400) of the total samples. Isolation rates for clinical mastitis were 6.5% (13/200) in cattle and 6% (3/50) in buffaloes, while subclinical mastitis showed higher prevalence at 11.5% (15/130) and 20% (4/20), respectively. Antimicrobial susceptibility testing of 35 K. pneumoniae isolates showed 100% sensitivity Carbapenems (Imipenem/Meropenem), third-generation Cephalosporins (Ceftiofur/Cefotaxime), Aminoglycosides (Kanamycin/Gentamicin), and Marbofloxacin. Conversely, high resistance rates were identified in older-generation drugs, including Nalidixic acid (100%), Norfloxacin (88.5%), Amoxicillin (74.3%). Moreover, Erythromycin encountered total resistance (100%) and Tetracycline showed moderate efficacy (60%). The most frequent resistance profile was E, NA, AMX, NX (Erythromycin, Nalidixic Acid, Amoxicillin, Norfloxacin), which was observed in 25.7% (9/35) of the isolates. This was closely followed by the profile E, NA, AMX, NX, found in 22.8% (8/35) of the samples. All isolates (100%) surpassed the MAR index threshold of 0.2, which statistically indicates a "high-risk" source of contamination where antibiotics are frequently used or misused. PCR amplification targeting the gyrA gene successfully confirmed the molecular identity of all 35 K. pneumoniae isolates.

Conclusion: The presence of K. pneumoniae in dairy herds highlights a significant epidemiological threat and a rise in drug-resistant strains. To combat this, it is vital to implement strict surveillance, promote the responsible use of antimicrobials, and develop proactive prevention strategies to protect herd health.

Multidrug-Resistant Escherichia coli in Commercial Grasscutter (Thryonomys swinderianus) Farms: Prevalence and Association with Bio-Preservation Practices in Togo

Essozimna Sondou — 2026-04-02

Introduction: In Togo, limited data exist on the implementation of biosecurity and bio-preservation practices in animal production systems, particularly in grasscutter (Thryonomys swinderianus) farming. This study aimed to describe the level of intestinal microbiota contamination by multidrug-resistant E. coli strains in grasscutters and to explore farming practices—especially those related to bio-preservation that may influence the emergence or dissemination of multidrug resistance profiles.

Aim: The study aims to describe the level of intestinal microbiota contamination by multidrug-resistant E. coli strains in grasscutters and to explore farming practices, especially those related to bio-preservation, in relation to the emergence or dissemination of these multidrug resistance profiles.

Materials and Methods: The study was conducted on four grasscutter farms located in the south-western part of the Plateaux Region (Togo). Bio-preservation practices were assessed using an observation checklist. Fresh 113 faecal samples were collected in August 2020 and subjected to microbiological analyses. 106 E. coli Strains were isolated. Antibiotic susceptibility testing was performed using the Mueller-Hinton agar disk diffusion method on the isolated E. coli strains.

Results: The average level of bio-preservation control was 62.5%, with variations across sites. Antibiotic susceptibility tests performed on 75% of isolates revealed high resistance frequencies to tetracycline, amoxicillin, trimethoprim, and piperacillin. No extended-spectrum β-lactamase (ESBL)-producing strains were detected; however, 3.8% exhibited high-level penicillinase activity and 2.5% showed low-level cephalosporinase activity. Multidrug resistance was observed in 26.3% of isolates, and 56.2% were resistant to at least one antibiotic.

Conclusion: These findings highlight the need for improved bio-preservation and surveillance to mitigate AMR risks in grasscutter farming. Further studies covering additional regions and incorporating molecular analyses are needed to strengthen prevention and surveillance strategies within a One Health approach.

Fecal and Salivary Microbial Gene Markers for the Non-invasive Detection of Colorectal Cancer Progression

Naoko Nakano — 2026-04-02

Aims: To evaluate the diagnostic potential of previously reported (5ar, nan) and novel microbial gene markers in fecal and salivary microbiomes for the non-invasive detection of colorectal cancer (CRC) progression.

Study Design: Cross-sectional study.

Place and Duration of Study: Department of Gastroenterology and Hepatology, Fujita Health University, Toyoake, Japan, between June 2024 and July 2025.

Methodology: Fecal samples were collected from healthy controls (n = 65) and patients with colorectal adenoma (n = 38) or carcinoma (n = 27). Salivary samples were collected from healthy controls (n = 34) and the same patient cohorts. Microbial gene abundances were quantified via quantitative PCR, and microbiome composition was assessed using 16S rRNA gene sequencing. Group comparisons used the Kruskal-Wallis and Dunn’s tests. Beta diversity differences were evaluated by PERMANOVA.

Results: In fecal samples, the abundances of 5ar, nan, and the Fusicatenibacter saccharivorans 16S rRNA gene (fsr) showed a stepwise decline from the adenoma stage onward, with significantly lower levels in carcinoma versus controls (5ar, P = 0.0023; nan, P = 0.0012; fsr, P = 0.0004). Conversely, in saliva, the Fusobacterium periodonticum tyrosine phenol lyase gene (tpl) was significantly reduced only in the carcinoma group (P = 0.0180). Fecal beta diversity differed significantly between controls and both colorectal neoplasia groups (both P ≤ 0.001), whereas salivary beta diversity differed only between controls and carcinoma patients (P = 0.014).

Conclusion: Fecal and salivary microbial gene markers may serve as non-invasive, rapid, and cost-effective biomarkers for colorectal neoplasia. Fecal markers captured microbiota disruption at the adenoma stage (representing the early phase of CRC progression), whereas salivary markers predominantly reflected alterations specific to carcinoma (representing the later phase). Integrating these multi-niche biomarkers provides a promising clinical platform for early detection, monitoring of precursor lesions, and postoperative surveillance; however, validation in larger, independent cohorts is warranted.

Isolation and Characterization of Plant Growth Promoting Rhizobacteria from Agricultural Soils of North Telangana Region

E. Guravaiah — 2026-04-02

Background and Aims: Plant growth–promoting rhizobacteria (PGPR) constitute a diverse group of beneficial soil microorganisms that colonize the rhizosphere and enhance plant growth through multiple direct and indirect mechanisms, including nutrient mobilization and suppression of phytopathogens. In the present study, rhizospheric soil samples were collected from agricultural crop fields across four districts of North Telangana State to isolate and characterize potential PGPR strains.

Methodology: Bacterial populations were isolated using the serial dilution technique, and aliquots (0.1 mL) of diluted soil suspensions were spread onto nutrient agar plates and incubated at 25–30 °C for 24–48 hours to ensure optimal bacterial growth. The isolated strains were subsequently screened on selective media for key plant growth–promoting traits, including phosphate solubilization, indole-3-acetic acid (IAA) production, hydrogen cyanide (HCN) production, and siderophore synthesis.

Results: Among the isolates obtained, ten strains exhibited superior plant growth–promoting activities, however out of 10 bacterial isolates two isolates SP13 Brevudimonas diminuta, SP14 Acinetobacter baumannii were found to be most potential and novel strains and gives majority of the PGPR attributes, evidenced by prominent halo zones and clear inhibition zones surrounding the bacterial colonies.

Conclusion: These promising isolates were preserved and further characterized based on colony morphology for future studies. Given their eco-friendly nature and potential to enhance crop productivity and soil fertility, the identified PGPR isolates demonstrate strong potential for development as biofertilizers suitable for the agro-climatic conditions of Telangana State.

Impact of Environmental Toxicity on Systemic Inflammation and the Progression of Bacterial and Fungal Infections in a Rat Model

Kamagaté Moustapha — 2026-04-02

Background and Aims: The intensification of human activities in recent years has led to persistent environmental pollution, marked by the accumulation of heavy metals and pesticides due to their widespread and excessive use, raising serious health concerns. At the same time, the resurgence of infectious diseases and the emergence of resistant strains are complicating therapeutic management. This study aims to examine the correlations between exposure to pollutants, inflammatory response, and worsening of microbial infections

Study Design: Experimental study.

Place and Duration of Study: Laboratory of Biotechnology and Valorization of Bioactive Natural Substances Laboratory of the National Center for Floristics (CNF) (Abidjan, Côte d’Ivoire), between July 2023-december 2023.

Methodology: To examine the correlations between exposure to pollutants, inflammatory response, and the worsening of microbial infections. Thus, Wistar rats were exposed to three common environmental pollutants, lead (15 µg. L^-1) or glyphosate (0.5 mg/kg/day) orally or mercury (0.3 µg/m³) by inhalation over a 28-days period, and then infected with Escherichia coli (1 mL) or Candida albicans (0.1 mL) orally.

Results: The results obtained show that co-exposure to pollutants and infectious agents significantly worsened the physiological condition of the rats, inducing leukocyte disarray, persistent systemic inflammation, as well as variable immunosuppression responsible for increased susceptibility to infections. This impairment exhibited increasing severity depending on the toxin dose (mercury, lead, glyphosate). In contrast, in the absence of toxins, infections remained generally reversible, the maintenance of stable immune parameters. Furthermore, Escherichia coli isolates from rats exposed to lead or mercury showed resistance to fluoroquinolones and reduced sensitivity to beta-lactams and aminoglycosides, while glyphosate did not alter this profile. In addition, Candida albicans isolates remained sensitive to antifungals.

Conclusion: The study showed that exposure to lead and mercury caused severe immunosuppression persistent inflammation and promoted antibiotic resistance, while glyphosate activated persistent chronic systemic inflammation without altering microbial sensitivity.