RESEARCH

Effects of Electronic Cigarette Liquid on the Growth, Biofilm Formation, Lactic Acid Production, and Stress Tolerance of Streptococcus mutans

JEL Daquioag, LMR Foronda, and GM Penuliar

2025 | Philippine Journal of Science. 154 (2): 407-417.  .

In this study, we examined how e-cigarettes affect S. mutans, the primary bacterium responsible for dental caries. While high concentrations of e-liquid inhibited growth, sub-inhibitory levels did not significantly affect growth, biofilm formation, lactic acid production, autolysis, and stress tolerance. Nicotine content also had no significant impact at these lower concentrations. The findings suggest that e-cigarettes may not substantially alter S. mutans physiology, though the overall health risks of e-cigarettes remain a concern that requires further investigation.

Characterization of Campylobacter jejuni and Campylobacter coli isolates from chicken offal in Metro Manila, Philippines: Insights from virulence gene prevalence and multilocus sequence typing analysis

MSEP Subejano and GM Penuliar

2023 | Tropical Biomedicine, 40(4):422-429,

In this study, we investigated the genetic and virulence profiles of Campylobacter isolates from chicken offal sold in wet markets in Metro Manila. Using MLST, we identified 13 unique sequence types, including 9 unreported, and 3 clonal complexes, with ST-305 found in multiple markets. Virulence gene profiling showed that over half of the isolates carried key genes, with cadF present in all. Our findings reveal high genotypic diversity and the presence of virulence factors, that underscore the need for improved surveillance and control strategies to reduce the risk of Campylobacter-related infections.

In vitro and in vivo activity of Lactobacillus sakei L14 strain against Campylobacter jejuni DC3 strain

JRP Catacutan, MSEP Subejano, and  GM Penuliar

2022 | Journal of Veterinary Research, 66, 85–94.

In this study, we explored the role of LAB in the asymptomatic carriage of Campylobacter in chickens. Among the LAB isolates from poultry gut, L. sakei L14 showed strong in vitro anti-C. jejuni activity, particularly through cell-free supernatants harvested after 72 h. However, in vivo co-infection experiments in chickens did not reduce C. jejuni colonization, suggesting that L. sakei L14’s effects may involve indirect or host-mediated mechanisms rather than direct bacterial inhibition.

Isolation of Actinomycetes with Cellulolytic and Antimicrobial Activities from Soils Collected 

from an Urban Green Space in the Philippines

JEL Daquioag and GM Penuliar

2021 | International Journal of Microbiology, DOI: 10.1155/2021/6699430.

In this study, we investigated actinomycetes from soil in green spaces at the University of the Philippines Diliman to assess their cellulolytic and antimicrobial activities. Out of 235 purified isolates, 114 showed cellulolytic and 18 showed antimicrobial activity. Notably, isolates EWLG2 and EPNA9 exhibited high cellulase activity, while several others demonstrated antimicrobial effects against Candida spp. and bacteria, with MIC values ranging from 31.25 to 500 μg/mL. DNA sequencing identified active isolates as Bacillus and Streptomyces species. Our findings highlight the potential of urban green spaces as sources of microbes with applications in drug development.

Virulence-associated Gene Profile and Multilocus Sequence Type Analysis of Human and Fomite-derived Methicillin-resistant Staphylococcus aureus

JRP Calicaran and GM Penuliar

2021 | Philippine Journal of Science, 150(4), 817–825.

In this study, we analyzed 20 MRSA isolates from human and fomite sources in the Philippines to explore links between virulence-associated genes and sequence types. High prevalence of hemolysin genes hla and hld was observed, while the pvl gene was present in only 30% of the isolates, questioning its reliability as a CA-MRSA marker. MLST identified 6 new STs from 6 clonal complexes, including 3 new singletons. No significant association was found between VAG profiles and STs, likely due to the widespread presence of the VAGs across isolates.

Prevalence, Antibiogram and Virulence Gene Profiles of Uropathogenic Escherichia coli from Pregnant Women with Urinary Tract Infection

GL Serrano and GM Penuliar

2018 | Philippine Science Letters, 11(Supplement), 46–55,.

In this study, we investigated UPEC in pregnant women with UTIs at a hospital in Metro Manila. Among the samples, 21% tested positive for UTI, with 42% of those caused by UPEC. High levels of antibiotic resistance were found, particularly to ampicillin, amoxicillin-clavulanate, and cephalothin, along with multidrug resistance. Virulence genes for P fimbriae, Type 1 fimbriae, and Dr II adhesin were also detected. The study highlights the growing resistance of UPEC and recommends performing AST before treatment, with fosfomycin as an alternative therapy for UTIs in pregnant women.

Methicillin-resistant Staphylococcus aureus Carriage in a Residential Care Institution for the Elderly in Quezon City, Philippines

MGB Ayala, EC Cabrera, and GM Penuliar

2018 | Philippine Science Letters, 11(Supplement), 4–11.

In this study, we investigated MRSA carriage among elderly residents in a care facility in Quezon City. Nasal swabs from 66 asymptomatic individuals revealed a 16.7% MRSA prevalence. All isolates carried SCCmec type IV and were mostly multidrug-resistant, particularly to erythromycin, clindamycin, and rifampicin. However, all were susceptible to several other antibiotics including vancomycin and linezolid. A history of pulmonary tuberculosis was the only risk factor significantly associated with MRSA carriage. The findings highlight the need to review infection control and antibiotic practices in such facilities to prevent MRSA spread.

Comparison of clinical and environmental isolates of Acanthamoeba based on morphology, protease 

and gelatinase activity, and the cysteine proteinase gene

GM Penuliar, RR Matias, and FF Natividad

2010 | Science Diliman, 22, 9–18.

In this study, we compared clinical and environmental isolates of Acanthamoeba to assess whether morphology, enzyme activity, and the cysteine proteinase gene can distinguish pathogenic strains. While morphology showed limited differentiation, clinical isolates exhibited significantly higher protease activity and distinct zymography banding patterns compared to environmental ones. Additionally, CP gene amplification differed between the groups, with environmental isolates showing two bands and clinical isolates only one. These findings highlight the limitations of morphology-based classification and support the use of molecular and enzymatic markers for identifying pathogenic Acanthamoeba isolates.