Background and Aim: Methicillin-resistant Staphylococcus aureus (MRSA), an important opportunistic pathogen, is a Gram-positive coccus known to be resistant to β-lactam antibiotics. Its virulence depends on a large range of factors, mainly extracellular proteins, such as enzymes and exotoxins, that contribute to causing a wide range of diseases in human and animal species. The major reasons for the success of this pathogen are its great variability, which enables it to occur and thrive at different periods and places with diverse clonal types and antibiotic resistance patterns within regions and countries. Infections caused by antibiotic-resistant S. aureus bring about serious problems in the general population (humans and animals). Infections with these pathogens can be devastating, particularly for the very young, adults and immunocompromised patients in both humans and animals. This study aimed to determine the presence of MRSA in both apparently healthy and sick sheep brought to the veterinary hospital as well as veterinary staff and students on clinical attachment in the hospital. Materials and Methods: A total of 200 nasal swab samples were collected aseptically from sheep and humans (100 each) for the isolation of MRSA. The samples were processed by appropriately transporting them to the laboratory, then propagated in nutrient broth at 37°C for 24 h followed by subculturing on mannitol salt agar at 37°C for 24 h, to identify S. aureus. This was followed by biochemical tests (catalase and coagulase tests) and Gram staining. MRSA was isolated using Clinical Laboratory Standard Institute (CLSI) guideline and confirmed by plating onto Oxacillin (OX) Resistance Screening Agar Base agar. The antimicrobial susceptibility pattern of the MRSA isolates was determined using the disk diffusion method against 12 commonly used antimicrobial agents. Results: The total rate of nasal carriage of S. aureus and MRSA was found to be 51% and 43% in sheep and humans, respectively. The MRSA prevalence in male and female sheep was 18% and 8%, while 9% and 8% were for male and female human samples, respectively. The antimicrobial susceptibility test showed 100% resistance to OX, cefoxitin, oxytetracycline, cephazolin, and penicillin-G (Pen) by MRSA isolates from humans. Conversely, there was 100% susceptibility to ciprofloxacin, imipenem, and gentamicin; for linezolid (LZD), it was 87.5%, norfloxacin (NOR) (71%), and erythromycin (ERY) (50%) susceptibility was recorded. The MRSA isolates from sheep recorded 100% resistance to the same set of drugs used for human MRSA isolates and were equally 100% susceptible to gentamicin, imipenem, LZD, ciprofloxacin, NOR (92%), and ERY (50%). Conclusion: This study determined the presence of MRSA in sheep and humans from the Veterinary Hospital, Maiduguri. It appears that certain drugs such as ciprofloxacin, imipenem, and gentamicin will continue to remain effective against MRSA associated with humans and sheep. Reasons for the observed patterns of resistance must be explored to reduce the burdens of MRSA resistance. Furthermore, the present study did not confirm the MRSA resistance genes such as mecA and spa typing to ascertain the polymorphism in the X-region using appropriate molecular techniques. Hence more studies need to be conducted to elucidate these findings using robust techniques.

Tuberculosis (TB), caused by Mycobacterium tuberculosis, is one of the leading causes of death due to an infectious agent. Coinfection with HIV exacerbates M. tuberculosis infection outcomes in people living with HIV. Bacillus Calmette–Guérin (BCG), the only approved TB vaccine, is effective in infants, but its efficacy in adolescents and adults is limited. In this study, we investigated the immune responses elicited by BCG administered via i.v. or intradermal (i.d.) routes in SIV-infected Mauritian cynomolgus macaques (MCM) without the confounding effects of M. tuberculosis challenge. We assessed the impact of vaccination on T cell responses in the airway, blood, and tissues (lung, thoracic lymph nodes, and spleen), as well as the expression of cytokines, cytotoxic effectors, and key transcription factors. Our results showed that i.v. BCG induces a robust and sustained immune response, including tissue-resident memory T cells in lungs, polyfunctional CD4+ and CD8αβ+ T cells expressing multiple cytokines, and CD8αβ+ T cells and NK cells expressing cytotoxic effectors in airways. We also detected higher levels of mycobacteria-specific IgG and IgM in the airways of i.v. BCG-vaccinated MCM. Although i.v. BCG vaccination resulted in an influx of tissue-resident memory T cells in lungs of MCM with controlled SIV replication, MCM with high plasma SIV RNA (>105 copies/ml) typically displayed reduced T cell responses, suggesting that uncontrolled SIV or HIV replication would have a detrimental effect on i.v. BCG-induced protection against M. tuberculosis.

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), is one of the leading causes of death due to an infectious agent. Coinfection with HIV exacerbates Mtb infection outcomes in people living with HIV (PLWH). Bacillus Calmette-Guérin (BCG), the only approved TB vaccine, is effective in infants, but its efficacy in adolescents and adults is limited. Here, we investigated the immune responses elicited by BCG administered via intravenous (IV) or intradermal (ID) routes in Simian Immunodeficiency Virus (SIV)-infected Mauritian cynomolgus macaques (MCM) without the confounding effects of Mtb challenge. We assessed the impact of vaccination on T cell responses in the airway, blood, and tissues (lung, thoracic lymph nodes, and spleen), as well as the expression of cytokines, cytotoxic molecules, and key transcription factors. Our results showed that IV BCG induces a robust and sustained immune response, including tissue-resident memory T (T _RM ) cells in lungs, polyfunctional CD4+ and CD8αβ+ T cells expressing multiple cytokines, and CD8αβ+ T cells and NK cells expressing cytotoxic effectors in airways. We also detected higher levels of mycobacteria-specific IgG and IgM in the airways of IV BCG-vaccinated MCM. Although IV BCG vaccination resulted in an influx of T _RM cells in lungs of MCM with controlled SIV replication, MCM with high plasma SIV RNA (>10 ⁵ copies/mL) typically displayed reduced T cell responses, suggesting that uncontrolled SIV or HIV replication would have a detrimental effect on IV BCG-induced protection against Mtb.

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), is a major global health challenge, especially for people living with HIV (PLWH) not on antiretroviral therapy. We previously showed that intravenous Bacillus Calmette-Guérin (IV-BCG) provides robust protection in SIV+ Mauritian cynomolgus macaques (MCM). Here, we evaluate whether the immunogenicity and efficacy of IV-BCG in SIV+ MCM was impaired by eliminating BCG with drugs. SIV+ macaques were treated with an anti-BCG regimen of isoniazid, rifampicin, and ethambutol (HRE), starting either 1- or 3-weeks post-BCG vaccination. Five months post-vaccination, macaques were challenged with Mtb for 12 weeks. Protection conferred by IV-BCG was significant regardless of HRE timing. However, non-controllers, characterized by high viremia and reduced CD4+ T cells in the lungs, were significantly less protected than controllers. Thus, the robust efficacy of IV-BCG in SIV+ MCM is retained regardless of anti-BCG drug treatment, indicating that BCG does not need to survive long to provide protection. In contrast, SIV control was necessary for full protection induced by IV-BCG. Thus, our results support that viral control is critical for vaccine-elicited protection from TB in PLWH.

Effective means of improving Bacille Calmette-Guérin (BCG) immunogenicity to protect against pulmonary tuberculosis (TB) is needed, especially among people living with HIV. Intravenous (IV) administration of BCG previously showed significant enhancement of immune responses and conferred ~75% protection against TB. Using our SIV/M. tuberculosis (Mtb) coinfection model (to mimic HIV/Mtb coinfection) in Mauritius cynomolgus macaques (MCM), we evaluated the length of time necessary for live BCG to elicit a protective immune responses by varying the timing of anti-BCG drug (isoniazid, rifampicin, and ethambutol: HRE) initiation. MCM were infected with SIVmac239 and randomly assigned into 4 different vaccination groups 16 weeks after SIV infection: intradermal BCG (BCG ID No HRE), BCG IV with HRE started 1 week post BCG (BCG IV 1wk HRE), BCG IV with HRE started 3 weeks post BCG (BCG IV 3wks HRE), and BCG IV without HRE treatment (BCG IV No HRE). The HRE treatment lasted for 8 weeks. Airways samples were collected by bronchoalveolar lavage (BAL), whereas lung tissue and lymph node were harvested at necropsy in a subset of BCG ID and BCG IV 3wks vaccinated MCM 20 weeks after BCG but before (Mtb) challenge. The remaining MCM were challenged with Mtb Erdman strain (~15 CFU). CD4 and CD8 T cell levels increased in BAL in all IV vaccinated MCM. CD4 T cells producing IFNg, IL-2, IL-17, and TNF peaked after BCG and were maintained until necropsy. There were increased tissue-resident T cells and cytokine production in lungs of IV vaccinated MCM compared to BCG ID. No signs of BCG dissemination were apparent in any IV vaccinated MCM. We are currently evaluating protection against infection and disease in the SIV+ MCM in each vaccination group. Supported by grant NIH (R01 AI155345)