Mycoplasma hominis: Introduction, Morphology, Pathogenicity

Introduction

Table of Contents

Mycoplasma hominis is a species of bacteria belonging to the Mollicutes class. It is a unique microorganism as it lacks a cell wall, making it one of the smallest self-replicating organisms known. Due to this feature, it has a pleomorphic appearance, taking various shapes, including spherical, filamentous, or ovoid.

Mycoplasma hominis is a member of the human genital tract microbiota and is primarily associated with urogenital infections. It colonizes the mucous membranes of the human genital and respiratory tracts and can be transmitted through sexual contact, making it a sexually transmitted pathogen.

The bacterium is considered an opportunistic pathogen, which means it tends to cause infections when the host’s immune system is weakened or compromised. It can lead to a wide range of clinical conditions, such as urinary tract infections, pelvic inflammatory disease, postpartum fever, and infections in immunocompromised individuals.

Diagnosing M. hominis infections can be challenging due to its fastidious nature and slow growth on standard laboratory media. Specialized culture methods and molecular techniques, such as polymerase chain reaction (PCR), are typically employed for accurate identification.

Treatment of these infections usually involves antibiotics like tetracyclines, macrolides, or fluoroquinolones. However, antibiotic resistance has become a concern with this bacterium, emphasizing the need for appropriate antibiotic stewardship and monitoring.

As with any infection, prevention is crucial. Safe sexual practices, regular screenings, and maintaining a healthy immune system can help reduce the risk of M. infections.

Morphology

Mycoplasma hominis is a unique bacterium when it comes to morphology due to its lack of a cell wall. Here are some key characteristics of the morphology of M. hominis:

No Cell Wall: It is one of the few bacterial species that lack a cell wall. Most bacteria have a rigid cell wall that provides structural support and protection. Without a cell wall, M. hominis has a pleomorphic shape, meaning it can take on various forms, including spherical, filamentous, or ovoid. This flexibility allows it to adapt to different environments and evade the host’s immune response.
Membrane-Bound Organelles: Despite its minimalistic structure, Mycoplasma hominis possesses various membrane-bound organelles within its cytoplasm. These organelles include ribosomes, nucleoids (which contain the bacterial DNA), and other essential cellular components.
Small Size: Due to the absence of a cell wall, M. hominis is considered one of the smallest self-replicating microorganisms known. It typically measures between 0.3 to 0.8 micrometers (μm) in diameter and 1 to 2 μm in length.
Motility: It is typically non-motile. It lacks flagella, which are the whip-like appendages used by many bacteria for movement. However, some studies have reported gliding or twitching motility in certain strains of M. hominis, although this phenomenon is not well understood.
Polarity: It is polar, meaning it has distinct regions at its ends. These polar regions are essential for cell division and replication.
Staining: Due to the absence of a cell wall, M. hominis does not retain the crystal violet dye used in Gram staining, a common staining method used to differentiate bacterial species based on their cell wall properties. Instead, it is often Gram-variable or even Gram-negative when observed under a microscope.

Pathogenicity

Mycoplasma hominis is a pathogenic bacterium that can cause various infections in humans. Its pathogenicity is primarily associated with its ability to colonize and infect the mucous membranes of the human genital and respiratory tracts. Here are some key points regarding the pathogenicity of M. hominis:

Genital Tract Infections: Mycoplasma hominis is commonly associated with urogenital infections. It can be transmitted through sexual contact and is considered a sexually transmitted pathogen. In women, it can cause conditions such as bacterial vaginosis, cervicitis, pelvic inflammatory disease (PID), and postpartum fever. In men, it can lead to urethritis and prostatitis.
Pregnancy Complications: M. hominis infections during pregnancy have been linked to adverse outcomes such as preterm birth, premature rupture of membranes, and chorioamnionitis (inflammation of the fetal membranes).
Opportunistic Infections:It is an opportunistic pathogen, which means it tends to cause infections when the host’s immune system is weakened or compromised. This makes it more likely to cause disease in individuals with underlying health conditions or immunosuppressed individuals.
Immunocompromised Individuals: It can pose a significant risk to people with weakened immune systems, such as those with HIV/AIDS or undergoing immunosuppressive therapy. It can cause severe and persistent infections in these vulnerable populations.
Antibiotic Resistance: M. hominis has shown increasing resistance to some antibiotics, which can complicate treatment and management of infections caused by this bacterium. Antibiotic resistance is a growing concern and highlights the importance of appropriate antibiotic usage and monitoring.
Respiratory Tract Infections: Although less common, Mycoplasma hominis can also infect the respiratory tract, leading to conditions like pneumonia and bronchitis, especially in immunocompromised individuals.

Lab Diagnosis

The laboratory diagnosis of Mycoplasma hominis infections can be challenging due to its unique characteristics and fastidious nature. Here are some common methods used for the lab diagnosis of M. hominis:

Microscopic Examination: Direct microscopic examination of clinical samples can be performed to detect Mycoplasma hominis. The bacterium can be visualized using special staining techniques such as the Papanicolaou stain or the Giemsa stain. Microscopy can reveal the typical pleomorphic and small-sized appearance of the bacteria.
Culture: It can be cultured on specialized agar media. A commonly used medium is the Mycoplasma agar, which contains nutrients and specific supplements to support the growth of Mycoplasma species. The culture plates are incubated at a temperature of 35-37°C under increased levels of CO2 since M. hominis requires an enriched environment for growth. However, this method is time-consuming as it may take several days to weeks for colonies to appear.
DNA Amplification Techniques: Polymerase chain reaction (PCR) is a highly sensitive and specific method used to detect Mycoplasma hominis DNA in clinical samples. PCR can rapidly amplify and detect the bacterial DNA, allowing for a quick and accurate diagnosis. This method is particularly useful in cases where the bacterial load is low or when rapid detection is required.
Serological Tests: Serological tests, such as enzyme-linked immunosorbent assays (ELISA), can detect antibodies against Mycoplasma hominis in the patient’s blood. However, these tests are not as commonly used for diagnosing acute infections as they are more suitable for detecting past exposures or monitoring disease progression.
Nucleic Acid Hybridization: This method uses specific probes that can hybridize with Mycoplasma hominis DNA in clinical samples. It can be used in conjunction with culture or PCR to enhance the sensitivity and specificity of the diagnosis.
Mass Spectrometry: Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is an emerging technique used for the rapid and accurate identification of microorganisms, including M. hominis. It analyzes the unique protein profile of the bacterium for identification.

It is important to collect appropriate clinical samples for diagnosis, depending on the suspected site of infection. Common sample types include urethral or cervical swabs for urogenital infections and respiratory samples for respiratory infections.

Treatment

The treatment of Mycoplasma hominis infections typically involves the use of antibiotics. However, due to the bacterium’s unique characteristics and increasing antibiotic resistance, the choice of antibiotics should be based on susceptibility testing and the patient’s clinical condition. Here are some common antibiotics used for the treatment of Mycoplasma hominis infections:

Tetracyclines: Tetracycline antibiotics, such as doxycycline and minocycline, are commonly prescribed for Mycoplasma hominis infections. They inhibit bacterial protein synthesis and have shown efficacy against Mycoplasma species.
Macrolides: Macrolide antibiotics, including erythromycin, clarithromycin, and azithromycin, are often used as an alternative treatment for Mycoplasma hominis infections. They also inhibit protein synthesis and can be effective against this bacterium.
Fluoroquinolones: Fluoroquinolone antibiotics like ciprofloxacin and levofloxacin have shown activity against M. hominis. They interfere with bacterial DNA synthesis and can be considered for treatment in cases of resistance to other antibiotics.

It is important to note that Mycoplasma hominis has shown increasing resistance to certain antibiotics, especially macrolides and fluoroquinolones. Therefore, antibiotic susceptibility testing should be performed whenever possible to guide the appropriate choice of antibiotics.

Treatment duration can vary depending on the severity of the infection, the site of infection, and the response to therapy. In some cases, a combination of antibiotics may be necessary, especially in severe or complicated infections.

It is essential to complete the full course of antibiotics as prescribed by the healthcare provider, even if symptoms improve. Premature discontinuation of antibiotics can lead to treatment failure and the development of antibiotic resistance.

For pregnant women with Mycoplasma hominis infections, treatment may be necessary to prevent complications, particularly in cases of preterm labor or premature rupture of membranes. The choice of antibiotics in pregnant women should be carefully considered to ensure the safety of both the mother and the unborn child.

Prevention

Preventing Mycoplasma hominis infections involves practicing safe sexual behaviors and maintaining good personal hygiene. Here are some key preventive measures:

Safe Sexual Practices: M. hominis is primarily transmitted through sexual contact, so practicing safe sex can significantly reduce the risk of infection. This includes consistent and correct use of condoms during vaginal, anal, and oral sex. Condoms create a barrier that helps prevent the exchange of bodily fluids, including the bacteria responsible for infections.
Limiting Sexual Partners: Reducing the number of sexual partners can also decrease the risk of contracting Mycoplasma hominis infections. Having fewer sexual partners reduces the potential exposure to the bacterium and other sexually transmitted infections (STIs).
Regular Screenings: If you are sexually active or have multiple sexual partners, it is essential to undergo regular STI screenings, including tests for Mycoplasma hominis. Regular screenings can help detect infections early, enabling prompt treatment and preventing further transmission.
Communication with Partners: Open and honest communication with sexual partners about STI risks and testing can lead to better prevention strategies and overall sexual health.
Hygiene Practices: Maintaining good personal hygiene is crucial to prevent the spread of Mycoplasma hominis. Regularly washing the genital area and hands before and after sexual activity can help reduce the risk of infection.
Avoiding Shared Personal Items: Avoid sharing personal items such as towels, washcloths, and undergarments, as this can potentially transmit the bacterium between individuals.
Avoiding Risky Behaviors: Engaging in risky behaviors, such as drug use or engaging in sexual activities under the influence of substances, can impair judgment and lead to an increased risk of infection.
Treating Sexual Partners: If one partner is diagnosed with a M. hominis infection, it is crucial for both partners to seek testing and treatment to prevent re-infection and further transmission.
Immunocompromised Individuals: Individuals with weakened immune systems should take extra precautions to protect themselves from Mycoplasma hominis infections. This may include regular medical check-ups and adherence to prescribed medications.
Prevention during Pregnancy: Pregnant women should be vigilant about their sexual health and undergo routine prenatal care to monitor for potential infections that may impact pregnancy outcomes.

Keynotes

Here are keynotes on Mycoplasma hominis:

It is a bacterium that belongs to the Mollicutes class. It is unique as it lacks a cell wall, making it one of the smallest self-replicating microorganisms known.
It is commonly found in the human genital tract and respiratory tract, colonizing the mucous membranes in these regions.
It is considered a sexually transmitted pathogen and is associated with various urogenital infections, including bacterial vaginosis, cervicitis, pelvic inflammatory disease (PID), and urethritis.
It can cause complications during pregnancy, such as preterm birth and premature rupture of membranes.
It is an opportunistic pathogen, meaning it tends to cause infections when the host’s immune system is weakened or compromised.
Diagnosis of Mycoplasma hominis infections can be challenging due to its fastidious nature. Diagnostic methods include microscopic examination, culture on specialized media, PCR, and serological tests.
Antibiotic treatment is the primary approach for Mycoplasma hominis infections. Commonly used antibiotics include tetracyclines, macrolides, and fluoroquinolones. Antibiotic resistance is a growing concern, so susceptibility testing is crucial.
Prevention involves practicing safe sex, limiting sexual partners, maintaining good personal hygiene, and undergoing regular STI screenings.
It is also a concern for immunocompromised individuals, as it can cause severe and persistent infections in this population.
Infections caused by Mycoplasma hominis should be taken seriously, and appropriate treatment and preventive measures can help reduce the incidence and complications associated with this bacterium.

Mycoplasma hominis: Introduction, Morphology, Pathogenicity, Lab Diagnosis, Treatment, Prevention, and Keynotes