Mycobacterium avium complex (MAC) infection in severely immunocompromised people living with HIV: Findings from a five-year cohort

Abstract

Background

We sought to clarify the current incidence, risk factors and symptoms of disseminated Mycobacterium avium complex (dMAC) infection in admitted people living with HIV in a hospital in the Southeast of Spain.

Methods

5-years observational, retrospective and single-centre study. Demographic, clinical and analytical variables, along with microbiological, treatment and follow-up were collected.

Results

Five cases of dMAC infection in severely immunocompromised people living with HIV people living were found. dMAC was diagnosed in 22.7% of patients under 100 CD4. All patients presented with fever and clinical manifestations of pneumonia, lymphadenopathy, or gastrointestinal symptoms. Despite low CD4 levels and high viral loads in some cases, primary prophylaxis had not been previously administered.

Conclusions

Until 2018, U.S. American guidelines recommended antimycobacterial prophylaxis for patients with low CD4 cell counts, a practice not adopted in Europe. Untreated dMAC infection is associated with high morbidity and mortality rates. dMAC infection represents a prevalent disease in severely immunosuppressed people living with HIV. dMAC requires a high index of suspicion in this population, in order to perform mycobacterial cultures from different samples.

Keywords

Human immunodeficiency virus Europe antibiotic

Background

Mycobacterium avium complex (MAC) comprises various slow-growing mycobacterial species, with M. avium, M. intracellulare and M. chimaera being the most significant human pathogens. These organisms are commonly found in water, house dust, and soil. Once they reach plumbing systems in homes or buildings, their hydrophobic nature enables them to attach to surfaces. While transmission among patients with pulmonary MAC is rare, clusters of infections often trace back to a shared water source, suggesting inhalation of infectious aerosols as the primary mode of transmission leading to pulmonary disease. Additionally, MAC can enter the body via the gastrointestinal tract or through direct inoculation from trauma or invasive procedures.^1–3

Immunocompromised patients, such as those living with HIV and a low T CD4-lymphocyte count, are particularly susceptible to MAC infections.² In these individuals, MAC is likely acquired through the gastrointestinal tract, with M. avium being the main species causing disease in over 95% of disseminated MAC cases. Strains isolated from hospital water closely resemble those found in patients with advanced HIV disease with MAC disease treated in those hospitals. The predominance of M. avium in disseminated disease may be partly attributed to its greater resistance to gastric acid compared to M. intracellulare.³

There is a clear relationship between a higher level of immunosuppression (typically described in HIV patients with <50 CD₄ lymphocytes/mm³) and an increased risk for MAC infection, which also leads to raised morbidity and mortality rates.^1–3 Other risk factors for MAC infection are HIV blood viral load (HIV VL) above 1000 copies/ml, the presence of other opportunistic infections and previous colonization of the respiratory of gastrointestinal tract with MAC.^1,3

The respiratory tract is the most frequent site of MAC infection in immunocompetent patients. Clinical manifestations of MAC pulmonary infection vary widely, encompassing asymptomatic colonization, indolent infection, and progressive symptomatic disease. Additionally, MAC has been reported to cause symptomatic disease at various extrapulmonary sites, with lymph nodes being the most common. MAC lymphadenitis primarily affects healthy children with normal immune systems.³

However, parenchymal lung disease caused by MAC is uncommon among patients with advanced HIV disease, the most common form being disseminated disease (dMAC). Clinically, patients with dMAC in the context of advanced HIV disease present with persistent high-grade fevers, deep night sweats, weight loss, anorexia, fatigue and diarrhoea often associated with colicky abdominal pain.³ Before the introduction of effective antiretroviral therapy (ART) this dMAC was the most frequent presentation.^4,5 After ART was widely available, localized disease became more prevalent possibly because new forms of MAC infected patients whose immune systems could not fully recover but were able to prevent disseminated disease.⁶

Neither Spanish GESIDA nor IDSA HIV Guidelines recommend primary prophylaxis for MAC disease in patients who immediately start ART.^1,7 Spanish GESIDA Guidelines suggest assessing prophylaxis if CD₄ T-lymphocytes are below 50/mm³ with detectable HIV viral load. IDSA guidelines recommend prophylaxis for patients living with HIV who already are on ART but remain viraemic, without possibilities for a suppressive regimen and if CD₄ T-lymphocytes are under 50/mm³. MAC disease is recommended to be ruled out before prophylaxis is initiated. Preferred prophylactic treatments are either azithromycin or clarithromycin. Rifabutin should be used when macrolides are contraindicated, always ruling out active TB disease.

Diagnosis is based on compatible clinical signs and symptoms, together with isolation of MAC from any normally sterile body fluids or tissues. Due to the heterogeneity of clinical presentation, there are no standardized diagnostic protocols. However, bacteriological confirmation in the laboratory is essential to diagnose MAC infection, emphasizing the critical need to obtain an adequate specimen during diagnostic evaluation.³

During the early stages of the HIV pandemic, certain studies emphasized the significance of conducting mycobacterial blood cultures, and current guidelines continue to stress the diagnostic potential of these cultures for disseminated MAC infection.^1–3

The prevalence of low CD4 levels amongst people living with HIV has significantly decreased compared to the 1990s and MAC incidence has continuously declined accordingly. This is obviously related to powerful modern ART with few adverse events, and it is also due to the massive performance of HIV testing, especially in at-risk populations, which leads to early diagnoses in most cases. Despite this trend, in 2022, 27.6% of the 2624 new HIV diagnoses in Spain reported a CD4 count below 200/mm³.⁸ The lack of current statistics on the percentage of MAC infections in immunocompromised HIV patients is striking.

Therefore, our objective was to evaluate the incidence, risk factors and symptomatology of dMAC infection in severely immunocompromised people living with HIV, together with the use of different microbiological samples to establish the diagnosis of this disease.

Methods

We conducted a 5-years observational, retrospective and single-centre study including all people living with HIV with dMAC infection at San Cecilio University Hospital (Granada, Spain). All enrolled patients provided informed consent to participate in the study. We conducted a review of each patient’s medical records. We examined patients’ demographic characteristic, CD4 cell count, HIV RNA load, previous history of ART, and other opportunistic infection at the time when their CD4 cell counts was <50 cells/mm³. Disseminated MAC infection was defined as a positive culture of MAC from blood or bone marrow. If there was generalized lymph node enlargement with suggestive symptoms and signs of dMAC, recovery of MAC from a lymph node was also defined as dMAC infection.

For the corresponding microbiological studies, specific blood cultures for mycobacterial examination (BACTECTM Lytic culture, BD) were incubated using the automated BD BACTECTM FX system. Other samples were inoculated into liquid medium using either the BACTEC^TM MGIT^TM 960 or VersaTREK^TM system following initial direct smear microscopy (auramine-rhodamine) and multiplex RT-PCR (AnyplexTM MTB/NTM Real-Time detection) to identify the presence of M. tuberculosis complex species or other non-tuberculous mycobacteria.

Following growth on incubation media, identification was performed using the GenoType Mycobacterium CM assay (Bruker) or MALDI-TOF, and genotypic susceptibility testing was conducted using the GenoType NTM-DR assay (Bruker). Phenotypic susceptibility was assessed by microdilution with the commercial SensitytreTM SLOMYCO2 system with subsequent interpretation of results using CLSI criteria.⁹ Microbiological studies were performed at the Hospital Universitario Virgen de las Nieves, Granada.

The Ethics committee (CEIM/CEI) of the province of Granada approved the study with the code 1250-N-22.

Results

Between January 2018 and December 2022: 84 patients with HIV were admitted to our Infectious Disease Unit. Five patients (5.95%) were diagnosed with dMAC infection, of whom 2 (40%) were female. Their mean age was 43.8 years. The clinical and analytical characteristics, treatment and evolution are displayed in Table 1. MAC infection was diagnosed in 22.7% of patients with fewer than 100 T-CD₄ lymphocytes (5 out of 22).

Table 1.

Main clinical characteristics of the five HIV-positive patients who met the criteria for disseminated Mycobacterium avium complex (MAC) infection.

Sex	Patient 1	Patient 2	Patient 3	Patient 4	Patient 5	Total (%)
Sex	Woman	Man	Woman	Man	Man	W: 40 M: 60
Age	52	48	58	28	33	Median: 48
MAC species	Mycobacterium avium	Mycobacterium avium	Mycobacterium avium	Mycobacterium avium	Mycobacterium avium
ART use	DRV/COBI/FTC/TAF No adherence	BIC / FTC / TAF No adherence	No	No	No
HIV VL (copies/ml)	33	114	38,000	121,000	852,000	Median: 38000
CD4-T lymphocyte count (CD4/mm3)	74	64	4	11	51	Median: 51
Symptoms
Fever	Yes	Yes	Yes	Yes	Yes	100
Dyspnoea	No	No	No	No	Yes	20
Cough	Yes	No	No	Yes	Yes	60
Abdominal pain	No	Yes	No	No	No	20
Diarrhea	No	Yes	No	No	No	20
Anaemia	Yes	Yes	Yes	Yes	Yes	100
Weight loss	Yes	Yes	Yes	No	No	80
Night sweats	No	Yes	No	Yes	Yes	80
Hemoglobin (g/dl)	11.7	8	11.9	11.6	11.4	Median: 11.6
Criteria for IRIS	Yes	Yes	No	Yes	No	Yes: 60 No: 40
Radiological findings
Pulmonary hilar lymphadenopathies	Yes	Yes	No	Yes	Yes	80
Interstitial pnemonia	No	No	No	No	Yes	20
Cavitated pneumonia	No	No	Yes	Yes	No	40
Pulmonary nodules	No	No	No	Yes	Yes	40
Hepatosplenomegaly	No	No	No	Yes	No	20
Diffuse colitis	No	Yes	No	No	No	20
Antimicrobials used against MAC	Amikacin, azithromycin, Ethambutol	Amikacin, azithromycin, Ethambutol, moxifloxacin, Rifampicin (withdrawn due to hepatotoxicity)	Azithromycin, Ethambutol, Rifampicin	Azithromycin, Ethambutol, moxifloxacin	Clarithromycin, Ethambutol, Rifabutin
Treatment duration against MAC	27 months	Currently under treatment	12 months	12 months	Currently under treatment
Other drugs used and indication	9 months of oral prednisone (IRIS)	1 month of oral dexamethasone (IRIS)	2 months of oral prednisone (Pneumocystis jirovecii coinfection)	1 month of oral prednisone (IRIS)	1 month of oral prednisone (Pneumocystis jirovecii)
Other previous opportunistic diseases and/or concomitant to MAC	Pneumocystis jirovecii pneumonia (concomitant)	Nodular Kaposi’s sarcoma	Pneumocystis jirovecii pneumonia + CMV (concomitants)	Esophageal candidiasis (concomitant)	Pneumocystis jirovecii pneumonia (concomitant)

ART: antiretroviral treatment. CMV: cytomegalovirus. COVID-19: coronavirus disease 2019. HVV6: human herpes virus 6. HIV: human. Immunodeficiency virus. HIV VL: HIV viral load in blood. IRIS: immune reconstitution inflammatory syndrome.

The main symptoms were fever, present in all five patients described (100%), followed by respiratory symptoms such as dyspnoea or cough (60%) and abdominal symptoms such as abdominal pain or diarrhoea (20%). All patients (100%) presented radiological findings consistent with MAC respiratory involvement (lymphadenopathies, cavitating pneumonia, interstitial pneumonia and/or pulmonary nodules). One patient (20%) had gastrointestinal symptoms in whom MAC was isolated in the colonic mucosal biopsy. Despite all five patients presented multifactorial anaemia, bone marrow aspiration (BMA) was only performed in one case (20%), in which the presence of non-tuberculous mycobacteria was detected by PCR.

Viroimmunological status was poor in all of them: although only 2 (40%) of them had <50 CD4 lymphocytes/mm3, all 5 (100%) had <75 and 3 (60%) of them had HIV VL above 35,000 copies/ml (the remaining two had detectable HIV VL but less than 150 copies/ml). No patient was under optimal ART; 3 (60%) of them were diagnosed of HIV at the time of the MAC disease, these patients with the highest HIV VL; the remaining 2 (40%) were theoretically under ART but without correct adherence, coinciding with lower HIV VL.

Regarding risk factors for dMAC (apart from poor viroimmunological control of HIV), it should be noted that all the patients previously presented other opportunistic infections: Pneumocystis jirovecii pneumonia (n:3; 60%), nodular Kaposi’s sarcoma (n:1; 20%) and esophageal candidiasis (n = 1; 20%).

As for the microbiological findings (Table 2), in addition to the blood culture, which was positive in all patients (100%), it is worth highlighting the isolation of MAC in other samples such as BAS or sputum (60%), which in cases where it was positive always preceded the blood culture.

Table 2.

Microbiological findings related to M.avium complex.

	Patient 1	Patient 2	Patient 3	Patient 4	Patient 5
Sample type
mBC	Positive	Positive	Positive	Positive	Positive
Sputum	Positive (negative AFB smear)	-	Positive (positive AFB smear)	Negative	Negative
BAS	Positive (positive AFB smear)	-	Negative	Negative	Positive (negative AFB smear)
TBNA of hilar adenopathy	Positive (positive AFB smear)	Positive (negative AFB smear)	-	-	-
BMA	-	Positive (negative AFB smear)	-	-	-
Other	-	Positive (only PCR positive in colon mucosal biopsies)	-	-	Positive (only PCR positive in lung biopsy)
First positive sample	BAS	mBC	BAS	mBC	BAS
Microbiological resistance detected for MAC
Genotypic (macrolides and aminoglucodises)	Non detected	Non detected	Non detected	Non detected	Non detected
Phenotypic	Moxifloxacin: S	Moxifloxacin: I	Moxifloxacin: S	Moxifloxacin: S	Moxifloxacin: S
	Clarithomycin: S	Clarithomycin: S	Clarithomycin: S	Clarithomycin: S	Clarithomycin: S
	Linezolid: S	Linezolid: R	Linezolid: R	Linezolid: S	Linezolid: R

mBC: mycobacterial blood culture. BAS: bronchial aspirate. BMA: bone marrow aspiration. TBNA: transbronchial needle aspiration. AFB: Acid-fast bacilli.

MAC was also isolated in other locations such as transbronchial needle aspiration (20%), bone marrow aspiration (20%), and even in biopsies such as colon (20%) and lung biopsy (20%). In biopsies, detection was only achieved by molecular techniques. M. avium subspecies was confirmed by molecular biology or MALDI-TOF techniques in each case.

Regarding sensitivity data, no mutations in the erm and rrl genes, associated with macrolide resistance, or in the rrs gene, associated with aminoglycoside resistance, were detected in any of the isolates. At the phenotypic level, minimum inhibitory concentrations (MIC) obtained by microdilution were interpreted according to CLSI¹⁰ criteria with the following results: 100% of isolates were sensitive to clarithromycin, 80% were sensitive to moxifloxacin and 20% showed an intermediate level of sensitivity, while 60% were resistant to linezolid and 40% were sensitive to this antibiotic.

Conclusions

As previously described, the most common site of MAC infection in immunocompetent patients is the respiratory tract. However, pulmonary parenchymal disease caused by MAC is uncommon among patients with advanced HIV disease. Otherwise, the typical patterns in people living with HIV are focal lymphadenopathies and disseminated infection.^2,3,10 This last form was found in the five patients analysed in our study, who typically presented with fever which was present in all the cases described here as well as anaemia. In relation to night sweats, it was recorded in all four patients, as well as weight loss. Only one patient presented with abdominal pain and diarrhoea. These simple clinical parameters seen to remain good predictor of mycobacterial disease in these patients’ group, similar to what has been reported by other authors.¹¹ In all the patients studied we found different pathological findings at respiratory level, in one of them also at digestive level together.

The current recommendations from the Spanish and American Infectious Diseases societies indicate that primary chemoprophylaxis for disseminated MAC is not widely recommended in HIV patients (regardless of the level of CD4 lymphocytes) who have just started ART and in whom we assume that viroimmunological control will be quickly achieved. However, primary chemoprophylaxis for disseminated MAC is indicated in patients with <50 CD4 lymphocytes/mm³ in whom good viroimmunological control has not been reached despite appropriate ART or who are not receiving ART, if blood cultures for mycobacteria are negative at that time.^1,3,5,12 In Spain, the country of our study, primary prophylaxis of disseminated MAC in people living with HIV with <100 CD4 lymphocytes/mm3 was never recommended due to the low incidence of the disease.⁴ The incidence and prevalence rates of MAC infections vary with time, location, and disease definition. In a study of a similar population (patients with CD4 cells counts <50 cells /mm3 and on ART) in the USA, the authors reported an incidence of 0.6/100 person-months.¹³ Another cohort study including six European countries and the USA found a lower incidence 5.8/1000 patient-years.¹⁴

When achieving a level of CD4 lymphocytes/mm³ above 100 with ART, the suspension of this prophylaxis would be indicated in the case it was previously started.^1,3,4,12 Arguments against primary prophylaxis are the economic cost, the pharmacological adverse effects, the increase in antimicrobial drug resistance and the low rate of MAC infection. In our series, in relation to antiretroviral treatment, none of the patients were on optimal ART, as three of them were diagnosed with HIV at the time of MAC, being these patients those with the highest HIV VL; while the remaining two were theoretically on ART but without correct adherence, coinciding with lower HIV VL. None of the patients studied received prophylaxis. A recent study in the USA examined the incidence of MAC infection among patients with CD4 cell counts of <50 cells/mm³ receiving combination ART and did not find a difference in the incidence of MAC between the prophylaxis and the non-prophylaxis groups.¹³

Early detection of this opportunistic infection is crucial, and performing mycobacterial blood cultures has been shown to be pivotal in patients with low CD4 counts, in conjunction with the diagnosis of CMV infection in the context of a diagnosis of fever of unknown origin.¹¹ Previous studies have highlighted the significance of blood cultures in patients with CD4 counts <100 cells/mm³ and unexplained fever, as persistent fever in this patient group may be the sole sign of MAC infection in the absence of specific symptoms.¹⁵ Additionally, mycobacterial blood cultures can serve as a valuable tool in diagnosing disseminated MAC infections, especially in patients with low clinical suspicion but high risk due to immunosuppression. Therefore, the performance of mycobacterial blood cultures in patients with low CD4 counts is strongly recommended as part of a comprehensive clinical management strategy to enhance timely detection and treatment of MAC infection. As for microbiological findings, in addition to blood culture, which was positive in all patients, and the isolation of MAC in invasive samples such as transbronchial needle aspirate, bone marrow aspirate, colon and lung biopsies, we highlight the isolation of MAC in other samples such as BAS or sputum (60%), which in the cases in which it was positive always preceded the blood culture.

Given the evidence provided, we believe that an active search for MAC infection should be mandatory in all patients with poor viroimmunological control (including at HIV diagnosis). Our short experience in recent years supports this statement. Mycobacterial blood cultures in patients with HIV infection and low CD4 lymphocyte count who present with fever should be always performed. The threshold of CD4 lymphocytes below which the risk of MAC infection is a matter of debate, but 100 CD4-T lymphocyte is a reasonable cut-off point until more evidence emerges in this regard.

In addition to blood cultures, a search for MAC in different organs should be based on clinical presentation (analysis by culture, staining and/or molecular techniques): sputum-BAS (cough, expectoration, dyspnoea), stool culture-colon mucosal biopsies (diarrhoea), BMA (cytopenias), skin biopsy (skin lesions), lymph node biopsy-TBNA (palpable or radiological lymph nodes).^2,4

In summary, actively screening for MAC in any affected organ in severely immunocompromised people living with HIV is good clinical practice, and collecting mycobacterial blood cultures should be highly recommended too.

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Ethical statement

ORCID iD

Emilio Guirao-Arrabal

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